Unit 2

Question 1

Describe how antibodies are produced in the body following a viral infection (6)

Answer 1

• Virus contains antigen
• Virus is engulfed by macrophage
• presents antigen to B-cell
• B-cell divides by mitosis
• Plasma cells produce antibodies
• Specific to antigen

Question 2

Describe how HIV is replicated after it has entered a human cell (4)

Answer 2

• Reverse Transcriptase uses HIV RNA to make DNA copy
• DNA used to make HIV RNA copies
• and HIV proteins made at host ribosomes
• Budding off from membrane of host cell

Question 3

What is a vaccine? (1)

Answer 3

A small dosage of antigens to stimulate production of antibodies

Question 4

Give two ways in which pathogens can cause disease when they enter the body of their host (2)

Answer 4

• Damage cells/tissues

- Produce toxins

Question 5

Phagocytes and Lysosomes are involved in destroying microorganisms. Describe how (3)

Answer 5

• Phagocytes engulf pathogens
• enclosed in a vaccine
• lysosomes have enzymes
• that digest molecules

Question 6

Describe how B-lymphocytes respond when they are stimulated by antigens (4)

Answer 6

• Divide by mitosis
• to produce plasma cells
• plasma cells produce antibodies
• and memory cells

Question 7

Describe the role of macrophages in stimulating B-lymphocytes (1)

Answer 7

• The antigen in membrane is presented to lymphocytes

Question 8

The destruction of T-cells by HIV leads to the death of an infected person. Explain how (2)

Answer 8

• Not enough T-cells to produce antibodies

- Person cannot fight infections

Question 9

Give two factors other than cost that should be considered when selecting an antibiotic to treat a bacterial disease (2)

Answer 9

• Side effects

- How much resistance the bacteria have built up

Question 10

Name the process by which bacterial cells divide (1)

Answer 10

Binary fission

Question 11

Describe how the Golgi apparatus is involved in the secretion of enzymes (1)

Answer 11

The golgi apparatus modifies the protein

Question 12

Describe how the RER is involved in the production of enzymes (2)

Answer 12

• RER has ribosomes to make proteins (like an enzyme)

Question 13

Describe how you could use cell fractionation to isolate chloroplasts from the leaf tissue (3)

Answer 13

• Homogenisation by grinding up the cells in a blender in a cold, isotonic, buffered solution
• Remove debris by filtration
• 2nd pellet formed from ultracentrifugation (has the chloroplast)

Question 14

Name the structures in a eukaryotic cell that cannot be identified using an optical microscope (2)

Answer 14

• mitochondria
• ribosome
• E.R.
• lysosome

Question 15

Describe how phospholipids are arranged in a plasma membrane (2)

Answer 15

• Phospholipids are arranged in a bilayer
• Hydrophobic tails face inside
• Hydrophilic head faces outside

Question 16

Explain why a person with mitochondrial disease can only exercise for a short time (2)

Answer 16

• They cannot produce much ATP if they have damaged mitochondria
• The ATP is needed for muscle contraction

Question 17

Explain why a transmission electron microscope was used to produce the image in the figure above (2)

Answer 17

• High resolution

- Can see the internal structure of organelles

Question 18

In coaliac disease, microvilli in epithelial cells are damaged. Explain why people with coaliac disease have low concentrations of amino acids in their blood (2)

Answer 18

• Damaged microvilli means they have less surface area of absorption
• due to less protein channels
• less amino acids are absorbed

Question 19

Name the type of bond that joins amino acids together in a polypeptide (1)

Answer 19

Peptide

Question 20

Describe the function of a chloroplast (2)

Answer 20

• The site of aerobic respiration

- Release ATP for active transport

Question 21

Why can electron microscopes produce an image with higher resolution than optical microscopes? (1)

Answer 21

• Electrons have shorter wavelengths than light

Question 22

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical microscope (4)

Answer 22

• Add a drop of water to the slide
• Obtain a thin section of plant tissue and place on the slide
• stain with iodine in potassium iodide
• Lower coverslip using a mounted needle

Question 23

Explain why it is important that the plant tissue was thin (or 1-cell thick) (1)

Answer 23

To allow light to pass through so it can be seen by an optical microscope

Question 24

What do both Eukaryotic and Prokaryotic cells have?

Answer 24

• Plasma membrane
• Cytoplasm
• Ribsomes
• DNA and RNA

Question 25

What do Eukaryotic cells have that Prokaryotic cells don’t?

Answer 25

• Nucleus
• Mitochondria
• ER
• Golgi Body

Question 26

What do Prokaryotic cells have that Eukaryotic cells don’t?

Answer 26

• Plasmids
• Flagella
• Protective waxy cuticle

Question 27

How do Eukaryotic cells divide?

Answer 27

Mitosis

Question 28

What is a virus?

Answer 28

Acellular, non-living particles

Question 29

What do viruses contain?

Answer 29

• Nucleic acids (DNA/RNA)
• Capsid (protein coat)
• (don’t have cytoplasm, nucleus, membrane-bound organelles, plasma membrane)