biology paper 1

• explain how a sperm cell is adapted for its function

  the function of the sperm cell is to carry the fathers genetic information and fertilise the egg.

  adaptations the sperm cell have include

  • it is streamlined to reduce energy requirements to travel to the egg.
  • the nucleus contains 1 set of chromosomes, this preserves the chromosome number when the egg is fertilised
  • has an acrosome that contains digestive enzymes that enables the sperm cell to penetrate the egg
  • has lots of mitochondria, for respiration, to release more energy for the cell
• explain how the nerve cell is adapted for its function

  • function: sends electrical impulses around the body
  • adaptations:
  • myelin insulates axon - speeds up transmission of nerve impulses
  • have synapses - junction which allow the pulse from one part to the other
  • dendrites increase surface area - other nerve cells can connect more easily
  • long axons - carry the electrical impulse from one part of the body to the other
• explain how muscle cells are adapted for their function

  • function - contract for movement
  • contain protein fibres - can change their length
  • packed full of mitochondria - for respiration providing energy for contraction
• explain how root hair cells are adapted for their function

  • function - absorb minerals and water
  • covered in hairs - increases surface area so can absorb minerals and water more effectively
  • do not contain chloroplast - they are underground so no photosynthesis
• explain how xylem cells are adapted for their function

  • function - carry water and dissolved minerals from water to the leaves
  • very thick walls containing lignin - provides support to the plant as the xylem’s cells are dead
  • end walls between cells have broken down - cells form a long tube so water and dissolved minerals can flow easily
  • no nucleus, cytoplasm, vacuole, chloroplasts - makes it easier for water and minerals to flow
• explain how phloem cells are adapted for their function

  • function - carry dissolved sugars up and down the plants
  • have pores called sieve pores, limited cytoplasm, no nucleus - allows dissolved sugars to move through the interior
  • companion cells - provide energy to phloem vessel using mitochondria from respiration
• explain how a red blood cell is adapted for its function

  • function - transport oxygen from the lungs to body cells
  • contains haemoglobin - binds itself to oxygen
  • no nucleus - so more room for haemoglobin
  • biconcave disc shape - increases surface area so increases oxygen diffusion rate
• Explain how bile helps the digestion of fats

  Bile is alkaline and so neutralises the digestive juices in the small intestine. it also emulsifies fats which gives them a larger surface area. This means tat enzymes work more efficiently.
• describe the roles of the liver and pancreas in digestion

  the liver produces bile which is alkaline and neutralises digestive juices. it also emulsifies fat which increases its surface area. the pancreas produces digestive enzymes such as protease, lipase and amylase.
• explain the lock and key theory

  the enzyme binds to the substrate because they are complimentary shapes. the substrate is broken down and the products are released. the enzyme remains unchanged.
• Adult stem cells

  • Advantages: Patient can give consent, procedure is well tested and relatively safe
  • Disadvantages: Painful procedure, can cause infection
• Embryonic stem cells

  • Advantages: Painless procedure, can treat many diseases
  • Disadvantages: Unreliable procedure, causes death to the embryo, poses ethical issues as the embryo can't give consent
• Evaluate the use of adult and embryonic stem cells to treat diabetes, paralysis, cancer
• Explain the function and structure of red blood cells

  Red blood cells are a biconcave disc shape and contain a pigment called haemoglobin. Oxygen combines with the haemoglobin to form oxyhemoglobin so that the red blood cells can transport oxygen from the lungs around the body. So that there is more space for this haemoglobin the cell does not have a nucleus.
• Describe how the composition of blood changes as it flows from the lungs to the body

  As blood flows from the lungs the amount of oxygen carried by the red blood cells decreases while the amount of carbon dioxide dissolved in the plasma increases.
• Describe the composition of blood

  Blood is made up of four components. It contains red blood cells for transporting oxygen, white blood cells which help defend the body from infection, platelets for blood clotting and plasma in which substances such as carbon dioxide and urea dissolve into.
• Compare the structure of arteries and veins

  Arteries do not have valves, while veins do. The arteries also have a thicker wall when compared to the vein. Finally, the artery has a narrower lumen when compared to veins.
• Describe what coronary heart disease is and the problems it causes

  Coronary heart disease is when layers of fat build up inside the coronary arteries. This reduces the flow of blood through the arteries and can result in a lack of oxygen for the heart muscle.
• Describe and explain some of the treatments for coronary heart disease

  Stents can be used to keep the coronary artery open and statins can be used to lower cholesterol levels which slows down the deposit of fatty material. In the event that the heart fails the patient may be able to have a heart transplant.
• How the human body defends itself from microorganisms

  1. Skin - dead layer difficult to penetrate

  2. Nose - hairs trap dust and microbes

  3. Trachea - mucus traps microbes, cilia move mucus up to throat

  4. Stomach - acid kills bacteria

  5. White blood cells produce antibodies to destroy pathogens

  6. White blood cells produce antitoxins to neutralise toxins
• Explain how white blood cells protect us from disease

  The white blood cells which carry out phagocytosis and ingest the microbes, they also produce antibodies which destroys pathogens, and produce antitoxins which counteract poisons released by the microbes.
• Explain how a bacterial infection makes us feel ill

  The bacteria reproduce rapidly and produce poisons.
• Describe what a vaccination is and explain how they protect from infection

  A vaccination involves a dead or inactive pathogen being injected into the person. This produces an immune response. The antigen on the vaccine stimulates the white blood cells to start making antibodies. The white blood cells destroy the pathogen without risk of getting the disease. When a person is re-infected the white blood cells produce antibodies more rapidly which leads to the pathogen being destroyed.
• Explain what antibiotics are and why they can’t be used to treat viral infections

  Antibiotics are drugs that are used to treat bacterial infections, they work by damaging the bacterial cell without harming your own cells. They can't be used to treat a viral infection as viruses are found within body cells, because antibiotics don't damage body cells they don't work.
• Developing new drugs

  1. Pre-clinical trials on cells, tissues and live animals to test toxicity, dosage and efficacy

  2. Clinical trials on healthy volunteers and patients at very low doses to check for safety and side effects

  3. Clinical trials on patients to find the optimum dosage and test for efficacy

  4. Double blind trials where patients are randomly allocated into two groups, one given the drug and the other a placebo

  5. Peer review of data to help prevent false claims
• Double blind trials

  • Patients and doctor do not know who has been given the drug and who has been given the placebo to remove bias
• Explain how a foetus may be affected of a mother smokes during pregnancy

  The cigarette smoke will contain carbon monoxide which occupies the mothers red blood cells and so reduces the amount of oxygen that the mothers blood contains.

  This means that the foetus receives less oxygen

  which reduces the rate of respiration in the foetus which causes the birth mass of the baby to be less.
• Compare malignant and benign tumours

  Both benign tumours and malignant tumours are growth of abnormal cells.

  However, benign tumours do not invade other areas of the body and are enclosed in a membrane, while malignant tumours do invade other areas of the body. Malignant tumours do this by some cells breaking off and travelling through the blood to form a secondary tumour elsewhere.
• How smoking can affect health

  1. Smoking raises blood pressure

  2. Smoking increases cholesterol

  3. Smoking leads to thickening of artery walls

  4. Chemicals in smoke cause mutations leading to uncontrolled cell growth causing cancer

  5. Smoking damages alveoli decreasing surface area causing shortness of breath and emphysema

  6. Chemicals in smoke damage cilia causing increased mucus production, shortness of breath, and increased risk of infection
• Smoking raises blood pressure, increases cholesterol, and leads to thickening of artery walls


  Increased risk of heart disease
• Chemicals in smoke cause mutations leading to uncontrolled cell growth


  Can cause cancer
• Smoking damages alveoli decreasing surface area


  Causes shortness of breath and leads to emphysema
• Chemicals in smoke damage cilia

  Causes increased mucus production, shortness of breath, and increased risk of infection
• why might sodium hydrogen carbonate be added to the water?

  to ensure that there is an excess of carbon dioxide and that this does not become a limiting factor
• how can temperature be controlled in the experiment 


  add the pondweed sample to a beaker of water, this helps maintain temperature
• an alternative method is to put discs of pondweed/seaweed in a beaker and measure the time to rise to the surface, why would the disks rise to the surface?


  they have made oxygen, which causes them to float to the surface
• explain how the lungs is for efficient exchange of gases by diffusion

  the lungs have lots of alveoli which increase the surface area for diffusion to take place. the alveoli walls are also very thin which provides a short diffusion pathway. the process of breathing keeps the lungs ventilated with the removal of carbon dioxide and the entry of oxygen which provides a steep concentration. finally, the lungs have a good blood supply, which removes oxygen and so there is a steep concentration gradient.
• Explain how the small intestine is adapted for efficient absorption of nutrients

  • the human small intestine is around 5 metres (very long) - providing a very large surface area for diffusion of digestion products
  • interior is covered with millions of villi - massively increase surface area for diffusion and absorption of molecules
  • very good blood supply - bloodstream rapidly removes products of digestion do increases the concentration gradient
  • thin membranes - ensures a short diffusion path
• Explain how protein is digested

  The protein is first broken down mechanically into smaller pieces by chewing in the mouth before the food is swallowed. Protease enzyme breaks down the protein in the stomach and small intestine. The protein is broken down into amino acids.
• Explain how starch is digested

  The starch is firstly broken down mechanically into smaller pieces by chewing in the mouth before the food is swallowed, as well as saliva, which contains the digestive enzyme amylase, breaks down the starch into smaller sugar molecules. Amylase enzymes then found in the small intestine continue the breaking down of starch into sugars.