Molecular Biology

Question 1

What is anabolism?

Answer 1

Synthesis of complex molecules from simpler molecules. Anabolic reactions are condensation reactions.

Question 2

What is catabolism?

Answer 2

Breakdown of complex molecules into simpler molecules Reactions include hydrolysis if macromolecules into monomers.

Question 3

Water molecules have a special charge distribution giving them what property?

Answer 3

Dipolarity

Question 4

Ionic compounds are hydrophobic / hydrophilic?

Answer 4

Hydrophilic, because they are attracted more strongly to the different poles of the water molecules.

Question 5

What is the importance of adhesion in water?

Answer 5

Adhesive forces between water molecules and cellulose in cell walls of plant leaves helps pull water out of xylem vessels when water evaporates from cell walls. Keeps cell walls moist and allows cells (spongy mesophyll) to act as a surface of gas exchange

Question 6

What is hydrolysis?

Answer 6

It is the splitting of water into its ionic components. Hydrolysis reactions are usually carried out to break down larger polymers into monomers.

Question 7

What is the monomer for cellulose?

Answer 7

Beta D Glucose. The linkage is called a 1-4 glycosidic link where carbon C1 binds to C4 in a condensation reaction to produce after. The orientations of the glucose units alternate, making a straight polymer chain.

Question 8

What is the monomer of starch? What kind of structure does it have?

Answer 8

Alfa D glucose which does not alternate and so has a helical shape, There are two types of starch. 1. Amylose: Only 1-4 glycosidic linkages, unbranched. 2. Amylopectin: Also has 1-6 linkages so is branched.

Question 9

What is the monomer of glycogen? How does its structure compare to that of starch?

Answer 9

It’s monomer is Alfa D glucose like starch. The only difference is that it is more branched (more 1-6 links than in amylopectin)

Question 10

What is the advantage of starch and glycogen being insoluble?

Answer 10

They do not greatly affect the osmoregularity of the cell environment. Excessive glucose storage on the other an and can lead to the risk of the cell bursting.

Question 11

Why don’t hydrogen bonds form between glycogen strands?

Answer 11

Because they are helical, they can not be aligned in a parallel array.

Question 12

Deacribe the three types of lipids.

Answer 12

1. Triglycerides: 3 fatty acids + 1 glycerol 2. Phospholipids: Amphipathic. 2 fatty acids + 1 glycerol 3. Steroids: molecule consists of four fused rings (ex: hormones)

Question 13

Besides energy per gram, what advantage do lipids have over carbohydrates as a means of energy storage?

Answer 13

Mass advantage of lipids is greater. Fats form pure droplets in cells, with no water associated, whereas each gram of glycogen is associated with about two grams of water. Important because carrying more a massive energy storage adds to the body weight, and carrying around this weight also requires energy.

Question 14

Exception to the saturated fatty acids and CHD correlation?

Answer 14

Maasai Tribe in Kenya.

Question 15

Example of a function of proteins as a pigment?

Answer 15

Rhodopsin: pigment in retina making rod cells light sensitive. It had a non amino acid component called retinal which absorbs photon and sends nerve impulse via optic nerve.

Question 16

Example of a function of proteins as an antibody?

Answer 16

Immunoglobulins are antibodies that bind to antigen or pathogens. Have specific binding sites giving specific immunity.

Question 17

Example of a function of proteins as a hormone?

Answer 17

Insulin binds specifically and reversible to insulin receptors on membranes of body cells.

Question 18

Example of a function of proteins as a structural protein?

Answer 18

Collagen has three polypeptides wound together to form a rope like conformation and is used to prevent tearing of skin, in tendons and ligaments for tensile strength.

Question 19

Why does catalysis only occur if the substrate and enzymes are in a liquid medium?

Answer 19

Liquid mediums allow the molecules to more about randomly making collisions between active site and substrate possible.

Question 20

Advantage of enzyme immobilization? (5 points)

Answer 20

1. Enzyme conc. can be higher 2. Products aren’t contaminated with enzyme 3. Enzyme can be reused to save money 4. Resistant to denaturation over wider temps + pH 5. Catalysis can be controlled by adding / removing enzyme from rxn mixture.

Question 21

What are three ways by which enzymes are immobilized? (3 points)

Answer 21

1. Attach to surfaces (glass) [adsorption] 2. Entrapment in membrane or gel 3. Aggregation by bonding enzymes together into particles.

Question 22

Advantages of lactose free milk (4 points)

Answer 22

1. Not a problem for lactose intolerant to drink milk 2. Galactose and glucose are sweeter. Less sugar is required to make sweet. 3. Lactose tends to crystallize during ice cream production causing gritty texture. Glucose and galactose are more soluble, so they remain dissolved and a smoother texture ice cream produced. 4. Bacteria ferment glucose + galactose faster so yoghurt or cottage cheese production is faster.

Question 23

What kind of sugar do DNA molecules have?

Answer 23

Pentose sugar

Question 24

What were the two alternative theories that were rejected in place of the semi conservative replication mechanism of DNA?

Answer 24

1. Conservative replication : Bith parent strands remain together, two new strands are made together. 2. Dispersive replication: Every molecule produced by replication is a mix of old + new sections.

Question 25

Strong evidence for the semi conservative nature of DNA replication was published by which two scientists?

Answer 25

Meselson and Stahl.

Question 26

How does transcription begin? (2 points)

Answer 26

Enzyme RNA polymerase binds to promoter sequence on the DNA strand. The RNA polymerase then helps unwind the DNA strand by breaking hydrogen bonds.

Question 27

In genetic modification, E.coli bacteria can produce identical insulin that humans produce because?

Answer 27

The genetic code is universal

Question 28

What is PCR? (5 points)

Answer 28

1. Stands for Polymerase Chain Reaction. Is used to artificially replicate DNA. 2. It involves high temperature heating (95 ̊C) for short period of time (15 seconds) to separate the strands of the sample DNA as H bonds are broken. 3. Followed by the use of Taq DNA polymerase, which can withstand high temperatures. 4. The sample is heated to 72 ̊C, the ideal temperature for the enzyme to work. Enzyme replicates at about 1000 nucleotides per minute. 5. Large amounts of DNA can be synthesized in short spans of time.

Question 29

Define cell respiration.

Answer 29

Controlled release of energy from organic compounds to produce usable cellular energy in the form of ATP.

Question 30

What are two advantages of ATP production.

Answer 30

1. It is a molecule that can releases its energy very quickly 2. It can diffuse to any part of the body cells.

Question 31

What are the advantages and disadvantages of anaerobic respiration? (4 points, 2 each)

Answer 31

Advs: 1. It can supply ATP at an kverall faster rate than aerobic, becomes it is not limited by the rate at which oxygen is being supplied. 2. It maximizes the power of muscle contractions Disadvs: 3. Lactic acid and hydrogen ions are produced during this process 4. This it can only go on for about two minutes before the blood oH drops too low and intense exercise must be stopped.

Question 32

What are respirometers and what are some of the usual components of such setups?

Answer 32

Respirometers are devices used to measure the rate of respiration. They usually have: 1. A sealed air tight container with the specimen inside. 2. An alkali such as potassium hydroxide to absorb CO2. This way as oxygen is used up, the volume of air in the container reduces. 3. A capillary tube with fluid connected to the container allowing volume of air inside to be monitored.

Question 33

For experiments involving animal testing, under what ethical circumstances must an experiment not be done? (4 points)

Answer 33

An experiment must not be done if: 1. The animal will suffer pain 2. There is an unacceptable risk of the animal getting hurt 3. If an alternative can be used (ex: plant or seed) 4. If the animal can not return to its natural habitat once the experiment is complete.

Question 34

How did photosynthesis affect the oceans during pe historic earth?

Answer 34

Bacteria began to photo synthesize nearly 2 billion years ago. The O2 content of the atmosphere rose to around 2%. This caused dissolved iron in the oceans to to precipitate as iron oxide, which sank to the sea bed and formed rich deposits called banded iron formations.

Question 35

The absorption spectrum of chlorophyll peaks at which two colours?

Answer 35

Blue and red.

Question 36

What is the action spectrum of photosynthesis? Which two colours peak? Which peak is smaller?

Answer 36

It is a graph that shows the percentage of light (of a particular wavelength) used in photosynthesis. It peKs at blue and red. Red had a smaller peak.

Question 37

What was the theory of vitalism?

Answer 37

Theory that all living organisms were composed of organic materials which could only be produced in living organisms due to a ‘vital force’ Was falsified when urea was synthesized artificially a long with a number of other contradictory evidences

Question 38

Why do the mitochondria in the given picture look different?

Answer 38

They are in different planes (3D)