B2

Question 1

What are the features of a palisade mesophyll cell that make it optimal for photosynthesis?

Answer 1

1. Cells are elongated and cylindrical with many closely packed together to increase surface area to absorb as much light as possible.
2. Contains many chloroplasts, which contains chlorophyll, to trap/absorb sunlight energy.
3. Chloroplasts are moved by the cytoskeleton (proteins which can attach onto organelles and support the cell) upwards to absorb more sunlight OR downwards to prevent damage from too intense light.
4. A large permanent vacuole pushes chloroplasts to the outer edges of the cell. This increases the light energy they absorb and reduces the diffusion distance for CO2 into the chloroplast.
5. A large permanent vacuole also makes the cell turgid, stores water and dissolved substances from photosynthesis.
6. Thin and transparent cellulose cell walls so easy gas diffusion. This also allows light energy, needed for photosynthesis, to penetrate.
7. The plasma membrane is selectively permeable, it allows diffusion of CO2 and H2O (reactants) into the cell and allows O2 and glucose out of the cell (products).

Question 2

What is the importance of the chloroplasts inside a palisade cell?

Answer 2

1. Chloroplasts contain chlorophyll.
2. Chlorophyll traps light energy.
3. They are the site of the chemical reaction, photosynthesis.
4. Sunlight is converted into chemical energy as CO2 is converted to glucose
   (see equation above).
5. Glucose is then available for respiration.
6. Can also result in the production of starch/sucrose/ lipids/amino acids/DNA/cellulose/vitamins which enables cellular growth.

Question 3

Explain how the vacuole in a palisade mesophyll cell helps to increase the rate of photosynthesis.

Answer 3

1. Vacuole is large so takes up a lot of space
2. This pushes the chloroplasts to the edge of the cell
3. They therefore receive more light energy
4. There is also a shorter diffusion distance for diffusion

Question 4

What organelles in a palisade mesophyll cell give it a rigid structure?

Answer 4

Vacuole and cell wall

Question 5

What is labelled A in the diagram?

Answer 5

Head

Question 6

What is labelled B in the diagram?

Answer 6

Acrosome

Question 7

What is labelled C in the diagram?

Answer 7

Cell membrane

Question 8

What is labelled D in the diagram?

Answer 8

Nucleus

Question 9

What is labelled E in the diagram?

Answer 9

Mitochondria

Question 10

What is labelled F in the diagram?

Answer 10

Tail/Flagellum

Question 11

Why does a sperm cell contain many mitochondria?

Answer 11

Produce large amounts of ATP via aerobic respiration to provide energy for motility

Question 12

What does the acrosome contain in a sperm cell?

Answer 12

Digestive enzymes

Question 13

Why do sperm cells require enzymes?

Answer 13

To digest the zona pellucida of the egg cell

Question 14

What is labelled A in the diagram?

Answer 14

Corona radiata

Question 15

What is labelled B in the diagram?

Answer 15

Nucleus

Question 16

What is labelled C in the diagram?

Answer 16

Cytoplasm

Question 17

What is labelled D in the diagram?

Answer 17

Zona pelluccida

Question 18

Why is it important that the cytoplasm in an egg cell have a large volume?

Answer 18

contain lots of nutrients, lots of organelles and many mitochondria to supply large quantities of ATP for cell division, protein synthesis and DNA replication

Question 19

What is the function of the zona pellucida?

Answer 19

Act as a thick transparent protective layer around the egg cell

Question 20

What is the function of the corona radiata?

Answer 20

Supply protein to the fertilised egg

Question 21

What will a fertilised egg cell need to do to become an embryo?

Answer 21

Divide by mitosis

Question 22

What changes happen to the egg cell upon fertilisation?

Answer 22

1. The zona pellucida will harden becoming impermeable to any other sperm cells.
2. This prevents more than one sperm cell entering the egg cell (called polyspermy).

Question 23

Are gametes (sperm and egg cells) haploid or diploid?

Answer 23

Haploid

Question 24

Explain why root hair cells have long “hair like” projections.

Answer 24

Increase surface area to increase the rate of absorption of water and ions

Question 25

What is the function of the plasma membrane in a root hair cell?

Answer 25

contains specific carrier and channel proteins to allow ions to cross into the cytoplasm by diffusion or active transport

Question 26

What does active transport need to happen?

Answer 26

ATP made in aerobic respiration in the mitochondria

Question 27

Which organelle makes ATP?

Answer 27

Mitochondria

Question 28

What process makes ATP?

Answer 28

Respiration

Question 29

How is a root hair cell specialised to carry out a lot of active transport of mineral ions?

Answer 29

Contains many mitochondria

Question 30

How is the cell wall of the root hair cell specialised?

Answer 30

It is think allowing a short diffusion pathway increasing the rate of diffusion of ions and water

Question 31

Why does a root hair cell contain no chloroplasts?

Answer 31

More room for absorbed water and ions. Hidden from light so can't photosynthesise

Question 32

Name the cell pictured

Answer 32

Root hair cell

Question 33

Draw and label a root hair cell

Answer 33

Question 34

Give an example of a foreign particle that might be recognised by a white blood cell triggering an immune response.

Answer 34

Virus, bacteria, fungi, pollen, transplanted cell

Question 35

What are the two main types of lymphocyte?

Answer 35

T lymphocytes and B lymphocytes

Question 36

What does a B lymphocyte produce?

Answer 36

Antibodies that are specific to the pathogen which will lead to its destruction

Question 37

What happens to a B lymphocyte when it recognises a pathogen?

Answer 37

1. Divides by mitosis to make lots of identical cells 2. Some will become plasma cells 3. Plasma cells release lots of a specific antibody into the blood 4. Some cells become memory cells

Question 38

What do memory cells do?

Answer 38

Remain in the blood stream in case the same type of pathogen enters the body again to give a more rapid response to produce more antibodies faster

Question 39

How do vaccines work?

Answer 39

They contain part of a pathogen and encourage B lymphocytes to produce antibodies and memory cells

Question 40

What is the role of a helper T lymphocyte?

Answer 40

Send chemical signals to the B lymphocytes stimulating the B lymphocytes to divide by mitosis

Question 41

What type of white blood cell can directly destroy cancer cells or infected body cells?

Answer 41

T lymphocyte

Question 42

Describe the shape of the nucleus of a neutrophil

Answer 42

Lobed

Question 43

Why does a neutrophil have a lobed shaped nucleus?

Answer 43

It makes the neutrophil flexible so they can easily squeeze between the cells that make up the capillary wall to move to the site of infection

Question 44

Describe the importance of lysosomes in a neutrophil

Answer 44

1. Neutrophils contain many lysosomes. 2. Lysosomes fuse with engulfed pathogen (called the phagosome) to form a phagolysosme. 3. Lysosomes contain enzymes which destroy pathogens or foreign substances which have been engulfed by the neutrophil. 4. This process is called phagocytosis.

Question 45

What type of cell is pictured here?

Answer 45

Neutrophil

Question 46

What are the similarities between lymphocytes and neutrophils?

Answer 46

1. Both cells have nuclei/mitochondria/RER/ribosomes. 2. Both cells are made from stem cells that are in the bone marrow (of long bones). 3. Both are transported in blood plasma, migrate to tissue fluid and are present in the lymphatic system to provide defense against pathogens.

Question 47

What are the differences between lymphocytes and neutrophils?

Answer 47

1. There are 3x as many neutrophils as T and B lymphocytes combined. 2. T and B cells have a large nucleus and are smaller than neutrophils. 3. Neutrophils have a lobed nucleus which makes the cell flexible and able to squeeze through the capillary wall. Lymphocytes cannot do this and remain in the blood. 4. They have antigen receptors on its cell surface membrane which can bind to antigens on a pathogen whereas a neutrophil does not. 5. T and B cells are part of the adaptive and specific immune response whereas neutrophils are only involved in innate immunity. 6. T and B cells have immunological memory whereas neutrophils do not. 7. B cells produce antibodies and become memory cells (when stimulated by T helper cells) whereas neutrophils only involved in phagocytosis. 8. Neutrophils contain many lysosomes for phagocytosis whereas lymphocytes have less lysosomes. 9. Cytotoxic T cells destroy virally infected and cancerous cells whereas neutrophils do not.

Question 48

What is the role of the red blood cell?

Answer 48

To carry oxygen from the lungs to the respiring tissues for aerobic respiration

Question 49

What molecule in a red blood cell binds to oxygen?

Answer 49

Haemoglobin

Question 50

What type of cell has no organelles?

Answer 50

Red blood cell

Question 51

Why does a red blood cell contain no organelles?

Answer 51

Increase space for haemoglobin to give more efficient transport of oxygen and carbon dioxide

Question 52

What shape are red blood cells?

Answer 52

Biconcave

Question 53

Why are red blood cells small?

Answer 53

To squeeze through capillaries

Question 54

Explain why red blood cells have a biconcave shape?

Answer 54

Increase surface area to volume ratio so that: 1. Haemoglobin molecules are close to the cell membrane 2. short diffusion distance of oxygen to haemoglobin 3. Increase rage of diffusion across plasma membrane

Question 55

What feature of red blood cells makes them flexible?

Answer 55

Biconcave shape