cells

Question 1

What is the function of the Ribsosomes

Answer 1

Site of Protein synthesis;

Question 2

What is the function of the Nucleus

Answer 2

Contains genetic material / DNA;
Controls cell activity;

Question 3

What is the function of the Mitochondria

Answer 3

Site of aerobic respiration;
ATP production;

Question 4

What is the function of the Smooth Endoplasmic Reticulum

Answer 4

Encrusted in Ribosomes;
Site of protein synthesis;
Transports and stores protein within the cell

Question 5

What is the function of Golgi Apparatus

Answer 5

Modifies/packages/sorts proteins;
Produces vesicles;

Question 6

What is the function of Lysosomes

Answer 6

Contains digestive enzymes;
Digests worn out organelles/autolysis;

Question 7

What is the function of Cell surface membrane

Answer 7

Made of a Phospholipid Bi-layer;
Controls what enters the cell/ is selectively permeable;
Can be folded to increase SA;

Question 8

What is the function of Chloroplasts

Answer 8

Contain thylakoids, stacked into Granum;
Site of photosynthesis;

Question 9

What is the function of Capsule

Answer 9

Protects cell from immune systems;
Aids bacteria sticking together;

Question 10

What is the function of Plasmid

Answer 10

Circular DNA;
Contains antibiotic resistance genes;

Question 11

What is the function of Cell Wall

Answer 11

Provides rigid shape / structure;
Stops osmotic lysis;

Question 12

What is the function of Flagellum

Answer 12

Allows movement/propulsion;

Question 13

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

Answer 13

. DNA in nucleus is code (for protein);
2. Ribosomes/rough endoplasmic reticulum produce (protein);
3. Mitochondria produce ATP (for protein synthesis);
4 Golgi apparatus package/modify; OR Carbohydrate added/glycoprotein produced by Golgi apparatus;
5 Vesicles transport OR Rough endoplasmic reticulum transports;
6. (Vesicles) fuse with cell(-surface) membrane;

Question 14

Describe the differences between Eukaryotic and Prokaryotic cells

Answer 14

Comparisons
1. Nucleotide structure is identical;
2. Nucleotides joined by phosphodiester bond;
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone);
3. DNA in mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes;
Contrasts
4. Eukaryotic DNA is longer;
5. Eukaryotic DNA contain introns, prokaryotic DNA does not;
6. Eukaryotic DNA is linear, prokaryotic DNA is circular;
7. Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not;

Question 15

State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell.

Answer 15

Plant v prokaryote
1. (Associated with) histones/proteins v no histones/proteins;
2. Linear v circular;
3. No plasmids v plasmids;
4. Introns v no introns;
5. Long(er) v short(er);

Question 16

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

Answer 16

1. Cholera bacterium is prokaryote;
2. Does not have a nucleus/nuclear envelope/ has DNA free in cytoplasm/has loop of DNA;

3 and 4 Any two from: [No membrane-bound organelles/no mitochondria / no golgi/no endoplasmic reticulum];
5 Small ribosomes only;
6 and 7 Any two from [Capsule/flagellum/plasmid / cell wall]

Question 17

Give one advantage of using a TEM rather than a SEM.

Answer 17

1. Higher resolution;
2. higher (maximum) magnification / higher detail (of image);
   OR
3. Allows internal details / structures within (cells) to be seen / cross section to be taken;

Question 18

Give one advantage of using a SEM rather than a TEM.

Answer 18

Thin sections do not need to be prepared / shows surface of specimen / can have 3-D images;

Question 19

Scientists use optical microscopes and transmission electron microscopes to investigate cell structure. Explain the advantages and limitations of using a TEM to investigate cell structure.

Answer 19

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 Must cut section / thin specimen;
7 Preparation may create artefact;

Question 20

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

Answer 20

a) Prevents osmosis / no (net) movement of water So organelle/named organelle does not burst/shrivel;
b) Reduce/prevent enzyme activity so organelles are not digested / damaged;
c) Maintain a constant pH so proteins do not denature;

Question 21

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

Answer 21

1. Cell homogenisation to break open cells and release organelles;
2. Filter to remove (large) debris/whole cells;
3. Use isotonic solution to prevent osmotic damage to mitochondria / organelles;
4. Keep cold to prevent/reduce damage to organelles by enzyme;
5. Use buffer to maintain pH and prevent protein/enzyme denaturation;
6. Use differential Centrifuge (at high speed/1000 g) to separate nuclei / cell fragments / heavy organelles;
7. Re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom;
8. Observe pellet with a microscope to identify mitochondria;

Question 22

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

Answer 22

1. Glycerol joined to two fatty acid tails Phosphate group joined to glycerol on opposite side. (joined by condensation reaction with ester bond).;
2. Phospholipid has hydrophilic head (phosphate and glycerol) and hydrophobic tails (fatty acid chains)
3. Arrange to form a phospholipid bilayer; (Hydrophilic head facing out. Hydrophobic fatty acid chains facing in)