PROGRESS TEST

Question 1

How can you tell if a cell is undergoing mitosis when observing it under a microscope?

Answer 1

Chromosomes are condensed and therefore visible
Double the amount of DNA

Question 2

Contrast how an optical microscope and a
transmission electron microscope work
and contrast the limitations of their use when studying cells.

Answer 2

1. TEM use electrons and optical use light;
2. TEM allows a greater resolution;
3. So with TEM smaller organelles can be seen and in greater detail
4. TEM view only dead specimens and optical can view live specimens;
5. TEM does not show colour and optical can;
6. TEM requires thinner specimens;
7. TEM requires a more complex and time consuming preparation;
8. TEM focuses using magnets and optical uses (glass) lenses;

Question 3

Define the mitotic index.

Answer 3

The ratio of the number of cells undergoing mitosis to the total number of cells in a specimen

Question 4

Name the stages of mitosis in order

Answer 4

Prophase
Metaphase
Anaphase
Telophase

Question 5

Why does glycogen need to be more highly branched than starch?

Answer 5

• Animals are more active than plants
• higher respiratory rate
• need to access glucose more rapidly, so more branches means more glucose can by hydrolysed at once.

Question 6

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

Answer 6

1. Cell homogenisation to break open cells
2. Filter to remove large debris;
3. Use isotonic solution to prevent damage to organelles;
4. Keep cold to reduce damage by enzymes /
5. Use buffer to prevent protein / enzyme denaturation;
6. Centrifuge at lower speed to separate heavy organelles;
7. Re-spin supernatant at higher speed to get organelle at bottom

Question 7

What is the name of the reaction that breaks bonds between monomers?

Answer 7

Hydrolysis

Question 8

What do we call a molecule that consists of many monosaccharides bonded together?

Answer 8

Polysaccharide.

Question 9

Draw the structure of alpha and beta glucose.

Answer 9

alpha - hydogen at top
beta - hydrogen at bottom

Question 10

What type of bond joins the components of a triglyceride?

Answer 10

Ester bonds

Question 11

Compare and contrast the structure and properties of triglycerides and phospholipids

Answer 11

BOTH
1. contain ester bonds between glycerol and fatty acid;

2. contain glycerol;
3. have saturated or unsaturated Fatty acids ;
4. insoluble in water;
5. contain C, H and O but phospholipids also contain P;

DIFF
6. Triglyceride has three fatty acids and phospholipid has two fatty acids plus phosphate group;

7. Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;
8. Phospholipids form monolayer in water but triglycerides don’t;

Question 12

Give the equation for calculating magnification from size of object and image.

Answer 12

Magnification = Size of image / Size of Object

Question 13

What does secondary structure mean?

Answer 13

• Folding, due to hydrogen bonds, of the polypeptide chain into alpha helix or beta pleated sheet.

Question 14

What does the RER do?

Answer 14

Synthesises proteins

Question 15

What does the SER do?

Answer 15

Synthesises lipids

Question 16

Describe the DNA in a prokaryote

Answer 16

• Short
• Circular not linear
• Plasmids
• Not associated with histones
• no introns

Question 17

Contrast the structure of a bacterial cell and the structure of a human cell.

Answer 17

1. Bacterial cell is much smaller than a human cell;
2. Bacterial cell has a cell wall but human cell does not;
3. Bacterial cell lacks a nucleus but human cell has a nucleus;
4. Bacterial cell lacks membrane-bound organelles but human cell has membrane-bound organelles;
5. Bacterial ribosomes smaller than human ribosomes
6. Bacterial DNA is circular but human DNA is linear;
7. Bacterial DNA is ‘naked’ whereas human DNA is bound to histones / proteins

Question 18

What does the golgi body do?

Answer 18

• Modifies proteins (eg forms glycoproteins)
• forms vesicles to transport modified proteins to cell membrane

Question 19

What organelle is used by phagocytes to digest pathogens?

Answer 19

lysosomes

Question 20

What type of biological molecule are triglycerides?

Answer 20

lipids

Question 21

What organelles are in the first two pellets when centrifuging cell organelles?

Answer 21

nucleus then mitochondria

Question 22

Describe the structure of proteins.

Answer 22

1. Polymer of amino acids;
2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding in alpha helix and or beta pleated sheets of polypeptide chain due to hydrogen bonding;
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
7. Quaternary structure is two or more polypeptide chains.

Question 23

What would you call many amino acids bonded together?

Answer 23

Polypeptide

Question 24

Draw a sketch of the structure of an amino acid

Question 25

Explain why an enzyme can only catalyse one particular reaction.

Answer 25

Each enzyme has a unique tertiary structure Active site complimentary to one substrate

Question 26

What type of carbohydrate are glucose, galactose and fructose?

Answer 26

Monosaccharides

Question 27

a. What monomers make up sucrose

Answer 27

glucose and fructose

Question 28

b. What monomers make up lactose

Answer 28

glucose and galactose

Question 29

c. What monomers make up maltose

Answer 29

glucose and glucose

Question 30

What type of bond joins the monomers on carbohydrates?

Answer 30

Glycosidic bonds.

Question 31

What is the difference between a triglyceride and a phospholipid?

Answer 31

Triglyceride is made of glycerol attached to 3 fatty acids In phospholipids one of the fatty acids is substituted by a phosphate group

Question 32

What is the name of the reaction that joins two monomers together?

Answer 32

Condensation

Question 33

Explain six properties that make water important for organisms.

Answer 33

1. A metabolite in photosynthesis/respiration; 2. A solvent so allowing transport of substances; 3. High heat capacity so buffers changes in temperature; 4. Large latent heat of vaporisation so provides a cooling effect (through evaporation); 5. Cohesion (between water molecules) so supports columns of water (in plants); 6. Cohesion (between water molecules) so produces surface tension supporting (small) organisms;

Question 34

Describe how the structures of starch and cellulose molecules are related to their functions

Answer 34

**Starch** 1. Helical/ spiral shape so compact; 2. Large and insoluble so osmotically inactive; 3. Branched so glucose is easily released for respiration; 4. Large molecule so cannot leave cell **Cellulose** 5. Long, straight, unbranched chains of β glucose; 6. Joined by hydrogen bonding; 7. 7. To form microfibrils; 8. 8. Provides rigidity and strength;

Question 35

What is the role of DNA helicase and DNA polymerase?

Answer 35

DNA helicase breaks hydrogen bonds DNA polymerase joins adjacent nucleotides together

Question 36

Explain what a non-competitive inhibitor does?

Answer 36

- Not a similar shape to active site - attaches allosteric site of enzyme - causes active site to change - fewer ES complexes formed.