Biology 6-10

Question 1

Describe the process of genetic modification/engineering.(5)

Answer 1

1. Scientists identify a gene which makes an organism resistant to herbicides.
2. They remove it from the DNA of the organism by snipping it out using ‘restriction enzymes’.
3. A loop of bacterial DNA called plasmid is then prepared for the gene to be inserted. Restriction enzymes cut out the plasmid.
4. Gene is inserted in plasmid - the ‘sticky ends’ of the plasmid allow Ligase to join the DNA strands together.
5. The plasmid is introduced into the DNA of the organism’s cells. (known as a vector because it carries a gene into another organism)

Question 2

Recall 3 examples of genetic modification.

Answer 2

1. Sheep have been genetically engineered to produce drugs in their milk to treat human diseases
2. GM crops are genetically modified to be resistant to viruses/insects
3. Bacteria have been genetically engineered to produce human insulin to treat people with diabetes

Question 3

What is an embryonic stem cell?

Answer 3

A cell that can give rise to any cell type (pluripotent)

Question 4

What is differentiation?

Answer 4

The process by which a cell changes to become specialised (for its job).

Question 5

When do cells lose the ability to differentiate?

Answer 5

When an animal matures

Question 6

Other than embryonic stem cells, what is the other type of stem cells? What makes them different from embryonic stem cells? Where are they found?

Answer 6

ADULT stem cells - in the bone marrow and can only turn into certain types.

Question 7

Describe the process of natural selection

Answer 7

1. Variation (genetically) within populations of organisms
2. Leads to differential survival
3. Those with better characteristics are best adapted to survive
4. These organisms can reproduce
5. So the genes/alleles/characteristics are passed down to the next generation

Question 8

What is a common example of evolution through natural selection?

Answer 8

Antibiotic resistance/ MRSA

Question 9

What are the two types of variation?

Answer 9

1. Genetic / Inherited

2. Environmental

Question 10

When can extinction occur?

Answer 10

When organisms cannot adapt quickly enough to the changing environment/competition.

Question 11

What are enzymes?

Answer 11

Biological catalysts

Question 12

What does ‘biological catalyst’ mean?

Answer 12

A substance that increases the rate of metabolic/biochemical reactions WITHOUT UNDERGOING ANY PERMANENT CHANGE ITSELF

Question 13

Describe the mechanism of enzyme action.

Answer 13

1. The enzyme has a specific indentation called the active site where only a specific substrate can attach.
2. When the substrate and the enzyme attach, enzymes split it up to form products.

(lock-and-key model)

Question 14

How does temperature affect the mechanism of enzyme action (3) ?

Answer 14

1. At a higher temperature, the K.E. of the substrate molecules increases so the chance that it hits an enzymes increases so rate-of-reaction increases
2. If it gets too hot, the bonds holding the enzyme will break
3. This means the active site’s shape will change so it cannot match the substrate’s shape - the enzyme is denatured (cannot function)

Question 15

What does a temperature/rate-of-reaction graph look like with enzymes?

Answer 15

Increases until it hits a peak (normally at 37 C - this is its optimum) then sharply decreases

Question 16

How does pH affect the mechanism of enzyme action?

Answer 16

1. High/low pH will affect the bonds holding the enzyme together
2. This changes the shape of the active site and denatures it

Question 17

What does a pH/rate-of-reaction graph look like with enzymes?

Answer 17

Increases (not starting from origin) until it hits a peak (normally 7) then decreases