AQA 9-1 Biology Paper 1 exam with 100% correct answers 2024

Root hair cells take up water from the soil. Explain one way in which the root hair cell is adapted to this function. [2 marks] - answer-either large surface area [1] for more / faster osmosis [1] OR allow thin (cell) walls [1] for short(er) diffusion distance [1] Explain why the mean rate of water uptake is higher on a hot day than on a cold day. [3 marks] - answer-(on hot day) more water lost [1] more transpiration or more evaporation [1] so more water taken up (by roots) to replace (water) loss (from leaves) [1] The concentration of mineral ions in the soil is lower than in root hair cells. Root hair cells take up mineral ions from the soil. Root hair cells contain mitochondria. Explain why root hair cells contain mitochondria. [4 marks] - answer-(aerobic) respiration occurs in mitochondria [1] (mitochondria / respiration) release energy [1] (energy used for) active transport [1] to transport ions, against the concentration gradient or from a low concentration to a high concentration [1] Explain how different types of organism defend themselves against microorganisms. [6 marks] - answer-Level 3: Relevant points (reasons/causes) are identified, given in detail and logically linked to form a clear account. Indicative content: ANIMALS: skin - sebum/oils to kill microbes; dead layer difficult to penetrate nose - hairs keep out dust and microbes trachea/bronchi - mucus traps microbes; cilia move mucus stomach - (hydrochloric) acid kills bacteria white blood cells - produce antibodies; produce antitoxins; engulf microbes/phagocytosis PLANTS: cell wall - tough / difficult to penetrate waxy cuticle - tough / difficult to penetrate dead cells / bark - fall off, taking pathogens with them production of antibacterial chemicals - kill bacteria FUNGI: antibiotic production - kill bacteria {preventing contamination in an experiment to grow bacteria} [3 marks] - answer-any three from: -sterilise agar (before use) -sterilise (Petri) dish before use -disinfect bench (before use) -pass inoculating loop (through flame) -secure lid with (adhesive) tape -minimise exposure of agar / culture to air / lift and replace lid as quickly as possible Give two advantages of using the stem cell trachea compared with a trachea from a dead human donor. [2 marks] - answer-no need to wait for a donor or can be done immediately [1] (so) no risk of rejection or no need for immunosuppressant drugs [1] Sometimes the stem cell trachea is not strong enough. Doctors can put a stent into the trachea. Suggest how a stent in the trachea helps to keep the patient alive. [2 marks] - answer-stent opens up the trachea [1] allowing air to flow through or allowing patient to breathe [1] Stem cells can also be obtained from human embryos. Evaluate the use of stem cells from a patient's own bone marrow instead of stem cells from an embryo. Give a conclusion to your answer. [6 marks] - answer-Level 3: A judgement, strongly linked and logically supported by a sufficient range of correct reasons, is given. indicative content: embryos advantages: -can create many embryos in a lab -painless technique -can treat many diseases / stem cells are pluripotent / can become any type of cell (whereas bone marrow can treat a limited number) embryos disadvantages: -harm / death to embryo -embryo rights / embryo cannot consent -unreliable technique / may not work bone marrow advantages: -no ethical issues / patient can give permission -can treat some diseases -procedure is (relatively) safe / doesn't kill donor -tried and tested / reliable technique -patients recover quickly from procedure bone marrow disadvantages: -risk of infection from procedure -can only treat a few diseases -procedure can be painful both procedures advantage: -can treat the disease / problem both procedures disadvantages: -risk of transfer of viral infection -some stem cells can growout of control / become cancerous Figure 6 shows two guard cells surrounding a closed stoma and two guard cells surrounding an open stoma When light intensity is high potassium ions are moved into the guard cells. Describe how the movement of potassium ions into the guard cells causes the stoma to open. [4 marks] - answer-(potassium) ions increase the concentration of the solution (inside guard cells) or (potassium) ions make cell more concentrated / less dilute [1] water moves into the (guard) cell by osmosis [1] cell swells unevenly (so stoma opens) [1] as inner wall is less flexible than outer wall or thick part of the wall is less flexible than the thin part (of the wall) [1] A virus called RSV causes severe respiratory disease. Suggest two precautions that a person with RSV could take to reduce the spread of the virus to other people. [2 marks] - answer-any two from: -regular hand washing or -use hand sanitiser / alcohol gel -cover nose / mouth when coughing / sneezing -put used tissues (straight) in the bin -don't kiss uninfected people or -don't share cutlery / cups / drinks with uninfected people -clean / disinfect / sterilisesurfaces regularly One treatment for RSV uses monoclonal antibodies which can be injected into the patient. Scientists can produce monoclonal antibodies using mice. The first step is to inject the virus into a mouse. Describe the remaining steps in the procedure to produce monoclonal antibodies [3 marks] - answer-any three from: -stimulate (mouse) lymphocytes to produce antibody -combine (mouse) lymphocyte with tumour cell or -(create a) hybridoma -clone (hybridoma) cell -(hybridoma) divides rapidly and produces the antibody Describe how injecting a monoclonal antibody for RSV helps to treat a patient suffering with the disease. [2 marks] - answer-any two from: -(monoclonal) antibody binds to virus or -antibody binds to antigen on surface of virus -(monoclonal) antibody is complementary (in shape) / specific to antigen (on surface of virus) -white blood cells / phagocytes kill / engulf the virus(es) Describe the route taken by oxygenated blood from the lungs to the body cells. [4 marks] - answer-(blood) travels through (the) pulmonary vein [1] (blood) enters left atrium [1] (blood) enters (the) left ventricle [1] (blood) leaves the heart via / through (the) aorta [1] The digestive system and the breathing system both contain specialised exchange surfaces. • In the digestive system, digested food is absorbed into the blood stream in structures called villi. • In the breathing system, gases are absorbed into the blood stream in the alveoli. Figure 7 shows the structure of villi and alveoli. Explain how the villi and the alveoli are adapted to absorb molecules into the bloodstream. [6 marks] - answer-Level 3: Relevant points (reasons/causes) are identified, given in detail and logically linked to form a clear account. Indicative content: S = structural F = functional -(S) both have a large surface area -(S) villi have many microvilli -(S) alveolar walls are not flat / are folded -(F) to maximise diffusion (of gases) / absorption of (food) molecules -(S) both have many capillaries / good blood supply / capillaries near the surface -(F) to maintain concentration / diffusion gradient -(S) both have thin walls / walls that are one cell thick / one cell thick surface -(F) to provide a short diffusion distance (for molecules to travel) -(S) villi have many mitochondria -(F) to provide energy for active transport (of food molecules) -(S) cells of the villi have microvilli / more projections -(F) to further increase the surface area/ increase the number of proteins in the membrane / to allow more active transport to take place Enzymes speed up chemical reactions. Explain how amylase breaks down starch. [3 marks] - answer--starch / substrate fits into active site (of enzyme) [1] -shape of active site is unique / complementary to substrate [1] or -substrate is specific to active site / enzyme [1] -bonds (within starch / substrate or -between sugar molecules) are broken [1]