April 2026 Mock exam corrections
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What enzymes are secreted by the pancreas?
Lipase, Amylase and protease
What does each enzyme in the pancreas do?
Lipase- breaks down fats into glycerol and fatty acids Amylase- breaks down starch into sugars Protease- breaks down proteins into amino acids
Which organ do the enzymes reach?
Small intestine
What happens to the food molecules after the enzymes have broken them down?
The food molecules are absorbed by the small intestine into the blood stream and carried around the body to be used for respiration and growth (amino acids are used to build proteins and tissues)
Describe 3 features of alveoli that help maximise gas exchange
Alveoli have large surface area Alveoli have thin walls that are one cell thick Alveoli have a good blood supply with many capillaries
Explain how a reduced amount of oxygen entering the blood will affect the human body
Less oxygen entering the blood causes less aerobic respiration Less energy is released This results in less muscle contraction and person becomes more out of breath
What is a dependent variable
This is what you measure in the experiment
What is an independent variable
This is what you change in the experiment (its the thing you change to see its effect on another variable)
What is control variable
something you keep the same in the experiment so it doesn’t affect your results
Why is a control variable important?
it makes the experiment a fair test. Ensures a fair test → Only the independent variable changes, while everything else stays the same Makes results valid → You know the outcome is caused by what you changed, not something else [ Improves reliability → Results are more consistent and can be repeated
Why does bread taste sweet in the mouth?
Bread contains starch Amylase in saliva breaks down starch to sugar Sugar tastes sweet
The leaf tissue that contains the most chloroplasts is the
Palisade mesophyll
The leaf tissue that contains many air spaces is the
Spongy mesophyll
The plant tissue that can differentiate throughout the life of the plant is
Meristem
Xylem tissue transports water through the plant. The walls of the xylem cells contain cellulose. Name the other substance that strengthens xylem tissue
Lignin
Phloem tissue transports dissolved sugars around a plant. Name the process that transports dissolved sugars around a plant.
Translocation
The phloem tissue transports sugars to other parts of the plant. The concentration of dissolved sugars in the phloem cell in Figure 3 is higher than in cell Y Explain how sub-cellular structures help to move dissolved sugars from cell Y into the phloem cell
Cells contain mitochondria which carry out aerobic respiration Respiration releases energy which is needed for active transport Active transport moves dissolved sugars against the concentration gradient into the phloem
New phloem cells form when unspecialised plant cells differentiate and become specialised. Describe one change in structure that occurs when an unspecialised cell differentiates to form a phloem cell
Cell loses its nucleus Loss of cytoplasm loss of mitochondria
A student investigated the effect of concentration of salt solution on the mass of uncooked potato pieces Plan a method that could be used to obtain results
Cut potato chips into same sizes Measure and record the mass of potato pieces Place potato pieces into different concs of salt solution Use at least 3 different concs Leave potato pieces in the solutons for the same amount of time Remove the pieces and blot dry Measure the final mass and calculate the percentage change in mass Repeat each conc at least 3 times calculate mean percentage change in mass
What is a partially permeable membrane
Where in a plant are stem cells found?
Stem cells are found in meristems such as the tips of roots and shoots
Describe what happens in each of the three stages of the cell cycle in mitosis.
Stage 1: Cell grows and increases number of sub-cellular structures DNA replicates to form 2 copies of each chromosome Chromosomes line up in middle of cell (Metaphase) Stage 2: Mitosis occurs Chromosomes separate to opposite ends of the cell. Nucleus divides Stage 3: Cytoplasm and cell membrane divide to form 2genetically identical cells (cytokinesis)
What is mitosis used for ?
Growth (increasing number of cells) Repair and replacement (replaces damaged or worn out cells e.g skin, blood cells) Asexual reproduction (identical offspring are produced)
Figure 2 shows how embryonic stem cells are produced in therapeutic cloning for use in patients. Give two advantages and two disadvantages of therapeutic cloning in medical treatments.
Advantage: Stem cells can differentiate into many different types of cells Advantage: They could be used to replace damaged tissues and treat diseases Disadvantage: Potential life is destroyed (as involves using and destroying embryos) Disadvantage: There could be a shortage of donors