AQA A Level Biology Paper One Revision: Exam Questions and Answers, Exams of Advanced Education

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AQA A LEVEL BIOLOGY PAPER ONE REVISION

EXAM

What's the type of bond between glycerol and a fatty acid in a phospholipid? Ester bonds How would a fatty acid be unsaturated? If it contained a double bond between adjacent carbon atoms in the hydrocarbon chain. Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum. Red blood cells would be free in blood, and not supported by other cells which ensures that cholesterol will maintain its shape. E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.

• Cells are unable to change shape due to the cell having a cell wall.
• This makes the cell rigid since it is made of murein. Explain the difference between starch molecules and cellulose molecules
• Starch formed w a glucose, Cellulose w b glucose
• Position of hydrogen and hydroxyl groups on carbon atom 1 are inverted. How is starch adapted for its role?
• Insoluble , meaning that it doesn't affect water potential. How is cellulose adapted for it's function in plant cells?
• Long and straight chains -Become linked together with hydrogen bonds which form fibrils
• Provides strength for cell wall. How is mRNA produced in the nucleus of a cell?

DNA helicase breaks down hydrogen bonds

• One DNA strands acts as a tempalte
• RNA nucleotides exposed to bases
• Attraction linked to the base pairing rule
• RNA Polymerase joins RNA nucleotides together
• Pre-mRNA spliced to remove introns. Describe the structure of proteins
• Polymer of amino acids;
• Joined by peptide bonds;
• Formed by condensation; Describe how proteins are digested in the human gut? hydrolysis of peptide bonds occur so: endo - break polypeptides to smaller peptide chains exo - remove terminal amino acids di - hydrolyze dipeptides to amino acids What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer. Maltose, since amylase is produced during chewing. how is starch similar to cellulose?
• both are polymers
• both contain glucose
• have 1,4 links What organ produces amylase and maltose? pancreas Why is maltose only hydrolyzed by maltase? Active site of enzyme has complementary shape to substrate maltose Only maltose can bind, forming an enzyme substrate complex. How do you identify is DNA is single stranded?

If it does not have the same amount of A and T or G and C DNA Polymerase joins nucleotides to form new strand DNA Prokaryotic Cell differences to Eukaryotic Cells

• Circular
• No introns Why are Humans and X genetically similar, but different They have different genes triplets are in different places so different amino acids code for different proteins Cutting x thin for optical microscope For more light to pass through so a single cell can be viewed DNA has antiparallel strands Shape of nucleotides is aligned differently Enzymes with specific shapes have active sites ONLY substrates with specific shapes can bind with active site How can nerve cells be affected by a virus? The outside of a virus has proteins, with complementary shapes to the receptor Receptor only found on membrane of nerve cells.

Advantage of programmed cell death Prevents the replication of viruses. Prevents replications of mutations/mutations of a cell How is DNA a polymer? It has repeating units Two ways ATP is a suitable energy source releases small amount of energy instant energy release Equation of ATP being synthesized by ADP ADP + Pi --> ATP Why do humans synthesize a huge amount of ATP?

• It cannot be stored
• Only releases a small amount of energy at a time Function of ATP metabolic processes provide energy for muscle movement changes shapes of carrier proteins for active transport secretes cell products net yield of ATP from anaerobic respiration 2 molecules advantage of ATP as an energy storage molecule in a cell cannot pass out of cell releases small amount of energy Advantage of mitochondria in muscle cells having more cristae

larger surface area for electron transport chain more enzymes for ATP production muscles use more ATP than skin cells How does centrifuging a culture obtain a cell-free liquid? Heavy cells form pellets which move to the bottom of the tube when centrifuged From there the liquid can be removed. One function of lisosomes break down cells What are the terms of cell fractionation? What temp should it be and what should be done at first? break open cells to remove debris the solution MUST be cold - to reduce activity of enzymes breaking down organelles. Name two structures in a eukaryotic cell that cannot be identified using an optical microscope ribosome endoplasmic reticulum Cellulose structure Long unbranched chains of beta glucose hydrogen position and hydroxyl groups on carbon one inverted 1: How is starch adapted for its function in plant cells?

Insoluble, doesn't affect water potential cellulose adapted for plant cells long + straight chains linked together by hydrogen bonds to form fibrils provide strength to cell wall why would marker genes be used? to see what has successfully reacted successful reactions will glow How to use an optical microscope add drop of water to slide obtain thin section of tissue and place on slide stain with iodine in potassium iodide lower cover slip using mounted needle What is the chloroplast's function? photosynthesis Advantage of transmission electron microscope High resoloution Can see internal structures of organelles how phospholipids are arranged in the lipid bilayer bilayer hydrophobic tails to inside phosphate heads to the outside How is the RER involved in the production of enzymes has ribosomes to make proteins (which is what an enzyme is) How is golgi apparatus involved in secretion of enzymes

Golgi apparatus modifies proteins. Why should you not push the cover slip sideways in a glass slide Pushing hard would spread the issue, but pushing sideways would break chromosomes protein synthesis Ribosomes what organelle modifies protein Golgi apparatus what organelle site of aerobic respiration mitochondria Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid Large dense cells, spinning allows pellets to move to the bottom of the centrifuge. Liquid can be removed. Lysosomes break down food and worn out cell parts one advantage of different percentage of cholesterol in RBC compared with cells lining ileum RBC are free in blood which means that cholesterol can maintain shape high blood pressure leads to an accumulation of tissue fluid how tissuse fluid is formed 2 ways pathogens cause disease releases toxins that kills cells how does the monoclonal antibody prevent the regulatory protein from working tertiary structure complimentary to regulatory protein binds to form complex

regulatory protein is not complementary to receptor the advantage of closing stomata water is lost through stomata, closure prevents water loss, this maintains the water content of cells how does the uptake of co2 increase when stomata closes? through the upper surface of the leaf (waxy cuticle) how would the mutation of a tumor suppressant gene result in tumor formation? tumor suppressor would not be able to control cell division meaning that rate of cell division would be too fast. why would there be a % decrease in people vaccinated fewer cases would be reported

fear of side effects why is a virus described as inactive no more cells are infected, virus is not replicating advantage of cell death prevents cell replication limitations of a TEM to investigating cell structure cell must be dead image produced is not 3D specimen must be thin principles of a TEM microscope electrons pass through thin specimen denser parts absorb more electrons dense parts are darker electrons have short wavelength so there is a high resoloution interphase + mitosis = two genetically identical cells. how?

• dna is replicated via complementary base pairing
• two identical chromatids produced
• each chromatid moves to opposite ends of the cell. two structures in a eukaryotic cell which is not visible in optical microscope ribosomes cell surface membrane how tissue fluid formed outward pressure forces small molecules out of capilary why hydrostatic pressure falls from the arteriole end of the capilary to the venule end of the capilary friction against capillary lining. mechanism that causes forced expiration (4) contraction of intercostal muscles decrease in volume of chest air pushed down a pressure gradient how oxygen in the air reaches capillaries surround alveoli in lungs trachea, bronchi + bronchioles down pressure gradient down diffusion gradient across alveolar epithelium across capillary endothelium In vitro cloning gene copies are made outside of living organism using the polymerase chain reaction (EG PCR) in vivo cloning gene copies are made within a living organism as it grows and divides. (so bacteria)

EG - INSULIN IS MADE FROM PUTTING INSULIN GENE INTO BACTERIA,

BACTERIA REPLICATES THE GENE.

DNA ligase linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain. seals phosphodiester backbone in vivo cloning insertion vector DNA isolated. cut open using same restriction endonuclease that isolated the DNA fragment with targeted gene. sticky ends of vector of DNA are complementary to stick ends of DNA fragment containing gene. vector DNA + fragment are mixed together w DNA ligase. joins sticky ends of DNA fragment to sticky ends of vector DNA. adaptation for organisms in cold environments small S:O to vol ratio more heat is retained method on how to find the surface area of a leaf

• draw around leaf on graph paper
• count squares
• multiply by two two features of xerophytes hairs on leaves so - increase in humidity curled leaves - reduction in air movements uptake of co2 falls to 0 when there is no light, why? no use of co2 in photosynthesis in the dark no diffusion gradient (maintained) for co2 in leaf relationship between temp of water, oxygen in water + rate of ventilation

as water temp increases, oxygen conc falls and ventilation rate increases countercurrent flow and how it leads to efficient gas exchange in the gills of the fish: water and blood flow in opposite directions maintains diffusion gradient across the whole length of the lamellae volume of water passing over gills increases if the temp of water increases. why? increased metabolism so less oxygen is dissolved in water process which oxygen passes from an alveolus in the blood simple diffusion structure of an amino acid polymer of amino acids joined by peptide bonds formed by condensation primary structure in order of amino acids secondary structure is folding of polypeptide chain due to hydrogen bonds how proteins are digested hydrolisis of peptide bonds endopeptidases break polypeptides into smaller peptide chains expopeptidases remove terminal amino acids dipeptidases hyrolisise dipeptides into amino acids how mrna is produced in the nucleus of the cell dna helicase breaks hydrogen bonds only one dna strand act as template rna nucleotides attracted to exposes bases attraction according to base pairing rule RNA polymerase joins RNA nucleotides together pre-mrna spliced to remove introns why maltose is hydrolyzed by maltase

active site is complementary to maltase ONLY maltose can bind to form an enzyme substrate complex function of coronary arteries carry oxygenated blood to heart muscles The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why. aorta is directly linked to heart aorta has elastic tissues aorta has stretch one advantage of capillaries are narrow large surface area of blood in contact with walls of capillaries importance of maintaining a constant blood ph to avoid enzymes in blood being affected by change in pH this could lead to a change in shape of hemoglobin so less oxygen would be able to bind with hemoglobin how are sickle cells adapted for mass transport very little cytoplasm so it is more easier for thick walls to resist pressure one other way in which companion cells are adapted for the transport of sugars between cells mitochondria release energy for active transport how is a high pressure produced by translocation in the leaves water potential becomes lower water enters phloem by osmosis increased volume of water = increased pressure comparison of facilitated diffusion and active transport facilitated diffusion: involves channel proteins. does not use atp. down a conc gradient.

active transport: only involves carrier proteins. uses atp. against a conc gradient. mass flow hypothesis for mechanism of translocation in plants leaf sugars actively trasnported by phloem by companion cells lowers WP of sieve cell increase in pressure causes mass movement sugars used conversed in roots (stored as starch) for respiration for storage common difference between two amino acids different R group deletion of the sixth base in DNA would = change in nature of protein but substitution would not. why? all code for same amino acid deletion would cause frame shift. how mutation would = production of a protein with a missing amino acid loss of triplet stop codon formed production of protein with 1 amino acid missing could = genetic disorder. how/why? change in active site - so the protein is non functional. (or fewer E-S complexes formed) how could monoclonal antibodies stop the growth of a tumor? antibody has specific tertiary structure. complementary shape to the receptor protein. this prevents the growth factor from binding to the receptor. two ways meiosis produces genetic variation independent segregation crossing over two reasons why population may have little genetic diversity

inbreeding population may have been very small how courtship behaviour would lead to an increase in mating recognition of the opposite sex + same species, stimulates the production of gamestes. hierarchy groups within groups independent segregation in meiosis allows combination of maternal + paternal chromosomes. mutations and how it can lead to the production of a non-functional enzyme change in base change in amino acid sequence change in hydrogen bonds change in tertiary structure and active site substrate no longer complimentary genetic diversity The number of different alleles of genes in a species or population. heirarchy groups within groups what is a species groups of organisms with similar features independent segregation to provide genetic variation allows different combination of maternal and paternal chromosomes. Phylogenetic group grouped according to evolutionary links how is carbon dioxide converted to other substances in the light independent stage of photosynthesis?

carbon dioxide combines with RuBp produces 2 glycerate 3-phosphate GP converted to triose phosphate using reduced NADP and energy from ATP, triose phosphate converts to glucose. Primary, Secondary and Quaternary Structure of Amino Acids

• Primary structure is order of amino acids;
• Secondary structure is folding of polypeptide chain due to hydrogen bonding.
• Quaternary Structure is two or more polypeptide chains. reverse transcriptase An enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis. RNA polymerase Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription Lymphocytes A type of white blood cell that make antibodies to fight off infections mass transport in plants The transport of water and solutes in the xylem and phloem xylem carries water source cell - facilitated diffusion of glucose into companion cell, active transport into phloem - through sieve cells (negatively charged at the top) glucose travels down phloem which travels to companion cells and then sink cells by active transport.

• charged. Capsid

Outer protein coat of a virus Helper T cells help the immune system by increasing the activity of killer cells and stimulating the suppressor T cells