AQA A-LEVEL BIOLOGY- PAPER 1, Exams of Advanced Education

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AQA A-LEVEL BIOLOGY- PAPER 1

What type of theory can cell theory be described as? - A unifying concept What is a unifying concpet? - A concept that is universally accepted among the scientific community What are the three main ideas that Cell Theory states? - - All living organisms are made up of one or more cells -Cells are the basic functional unit

• New cells are produced from pre-existing cells Describe what is meant by this statement: "Cells are the basic functional unit" - That cells are the basic unit of structure and organization within an organism Name sub-cellular structures that compose the structure of Eukaryotic Cells - Cell Surface Membrane Cell wall Mitochondria Nucleus Chloroplasts Ribosomes Rough and Smooth Endoplasmic reticulum Nucleolus Golgi Apparatus (vacuoles) Vesicles Lysosomes Centrioles Microtubules What are all cells surrounded by? - a cell surface membrane What is the function of the plasma membrane? - To control the exchange of materials between the internal and external environment of the cell What is the plasma membrane formed from? - phospholipid bilayer What is a phospholipid? - It is a lipid that has a phosphate group attached to the glycerol and only two fatty acid chains. Estimate the diameter of the phospholipid bilayer of the cell surface membrane - ~10nm in diameter What term can be used to describe the plasmsa membrane - partially permeable

Define partially permeable - membrane that allows some substances to cross but not others. Where are cell walls formed? - Outside the cell surface membrane What is the function of the cell wall? - A rigid layer that supports the cell and provides shape while simultaneously providing protection How is the structural support of the cell wall provided in plants? - Through the polysaccharide cellulose How is structural support of the cell wall provided in most bacterial cells? - Peptidoglycan (a.k.a. murein) How can the cell wall be described? - Freely permeable to most substances What are plasmodesmata? - Narrow threads of cytoplasm (surrounded by plasma membrane) connect the cytoplasms of neighbouring plant cells together Describe the function of the mitochondria - They are the site of aerobic respiration within eukaryotes Describe the features of the Mitochondria's membrane - They are surrounded by a double membrane with the inner membrane folded to form structures called cristae. What are the functions of Cristae? - -Increase surface area of the inner membrane -allows inner membrane to accommodate large numbers of the protein complexes needed for: solute transport, electron transport, ATP synthesis What is the area within the Mitochondria's double membrane called? - the matrix What is the function of the matrix which is formed by the cristae? - To contain enzymes required for aerobic respiration resulting in the synthesis of ATP Other than enzymes what else can be found in the matrix and state its purpose - Small pieces of mitochondrial DNA and ribosomes are also found in the matrix which are required for replication Are mitochondria visible under light microscopes - Just as they are large organelles Other than the plasms membrane what is present in all eukaryotic cells? - Nucleus and it is relatively large What separates the nucleus from the cytoplasm - A double membrane called the nuclear envelope which contains many nuclear pores

Why are nuclear pores important? [two marks in and out] - They act as important channels for:

• mRNA and Ribosomes to travel out
• enzymes and signaling molecules to travel in. Give an example of an enzyme required in the nucleus - DNA polymerase What can be found within the nucleoplasm? - Chromatin When does chromatin dissolve into Chromosomes? - During the prophase stage of mitosis What do Chromosomes consist of? - Chromosomes consist of linear DNA tightly wound around proteins called histones What sub-cellular structure do most nuclei contain at least one of? - Nucleolus What is the function of the nucleolus? - To be the site of ribosome production What are Chloroplasts - A membrane bound organelle which act as the site of photosynthesis Compare the size of a chloroplast to a mitochondrion - larger Describe the membrane of a chloroplast? - Chloroplasts are surrounded by double membranes. What is the stroma? - The fluid filled internal space within a chloroplast Which structures can be found within the stroma? - - Thylakoids
• Grana
• Small circular pieces of Chloroplast DNA
• Ribosomes
• Lipid Droplets
• Starch Granules What are thylakoids? - Membrane-bound compartments which contain chlorophyll What is chlorophyll? - Chlorophyll is a green photosynthetic pigment embedded within the thylakoid membrane in chloroplasts What is the function of chlorophyll? - To absorb the wavelengths of visible light between 400 and 700 nanometers to provide energy for the light dependent stages of photosynthesis

What do thylakoids stack to form? - Structures called grana What are grana joined together by? - lamellae What are lamellae in Chloroplasts? - Thin and flat thylakoid membranes used to join the Grana together What are the small circular pieces of Chloroplast DNA and ribosomes used for? - To synthesize proteins (including enzymes) needed for chloroplast replication and the Calvin cycle What are the lipid droplets and starch granules required for? - Metabolic processes and the Calvin cycle in Chloroplasts Where does the light dependent stage of photosynthesis take place? - Thylakoids Where does the light independents stage of photosynthesis take place? - Stroma Where are ribosomes formed and assembled? - Nucleolus Describe Ribosomes - Small organelles that are a complex consisting of a large subunit and a small subunit which are made from almost equal amounts of proteins and ribosomal RNA (rRNA) and are the site of protein synthesis What is a feature of the Chloroplast's Double Membrane? - An intermembrane space between the two membranes Which component of protein synthesis takes place in the ribosomes? - Translation What are the two types of ribosomes? - 80s Ribosomes 70s Ribosomes Describe 80s ribosomes - found in eukaryotic cells and consist of a large 60s subunit and a small 40s subunit Describe 70s Ribosomes - Found in prokaryotes and certain double membraned organelles such as mitochondria and chloroplasts and consist of large 50s and Small 30s subunits What does the 's' stand for in ribosome measurement? - Svedbergs What is a svedburg? - A svedburg is a unit to measure how fast molecules move in a centrifuge What are the two types of Endoplasmic Reticulum? - Rough and Smooth Endoplasmic Reticulum

Describe the structure and function of the Rough ER - Formed from continuous folds of flattened membrane sacs that's CONTINUOUS WITH THE NUCLEAR ENVELOPE!!!

• They have a surface covered in ribosomes They fold and process proteins synthesized by these ribosomes. Describe the structure and function of the Smooth ER - Formed from continuous folds of flattened membrane sacs.
• No ribosomes on surface
• Involved in production processing and storage of:
  • lipids
  • Carboydrates
  • Steroids Describe the structure and function of the Golgi - A sub cellular structure consisting of flattened membrane sacs Modifies proteins and lipids before packaging them into golgi vesicles for export What happens to lipids and proteins placed in golgi vesicles - The vesicles transport the proteins and lipids to their required desitnations What happens to proteins that go through the golgi Body - They are either:
• Exported (e.g. hormones such as insulin)
• Put into lysosomes (e.g. hydrolytic enzymes to prevent damage)
• Delivered to membrane bound organelles Describe a vacuole that can be found in plants - A permanent vacuole is large and applies turgor pressure on cell wall to keep the tissue rigid. It contains cell sap Contains a central vacuole Describe the membrane that can be found on a permanent vacuole - A single selectively permeable membrane called the tonoplast Describe animal vacuoles - small and not permanent What are vesicles? - Membrane bound sacs used for transport and storage Describe the structure of a vesicle - - Vesicle surface
• Surrounded by a bilayer membrane
• Internal water

What are lysosomes? - Specialized forms of vesicles that contain hydrolytic enzymes What are hydrolytic enzymes? - Enzymes that break down biological molecules with water in hydrolysis reactions. What are the function of lysosomes? - To break down waste materials such as worn out organelles, used in the immune system during phagocytosis and used for apoptosis What is apoptosis? - programmed cell death What is a centriole? - Small hollow fibre cylinders found in animal cells and some plant cells Where are centrioles not found? - Flowering plants and most fungi What do two centrioles perpendicular to one another form? - centrosome What is a centrosome - An organelle that is located near the nucleus responsible for forming spindle fibres during cell division What are microtubules? - hollow structures made up of the protein tubulin, they maintain a cells shape as they make up the cytoskeleton of the cell What is the function of the cell's cytoskeleton? - To provide support and help cell movement What is the approximate of microtubules? - 25 nanometers What do microtubules consist of? - alpha and beta tubulin which combined form dimers What do dimers join together to form? - protofilaments How many protofilaments in a cylinder make a microtubule? - 13 What is Chitin? - A fibrous substance consisting of polysaccharides which are major components in the cell walls of fungi What are microvilli? - Cell membrane extensions increasing surface area for absorption What are cilia? - Hair like projections made from microtubules to allow movement of substances over cell surface What are flagella - Even longer hair like projections made of longer microtubules which contract to provide cell movement What do structural adaptations include? - shape of cell

organelles that cells contain (or don't) What are the structural adaptations of Red Blood Cells? - - Bi concave shape and don't contain a nucleus --> more space inside to transport O --> Can easily pass through narrow blood vessels Compare the sizes of the prokaryotic cells and eukaryotic cells - Prokaryotic cells are much smaller than eukaryotic cells (2-3 orders of magnitude smaller) How do prokaryotic cells differ from eukaryotes? - - Cytoplasm lacking membrane bound organelles

• having 70s ribosomes
• No nucleus --> single circular DNA loop free in cytoplasm
• Cell wall made of murein (peptidoglycan) What few additional structures do some prokaryotes have and what does this allow for?
• Plasmids Capsules Flagellum Differentiate species from others and act as a selective advantage What are plasmids? - Plasmids are small rings of extra DNA that are sperate from the main circular DNA loop which contain genes that code for specific features (e.g. antibiotic resistance) and can be passed between prokaryotes What are capsules and elaborate on their function? - (slime) capsules are a final outer layer that surround some prokaryotes which help to prevent bacteria from drying out and protect them from attack by immune system cells of the host organism What are flagella? - Some prokaryotes may have more than one long tail like structure which contract or rotate enabling the prokaryote to move. What is a mesosome? - Infolding of the plasma membrane which increase surface area and could allow for photosynthesise or nitrogen fixation to occur What are pili? - Protein filaments on the edge of a cell wall that helps bacterial cells attach to surfaces and to one another and involved in plasmid conjugation. What can microscopes be used for? - to analyse components and observe organelles Define magnification - how many times larger the image observed of a specimen is compared to the actual size of the specimen.

Define resolution - The ability to distinguish between to separate points What are the two types of microscope? - Optical (light) microscope Electron Microscope How do optical microscopes form an image? - They use light to form an image Describe the resolution of an optical microscope and give an explanation for this - The resolution of optical microscopes are limited due to the fact when using light, it is impossible to distinguish between two objects that are closer than half the wavelength of light. Light has a wavelength of 500-650 nanometers so optical microscopes cannot distinguish between objects closer than half this value. What is the resolution of optical microscopes? - 200 nm What can optical microscopes be used to observe? - eukaryotic cells, their nuclei and large subcellular structures What sub-cellular structures can optical microscopes be used to observe? - mitochondria and chloroplasts as they're relatively large Give examples of organelles that CANNOT be viewed using optical microscopes? - ribosomes, ER and lysosomes What is the magnification of optical microscopes? - x How do electron microscopes form an image? - using a beam of electrons Describe the resolution of electron microscopes and elaborate on the reasoning for this

• Allows for greater resolution compared to optical microscopes giving a more detailed image and this is due to electrons having a much smaller wavelength than light meaning objects closer together can be distinguished What is the resolution of electron microscopes and compare this to optical microscopes? - 0.2nm x1000 more than an optical microscope What is the magnification of electron microscopes? - x1 500 000 What can electron microscopes be used to view? - small organelles What are the two types of electron microscopes? - scanning electron microscope transmission electron microscope

How do transmission electron microscopes operate? - Transmission electron microscopes use electromagnets to focus a beam of electrons which is then transmitted through the specimen. Under TEMs which part of the specimen will absorb more electrons - Denser parts of the specimen How are denser parts of specimens viewed on an electron micrograph produced by a TEM - Will appear darker on the final image produced and this provides contrast between different parts of the image being observed What are the advantages of Transmission Electron Microscopes? - + Higher resolution

• Higher magnification
• allow internal structures of cells to be seen What are the disadvantages of TEMs - - Difficult and lengthy preparation process for the specimen

• Can only be used with very thin specimens
• Cannot be used to observe live specimens
• Do not produce colour images
• Must be kept in humidty, temperature, pressure controlled rooms and can only view specimens under vacuum conditions
• Artefacts can be introduced Name a difficulty of the preparation process of TEMs - all water must be removed from the specimen Why can't live specimens be observed under electron microscopes? - Due to the vacuum conditions. What are artefacts? - structures that look genuine but are instead results of preserving and staining. How do scanning electron microscopes operate? - by scattering a beam of electrons across the specimen. this beam bounces off the surface of the specimen and an image is formed from the detection of these deflected electrons. What type of image can SEMs show? - 3D images showing the specimen's surface What are the advantages of SEMs? - + Can be used on thick and 3D specimens

• Allow the external 3D structure of specimens to be observed.

What are the disadvantages of SEMs? - - Lower magnification and resolution than TEMs

• Cannot view live specimens
• No colour images What is the storage polysaccharide of plants? - starch What is stored inside starch grains? - some sugars formed in photosynthesis are stored as starch Where are starch grains usually found? - Stroma of Chloroplasts Storage organs (e.g. potato tubers) Seeds How can starch grains be seen by light microscopes? - Starch grains are large enough to be seen under light microscopes but require staining first What is used to stain starch grains? - Iodine aqueous in potassium iodide can be used to stain starch gains This causes starch grains to become darker in colour as the iodine in potassium iodide turns blue-black in starch presence which makes the starch grains easier to see. What are the two types of light microscope lenses? - - objective lens
• eyepiece lens (usually x10) What is total magnification equal to? - total magnification = eyepiece lens x objective lens What happens if two points cannot be resolved? - They will be observed as a single point Why is the resolution of microscopes limited by the wavelength of light? - As light passes through a specimen, it will defract. The longer the wavelength, the more diffraction occurs and therefore the increased likelihood that two diffracted waves will overlap as points get closer together Why is it significant that electrons have a shorter wavelength than visible light? - The beams can be much closer before diffracted beams overlap Describe how visible light travels through a specimen in a light microscope - Light is shined through the specimen and this light is passed through an objective lens then an eypeice lens which magnifies the specimen to produce an enlarged image visible to the naked eye.

State the conditions the specimens can be in optical microscopes - living dead What are light microscopes useful for looking at - Whole cells small organisms tissues within organs Describe how electrons travel within a specimen in an electron microscope - Electrons are fired in beams from an electron gun at the specimen either a broad static beam or a small beam moving across the specimen. The electrons are then detected by an electromagnetic lens, showing the image Why is the magnification and resolution higher in electron microscopes - Due to increased frequency and therefore shorter wavelength of electrons compared to visible light What are electron microscopes used to view - Organelles Viruses DNA Looking at overall cell structure in more detail What are the advantages of the vacuum in electron microscopy - Can provide a snapshot of the processes occurring in the cell at that time e.g. a specific stage of mitosis Which electron microscope utilizes a broad static beam? - Transmission Electron Microscope Which electron microscope utilizes a Small beam moving across the specimen? - Scanning Electron Microscope Why do sometimes only specific organelles need to be studied? - To look at the appearance of that specific organelle Conduct research on the specific organelle What are theconditions of studying a single organelle? - A pure sample is required What is cell fractionation - The process of separating out different cell components and organelles from each other. What must you do in order to carry out cell fractionation? - To carry out cell fractionation you need to break up a suitable sample of tissue and then centrifuge the mixture at different speeds. What are the 3 stages of cell fractionation? - Homogenisation Filtration

Ultracentrifugation What is homogenisation? - Homogenisation if the process of breaking up cells in a homogeniser Before homogenisation occurs what must happen to the tissue sample? - The tissue sample containing the cells must be placed in an ice-cold, isotonic buffer solution before Homogenisation occurs Why must the sample be placed in an ice cold soution? - To reduce the activity of enzymes that can potentially break down organelles Why must the sample be placed in an isotonic solution? - To leave the water potential unaffected therefore preventing water osmosing into organelles What are the possible consequences of water moving into organelles during cell fractionation? - expansion, damage or even lysis Why must the solution be buffered? - to maintain pH in order to prevent the denaturing of proteins What is the result of homogenisation? - The homogeniser will break the cell's plasma membrane causing all the organelles to be released into a solution called the homogenate What does filtration involve? - Filtration involves the homogenate being filtered through a gauze Why is filtration required during cell fractionation? - To remove any large cell/tissue debris that wasn't initally broken up during homogenisation. What happens to the cell organelles during filtration? - They are much smaller than the debris so aren't filtered and pass through the gauze What is the result of filtration? - It leaves a solution called the filtrate which contains a mixture of organelles What happens to the filtrate following filtration? - it is placed in a tube which is then spun at variable speeds in a centrifuge Define ultracentrifugation - The process by which the fragments in the filtered homogenate are separated in a centrifuge into relative fractions Describe the process of ultracentrifugation [6] - - Firstly the filtrate is spun at a low speed.

----> this causes the largest and heaviest organelles to settle at the bottom of the tube forming a thick sediment known as a pellet. ----> The rest of the organelles remain suspended in the solution above the pellet called the supernatant

• the supernatant is then drained off and placed in a separate tube which is then spun at a higher speed ----> this causes the next heaviest fraction of organelle to settle at the bottom and form a new pellet and supernatant
• this process is repeated at increasing speeds until all fractions are separated or desire organelle is obtained. What is the general order of mass (and therefore fractions) organelles? {From heaviest to lightest} - - Nuclei
• Chloroplasts
• Mitochondria
• Lysosomes
• Endoplasmic reticulum
• Ribosomes What can artefacts be caused by? - dust air bubbles fingerprints What are artefacts generally a result of? - the result of a specimen's preparation -> sample can be squashed and stained which can generate artefacts How can artefacts be avoided? - with careful sample preperation Where are artefacts most common in? - (Especially TEM) electron micrographs due to lengthy preparation process. When preparing a specimen, why must you lower the coverslip with a needle? - To ensure no air bubble are trapped leading to artefacts which could obstruct the specimen view What is a retrovirus? Give an example. - Virus contains RNA instead of DNA. HIV is an example Why are retroviruses hard to cure? - as they tend to often mutate What is a virus? - A small acellular non living infectious agent that replicates within cells What is the structure of an HIV virus? - - 2 RNA strands
• Protein capsid coating

• Attachment proteins
• A viral envelope consisting of a phospholipid bilayer and glycoproteins Describe the genetic material of viruses - Contains a genome with these variable characteristics: -circular or linear -single or double stranded -DNA or RNA What enzyme is present within viruses? - reverse transcriptase What are the stages of viral replication? - attachment, penetration, synthesis, assembly, release What is the alternative name of a T-Helper Cell - CD Describe the process of HIV replication - HIV attaches to the receptors on the cell surface of a T-Helper cell (CD4) HIV envelope and CD4 cell membrane fuse allowing virus to enter CD4 cell Within the CD4, HIV released and uses an enzyme called reverse transcriptase to convert its genetic material; HIV RNA into HIV DNA meaning this genetic material can enter CD4 nucleus and their genetic material combine These replicated proteins move to cell surface Virus is pushed out of host cell and the infectious virus is released. Which enzyme allows HIV genetic information to enter the CD4 nucleus? - intergrase Describe the difference in size between Eukaryotes and prokaryotes - Eukaryotes much bigger:
• Prokaryotes: 0.5-5 micrometers in diameter
• Eukaryotes around 100 micrometers in diameter Describe the difference in genomes between prokaryotes and eukaryotes - Prokaryotes: --> Circular DNA with no proteins found cytoplasm Eukaryotes: --> DNA associated with proteins called histones which form into chromosomes Describe the difference in cell division between prokaryotes and eukaryotes - Prokaryotes: --> Binary Fission - No spindle required

Eukaryotes: --> Occurs by mitosis or meiosis and requires a spindle to separate chromosomes Describe the difference in ribosomes in prokaryotes and eukaryotes - Prokaryotes: 70s Eukaryotes: 80s Describe the existence of membrane bound organelles in prokaryotes - No membrane bound organelles List the total number of organelles in prokaryotes - very few List single membrane bound organelles present in eukaryotes - Lysosomes Golgi Vacuoles List the double membrane bound organelles in eukaryotes - Nucleus Mitochondria Chloroplasts List the organelles with no membrane in eukaryotes - Ribosomes Centrioles Microtubules Describe the composure of the cell wall in prokaryotes - Peptidoglycan and murein What is peptidoglycan? - a network of polysaccharides cross-linked by polypeptides Describe the cell wall in eukaryotes - Made of cellulose in plants (or lignin) Made of chitin in fungi What is chitin? - A structural polysaccharide which is similar in structure to cellulose but contains nitrogen Why must you start with the lowest power objective lens? - It is easier to find what you are looking for in the field of view This helps to prevent damage to the lens or coverslip incase the stage has been raised too high What is used to take measurements of cells within microscopes? - graticules What is a graticule? - A small disc in the eyepiece lens which has an engraved scale of a series of fine lines to be used as a ruler in the field of view

What is a stage micrometer? - A millimeter long ruler etched onto a slide. it has 100 divisions, each of 0.01mm or 10 micrometers. It is used to calibrate the eyepiece graticule How do you calibrate an eyepiece graticule? - calibration -place stage micrometer on the stage of a microscope -focus on the scale on the stage micrometer using the low power objective lens -align the scales of the eyepiece graticule and stage micrometer -count the number of divisions on the eyepiece graticule that are equivalent to 100 micrometers on the stage micrometer -calculate the length of one eyepiece division -repeat for the medium and high power objective lens The presence of which sub cellular structure in a micrograph is a good indicator of cell type - Vacuole Evaluate the use of light microscopes and electron microscopes - Electron Microscope:

• Large and it's specific requirements and installation means it isn't portable
• Vacuum required
• Complex sample preparation
• Over 500 000x magnification
• Resolution 0.5nm
• Specimen must be dead Light microscope:
• More portable
• Vacuum not required -Easy sample preparation
• x2000 magnification
• 200nm resolution
• Specimen can be both dead and alive Why can phospholipid bilayers not be viewed underneath a light microscope? - The width of the phospholipid bilayer is about 10nm The maximum resolution of a light microscope is 200nm (half the smallest wavelength of visible light, 400nm) Any points that are separated by a distance less than 200nm (such as the 10nm phospholipid bilayer) cannot be resolved by a light microscope and therefore will not be distinguishable as "separate" What are lipids? - Macromolecules containing carbon, hydrogen and oxygen How do lipids differ from carbohydrates in structure? - Lipids contain a lower proportion of oxygen

Give two properties of al lipids - Non-Polar Hydrophobic (insoluble in water) What are the two main groups of lipids? - triglycerides and phospholipids What are the monomers of triglycerides - (3) glycerol and fatty acids What is glycerol? - an alcohol with 3 hydroxyl groups What is an alcohol? - an organic molecule containing a hydroxyl bonded to a carbon atom Describe the structure of Fatty Acids - A methyl group attached to the end of a hydrocarbon chain known as the R group and at the other end there is a carboxyl group What is the formula for a fatty acid? - RCOOH What are the two ways fatty acids can vary? - - Length of the R group hydrocarbon chain

• Whether or not the fatty acids are saturated or not Which types of fat utilise saturated fatty acids? - animal fats Which types of lipids utilise unsaturated fatty acids? - vegetable oils What are the different states unsaturated fatty acids can adopt? - they can be mono or poly unsaturated What is a cis fatty acid? - A form of an unsaturated fatty acid that has the hydrogens lying on the same side of the carbon-carbon double bond What is a trans fatty acid? - If H atoms are on opposite sides of the double bond they are trans-fatty acids and cannot form enzyme-substrate complexes, therefore, are not metabolised. They are linked with coronary heart disease How are triglycerides formed? - esterification (a type of condensation reaction formed between the carboxyl group of the fatty acid and the hydroxyl group of glycerol How many molecules of water are released during the formation of triglycerides and why? - 3 water molecules:
• The formation of an ester bond requires a condensation reaction
• For each ester bond a water molecule is released
• Three fatty acids join one glycerol molecule to form a triglyceride, each join requiring an ester bond

• Therefore for a single triglyceride to form, three water molecules and need to be released What are the implications with the fact that triglycerides have many carbon hydrogen bonds with very little oxygen - They are highly reduced. How does the oxidation state of triglycerides allow it to be used as a viable energy source during cellular respiration? - Long hydrocarbon chains which contain many carbon hydrogen bonds with very little oxygen Why during cellular respiration can triglycerides be used to release energy? - The heavily reduced triglycerides are oxidised. Which causes the bonds to break releasing energy to produce ATP Compare energy storage in triglycerides to carbohydrates - Triglycerides store 37kJ compared to carbohydrates storing 17kJ Why do triglycerides not cause water uptake and what does this mean? - they are hydrophobic meaning more can be stored How do plants store triglycerides? - they store them as oils in their seeds and fruit. Why are the oils stored in plants liquid at room temperature - They are unsaturated so contain double bonds and therefore have kinks within its structure of the fatty acid chains which alter their properties How do mammals store triglycerides? - In adipose tissues as oil droplets What is the advantage of the method animals store triglycerides? - They can use it as insulation and as an energy source when food is scarce (hibernation) What does the oxidation of the carbo-hydrogen bonds release? - The oxidation of these bonds release a large amount of water during cellular respiration. How does the water released by the carbon hydrogen bonds help desert animals? - Desert animals retain this water in situations where water is scarce How does the water released by carbon hydrogen bonds help birds and their embryos - Bird and reptile embryos in their shells use this water Explain the relationship between the presence of fat tissue correlates to buoyancy in animals - Low density of fat tissue increases the ability of animals to float What can the adipose tissue work to protect? - Organs from damage

Name the uses of insulation for triglycerides - - used in myelin sheaths which surrounds nerve fibres which provides insulation which increases the speed of nervous impulse transfer

• Triglycerides compose part of the adipose tissue layer below the skin which insulates against heat loss. What is a phospholipid? - a lipid containing a phosphate group in its molecule attached to glycerol and 2 fatty acid monomers. Why are the phosphate heads soluble in water? - The phosphate gives extra electrons and therefore the phosphate is polar What is an alternative to the term soluble in water - hydrophilic Describe the solubility of the fatty acid tails of phospholipids? - They are non polar so are insoluble in water What is an alternative to the term: insoluble in water? - Hydrophobic What can be used to describe the overall solubility of phospholipids? - They are amphipathic What does ampipathic mean? - A molecule which contains both hydrophobic and hydrophilic components What is the result of phospholipids being amphipathic? - They have both hydrophobic and hydrophilic parts and form monolayers and bilayers What are the roles of phospholipids? - The main component of plasma membranes and insulation Why do plasma membranes act as a barrier to water soluble substances - Due to the presence of hydrophobic fatty acid tails and a hydrophobic core is created when a phospholipid bilayer forms What forms Hydrogen bonds with water? - the hydrophilic phosphate heads If hydrophilic phosphate heads are forming hydrogen bonds with water, what does it allow for? - For the cell membrane to compartmentalize which increases efficiency as it enables the cell to organize specific roles into organelles How does the saturation of phospholipids correlate to the fluidity of the cell membrane?
• Saturated fatty acid tails will mean the membrane will be less fluid Unsaturated fatty acid tails mean the membrane will be more fluid.

What do phospholipids control? - Membrane protein orientation What is meant by the term membrane protein orientation? - Weak hydrophobic interactions between phospholipids nd membrane proteins hold the proteins within the membrane but still allow movement within the layer Explain the differences in function between phospholipids and triglycerides - Phospholipids are used as cell membrane components Triglycerides are used for energy storage What can and can't dissolve lipids? - Water - Can't Ethanol - Can Why are unsaturated fatty acids not straight? - As the double bonds present causes the unsaturated fatty acids to kink (bend slightly) What is the main use for triglycerides? - Energy storage molecules Why is the main use for triglycerides energy storage? - the long hydrocarbon tails of fatty acids in triglycerides contain large amounts of chemical energy which can be released when the fatty acids are broken down. Furthermore they are insoluble meaning they don't affect internal water potential. How does a phospholipid bilayer cell membrane act? - As a barrier control what substances can enter and leave the cell. Define a monomer - The smaller single units from which larger molecules are made Define a polymer - Polymers are large molecules which consist of many smaller repeating monomer units joined together Give examples of monomers - Monosaccharides, amino acids and nucleotides What is a condensation reaction? - A reaction in which joins two molecules together to form a chemical bond (usually covalent) and involves the elimination of a water molecule What is a hydrolysis reaction? - a reaction which a chemical bond (usually covalent) between two molecules is broken due to the addition of a water molecule What are monosaccharides? - The monomers from which larger carbohydrates are made Give three examples of monosaccharides - glucose, fructose, galactose

What are disaccharides? - A small molecule formed when two monosaccharides are joined together through a condensation reaction forming a glycosidic bond between the two hydroxyl groups. Give examples of disaccharides - sucrose, maltose, lactose What is maltose? - A disaccharide formed by the condensation of two alpha glucose molecules and is a reducing sugar What is lactose - Lactose is a disaccharide formed by condensation of a glucose molecule and a galactose molecule and is a reducing sugar What is sucrose? - Sucrose is a disaccharide formed by the condensation of a glucose molecule and a fructose molecule and is a non reducing sugar What are the two isomers of glucose? - alpha glucose and beta glucose What is a polysaccharide? - A complex carbohydrate that is formed from many monosaccharide units What are glycogen and starch formed by? - condensation of alpha glucose What is cellulose formed by? - condensation of beta glucose What is the biochemical tests for reducing sugars? - Benedict's test What is the biochemical test for starch - Iodine in potassium iodide solution What are the two groups of lipid? - triglycerides and phospholipids What is an isomer? - each of two or more compounds with the same molecular formula but a different arrangement of atoms within their structure in the molecule and therefore different properties. What are triglycerides composed of? - 1 glycerol and 3 fatty acids What does a condensation reaction between a glycerol and a fatty acid form? - an ester bond What are the different properties for triglycerides and phospholipids related to? - their different structures What are amino acids? - The monomers from which proteins are made What is the overall general structure of amino acids? - R |

NH2 - C - COOH

|

H

What are the groups present in amino acids? - Amine Carboxyl Radical group What is an amine group? - NH2 What is a Carboxyl group? - COOH What is a radical group? - An R group represents a side chain How many different amino acids are there? - 20 different amino acids What differs between amino acids? - R group (side chain) What type of bond does a condensation reaction between two amino acids form? - A peptide bond What are dipeptides? - A small molecule consisting of two amino acids joined together in a condensation reaction What are polypeptides? - Large molecules which are formed by many amino acids joined together in long chains What is a functional protein? - consists of one or more polypeptides twisted, folded, and coiled into a unique shape and so may contain more than one polypeptide What is an organic molecule? - A molecule that contains carbon and hydrogen which can be found in a living organism What are the four orgnanic molecules? - carbohydrates, proteins , nucleic acids and lipids What are the monomers found in carboydrates? - Monosaccharides (glucose, fructose and galactose) What is the covalent bond type in carbohydrates? - glycosidic bond What is the polymer made in carbohydrates? - polysaccharides Give examples of polymers of carboydrates - Glycogen (animals) Cellulose (plants) Starch (plants)

What are the monomers of proteins - amino acids What is the covalent bond type in protiens? - peptide bond What are protein polymers called? - polypeptides What are examples of protein polymers? - Enzymes Antibodies Channel proteins Haemoglobin What are channel protiens? - Proteins used in active transport and facilitated diffusion through membranes What are the monomers of nucleic acids? - Nuecleotides What does a nucleotide consist of? - sugar , phosphate and nitrogen base What is the polymer of a nucleic acid? - polynucleotide Give examples of polynucleotides - DNA and RNA What is the difference between DNA and RNA - DNA is double stranded RNA is single stranded (contains the base urasil) What is glucose? - A hexose sugar that forms the isomers alpha and beta glucose. What makes a reducing sugar? - The ability to donate electrons to other compounds What are the monosaccharides in starch? - alpha glucose What is starch a polymer of? - The two polymers amylose and amylopectin What is amylose? - A long unbranched chain of alpha glucose but coiled What is amylopectin? - A long branched chain of alpha glucose containing both 1-4 and 1-6 glycosidic bonds What are the important properties of starch? - Insoluble Compact Branched What properties does the use of amylose provide starch? - Coiling which makes it compact so more starch can be stored within a smaller space

What properties does amylopectin provide for starch? - Branches which increase surface area for enzymes to hydrolyze glycosidic bonds allowing for glucose to be released quickly Why is it important for starch to be insoluble? - It has no osmotic effect on the water potential of the cell so more substances can be stored while the cell may still appropiately function What are the uses of starch? - Plants use starch as a way of storing excess glucose as it is too large to leave cells and is insoluble in water so it doesn't affect water potential It is hydrolysed to release glucose for respiration What are the monomers present in glycogen? - Alpha glucose Describe the structure of glycogen - A long branched chain of alpha glucose linked together by 1-4 glycosidic bonds with many more side branches which are linked to the main strand by 1-6 glycosidic bonds What are the properties of glycogen? [2] - - Lots of branches to increase surface area for enzymes to hydrolyse allowing glucose to be quickly released

• It is also a compact molecules so it's good for storage What are the uses of glycogen? - Animals store excess glucose as glycogen in muscles and the liver. Glycogen is therefore an energy store as it can be quickly hydrolysed to release glucose quickly when needed for respiration What are the monomers present in cellulose? - Beta glucose What is the structure of beta glucose? - Long unbranched straight chains with the glucose monomers joined together by 1-4 glycosidic bonds. The cellulose chains are then linked together by hydrogen bonds between glucose molecules to form microfibrils What are the bonds present in nucleic acids - phosphodiester bonds What are the properties of cellulose? - The hydrogen bonds between the cellulose chains make the microfibrils very strong but still flexible allowing them to provide support to the overall plant structure What is the use for cellulose? - A major structural component of plant cell walls and provides support in allowing cells to become turgid due to it being able to withstand the turgor pressure exerted upon it by the permanent vacuole. What are the uses for lipids? - Waterproofing

Insulation Energy source form membranes hormones What are the bonds present in lipid moelcules? - ester bonds formed by the condensation reaction between the hydroxyl groups on glycerol and the fatty acid chains Why are triglcerides insoluble in water? - The fatty acid chains are hydrophobic so repel water making them insoluble How can triglycerides be found in cells and why does this occur? - They bundle together as insoluble droplets as the hydrophobic tails face inwards and the hydrophilic glycerol heads face outwards and shield them from water. Why are triglycerides used as an energy store? - Used as an energy store as there is a lot of energy released when the heavily reduced fatty acid chains are broken down by oxidation Give an example of hormones lipids form - testosterone When saturated what is the ratio between carbon and hydrogen in fatty acids? - Carbon : Hydrogen 1 : 2 Name the different degrees that fatty acids can be unsaturated? - Mono or poly unsaturated Why do phospholipids form bilayers in water? - The hydrophilic head is attracted to the water but the hydrophobic tails repel from water. This means they form a double layer where the heads face outwards towards the water and the tails face inwards away from the water Describe the solubility of the centre of the bilayer and what does this mean? - The bilayer is hydrophobic so water soluble substances cannot easily pass through which creates a barrier and allows separation of solutions and can create different conditions on either side of the membrane What elements do amino acids consist of? - Carbon Hydrogen Oxygen Nitrogen What other element can amino acids contain and give an example? - sulfur, cysteine