Studying Cells

Question 1

What is the function of the nucleus? (2)

Answer 1

1. Contains genetic material/DNA
2. Controls cell activity

Question 2

What is the function of the mitochondria? (2)

Answer 2

1. Site of aerobic respiration
2. ATP production

Question 3

What is the function of the rough endoplasmic reticulum? (3)

Answer 3

1. Encrusted in ribosomes
2. Site of protein synthesis
3. Transports and stores proteins within the cell

Question 4

What is the function of the smooth endoplasmic reticulum? (1)

Answer 4

1. Site of lipid synthesis

Question 5

What is the function of the ribosomes? (1)

Answer 5

1. Site of protein synthesis

Question 6

What is the function of the golgi apparatus? (2)

Answer 6

1. Sorts, modifies and packages proteins and triglycerides
2. Produces vesicles

Question 7

What is the function of lysosomes? (2)

Answer 7

1. Contains digestive enzymes
2. Digests worn out organelles

Question 8

What is the function of the cell surface membrane? (3)

Answer 8

1. Made of a phospholipid bilayer
2. Controls what enters and leaves the cell / selectively permeable
3. Can be folded to increase surface area

Question 9

What is the function of chloroplasts? (2)

Answer 9

1. Contains thylakoids, stacked into granum
2. Site of photosynthesis

Question 10

What is the cell wall in algae and plants made from?

Answer 10

Cellulose

Question 11

What is the cell wall in bacteria made from?

Answer 11

Murein / Peptidoglycan

Question 12

What is the cell wall in Fungi made from?

Answer 12

Chitin

Question 13

What is the function of a capsule? (2)

Answer 13

1. Protects cell from immune systems
2. Aids bacteria sticking together

Question 14

What is the function of plasmid? (2)

Answer 14

1. Circular DNA
2. Contains antibiotic resistance genes

Question 15

What is the function of the cell wall? (2)

Answer 15

1. Provides rigid shape / structure
2. Stops osmotic lysis

Question 16

What is the function of flagellum? (1)

Answer 16

1. Allows movement

Question 17

Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells. (5)

Answer 17

1. DNA in nucleus is code (for protein)
2. Ribosomes / RER produce protein
3. Mitochondria produce ATP (for protein synthesis)
4. Golgi body sorts, packages and modifies protein into vesicles
5. Vesicles transport protein
6. Vesicles fuse with cell membrane

Question 18

Compare and contrast eukaryotic and prokaryotic cells (5)

Answer 18

COMPARISONS
1. Nucleotide structure is identical
2. Nucleotides joined by phosphodiester bonds
3. DNA in mitochondria is similar to DNA in prokaryotes
CONTRASTS
4. Eukaryotic DNA is longer whereas prokaryotic DNA is shorter
5. Eukaryotic DNA contains introns whereas prokaryotic DNA does not contain introns
6. Eukaryotic DNA is linear whereas prokaryotic DNA is circular
7. Eukaryotic DNA is associated with histones whereas prokaryotic DNA is not associated with histones

Question 19

State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell (3)

Answer 19

Plant Vs Prokaryote
1. Associated with histones vs not associated with histones
2. Linear vs circular
3. No plasmids vs plasmids
4. Introns vs no introns
5. LongER vs shortER

Question 20

The structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine. Describe how the structure of a cholera bacterium is different. (4)

Answer 20

1. Cholera bacterium is prokaryote
2. Does not have a nucleus
   3 and 4. any two from: no membrane-bound organelles/ no mitochondria/ no golgi/ no no endoplasmic reticulum
3. Small/ 70s ribosomes
   6 and 7. any two from: capsule/ flagellum/ plasmid/ cell wall

Question 21

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

Answer 21

1. Mitochondrion
2. Ribosome
3. Endoplasmic reticulum
4. Lysosome
5. Cell - surface membrane

Question 22

Describe how the student could have used an eyepiece graticule to determine the mean diameter of stomata (3)

Answer 22

1. Measure each stomata using an eye piece graticule
2. Calibrate the eyepiece graticule against a stage micrometre
3. Take at least 5 measurements and calculate a mean

Question 23

Give one advantage of using a TEM rather than a SEM. (1)

Answer 23

1. Higher resolution
2. Higher magnification
   OR
3. Allows internal details to be seen

Question 24

Give one advantage of using a SEM rather than a TEM. (1)

Answer 24

1. Thin sections don’t need to be prepared
2. Can have 3D images

Question 25

Explain the advantages and limitations of using a TEM to investigate cell structure. (5)

Answer 25

ADVANTAGES 1. Small objects can be seen 2. TEM has high resolution 3. Electron wavelength is shorter LIMITATIONS 4. Cannot look at living cells 5. Must be in a vacuum 6. Thin specimen required 7. Preparation may create artefacts

Question 26

Name 2 structures found within a eukaryotic cell that can be identified using a transmission electron microscope (2)

Answer 26

1. Mitochondrion 2. Ribosome 3. Endoplasmic Reticulum 4. Lysosome 5. Cell - surface membrane

Question 27

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

Answer 27

1. Add a drop of water to the microscope slide 2. Get a thin section of plant tissue and float on the drop of water 3. Stain with KI solution 4. Lower the cover slip using a mounted needle to avoid air bubbles

Question 28

Scientists isolated mitochondria from liver cells. They broke the cells open in an ice-cold, buffered, isotonic solution. Explain the solution was a) isotonic b) ice cold c) buffered

Answer 28

a) prevents osmosis so organelle doesn't burst/shrivel b) reduce enzyme activity so organelles are not digested c) maintain a constant pH so proteins don't denature

Question 29

Describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells. (5)

Answer 29

1. Cell homogenisation to break open cell and release organelles 2. Filter to remove debris 3. Use isotonic solution to prevent osmotic damage 4. Keep cold to reduce enzyme activity 5. Use buffer to maintain pH and prevent protein denaturation 6. Use centrifuge and spin at high speed to separate nuclei and heavy organelles 7. Re-spin at highER speed to get mitochondria in pellet 8. Observe pellet with microscope to identify mitochondria

Question 30

Describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane. (3)

Answer 30

1. Glycerol joined to two fatty acid tails and phosphate group joined to glycerol on opposite side 2. Phospholipid has hydrophilic head and hydrophobic fatty acid tails 3. Arrange to form a phospholipid bilayer