Paper 1 AQA A level Biology 2023, Exams of Nursing

Download Paper 1 AQA A level Biology 2023 and more Exams Nursing in PDF only on Docsity! Paper 1 AQA A level Biology 2023 Explain why plasma membranes are said to have a fluid mosaic structure. - correct answer 1. Fluid because the phospholipids are constantly moving. 2. Mosaic because the proteins are scattered throughout the membrane-like tiles in a mosaic. What effect does cholesterol have on the cell membrane? - correct answer 1.Cholesterol molecules fit between the phospholipids and bind to the hydrophobic tails of the phospholipids. 2.Causes them to pack together more closely, restricting the movement of other molecules in the membrane. 3.Cholesterol makes the membrane less fluid and more rigid. 4.Cholesterol helps to maintain the shape of animal cells, which is important because animal cells don't have cell walls (especially important for cells which are not supported by other cells e.g. red blood cells). State 3 functions of glycolipids in the cell membrane. - correct answer 1. Act as recognition sites. 2. Maintain the stability of the membrane. 3. Help cells attach to one another and so form tissues. State 3 functions of glycoproteins in the cell membrane. - correct answer 1.Act as recognition sites.2.Help cells to attach to one another so form tissues.3.Allow cells to recognise one another e.g. lymphocytes can recognise an organisms's own cells. Describe the functions of membranes within cells. - correct answer 1.Control the entry and exit of materials in membrane-bound organelles such as mitochondria and chloroplasts.2.Separate organelles from cytoplasm so that specific metabolic reactions can take place.3.Provide an internal transport system e.g. endoplasmic reticulum.4.Isolate enzymes which could damage the cell e.g. lysosomes.5.Provide surfaces on which reactions can occur e.g. protein synthesis on ribosomes on rough ER. Suggest reasons why most molecules do not diffuse freely through the cell membrane. - correct answer 1.They're not lipid soluble.2.Too large to pass through protein channels.3.Have the same charge as the charge on the protein channels, so they are repelled even if they are small enough to pass through the channel.1 State two factors which affect the permeability of cell membranes - correct answer .1.Temperature2.Solvent concentration How can substances move across a cell surface membrane? - correct answer 1.Simple diffusion (passive)2.Facilitated diffusion (passive)3.Osmosis (passive)4.Active transport (active)5.Co-transport (active) Paper 1 AQA A level Biology 2023 Describe how substances can move across a cell surface membrane. - correct answer 1.Small/non- polar/lipid-soluble substances can cross by simple diffusion down a concentration gradient.2.Large/polar molecules - pass through channel proteins/carrier proteins, by facilitated diffusion, down a concentration gradient.3.Water - moves by osmosis from an area of high water potential to an area of lower water potential.4.Active transport - moves substances against a concentration gradient, involves protein carriers and requires ATP.5.Glucose/amino acids can be co-transported across a cell membrane alongside sodium ions.* DON'T EVER SAY THAT A MOLECULE MOVES 'ACROSS' OR 'ALONG' A CONCENTRATION GRADIENT - MAKE SURE YOU SAY 'UP' OR 'DOWN' OR 'AGAINST' Define diffusion. - correct answer The net movement of molecules or ions from an area of higher concentration to an area of lower concentration until evenly distributed.Define osmosis.The movement of water from a region of higher water potential to a region of lower water potential across a partially permeable membrane. Define active transport. - correct answer The movement of molecules from an area of lower concentration to an area of higher concentration using ATP and carrier proteins. State factors which affect the rate of diffusion. - correct answer 1.Concentration gradient2.Area over which diffusion takes place3.Thickness of exchange surface4.Temperature5.Size of molecules (smaller the molecule, the faster the rate of diffusion).2 What is meant by the term simple diffusion - correct answer .The diffusion of molecules directly through a cell membrane.(most molecules don't easily pass across the cell surface membrane - those that do are small, non-polar molecules). What is Ficks Law? - correct answer The rate of diffusion is proportional to : (Surface Area x Concentration) Thickness1.The larger the SA, the faster the rate of diffusion.2.The higher the concentration gradient, the faster the rate of diffusion.3.The thinner the exchange surface, the faster the rate of diffusion. What is meant by the term passive process. - correct answer No energy is needed for it to happen. Why are oxygen and carbon dioxide able to diffuse across cell membranes? - correct answer 1.They're small, so they can pass through the spaces between the phospholipids.2.They're non-polar, so they are lipid-soluble and so can dissolve in the phospholipid bilayer. Paper 1 AQA A level Biology 2023 What happens if an animal cell is surrounded by a concentrated salt/sugar solution? - correct answer 1.It shrinks because water leaves the cell by osmosis.2.Water moves from area of higher water potential in the cell to area of lower water potential in the solution .What happens if a plant cell is surrounded by a concentrated salt/sugar solution? - correct answer 1.Water leaves the cell by osmosis2.but the cell wall prevents the cell from shrinking by keeping the cell rigid. Describe two ways in which osmosis and diffusion are similar. - correct answer 1.Both are passive and so don't require ATP.2.Both involve movement down a concentration gradient. Give two differences between osmosis and facilitated diffusion. - correct answer 1.Osmosis only involves the movement of water.2.Facilitated diffusion involves carrier proteins.5 Why can glucose molecules not pass easily through the phospholipid bilayer? - correct answer Only lipid-soluble substances diffuse across the phospholipid bilayer easily, Water-soluble substances like glucose, diffuse very slowly. Suggest two changes to the cell surface membrane that would increase the rate at which glucose could be transported in the cell. - correct answer 1.More proteins with pores which span the phospholipid bilayer.2.Increase the surface area of the cell surface membrane with microvilli .State two properties that a drug should have if it is to enter a cell rapidly. - correct answer 1.Lipid- soluble2.Small What is a co-transporter? - correct answer A type of carrier protein that can bind two molecules at a time (the concentration of one of the molecules is used to move the other molecule AGAINST its own concentration gradient). Describe how glucose is absorbed by co-transport in the mammalian ileum (final part of the small intestine). - correct answer 1.Sodium ions are actively transported out of the ileum epithelial cells by the sodium-potassium pump.2.Creates a concentration gradient, causing sodium ions to diffuse into the epithelial cells down their concentration gradient via sodium-glucose co-transporter proteins.3.The co- transporter carries glucose into the cell with the sodium.4.The concentration of glucose inside the cell Paper 1 AQA A level Biology 2023 increases.5.Glucose diffuses out the cell into the blood, down its concentration gradient through protein channels, via facilitated diffusion. Why is it necessary for glucose to be absorbed from the lumen of the ileum by co-transport? - correct answer The concentration of glucose in the ileum is too low for glucose to diffuse out through the epithelial cell surface membrane into the blood. Suggest three ways in which the rate of movement across a membranes can be increased. - correct answer 1.Increasing the surface area.2.Increasing the concentration gradient across the membrane.3.Increasing the density of protein channels and/or carrier proteins. •Describe how you could use a graph of your results to find the sodium chloride solution with the same water potential as the potato tissue. - correct answer •Plot a graph with concentration on the x-axis and percentage change in mass on the y-axis.•Find the concentration where the curve crosses the x-axis (i.e. where the percentage change is zero).•*if your results are given as a ratio of mass at the start:mass at the end instead of percentage change, find the sodium chloride concentration where the ratio is 1 i.e. there was no change in mass during the experiment. •What is the advantage of giving your results as a ratio/percentage change. - correct answer Allows a comparison to be made when all the cylinders/discs had a different starting mass. •Explain why taking additional readings at each concentration of sodium chloride would improve the reliability of the results. - correct answer It allows for anomalies to be identified and enables a mean to be calculated. •Explain why additional readings could improve the graph. - correct answer The more readings used to plot a graph, the more accurate the curve of best fit will be and therefore the the point where the line crosses the x-axis will be more accurate. Also, it allows you to plot standard deviation values and error bars to show how spread the results are. •State how evaporation would affect the water potential of the solution in the test tubes. - correct answer It would lower the water potential. •Explain why it is important to use potato cylinders taken from potatoes of the same variety. - correct answer To ensure the cells have the same water potential / so there are no genetic differences.8 Paper 1 AQA A level Biology 2023 •The potato skin is removed from the cylinders - correct answer suggest one reason why the potato skin could have affected osmosis. ,Potato skin is impermeable to water / the skin is a different tissue so the cells of the skin will have a different water potential. •Explain why the student blotted dry the outside of each cylinder before reweighing. - correct answer water will affect the mass of the potato cylinder and the student only wants to measure the water that was taken up (or lost) by the potato cylinder due to osmosis. •Explain why the percentage increase in mass of a small cube would be greater than the percentage increase in mass for a large cube. - correct answer Due to the larger surface area:volume ratio of the small cubes for osmosis. •Explain why the potato cylinder in distilled water gained mass. - correct answer Water moved into the potato cells by osmosis, from a less negative water potential outside the cells to a more negative water potential inside the cells. Explain what is meant by the term eukaryotic cell. - correct answer •Cell that has a membrane-bound nucleus and chromosomes.•Has other membrane-bound organelles, such as mitochondria and endoplasmic reticulum. Give examples of eukaryotic cells. - correct answer Animal cells / Plant cells / Fungi / Algae Give an example of a prokaryotic cell. - correct answer Bacteria Describe the structure and function of the cell-surface membrane. - correct answer Structure - membrane found on surface of animal cells and just inside the surface of other cells / made mainly of lipids and proteins.Function:•Regulates the movement of substances into and out of the cell.•Has receptor molecules on it (allows it to respond to e.g. hormones). Describe the structure and function of the nucleus. - correct answer Structure:•Surrounded by nuclear envelope (double membrane with many pores).•Contains chromosomes (consist of linear DNA + histone proteins).•Contains one or more nucleoli (singular = nucleolus)Function: •Contains genetic material of the cell in the form of DNA - therefore controls the cell's activities.•Pores allow movement of substances e.g. mRNA between the nucleus and the cytoplasm.•Nucleolus manufactures ribosomes.10 Paper 1 AQA A level Biology 2023 Suggest how a leaf cell is adapted to its function of absorbing light for photosynthesis. - correct answer 1.Packed with chloroplasts.2.Regular shaped, so cells can be closely packed together to form a continuous layer for efficient absorption of sunlight. Suggest how a sperm cell is specialised for its role in sexual reproduction. - correct answer 1.Have lots of mitochondria to provide ATP for movement generated by the tail.2.Very small and thin, which helps them to move easily. Suggest how neutrophils are adapted to their function of ingesting and destroying microbes. - correct answer 1.Large amounts of lysosomes, which contain enzymes to destroy ingested microbes.2.Have a lobed nucleus, which allows for greater flexibility. Suggest how a root hair cell is adapted to its function of absorbing water and minerals from the soil. - correct answer 1.Large surface area due to hair-like projections, which increases the uptake of minerals and water.2.Have a large amount of mitochondria for active transport. What is meant by the term prokaryotic? - correct answer 1.A cell of an organism belonging to the kingdom Prokaryote.2.Do not have a nucleus OR membrane-bound organelles. What is a plasmid? - correct answer 1.A small, circular piece of DNA found in bacterial cells, that is separate from the main circular DNA molecule.2.Plasmids can be passed between prokaryotic cells.3.Not all prokaryotes contain plasmids, some contain more than one plasmid. What is a flagellum? - correct answer A long hair-like structure that rotates to make the prokaryotic cell move. How do prokaryotic cells differ from eukaryotic cells? - correct answer 1.Prokaryotic cells don't contain a nucleus - DNA floats free in the cytoplasm.2.Prokaryotic DNA is circular DNA.3.Prokaryotic DNA is not attached to histone proteins.4.Prokaryotes are much smaller than eukaryotic cells.5.Prokaryotes have no membrane-bound organelles.6.Prokaryotes have smaller ribosomes.7.Prokaryotes have a cell wall composed of murein (a glycoprotein).Name 3 features of a prokaryotic cell, which would not be found in a eukaryotic cell.1.One or more plasmids.2.A capsule surrounding the cell.3.One or more flagella.14 Describe the structure and function of the prokaryotic cell wall.Made of murein - the cell wall supports the cell and prevents it from changing shape. - correct answer Paper 1 AQA A level Biology 2023 What is the function of the capsule in prokaryotic cells? - correct answer To protect bacteria from attack by cells of the immune system. Give an example of a gene which is carried on a plasmid? - correct answer Genes for antibiotic resistance. What is a virus? - correct answer 1.Acellular and non-living.2.Consist of nucleic acids surrounded by a capsid (protein coat).3.Attachment proteins stick out from the capsid - allow the virus to attach to host cells.4.No plasma membrane or cytoplasm or ribosomes.5.Viruses can't reproduce independently - they invade and reproduce inside host cells. Method by which prokaryotic cells replicate? - correct answer Binary fission Describe how a prokaryotic cell divides. - correct answer 1.The circular DNA and plasmid(s) replicate.2.The main DNA loop is replicated once, plasmids can be replicated multiple times.3.The cells gets bigger and the DNA loops move to opposite poles of the cell.4.The cytoplasm begins to divide and new cell walls begin to form.5.The cytoplasm divides and two daughter cells are produced.6.Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of the plasmid(s). How to calculate the number of bacteria at the end of a growth period? - correct answer bacteria at beginning of growth period x 2number of divisionse.g. if 1 bacteria divides 25 times, there will be 1 x 225 bacteria Why can some viruses only infect one cell type? - correct answer 1.Different viruses have different attachment proteins.2.Therefore they require different receptor proteins on host cells.3.Therefore, some viruses can only bind to and infect certain cell types. Define magnification. - correct answer The number of times bigger the image/drawing is compared to the real size of the specimen. Define resolution. - correct answer The minimum distance needed to differentiate between two adjacent objects. Paper 1 AQA A level Biology 2023 Distinguish between magnification and resolution. - correct answer 1.Magnification is how many times bigger the image is compared to the real object.2.Resolution is the minimum distance apart that two objects can be in order for them to be distinguished as two separate objects. Why will increasing the magnification not necessarily increase the resolution? - correct answer 1.Microscopes have a limit of resolution.2.Beyond the limit of resolution, increasing the magnification will result in larger, but more blurred images. State the formula for calculating magnification. - correct answer magnification = size of image/size of object* make sure you convert the numbers into the same units before doing the calculation. Why can organelles appear different in images? - correct answer They can be viewed from different angles and at different depths. Explain the principles and limitation of a light microscope. - correct answer Principles:1.They use light to form an image.2.They have a maximum resolution of 0.2 μm.3.They have a maximum useful magnification of about x1500.Limitations:1. They have a poor resolution so can't be used to view organelles smaller than 0.2μm, this includes ribosomes, endoplasmic reticulum and lysosomes. Name structures in a eukaryotic cell that cannot be identified using a light microscope. - correct answer 1.Lysosomes2.Ribosomes3.Endoplasmic reticulum Which organelles can be seen using a light microscope? - correct answer 1.Nucleus2.Possibly the mitochondria, but not in much detail.Which microscope has the higher resolution?TEM > SEM > LM Why do electron microscopes have a higher resolution than light microscopes? - correct answer 1.Electron microscopes use electrons which have a shorter wavelength.2.Light microscopes use light which has a large wavelength. What is the difference between TEMs and SEMs? - correct answer 1.In transmission electron microscopes, the electrons pass through the specimen.2.In scanning electron microscopes, the electrons bounce off the specimen's surface.16