AQA A level biology paper 1 Questions & Answers 100% Correct!!, Exams of Biology

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AQA A level biology paper 1 Questions

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Describe how oxygen in the air reaches capillaries surrounding alveoli in lungs - ANSWERTrachea and bronchi and bronchioles; Down pressure gradient; Down diffusion gradient; Across alveolar epithelium; Across capillary endothelium/epithelium; Difference between species richness and index of diversity - ANSWERSpecies richness measures only number of (different) species / does not measure number of individuals; Explain how cellulose molecules are adapted for their function in plant cells - ANSWERLong and straight chains; Become linked together by many hydrogen bonds to form fibrils; Provide strength (to cell wall); Describe how mRNA is produced in the nucleus of the cell - ANSWERHelicase; Breaks hydrogen bonds; Only one DNA strand acts as template; RNA nucleotides attracted to exposed bases; (Attraction) according to base pairing rule; RNA polymerase joins (RNA) nucleotides together; Pre-mRNA spliced to remove introns; What two types of molecule is a ribosome made from? - ANSWERnucleotide and protein Describe the role of a ribosome in the production of a polypeptide - ANSWERmRNA binds to ribosome; Idea of two codons/binding sites; (Allows) tRNA with anticodons to bind/associate; (Catalyses) formation of peptide bond between amino acids (held by tRNA molecules); Moves along (mRNA to the next codon)/translocation described; Describe how phagocytosis of a virus leads to presentation of its antigens. - ANSWERPhagosome/vesicle fuses with lysosome; (Virus) destroyed by lysozymes/hydrolytic enzymes; Peptides/antigen (from virus) are displayed on the cell membrane; Explain three ways in which an insects tracheal system is adapted for efficient gas exchange - ANSWERTracheoles have thin walls so short diffusion distance to cells; Highly branched/large number of tracheoles so short diffusion distance to cells;

Highly branched/large number of tracheoles so large surface area (for gas exchange); Tracheae provide tubes full of air so fast diffusion (into insect tissues); Fluid in the end of the tracheoles that moves out (into tissues) during exerciseso faster diffusion through the air to the gas exchange surface; OR Fluid in the end of the tracheoles that moves out (into tissues) during exerciseso larger surface area (for gas exchange); Body can be moved (by muscles) to move air so maintains diffusion/concentration gradient for oxygen/carbon dioxide; Improving quality of scientific drawings - ANSWERDon't use shading; Only use single lines/don't use sketching(lines)/ensure lines are continuous/connected; Add further labels/annotations; Don't cross label lines; Add magnification/scale (bar); When investigating mitosis, why do we stain the root tip? - ANSWERIt is the place where mitosis takes place When investigating mitosis, why do we squash the root tip? - ANSWERTo allow light through What is the role of the spindle in mitosis? - ANSWERAttachment of centromeres Describe how a peptide bond is formed between two amino acids to form a dipeptide. - ANSWERCondensation reaction between NH2 and COOH- forms a peptide bond How is the structure of starch adapted to its function? - ANSWERhelix shape- compact branches so glucose is easily released for respiration large so can't leave cell Why are some food molecules absorbed by active transport? - ANSWERIt is necessary to use active transport when the food is going against the concentration gradient Give one substance that plants absorb by active transport - ANSWERnitrate Explain the advantages of lipid droplet and micelle formation - ANSWER- droplets increase surface area

• faster hydrolysis
• micelles carry fatty acids and glycerol through membrane How do you use the eyepiece graticule to determine the mean diameter of stomata?
• ANSWERcalibrate eyepiece graticule against stage micrometer work out diameter of each stomata you can see in EPG add up every value

divide by amount of values Explain how the structures of the walls of arteries and arterioles are related to their functions. - ANSWER- even pressure

• elastic tissue which stretches
• endothelium is smooth- reduces friction How is starch similar to cellulose? - ANSWER- both are polymers
• contain carbon, hydrogen and oxygen How is the structure of starch different to cellulose? - ANSWER- starch contains alpha glucose
• no micro fibrils how are sieve tubes adapted for mass flow? - ANSWER- few organelles- easier flow What happens to excess tissue fluid? - ANSWER- removed by lymphatic system
• returned to the blood Tissue fluid accumulates in the tissues of people who do not eat enough protein. Explain why - ANSWER- less protein in blood
• water potential gradient is lower Why might a population show low levels of genetic diversity? - ANSWER- small population
• interbreeding What is meant by a hierarchy? - ANSWER- no overlap
• groups within groups Percentage increase - ANSWERActual increase ÷ original value x 100. Percentage decrease - ANSWERActual decrease ÷ original value x 100. Magnification - ANSWERI/ A x M Functions of carbohydrates - ANSWER- energy source
• energy store
• structure What is a monomer? - ANSWERsmaller units from which larger molecules are made What is a polymer? - ANSWERmolecules made from many monomers joined together Properies of glucose - ANSWER- rich in hydrogen- used as an energy source
• bonds contain energy and can be broken in respiration to release energy
• soluble

condensation reaction - ANSWERjoins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water hydrolysis reaction - ANSWERbreaks a chemical bond between two molecules and involves the use of a water molecule what is maltose formed from? - ANSWERtwo alpha glucose molecules what is lactose formed from? - ANSWERglucose and galactose What is sucrose formed from? - ANSWERglucose and fructose properties of starch - ANSWER- compact

• helix shape
• much can be stored
• branched chains- glucose can easily be released
• store of glucose in plants
• large so can't leave the cell
• amylose and amylopectin properties of glycogen - ANSWER- insoluble
• compact
• store of glucose in animals
• no osmotic effect
• 1,4 and 1,6 glycosidic bonds
• chains shorter so coil less
• highly branched properties of cellulose - ANSWER- strong
• tough
• insoluble
• good for maintaining the structure of the plant
• 1,4 glycosidic bonds
• can resist osmotic pressure test for starch - ANSWER- add iodine
• turns blue/black test for a reducing sugar - ANSWER- heat with benedictus
• turns brick red What is a protein made from? - ANSWERcarbon, hydrogen, oxygen, nitrogen and sometimes sulphur Primary structure of a protein - ANSWER- polypeptide
• sequence of amino acids
• peptide bonds
• condensation reactions secondary structure of a protein - ANSWER- alpha helix

• beta pleated sheets
• hydrogen bonds tertiary structure - ANSWER- 3D shape
• ionic bonds
• disulphide bridges
• hydrogen bonds
• hydrophilic and hydrophobic quaternary structure - ANSWERMake one polypeptide chain joined chemically Structure of an amino acid - ANSWER- central carbon
• carboxyl group
• amino group
• r group How do amino acids differ? - ANSWERdifferent r groups How are amino acids joined - ANSWERcondensation reactions between the carboxyl group of one and amino group of another. the s creates a peptide bond fibrous protein - ANSWER- structural -insoluble
• polypeptides in parallel chains
• collagen globular proteins - ANSWER- soluble
• transportation
• 3D
• involved in metabolic reactions
• less stable;
• enzymes haemoglobin test for proteins - ANSWERadd biruet, turns purple properties of lipids - ANSWER- made up of carbon, hydrogen and oxygen
• fats, oils, waxes
• insoluble
• good source of energy
• poor conductors of heat triglyceride - ANSWERone molecule of glycerol and three fatty acid molecules phospholipids - ANSWER1 glycerol, 2 fatty acids, 1 phosphate three types of lipids - ANSWER- triglycerides- fat for energy store
• phospholipids- membranes
• cholesterol- memrbanes, stability and hormones

functions of lipids - ANSWER- cell membranes

• prevent water soluble substances entering and leaving the cell
• allow lipid soluble substances to enter and leave the cell
• high energy store
• protects organs
• myelin sheath saturated fatty acid - ANSWERno double carbon bonds unsaturated fatty acid - ANSWERdouble carbon bonds present structure of ATP - ANSWER- ribose pentose sugar
• adenine nitrogenous organic base
• three phosphate groups hydrolysis of ATP - ANSWERADP +Pi advantages of ATP for its function as an energy source - ANSWER- only one enzyme needed to hydrolyse it
• doesn't need to be stored
• water soluble properties of water - ANSWER- high specific heat capacity - lots of energy to change temp
• ice less dense than liquid
• high latent heat vaporisation - lots of heat energy needed for it to evaporate
• solvent
• adhesive- sticks to other surfaces
• metabolite
• cohesive successful collision - ANSWER- collision with active site
• molecules must collide with sufficient energy inducted fit theory - ANSWERenzyme will change shape to hold around the substrate effect of temperature on enzymes - ANSWERAs the temp. increases there's more kinetic energy meaning there's more collisions between the substrate and enzyme. The energy of these collisions also increases which means each collision is more likely to result in a reaction. This increases the rate. Above the optimum, the vibrations break some of the bonds that hold the enzyme in shape. The active site changes shape and the enzyme and substrate no longer fit - enzyme is denatured so no longer functions as a catalyst. effect of non-optimum pH on enzymes - ANSWER- bonds in tertiary structure break
• change in active site
• enzyme is denatured competitive inhibitor - ANSWERcompetes with substrate for active site

non-competitive inhibitor - ANSWERchanges shape of active site an inhibitor that binds to an enzyme at an allosteric site. properties of enzymes - ANSWERspecific to a reaction, reusable, do not affect products DNA - ANSWERholds genetic information RNA - ANSWERtransfers genetic information from DNA to the ribosomes base pairing - ANSWERA-T C-G Semi conservative replication - ANSWERdouble strand separates free nucleotides bind to exposed bases DNA polymerase joins sugar phosphate back bone How does the structure of RNA differ from DNA - ANSWERRNA single stranded, DNA double stranded RNA- ribose, DNA- deoxyribose cell surface membrane - ANSWERcontrols the passage of subtances in and out of the cell nucleus - ANSWERcontains DNA which holds the genetic information necessary for controlling the cell Micochondria - ANSWER- produced ATP during respiration

• aerobic respiration lysosome - ANSWERcell organelle filled with enzymes needed to break down certain materials in the cell ribosomes - ANSWERsite of protein synthesis Rough Endoplasmic Reticulum (RER) - ANSWERsynthesises and transports proteins Smooth Endoplasmic Reticulum (SER) - ANSWERsynthesises lipids golgi apparatus - ANSWERpackages and processes molecules such as proteins for use in other parts of the cell forms lysosomes Organelles in a eukaryotic cell - ANSWER- cell surface membrane
• nucleus
• micochondria
• lysosomes
• ribosomes

- RER

-SER

• golgi body Organelles in a plant cell - ANSWER- nucleus
• ER
• golgi body
• lysosomes
• mitochondria
• chloroplasts
• vacuole
• ribosomes chloroplasts - ANSWERwhere photosynthesis takes place cell wall - ANSWERstrength, prevents the cell bursting vacuole - ANSWERcontains cell sap prokaryotic cell - ANSWERcytoplasm that lacks membrane bound organelles no nucleus murrain cell wall one or more plasmids- small loops of DNA a capsule one or more flagella what is a virus made from? - ANSWER- core of nucleic acid
• protein coat of capsid how does a virus invade a cell? - ANSWER- virus attaches to a host cell
• virus inserts viral nucleic acid into the host cell
• viral nucleic acid replicates
• synthesis of viral protein
• host particles assemble
• host cell bursts magnification - ANSWERmaking things larger resolution - ANSWERdistinguishing between two objects that ate close together Optical microscope - ANSWERuses a series of lens to magnify images with light TEM - ANSWERuses beams of electrons cell fractionation - ANSWER- homogenisation (blender)
• resultant fluid filtered
• tube of filterate placed in centrifuge
• heaviest organelles to bottom
• fluid at top removed

osmosis - ANSWERDiffusion of water through a selectively permeable membrane active transport - ANSWERthe movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy. diffusion - ANSWER- movement of molecules

• high to low concentration facilitated diffusion - ANSWERuse of proteins to assist diffusion Differences between active transport and facilitated diffusion - ANSWER- AT requires energy, FD does not
• AT against conc gradient
• AT- carrier proteins, FD channel and carrier proteins factors that affect the rate of diffusion - ANSWER- temperature
• surface area
• difference in concentration on either side of the membrane
• how thick the exchange system is co- transport in the ileum - ANSWER1. NA+ actively pumped out cell to capillary, K+ in

2. low conc of Na+ in cell
3. Na+ moves out of lumen into epithelial cell, glucose carried with it
4. glucose into blood plasma by FD Interphase - ANSWER- cell makes a copy of its chromosomes

• cell grows
• normal physiological functions Prophase - ANSWER- chromosomes coil, shorter and fatter
• nuclear envelope disappears
• spindle formed
• each chromosome constsist of two chromatids metaphase - ANSWER- one or more spindle fibres attaches to centromeres of each chromosome
• chromosomes in middle of spindle anaphase - ANSWER- centromere divides
• spindle fibres shorten and pull chromatids to opposite poles telophase - ANSWER- chromosomes collect at opposite ends of the spindle
• new nuclear envelope
• chromosomes long and thin importance of mitosis - ANSWER- growth
• tissue repair
• asexual reproduction

interphase on microscope - ANSWERno chromosomes visible prophase on microscope - ANSWERchromosomes randomly arranged metaphase on microscope - ANSWERchromosomes at equator anaphase on microscope - ANSWERchromosomes in two sets being pulled apart and drawn to opposite poles role of the spindle fibre - ANSWER- contracts to seperate chromatids

• attached centromeres how do cells control their own division - ANSWER- programmed cell death
• loosing the ability to divide binary fission - ANSWER1. circular DNA replicates and both copies attach to cell membrane

2. cell membrane grows between two DNA molecules
3. new cell wall forms 4, two identical daughter cells formed antigen - ANSWERany part of an organism or substance that is recognised as foreign by the immune system antibodies - ANSWERprotein specific to antigen produced by B cells how does a vaccine lead to antibodies - ANSWER1. vaccine contains antigen from pathogen
4. macrophage presents antigen on surface
5. t cell with complementary receptor protein binds to antigen
6. t cell stimulates b cell
7. with complementary antibody on surface
8. b cell secretes antibody
9. b cell divides to form clone cell Passive immunity - ANSWERintroduction of antibodies into individuals from an outside source phagocytosis - ANSWER1. phagocyte recognises antigens on a pathogen
10. pseudopodia surround and engulf pathogen by endocytosis
11. phagocytic vacuole formed
12. lysosomes fuse with phagocytic vacoule
13. enzymes break down pathogen
14. useful products absorbed
15. antigen is displayed active immunity - ANSWERproduced by stimulating the production of antibodies by the individuals own immune system

stages of the immune response - ANSWER1. phagocytes engulf pathogen by phagocytosis

2. phagocytes active T-lymphocyte cells
3. t cells activate b cells
4. b lymphocyte plasma cells produce antibodies
5. memory cells produced- long term immunity replication of HIV - ANSWER1. HIV binds to t helper cell surface
6. HIV inserts capsid into t helper cell
7. RNA, integrase and reverse transcriptase released from capsid
8. integers inserts DNA into T helper cell
9. genes are expressed and HIV proteins are synthesied
10. HIV viruses are released cellular immune response - ANSWERproduced memory cells humoral immune response - ANSWERantibodies describe how presentation of an antigen leads to the secretion of an antibody against this virus antigen - ANSWER- helper T cell binds to antigen

• helper T cell stimulates B cell
• B cell divides by mitosis
• forms plasma cell exopeptidase - ANSWERhydrolyse peptide bonds on the end of the peptide endopeptidases - ANSWERincrease SA for expeptidases dipeptidases - ANSWERhydrolyse peptide bond between amino acids of dipeptidases lipid digestion - ANSWER1. bile salts emulsify lipids

2. lipids now small droplets
3. large surface area for the lipase enzyme to digest lipids into monoglycerides and fatty acids
4. form micelles which help move monoglycerides and fatty acids towards ileum epithelium
5. micelles constantly break up and reform releasing the lipid soluble monoglycerides and fatty acids gills - ANSWERfilaments of tissue that are highly branched and folded- large SA for gas exchange human gas exchange system - ANSWER- trachea- structure and support

• bronchi - produce mucus to trap dirt particles
• bronchioles- control flow of air in and out alveoli
• alveoli- transport air
• diaphgram- contracts to increase SA of lungs inspiration - ANSWER1. external intercostal muscles and diaphragm contract

2. rib cage up and outwards, diaphgram flattens
3. volume of thoracic cavity increases, lung pressure decreases
4. air flows down trachea and into lungs features of a good exchange system - ANSWER- large SA

• thin walls
• good supply of blood palisade mesophyll - ANSWERcells orientate themselves so they are perpendicular to the light so there is more chance all light will be absorbed upper epidermis - ANSWERprotective, transparent to let light through to mesophyll cells waxy cuticle - ANSWERwaterproof layer, reduces water loss stomata - ANSWERlet air in and out guard cells - ANSWERopen and close stomata spongy mesophyll - ANSWERwhere gas exchange takes place cohesion tension hypothesis - ANSWER1. water evaporates

2. cell has lower water potential
3. water drawn out of xylem
4. creates tension
5. cohesive forces
6. water pulled up as a column transport in phloem - ANSWER1. sucrose actively loaded
7. reduces water potential
8. water follows by osmosis
9. increases hydrostatic pressure in sieve tube element
10. water moves down to lower hydrostatic pressure at sinks 6 sucrose removed from sieve tubes
11. water moves out of sieve tubes
12. reduces hydrostatic pressure active transport in phloem - ANSWER1. H+ out by active transport
13. creates higher concentration of h+ outside the cell
14. H+ in by facilitated diffusion using co-transporters for sucrose
15. sucrose down conc gradient into cells via plasmodesmata Describe the structure of HIV - ANSWERAttachment proteins to bind to CD receptor Lipid envelope Matrix Capisid with RNA and reverse transcriptase inside Describe the ELISA test - ANSWER1. put antigens in the bottom of a beaker

2. add blood
3. wash the beaker to remove any antibodies
4. add secondary antibodies
5. add the solution examples of polymers - ANSWER- carbohydrates- monomers joined by glycosidic bonds

• proteins - monomers joined by peptide bonds
• lipids- monomers joined by ester bonds Structure of haemoglobin - ANSWER- quarternary - 4 polypeptide chains
• each polypeptide chain has a haem group
• heam group contains an iron ion partial pressure of oxygen - ANSWERmeasure of the concentration of oxygen high PO2 - ANSWERheamoglobin has a high affinity for O2 and oxygen binds to haemoglobin low PO2 - ANSWERhaemoglobin has a low affinity for O2 and oxygen dissocates from haemoglobin How are capillaries adapted for the exchange of materials? - ANSWER- thin permeable walls
• 1 cell thick
• large surface area describe a capillary - ANSWER- links up arteries and veins
• no muscle
• no elastic tissue
• no valves describe an artery - ANSWER- carries blood away from the heart
• thick muscular walls
• lots of elastic tissue
• blood under high pressure
• blood flow is rapid
• no valves describe a vein - ANSWER- carries blood back to the heart
• thin musular walls
• little elastic tissue
• blood under low pressure
• slow blood flow
• valves functions of blood - ANSWER- defends the body against disease
• maintains diffusion gradients
• distributes heat around the body

white blood cells - ANSWER- protect the body from pathogens

• 5 types
• all have a nucleus
• irregular in shape What does blood plasma contain? - ANSWER1. plasma proteins- albumins and antibodies

2. absorbed food molecules
3. excertory waste products
4. hormones salt and heat circulation - ANSWER1. heart
5. aorta
6. artery
7. arterioles
8. capillaries
9. venules
10. veins
11. vena cava 9 heart artery structure - ANSWER- lumen short diameter- less blood in contact with walls- less friction

• elastic tissue- stretches to let blood at high pressure through
• collagen tissue - maintains shape
• smooth muscle tissue- maintains blood pressure how does blood flow through veins? - ANSWER- skeletal muscles squeeze vein walls to push blood back to the heart
• valves prevent the backflow of blood why is the water potential more negative at the venule end of the capillary? - ANSWER- water has left the capillary
• protein is too large to leave the capillary
• this increases the concentration of the blood How does high blood pressure lead to the accumulation of tissue fluid? - ANSWER- high blood pressure- higher hydrostatic pressure
• increases outward pressure from arterial end of capillary
• increases concentration of the blood why isn't there exchange between the blood in the arteries, arterioles, venules and veins? - ANSWERthe walls are impermeable what is a gene? - ANSWERa gene is a DNA base sequence that codes for:
• the amino acid sequence of a polypeptide
• a functional RNA tRNA - ANSWERtransfer RNA; type of RNA that carries amino acids to the ribosome

mRNA - ANSWERmessenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome translation - ANSWERproduction of polypeptides from the sequence of condons carried by mRNA transcrption process - ANSWER- hydrogen bonds between bases break by DNA helicase

• DNA unzips
• free RNA nucleotides pair with exposed bases on template strand- complementary base pairing
• condensation reactions catalysed by RNA polymerase creates mRNA
• mRNA molecule leaves nucleus via nuclear pore transcription - ANSWERthe production of mRNA from DNA What is a codon? - ANSWERthree nucleotides that code for an amino acid what is the locus? - ANSWERthe fixed position of genes on a chromosome what happens in splicing? - ANSWERintrons are removed What form does the DNA take in a prokaryotic cell? - ANSWER1. DNA molecule is one short and circular chromosome

2. called a nucleoid
3. not associated with proteins proteome - ANSWERfull range of proteins a cell is able to produce rRNA - ANSWERpart of the structure of the ribosome genome - ANSWERcomplete set of genes in a cell What form does the DNA take in a eukaryotic cell? - ANSWER- DNA molecule is in the nucleus and is long and linear

• DNA molecule is coiled around proteins called histones
• DNA molecule and it's associated histones form chromosomes What does DNA helicase do? - ANSWERbreaks hydrogen bonds between base pairs intron - ANSWERsequence of DNA that is not involved in coding for a protein exon - ANSWERcoding segments of eukaryotic DNA alleles - ANSWERdifferent versions of a gene the nature of the genetic code - ANSWER- triplet code- 3 bases code for one amino acid
• degenerate- all amino acids have more than one triplet code

• some combinations are stop codes
• universal protein syntesis - ANSWERtranscption and translation of genes which lads to the synthesis of polypeptides what is produced in transcription in prokaryotic cells? - ANSWERmRNA is produced directly What is produced in transcription in eukaryotic cells? - ANSWER- pre-mRNA
• pre-mRNA is then spliced to form mature mRNA gene mutation - ANSWERa random change in the DNA base sequence of a gene which results in a change in the amino acid sequence base deletion - ANSWERa part of a chromosome or a sequence of DNA is lost during DNA replication base subsitution mutation - ANSWERone base is swapped for another during DNA replication frame shift mutation - ANSWERcaused by insertions or deletions of several nucleotides in a DNA sequence Neutral mutation - ANSWERmutations that are neither beneficial nor detrimential for an organisms ability to survive chromosome mutation - ANSWERunpredictable change in a chromosome that affects the entire chromosome what is the spontaneous rate? - ANSWERthe frequency of mutations within an organism method to reduce biodiversity-woodland clearance - ANSWER- increases area of farmland
• reduces number of trees/ number of tree species
• destroys habitats method to reduce biodiversity- hedgerow removal - ANSWER- increases area of farmland
• reduces number of trees/ tree species
• destroys habitats method to reduce biodiversity- pesticides - ANSWER- directly kills the pests
• any species that feed on pests will loose a food source so their numbers could decrease method to reduce biodiversity- herbicides - ANSWER- chemicals that kill unwanted plants
• reduces number of organisms that feed on the plants

method to reduce biodiversity- monoculture - ANSWER-when farmers have fields containing only one plant

• supports fewer organisms What is needed to calculate the index of diversity? - ANSWER- number of organisms of all species
• total number of organisms of one species Ways of studying evolutionary relationships? - ANSWER- genome sequencing
• amino acid sequences
• immunological comparisons directional selection - ANSWERwhere individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce stabilising selection - ANSWERwhere individuals with characteristics towards the middle of the range are more likely to survive and reproduce what is a genetic bottleneck? - ANSWERAn event that causes a big reduction in a population chromatid - ANSWERone strand of a replicated chromosome telophase - ANSWER- the two sets of seperated chromosomes collect at opposite ends of the cell
• a new nuclear envelope forms
• chromosomes become long and thin crossing over - ANSWERpieces of chromosomes or genes are exchanged non-dysjunction - ANSWERthe failure of homologus pairs to seperate in meiosis bivalent - ANSWERa homologus pair after replication indepedent assortment - ANSWERthe random alignment of bivalents in metaphase 1 recombinant - ANSWERa cell/organism whose genetic material was produced when segments of DNA from different sources are joined Independent segregation - ANSWERit is a matter of chance to which member of each pair of chromosomes goes into which daughter cell homologus pair - ANSWER- same genes
• same loci
• centromere in same position haploid - ANSWERAn organism or cell having only one complete set of chromosomes.

diploid - ANSWERcontaining two complete sets of chromosomes, one from each parent. describe what happens to the chromosomes during meiosis. - ANSWER- chromosomes condense

• chromosomes associate in homologus pairs
• crossing over
• join to spindle fibres at equator
• chromosomes move to opposite poles
• pairs of chromatids are seperated What occurs when plant tissue is placed in a hypotonic solution? - ANSWERWater moves into the plant tissue by osmosis, plant tissue increases in mass What is water potential determined by? - ANSWER- the concentration of solutes
• higher the solute concentration the lower the water potential Why is the percentage change used rather than the actual change in mass? - ANSWERAllows comparisons How is beetroot used to measure the permeability of membranes? - ANSWERThe higher the permeability, the more red pigment that leaks out into the surrounding solute within a given time. A colorimeter can be used to determine the absorbance, hence concentration of pigment. How should label lines in a diagram be drawn? - ANSWER- with a ruler
• no arrows
• without crossing other lines
• in pencil How should a diagram be drawn? - ANSWER- large diagram- at least half the space
• no shading How do fish use their gills and the counter current system - ANSWERWater containing oxygen goes into the gills mouth and passes through the gills -Each gill is made of small plates called gill filaments which give a larger SA for gas exchange -The filaments are covered in lamellae which increase SA even more. -The lamellae have lots of blood capillaries and a thin surface area for increased diff. -Blood flows through lamellae in one direction and water in another, making the counter-current system -This maintains the concentration gradient between water and blood. What are the different types of lung diseases? - ANSWER- asthma
• fibrosis
• pulmonary tuberculosis
• Emphysema How does tuberculosis affect the lungs? - ANSWER- immune system builds wall around bacteria in the lungs, forming small hard lumps known as tubercles

• cells with tubercles die
• gas exchange surface is damaged
• can cause fibrosis how does fibrosis affect the lungs? - ANSWER- fibrosis= scar tissue in the lungs
• can be the result of an infection
• scar tissue is less elastic than normal lung tissue
• lungs less able to expand
• diffusion is slower across thick scar tissue How does asthma affect the respiratory system? - ANSWER- smooth muscle becomes swollen and secrete mucus
• constriction of the airways
• air flow out the lungs is restricted How does emphysema effect the lungs? - ANSWER- infammation
• attracts phagocytes
• phagocytes break down elastin
• alveoli expel air
• air trapped in alveoli
• breaks down alveoli wall Outline the two types of RNA in protein synthesis. - ANSWERmRNA- carries genetic code from DNA to ribosomes tRNA- translation, carries amino acids to ribosomes What is the advantage of a product formed in a pathway inhibiting an enzyme? - ANSWERStops the pathway when enough substrate is formed Microvilli - ANSWERIncreases the surface area of the cell. Why is the plasma membrane described as fluid mosaic? - ANSWERFluid- molecules can move around Mosaic- not just phospholipids What is the bond between a nucleotide and a base? - ANSWERCovalent What is the bond that joins nucleotides? - ANSWERphosphodiester What makes DNA a good information storage molecule? - ANSWER- long
• coiled The length of the section of DNA that codes for the complete polypeptide is longer than the mRNA used to transcribe it. Give two reasons why. - ANSWER- introns
• stop/start triplets How does mitosis differ from binary fission? - ANSWERIn mitosis, the nuclear envelope breaks down and spindle fibres form. There are no plasmids to replicate. In binary fission, both the circular DNA molecule and any plasmids in the cell undergo

DNA replication. Unlike mitosis, there is no nuclear envelope to break down and there are no spindle fibres. Describe how new viruses are made after HIV infects a T cell - ANSWER- HIV inserts RNA into host cell

• Copy made
• Cell makes new viruses
• Virus released from cell Describe how oxygen reaches a respiring muscle cell in an insect - ANSWERDiffuses through spiracles; diffuses along tracheae and trachioles; dissolves in fluid at end of tracheoles; diffuses into muscle cell Describe how the digestion products of the cheese are absorbed in the gut. - ANSWERSmall-chain fatty acids diffuse through cell into capillary; long chain fatty acids and glycerol and monoglycerides (any 2); recombine to form triglycerides; packaged into chylomicrons; with cholesterol and phospholipids. Describe how a piece of cheese, composed mainly of fat, is digested in the human gut. - ANSWERLipase; from pancreas; in small intestine; lipids/triglycerides to fatty acids and glycerol Lactose is a disaccharide found in milk. Describe how it is digested and absorbed in the human gut. - ANSWERDigested by lactase in membrane of (gut) epithelial cell; glucose and galactose/monosaccharides pass into cytoplasm. Describe one feature of a plant cell that identifies it as a xylem vessel. - ANSWERThe cell is hollow, with just a cell wall and no cell contents inside. Explain two ways in which cells produced by meiosis are genetically different from each other. - ANSWERThey have different combinations of maternal and paternal chromosomes and different combinations of alleles Give one advantage of using a TEM rather than a SEM. - ANSWERHigher resolution / higher (maximum) magnification / higher detail (of image); Give one advantage of using a SEM rather than a TEM. - ANSWERThin sections do not need to be prepared / shows surface of specimen / can have 3-D images; Give one way in which the structure of an mRNA molecule is different from the structure of a tRNA molecule. - ANSWERDoes not contain hydrogen bonds / base pairs / contains codons / does not contain anticodon / straight / not folded / no amino acid binding site / longer; Give three ways in which courtship behaviour increases the probability of successful mating. - ANSWER- attracts same species
• attraction of mate
• indicates sexual maturity Where is maltase produced? - ANSWERsmall intestine

Where is amylase produced? - ANSWERSalivary glands, pancreas, small intestine Describe the part played by the diaphragm in causing air to enter the lungs during breathing. - ANSWER- diaphgram contracts

• flattens
• decrease in lung pressure
• air can enter Structure of DNA related to it's function - ANSWER- double stranded- both strands can act as a template for semi-conservative replication
• weak hydrogen bonds between bases- can be unzipped for replication
• long molecule- lots of information can be stored
• double helix- compact channel proteins - ANSWERallow movements of water soluble/polar molecules down a concentration gradient (facillitated diffusion) carrier proteins - ANSWERmovement of molecules against a concentration gradient surface proteins on a cell membrane - ANSWERcell recognition, receptors, antigens Order of cells heaviest-lightest (cell fractionation) - ANSWERnucleus, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, ribosomes Digestion of starch - ANSWER- amylase hydrolyses starch- maltose
• (amylase produced in salivary gland and pancreas)
• maltase- glucose
• hydrolysis of glycosidic bond diffusion in plants - ANSWER- O2 through stomata
• stomata opened by guard cells
• O2 into mesophyll
• O2 down concentration gradient Why is ventilation important? - ANSWERmaintains o2 conc gradient Test for lipid - ANSWERAdd ethanol, shake, add water, shake, lipid present= cloudy white emulsion Test for non- reducing sugar - ANSWERDo Benedicts, stays blue, boil with acid, neutralise with alkali, heat with Benedicts becomes brick red Non competitive inhibitor - ANSWER1. Bind to the enzyme at allosteric site (site away from active site)

2. Alters tertiary structure
3. Alters shape of active site
4. Enzyme no longer complementary so less substrate can bind Describe the structure of HIV - ANSWER1. RNA

2. Reverse transcriptase
3. Protein capsid
4. Lipid envelope
5. Attachment proteins ELISA test - ANSWER1. Add antibody to cells
6. Wash cells to remove excess antibody
7. Add substrate to cause colour change Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow slower. - ANSWERStomata closed, less CO2 uptake, less photosynthesis What are centrioles? - ANSWER What is reduction? - ANSWERgain of electrons Cellulose molecules are grouped together to form_ - ANSWERMicrofibrils Roles of lipids - ANSWERSource of energy Waterproof Insulation Protection Why do light microscopes have a lower resolution? - ANSWERThey have a long wavelength of light How far apart can light microscopes distinguish? - ANSWER0.2um How far apart can electron microscopes distinguish? - ANSWER0.1nm What conditions must be met to carry out cell fractionation? - ANSWER1. Cold- reduce enzyme activity
8. Isotonic- prevent organelles bursting or shrinking by osmotic gain or loss
9. Buffered- pH can't fluctuate Differences between prokaryotic and eukaryotic cells - ANSWER1. PC have no nucleus, EC do 2 PC DNA not associated with his tones, EC DNA is
10. PC have no membrane bound organelles, EC do
11. PC ribosomes are smaller (70s) than EC ribosomes (80s) When does a tumour become cancerous? - ANSWERWhen it changes from benign to malignant Cell mediated response - ANSWERT lymphocytes Hi moral response - ANSWERB lymphocytes

What are the two types of white blood cells? - ANSWERphagocytes and lymphocytes How do cytotoxic T cells kill? - ANSWER- produces protein perforin

• this makes holes in cell surface membranes
• cell membrane freely permeable to all substances
• cell dies What do Hb with high affinity for oxygen do? - ANSWERAssociate more readily, release less easily What is the Bohr effect? - ANSWERGreater the concentration of co2, more readily hb releases its oxygen What amino acid does the start triplet code for? - ANSWERMethionine What is classification? - ANSWEROrganising living things into groups Why is courtship behaviour necessary? - ANSWER- enables individuals to recognise members of the same species
• identify a mate that is capable of breeding What is phylogenetic classification? - ANSWER- based on evolutionary groups
• classifies species into groups using shared features
• arranges groups into a hierarchy What are the three domains? - ANSWERBacteria, Archaea, Eukarya What are the taxonomic categories? - ANSWERDomain, Kingdom, Phylum, Class, Order, Family, Genus, Species Why is it better to compare DNA base sequences rather than amino acids rather than investigating diversity? - ANSWERThe same aa can be coded for by more than one triplet so even if the aa of two organisms are the same, their DNA base sequence can be different what is a calibration curve? - ANSWERCalibration curves are graphs used to determine an unknown concentration of a sample by comparing the unknown to a set of standard samples with known concentrations What are centrioles? - ANSWERHollow cylinders containing a ring of microtubules arranged at right angles to each other. Involved in producing spindle fibres for cell division