Edexcel A level biology B topic 1 Question & Answers 2024, Exams of Nursing

Download Edexcel A level biology B topic 1 Question & Answers 2024 and more Exams Nursing in PDF only on Docsity!

Question & Answers 2024

What are carbohydrates made out of? - Correct Answers ✅carbon, hydrogen and oxygen What is a monosaccharide (with examples of 3)? - Correct Answers ✅Carbohydrates with a single sugar unit, such a glucose, fructose and ribose What is a disaccharide (with 3 examples)? - Correct Answers ✅A carbohydrate with two sugar units, including maltose, sucrose or lactose. What is a true polysaccharide (with three examples)? - Correct Answers ✅A long chain of sugars that has been made through condensation polymerisation, these include glycogen, starch and amylose. It contains 11+ sugar units. It doesn't have the sweet taste of many mono and disaccharides. What is the monosaccharide equation - Correct Answers ✅(CH2O)n How many carbons do monosaccharides have and what do we call each monosaccharide (with examples)? - Correct Answers ✅Between 3 and 6. 3 carbons - triose sugar (C3H6O3) In respiration, glucose is broken down into triose sugar

Question & Answers 2024

5 carbons - pentose sugar (C5H10O5), ribose and deoxyribose are both pentose sugars and make up genetic material. 6 carbons - hexose suagr (C6H12O6), often tastes sweet and include glucose, galactose and fructose. Why are carbohydrates important? - Correct Answers ✅They store energy in plant, fungi and bacterial cells. They also make up an important part of the cell wall. The best known carbohydrates are sugars and starch. Sucrose is a white crystalline sugar, glucose supplies energy in sports drinks, starch is found in flour and potatoes. They can come in the form of monosaccharides, disaccharides, oligosaccharides and polysaccharides. What is a dissacharide? Give an example. - Correct Answers ✅A molecule formed from the combination of two monosaccharides through a condensation reaction where water is lost. A covalent bond called a glycosidic bond forms between the two molecules. The reaction can be reversed by adding in water ( hydrolysis ). Sucrose is table sugar ad is formed by alpha glucose joining to a fructose. What is the source and monosaccharides of sucrose? - Correct Answers ✅source = stored in plants such as sugar cane monosaccharides = alpha glucose + fructose

Question & Answers 2024

What is the source and monosaccharides of lactose? - Correct Answers ✅source = milk sugar - main carbohydrate found in milk monosaccharides = alpha glucose + beta glucose What is the source and monosaccharides of maltose - Correct Answers ✅source = malt sugar - found in germinating seeds such as barley monosaccharides - 2 alpha glucose molecules How do we test for reducing sugars? How ca we make a non- reducing sugar test positive? - Correct Answers ✅We use a solution called Benedict's solution. It is bright blue and contains copper (II) ions. When heated gently, the Benedict's copper (II) ions are reduced to copper (I) ions. A precipitate is formed, turning the solution from bright blue to orange. All monosaccharides are a reducing sugar and some disaccharides are too. With non-reducing sugars, you can add a few drops of hydrochloric acid to hydrolyse the glycosidic bonds. Allow to cool then neutralise with sodium hydrogen carbonate which will now give a positive result as the sugars been broken down into its monosaccharide units. What is an isomer? - Correct Answers ✅compounds with the same molecular formula but different structural formulas Draw alpha glucose and beta glucose - Correct Answers ✅

Question & Answers 2024

Draw a ribose molecule - Correct Answers ✅ What is an oligosaccharide? - Correct Answers ✅a carbohydrate with 3-10 monosaccharide units Why do polysaccharides form good storage molecules? - Correct Answers ✅- Can form very compact molecules meaning a cell can store a large number of them.

• Glycosidic bonds can be easily broken, allowing from the quick release of monosaccharide units for cellular respiration.
• Not very soluble in water meaning they have little effect on water potential within a cell and causes no osmotic water movements. Where does hydrolysis occur? - Correct Answers ✅During digestion in the gut and in muscle and liver cells when carbohydrate stores are broken down to release sugars in cellular respiration. Where is starch found, what is it made of and what is its role. - Correct Answers ✅Starch is found in plants and stores energy. Sugars produces in photosynthesis are quickly converted into starch. It is insoluble, compact and can be rapidly broken down to release glucose when needed. It is made up of amylose and amylopectin.

Question & Answers 2024

What is amylose and amylopectin? - Correct Answers ✅Amylose = Unbranched polymer made up of 200 and 5000 glucose molecules. As the chain lengthens the molecule spirals, making it more compact for storage. Amylopectin = Branched polymer of glucose molecules. Branching chains have many terminal glucose molecules that can be broken off rapidly when energy is needed. What are the differences and similarities between amylose and amylopectin? - Correct Answers ✅Both are made of purely alpha glucose molecules. Amylose - Alpha glucose molecules joined by 1,4 glycosidic bonds which leads to ling, unbranched monomers Amylopectin - Alpha glucose molecules are joined by 1,4 glycosisdic bonds with a few 1,6 bonds. This leads to branching chains Why is carbohydrates good to eat before sports? - Correct Answers ✅Foods like pasta contain starch which is made of amylose and amylopectin. The amylopectin is branched, meaning branches can be quickly broken off to release glucose for cellular respiration. The amylose releases glucose over a longer period of time, keeping you going for longer. What does amylose look like? - Correct Answers ✅

Question & Answers 2024

What does amylopectin look like? - Correct Answers ✅ What is glycogen? - Correct Answers ✅Glycogen is sometimes referred to as 'animal starch'. It is the only carbohydrate energy store found in animals and is also found in fungi. It consists of alpha glucose and is very compact. It can be broken down rapidly meaning it is an ideal glucose source for active tissues that have a high rate of cellular respiration such as muscle and liver cells. What is the difference and similarities between glycogen and starch? - Correct Answers ✅Glycogen has far more 1,6 glycosidic bonds than starch. Both contain only alpha glucose but starch contains alpha glucose that has been arranged in two separate ways, meaning it can provide both long and short term energy. On the the hand, glycogen only provides short term energy. Glycogen forms granuals ad starch forms grains. How much of a starch grain is amylopectin? - Correct Answers ✅70- 80% with the rest being amylose What is cellulose made of? - Correct Answers ✅Beta-glucose monomers joined by beta-1,4-glycosidic linkages

Question & Answers 2024

What is the role of cellulose and where is it found? - Correct Answers ✅It makes up the majority of the cell wall which provides strength and support to plants. It forms long, straight chains with considerable strength. What makes cellulose similar to starch and glycogen? - Correct Answers ✅All there polysaccharides are made up of long chains of glucose joined by glycosidic bonds. What bonds the monomers of cellulose? - Correct Answers ✅Condensation reactions join beta glucose monomers. One beta monomer inverts, meaning the hydroxyl (-OH)group sticks out on both sides of the monomer. The hydrogen bonds form between partially positive charged hydrogen ions of the hydroxyl groups and the partially negatively charged atoms in other parts of the glucose monomers. This is called cross linking Why is cellulose not digested by many animals? - Correct Answers ✅They do not contain the needed enzymes to break down the 1, glycosidic bonds in the cellulose. It acts as roughage or fibre, meaning it is still important even though it cannot be digested. What is a lipid? - Correct Answers ✅A biological molecule with low solubility in water.It is used as an energy store and in cell membranes. It is made up of carbon, hydrogen and oxygen but has less oxygen than carbohydrates.

Question & Answers 2024

What are the two organic chemicals that make up lipids? - Correct Answers ✅Fatty acids and glycerol (C3H8O3) What is the structure of a fatty acid like? - Correct Answers ✅A long hydrocarbon chain with a carboxyl group attached to the end. How can fatty acids vary? - Correct Answers ✅- Their length can differ but is often between 15 and 17 carbon atoms long.

• They can be saturated or unsaturated What is the different between a saturated and an unsaturated fatty acid? - Correct Answers ✅A saturated fatty acid is when each carbon atom is joined to the next one by a single covalent bond, like in stearic acid. An unsaturated fatty acid, has one double bond and a polyunsaturated acid has more than one double bond, such as in linoleic acid. What is esterification? - Correct Answers ✅The process of triglyceride formation. It is when a condensation reaction occurs between the carboxyl group of a fatty acid and the hydroxyl group of glycerol. Water is removed and an ester bond is formed. If a saturated fatty acid was involved, the lipid is likely to be solid at room temp than those containing unsaturated fatty acids.

Question & Answers 2024

How is a triglyceride formed? - Correct Answers ✅~ By a condensation reaction between fatty acids and a glycerol ~ Ester bond is formed and a molecule of water is removed What is the use of lipids and why are they suited to each purpose? - Correct Answers ✅- Their hydrophobic nature makes them important in waterproofing mammals and birds, along with the surfaces of plants and insects.

• They are good insulators meaning they can be used in the sheath of nerves, making the impulses travel faster.
• Insulate animals against heat loss, like with whales where the blubber keeps them warm.
• Dissolve organic solvents meaning they do not interfere with water based reactions in the cells cytoplasm.
• Storing energy ( can store 3X that of carbohydrates )
• Oxidation of lipids produces carbon dioxide and oxygen which can be used to drive the production of ATP How is a phospholipid formed? - Correct Answers ✅When the hydroxyl group of a glycerol undergoes esterfication with a phosphate group instead of a a fatty acid. How do phospholipids react with water and why? - Correct Answers ✅The phosphate head carries a small negative charge and is soluble in

Question & Answers 2024

water. The fatty acid chains on the other hand are neutral and insoluble in water. When in contact with water, the polar phosphate head is hydrophillic and readily dissolves, whereas the lipid tails are hydrophobic so don't dissolve. How does a phospholipid bilayer formed? What about a micelle? - Correct Answers ✅When phospholipids are tightly packed in water, they form a monolayer with the hydrophillic heads pointing out in the water and the hydrophobic tails in air, or clusters called micelles. In a micelle, all the hydrophillic heads point out with the tails inside. Draw a lipid bilayer - Correct Answers ✅Phosphate heads move toward solution, fatty acid tails turn away Draw a phospholipid - Correct Answers ✅Remember that the head contains glycerol and a phosphate - the diagram is inaccurate slightly i just couldn't find the correct one. When will a phospholipid monolayer form? - Correct Answers ✅Between the surface of air and water. This is rare in living cells, so it usually forms a bilayer with the heads pointing outwards and protecting the tails on the inside. What is a unit membrane? - Correct Answers ✅A bilayer structure formed by phospholipids in an aqueous environment, with the

Question & Answers 2024

hydrophobic tails in the middle and the hydrophillic heads on the outside. What do all proteins contain? - Correct Answers ✅carbon, hydrogen, oxygen, nitrogen and many also contain sulfur. What are proteins made up of? - Correct Answers ✅Macromolecules made up of many small monomer units called amino acids joined by condensation reactions How many naturally occurring amino acids are there? - Correct Answers ✅about 20 Draw and describe the basic structure of all amino acids. - Correct Answers ✅- an amino groupd (NH2)

• a carbocyl group (COOH) that is attached to a carbon atom
• an R group that varies between amino acids. This affects the way the amino acid will bond with others in a protein
• a hydrogen atom How do amino acids form proteins? - Correct Answers ✅A condensation reaction occurs between the amino group of one amino acid and the carboxyl group of another. Water is lost and a peptide bond forms, creating a dipeptide molecule. When the polypeptide

Question & Answers 2024

begins to form, fold and coil or associates with another polypeptide, a protein is formed. Draw the formation of a dipeptide. - Correct Answers ✅ What bonds can form in proteins? - Correct Answers ✅hydrogen bonds, disulfide bonds, ionic bonds and peptide bonds (always present) Explain how hydrogen bonds form in proteins. - Correct Answers ✅The slight negative charge of the oxygen in a carboxyl group and the slight poitive charge of the hydrogen from the amino group attract when the two groups are close to each other. The forms a hydrogen bond which is weak, however the number of them makes them strong, holding the protein together and resulting in a coiling and folding of the chain. These bonds can easily break if the pH changes. Explain disulfide bonds in proteins - Correct Answers ✅A disulfide bond will form when two cysteine molecules are close together in the structure of a polypeptide. An oxidation reaction occurs between the two sulfur containing groups, creating a covalent bond called a disulfide bond. These are less common than hydrogen bonds but occur much more often, holding the polypeptide chains in place. How do ionic bonds form in a protein? - Correct Answers ✅Ionic bonds form between strongly positive and negative amino acid side

Question & Answers 2024

chains buried deep in the protein molecules known as salt bridges. They are strong bonds but not very common. Explain the effect of styling and perming hair on the protein found within it. - Correct Answers ✅Hair contains the protein keratin, with blow drying or straightening hair breaking the hydrogen bonds before reforming them in a different way which will remain until the hydrogen bonds are reformed in the original way. Perming hair breaks the disulfide bonds between the polypeptide chains, reforming them in a different place. This is permanent until the hair that has been permed is cut off. Briefly describe a proteins primary, secondary, tertiary and quaternary structure. - Correct Answers ✅Primary - the linear sequence of amino acids in a peptide Secondary - the repeating pattern in the structure of the peptide chains, such as in an a-helix or in pleated sheets Tertiary - the three dimensional folding of the secondary structure Quaternary - the three-dimensional arrangement of more than one tertiary polypeptide Describe a proteins primary structure. - Correct Answers ✅The sequence of amino acids that make up the polypeptide chain help together by polypeptide bonds.

Question & Answers 2024

Describe a proteins secondary structure. Give an example - Correct Answers ✅The arrangement of polypeptide chains in a structure held together by hydrogen bonds.

• A B-pleated sheet with a polypeptide chain folding into pleats held by hydrogen bonds between the amino and carboxyl groups is an example. Many fibrous proteins also have this structure.
• An a-helix is where a spiral coils with peptide bonds forming the backbone and the R-group sticking out in all directions. Sometimes, a polypeptide may have no regualar secondary strucutre and might just form a random coil. Explain the tertiary structure of a protein - Correct Answers ✅The 3D organisation on top of a proteins secondary structure. The amino acid chain with any a-helix or b-pleated sheets is folded into father complex shapes. Hydrogen bind, disulfide bonds and ionic bonds between amino acids hold the 3D shapes into place, with globular proteins being an example of a tertiary protein. Explain the quaternary structure of a protein - Correct Answers ✅The quaternary structure only occurs in proteins with several polypeptide chains. It describes how separate polypeptides fit together in three dimensions, with important enzymes and haemoglobin being examples.

Question & Answers 2024

What is a fibrous protein? - Correct Answers ✅A protein with little to no tertiary structure. They are long, parallel polypeptide chains that have occasional cross linkages, forming fibres. They are insoluble in water and are tough meaning they are ideal for structure in organisms. Give some examples of fibrous proteins. - Correct Answers ✅Connective tissues in tendons, matrix in bones, silk of spiders' webs, silkworm cocoons, and keratin that makes up hair, nails and horns are all examples. Why is collagen important and what is it? - Correct Answers ✅Collagen is a fibrous protein giving structure to tendons, ligaments, bone and skin. It makes up 35% of the bodies proteins and is extremely strong. It is made up of three polypeptide chains, each 1,000 amino acids long. What is collagens' primary structure? - Correct Answers ✅The primary strucutre is repeating sequences of glycine with two other amino acids- often proline and hydroxyproline. The three a-helix chains are arranged in a unique triple helix, held by a large number of hydrogen bonds and can be up to several mm long. Collagen fibres can combine with bone tissue giving them the strength of steel in some cases. What genetic illness defines when collagen helix's don't form properly and what is the resulting effect. - Correct Answers ✅Osteogenesis

Question & Answers 2024

imperfecta. The bone lacks tensile strength as a result, and is brittle and breaks easily. What do fibrous proteins look like? - Correct Answers ✅ What is a globular protein? - Correct Answers ✅A globular protein has a complex tertiary and sometimes even quaternary structure. They fold into spherical shapes, with their large size affecting how they behave in water. Why happens to globular proteins in water? - Correct Answers ✅The molecules form a colloid, explaining why globular proteins play an important role in holding molecules in place in the cytoplasm. Give some examples of globular proteins. - Correct Answers ✅- enzymes

• antibodies
• haemoglobin Explain haemoglobin. - Correct Answers ✅- made up of 574 amino acids arranged into 4 polypeptide chains held together by disulfide bonds.
• each chain is arranged around a conjugated protein and a globular protein

Question & Answers 2024

• haemoglobin is both a conjugated and a globular protein
• iron allows for haemoglobin to bind and release oxygen molecules
• arrangement of polypeptides determines how easily oxygen binds or is released. Explain a conjugated protein. Give 2 examples. - Correct Answers ✅When a protein is joined with or conjugated to another molecule called a prosthetic group. Haemoglobin is an example and as is chlorophyll which is joined to a magnesium containing prosthetic group. Explain glycoproteins in relation to being a conjugated protein. - Correct Answers ✅- proteins with a carbohydrate prosthetic group with the carbohydrate helping it to hold on to water and makes it harder for protein digesting enzymes to break them down.
• lubricants like mucus and synovial fluid in joints are glycoproteins with the water holding properties making the slippery, reducing friction. This is also how mucus in the stomach protects the protein walls from digestion Explain lipoproteins in relation to being a conjugated protein. - Correct Answers ✅- a lipoprotein is a protein conjugated with a lipid and is vital to transport chloroplast in blood
• lipid part enables it to combine with lipid cholesterol

Question & Answers 2024

Explain a HDL and an LDL - Correct Answers ✅- high density lipoproteins (HDL) are around 8-11nm in diameter and contain more protein, explaining why they are denser as ptein is more compact than lipids

• low density lipoproteins (LDL) are around 22nm in diameter and are less compact as they contain less protein and more lipid. How do we test for protein? - Correct Answers ✅- Add either 5% potassium or sodium hydroxide solution and 1% copper sulfate solution ( or add biuret reagent which is the two chemicals already mixed )
• when the reagent/s is added to a test solution, a purple colour indicated the presence of protein Define denaturation and explain how proteins may be denatured - Correct Answers ✅The loss of the 3D shape of a protein as a result of changing pH or temperature What is a nucleotide? - Correct Answers ✅Nitrogen base + sugar (ribose or deoxyribose) and phosphate group joined by a condensation reaction with TWO water molecules released. What is the role of a nucleotide? - Correct Answers ✅- provide energy to cells ion the form of ATP.
• provide the building blocks for the mechanism of inheritance in the form of DNA and RNA.

Question & Answers 2024

What does ATP stand for? - Correct Answers ✅adenosine triphosphate What are the pentose sugars in DNA and RNA and what is the difference between the two. - Correct Answers ✅DNA = deoxyribose RNA = ribose Deoxyribose contains one fewer oxygen atoms than ribose What are the the most common purine and pyrimidine bases? - Correct Answers ✅Purine = adenine and guanine Pyrimidine = cytosine, uracil and thymine What is the effect of the phosphate group on a nucleotide? - Correct Answers ✅- makes nucleotide molecules acidic

• is the reason nucleotides carry a negative charge What is ATP? - Correct Answers ✅A nucleotide with three phosphate groups attached. How does ATP provide energy to a cell? - Correct Answers ✅The third phosphate bond in the molecule is broken through hydrolysis, catalysed by ATPase. This produces ADP (adenosine diphosphate),

Question & Answers 2024

anouther nucleotide and a free inorganic phosphate group. One phosphate bond is broken as the ATP splits, using energy. Two futher bonds produce ADP and a stable phosphate group, releasing the energy needed for other reactions. How much energy is released per mole of ATP hydrolysised? - Correct Answers ✅34kJ How is the energy used from hydrolysing ATP? - Correct Answers ✅- building up new molecules

• active transport
• nerve impulses
• muscle contraction Where does the energy needed to synthesis ATP come from? - Correct Answers ✅redox reaction or breakdown reactions. What is a nucleic acid? How does it create proteins? - Correct Answers ✅Also called a polynucleotide, they are polymers made of nucleotide monomer units. They carry information needed to form new cells, with this information stored in DNA. This is then copied into RNA, used to produce proteins that build a cell and control its actions.

Question & Answers 2024

What is genetic information stored in eukaryotic cells? - Correct Answers ✅chromosomes in the nucleus Where is the genetic information stored in prokaryotic cells? - Correct Answers ✅a single length of DNA floating freely in the cytoplasm How are polynucleotides built? - Correct Answers ✅- nucleotides are joined through phophodiester bonds between the sugar of one nucleotide and the phosphate of the next formed through condensation reactions. How many nucleotides are in a nucleic acid? - Correct Answers ✅sometimes millions What groups are at the end of each polynucleotide? - Correct Answers ✅A hydroxyl group at one end and a phosphate group at the other What is the difference between the formation of DNA and RNA? - Correct Answers ✅DNA is a nucleotide contain A, G , T and C nut RNA has A, U, G and C. What does polynucleotide look like? Explain it and draw. - Correct Answers ✅- single polynucleotide strand that can fold into complex shapes held in palce by hydrogen bond or remain thread like

Question & Answers 2024

• DNA has two polynucleotides twisted around eachother. Explain DNA's structure. - Correct Answers ✅DNA has two polynucleotides twisted around eachother. Sugars and phosphates form the backbone, pointing inwards from the sugar-phosphate backbones, the bases pair up in specific ways. Purine bases always bond with pyrimide bases, leading to the double helix. The two strands are held by hydrogen bonds between bases. Each twist has 10 base pairs. Where do hydrogen bonds form in DNA's double helix? - Correct Answers ✅Between the bases. These form between the amino and caronyl groups of the purine and pyrimide bases of opposite strands. There are three bonds between C and G but only two between A and T. How was the genome sequenced? - Correct Answers ✅- in the late 20th century, scientists world wide collaborated on the Human Genome Project where they wanted to identify and sequence the 3 billion base pairs that make up human DNA. They found out that people share 99.9% of DNA and took 13 years to complete despite being ahead of plan
• 2008 the 1,000 genome project began where scientists analysed the DNA of 1092 people worldwide. This took 6 years to do.
• in 2013, the 10K genome project focused one sequencing the genomes of 10,000 people with cancers and rare genetic diseases. This is expected to take only three years thanks to technological improvements.

Question & Answers 2024

Define a genome. - Correct Answers ✅the complete set of genes or genetic material present in a cell or organism What were the two models of DNA replication? - Correct Answers ✅The semiconservative and conservative replication models. Explain the semiconservative model for DNA replication. - Correct Answers ✅- assumed DNA is unzipped and new nucleotides align along each new strand. Each new double helix contains one strand of original DNA and one strand of new DNA. What was the Watson and Crick hypothesis? - Correct Answers ✅That the double helix would unzip along the hydrogen bonds, allowing for semi conservative replication to occur What is the conservative replication model? - Correct Answers ✅That the original double helix remained intact ans in some way instructed the formation of a new, identical helix made up of completely new material. What is the experimental evidence for the semi-conservative method of DNA replication? - Correct Answers ✅- Meselson and Stahl grew several generation of gut bacteria in a medium with only N15 isotopes which is denser than the usual N14. The bacteria took up this heavy

Question & Answers 2024

DNA to make proteins and DNA, meaning all of the bacteria was labelled with the heavy nitrogen.

• They then moved the bacteria with a medium contain N14 as the only nitrogen source
• They predicted that is conservative replication occurred, some bacteria would contain only N15 and some would contain only N14. If semi-conservative replication occurred, all bacteria would have a density between N15 and N14
• They found all DNA had a density between N15 and N14 meaning DNA must replicate semi-conservatively. Draw a diagram explaining semi-conservative replication. - Correct Answers ✅ What is a codon? - Correct Answers ✅a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule. How much of DNA is non-coding? - Correct Answers ✅98% What does non-coding DNA do? - Correct Answers ✅They are involved in regulating the protein-coding sequences, turning genes on or off.

Question & Answers 2024

What does coding DNA do? - Correct Answers ✅the 2% of human coding DNA codes for proteins, with some codons coding for certain amino acids and others coding for the beginning or ends or amino acid sequences. What is the genetic code? - Correct Answers ✅collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis. What does it mean to say DNA is degenerate? - Correct Answers ✅That one amino acid can be coded for by multiple codons, meaning a mutation could still result in the same amino acid and What are the three main functions of RNA in protein synthesis? - Correct Answers ✅- It carries the instructions from a polypeptide from the DNA in the nucleus to the ribosomes where the proteins are made.

• It picks up specific amino acids from the protoplasm and carries them to the surface of the ribosomes.
• Makes up the bulk of the ribsomes themselves Explain mRNA - Correct Answers ✅- formed in the nucleus
• codes for one polypeptide
• forms on the template / antisense strand