AQA Biology GCSE - Question errors

Explain how the student could modify the investigation to determine the concentration of the solution inside each egg.

• Use five different concentrations of sugar solution in a beakers

• Plotting percentage change of mass using a graph

• Determine the concentration where the line crosses the zero percentage change line

How mAB are produced

1. Inject a mouse with the virus to trigger immune responses.

2. The mouse's immune system will produce antibodies, lymphocytes that are specific to the virus.

3. Lymphocytes aren't fast-growing, so you will fuse them with tumor cells to produce hybridomas.

4. Find the hybridoma which makes monoclonal antibodies specific to the virus.

5. Hybridomas are collected and purified

In a person with CF, cells lining the lungs and digestive system create too much mucus.

The mucus can:

• block the duct leading from the pancreas to the small intestine

• block the tubes leading to the alveoli in the lungs.

Explain why children with CF grow more slowly than children without CF.

Describe how scientists may use stem cells to create healthy lungs that are not rejected by the CF patient.

• Take stem cells from bone marrow of patient

• Remove faulty gene

• Use stem cells to create an embryo

• Remove the stem cells from embryo, then allow it to divide into lung cells.

Therapeutic cloning

• Remove nucleus from donor egg cell

• Take out nucleus from patient's body cell

• Then insert this nucleus to the donor egg

• Electrically shock the cell, so cell divides into an embryo

• Extract stem cell from embryo

• Stem cells can differentiate into any type of cell

Explain why the indicator in both tubes became colourless.

• Lipase breaks down fat into fatty acids.

• Fatty acids lower pH, so fatty acids will cause pH to be below 10.

Explain the difference in the results for the two test tubes in Table 9

• Bile emulsifies fat,into tiny droplets

• Creating a larger surface area for lipase to work on.

• Therefore, lipase breaks it down much faster

2020

Describe how the human body:

• prevents pathogens from entering

• defends itself against pathogens inside the body.

See paper

Describe the transport of water through a plant from the roots to the atmosphere.

• Water is transported in xylem

• Water evaporates from leaves through the stomata

Explain why a person with a leaking heart valve has difficulty exercising.

Describe how small intestine is adapted for efficient absorption

Define the term double circulatory system.

• Blood is pumped to the lungs by the right side of the heart and

• Blood is pumped to the body by the left side of the heart

Explain why an axolotl may die in water with a low concentration of oxygen

• concentration gradient of oxygen is less steep

• So less oxygen diffuses into cells

• So less aerobic respiration occurs, so less energy is released

• So less metabolism

Explain why having only one ventricle makes the circulatory system less efficient than having two ventricles.

• Oxygenated and deoxygenated blood mixes

• Less oxygen reaches the body cells

Why is placebos used

• To avoid the patients thinking they feel better with the drug

• Avoid biased results

Explain how the monoclonal antibody works to treat pancreatic cancer/ 4.2.2.3

2020

How are the human lungs adapted for diffusion

Explain the ‘lock and key theory’ of enzyme action.

• Enzymes active site with a specific shape.

• Only a substrate with a complementary shape can fit into the active site

• So when the active site of an enzyme binds to the substrate

• It breaks the bonds within substrate to form products(smaller molecules)

Describe how the mAbs and a fluorescent dye could be used to see any Candida albicans pathogens on the slide.

• Bind fluorescent dye to mAbs

• Put fluorescent mAbs on the slide

• MAbs will bind to pathogens and show up under the microscope

Explain how increased phagocytosis of the Candida albicans pathogen will help the patient.

• More phagocytes engulf and digest the pathogen

• Therefore less damage to cells

2021

Give three uses of energy in respiration

• Movemnt

• Keeping warm

• Active transport

Explain what happens when red blood cells clump together

• They block capillaries

• So cells can’t respire

2022

What is thick, waxy cuticle on plant surface

Physical defence

Alveoli vs Villi adaptation

Use book

Explain how the monoclonal antibody for HIV helps to prevent a person with HIV developing AIDS

• Monoclonal antibody is specific to HIV antigen

• Monoclonal antibodies attach to HIV antigens so HIV cannot bind to cell

2023

• Blood transport

• Photosynthesis practical

2024

Alveoli adaptations

Explain the results for these three leaves

Leaf 1 - No light so no photosynthesis occurs

Leaf 2 - No carbon dioxide so no photosynthesis

Leaf 3 - Light and carbon dioxide present so leaf can photosynthesise

Leaf 1 and 2 - Glucose not made so glucose cannot be converted to starch

Explain the effect of increasing temperature and increasing carbon dioxide concentration on the rate of photosynthesis shown in Figure 7

• Increasing temperature while keeping the carbon dioxide concentration constant, increases the rate of photosynthesis

• Increasing the temperature increases the kinetic energy of the particles, which increases the number of collisions between the particles.

• Increasing carbon dioxide concentration increases the reactants

• All rates plateau at a certain point due to another factor being limiting

Explain the results at 30 °C and at 90 °C.

Explain why the metabolic rate of a fish is higher when swimming compared with when resting.

• More movement, needs more energy

• So more respiration occurs for more muscle contractions

Weak topics

Osmosis - mark scheme wording

How are gills adapted to maximised exchange of oxygen between water and blood

• Gills have many filaments with lots of lamellae to increase the surface area to volume ratio for faster rate of diffusion.

• Good blood supply to maintain a steep concentration gradient.

• Countercurrent flow - blood flows opposite direction to water to keep oxygen concentration gradient high.

• Lamellae walls are one cell thick - So oxygen has a short diffusion pathway, moving quickly into blood

How are alveoli adapted for diffusion

• Large surface area to volume ratio - To maximize the rate of gas exchange

• Moist lining

• Thin walls - So gases have a short diffusion distance

• Good blood supply - Maintain concentration gradient

How is the small intestine adapted for diffusion

• Villi and microvilli - Increase the surface area to volume ratio, so gases have a larger space to diffuse

• Villi is one cell thick - Short diffusion distance for gases

• Good blood supply - Maintain concetration gradient

How is the leaves adapted for diffusion

• Gases move by diffusion: carbon dioxide enters the leaf, while oxygen and water vapour leave.

• Stomata on the underside of the leaf allow this gas exchange.

• Guard cells control the opening and closing of stomata to reduce water loss.

• Air spaces increase the surface area for efficient gas exchange.

Bile

• Bile neutralises stomach acid, creating an alkaline environment in the small intestine, which provides the optimum pH for enzymes to work effectively.

• Bile emulsifies fats into small droplets, increasing the surface area of fat for lipase, which speeds up the rate at which lipase can break down lipids into fatty acids and glycerol.

Lungs - Basic pathway of air

• Air enters the lungs through the trachea.

• The trachea is supported by rings of cartilage, which prevent it from collapsing when you inhale.

• The trachea splits into two bronchi, one going to each lung.

• The bronchi divide into smaller tubes called bronchioles.

• Bronchioles end in tiny air sacs called alveoli.

Alveoli – site of gas exchange

• Gas exchange happens in the alveoli.

• Oxygen diffuses from the air in the alveoli into the blood.

• Carbon dioxide diffuses from the blood into the alveoli to be exhaled.

Heart organisation - Also diagrams

Plant cell organisation

Measles

• Cause: Virus

• Spread: Sneezes or Coughes

• Symptoms: Red skin rash and fever.

• Treatment: Vaccine

HIV

• Cause: Virus

• Spread: Sexual contact or exchanging bodily fluids.

• Symptoms: Flu-like symptoms, attacks lymph nodes and immune cells.

• Treatment: Antibiotics.

• Prevention: Condoms

TMV

• Cause: Plant Virus

• Spread: Contact or contaminated tools

• Symptoms: A distinct mosaic pattern visible on leaves, discolouration of leaf limiting photosynthesis and stunting growth.

• Management: Using resistant plant varieties, proper sanitation of tools, removing and destroying infected plants.

Rose Black Spot

• Cause: Fungus

• Symptoms: Black/purple dots on leaves.

• Spread: In water and wind.

• Treatment: Fungicides or removing infected leaves.

Malaria

• Cause: Protist, mosquito is the vector

• Symptoms: Repeating fever that can be fatal.

• Spread: Infected mosquito bite

• Treatment: Mosquito nets and insecticides.

Salmonella

• Cause: Bacteria

• Symptoms: Fever, vomitting

• Spread: Eating contaminated food

• Treatment: Vaccination

Gonorrhoea

• Cause: Bacteria

• Symptoms: Thick yellow discharge, pain when urinating

• Spread: Sexual Contacts

• Treatment: Antibiotics

• Prevention: Condoms, regular screening.

Clinical Trials

• Preclinical Trials

  • Test on cells, tissues, and live animals.

  • Assess toxicity, dosage, and efficacy.

• Clinical Trials

  • Phase 1: Test on healthy volunteers & patients (low doses).

  • Monitor for safety and side effects.

  • Phase 2 & 3: Find optimum dosage and confirm efficacy.

• Double-Blind Trials

  • Patients randomly assigned to drug or placebo groups.

  • Neither doctor nor patient knows who receives the real drug.

• Peer Review

  • Ensures accuracy and prevents false claims before publication.

How monoclonal antibodies work

• Monoclonal antibodies are identical antibodies that target a specific antigen.

• They bind to specific antigens on target cells.

• They can be used to bind to cancer cells.

• They can carry drugs, toxins or radioactive substances to target cells.

• This allows targeted treatment, destroying specific cells.

Also

• Topic 4

• Required practicals -

• Metric converisions

• Read all 8 years and memorise