Unit 1: Essay Questions

Question 1

Give an account of cell differentiation under the following headings:

(i) Stem Cells (4)
(ii) Somatic Cells (4)
(iii) Germline Cells (2)

Answer 1

(i) Stem Cells (4)
1- Differentiation occurs when unspecialised cells become specialised.
2- Stem cells are unspecialised cells that can (divide to) form more stem cells.
3- Embryonic stem cells can differentiate/develop into any/all cell types.
4- Tissue/adult stem cells give rise to a more limited range of/fewer cell types.
5-
6-

(ii) Somatic Cells (4)
7-
8-
9-
Examples include - 
A)
B)
C)
D)
10-
11-

(iii) Germline Cells (2)
12-
13-
14-

Question 2

Give an account of DNA under the following headings:

i) The structure of DNA (5
(ii) The replication of DNA (5)

Answer 2

(i) The Structure of DNA (5)
1-
2-
3-
4-
5-
6-
7-

(ii) The replication of DNA (5)
8-
9
10-
11-
12-
13-
14-
15-

Question 3

Describe protein synthesis under the following headings:

i) Transcription of DNA (4
(ii) Translation of DNA (6)

Answer 3

(i)Transcription of DNA (4)
1-
2-
3-
4-
5-
6-

(ii) Translation of DNA (6)
7-
8-
9-
10-
11-
12-
13-
14-
15-

Question 4

Describe how proteins are assembled from the code on a mRNA strand (10)

Answer 4

1-
2-
3-
4-
5-
6-
7-
8-
9-
10-
11-
12-

Question 5

Discuss the production of ATP in the body (9)

Answer 5

1-
2-
3-
4-
5-
6-
7-
8-
9-

Question 6

Describe aerobic respiration under the following headings:

i) The Citric Acid Cycle (5
(ii) The Electron Transport Chain (5)

Answer 6

(i) The Citric Acid Cycle (5)
1-
2-
3-
4-
5-
6-
7-

(ii) The Electron Transport Chain (5)
8-
9
10-
11-
12-
13-
14-
15-

Question 7

Give an account of skeletal muscle cells under the following headings:

(i) Lactate Metabolism (4)
(ii) Slow Twitch Muscle Fibres (3)
(iii) Fast Twitch Muscle Fibres (3)

Answer 7

(i) Lactate Metabolism (4)
1-
2-
3-
4-
5-
6-

(ii) Slow Twitch Muscle Fibres (3)
7-
8-
9-
10-

(iii) Fast Twitch Muscle Fibres (3)
11-
12-
13-
14-
15-

Question 8

Describe the structure of DNA and the process of DNA replication (9)

Answer 8

Structure:
1- DNA is composed of nucleotides containing deoxyribose (sugar), phosphate and base.
2- There is a sugar phosphate backbone.
3- The four bases are adenine, thymine, cytosine and guanine.
4- Cytosine bonds/pairs with Guanine and Adenine bonds with Thymine.
5- Bases/two strands are joined by hydrogen bonds.
6- Strands are anti-parallel/run in opposite directions/3’ to 5’ and 5’ to 3’.
7- DNA/two strands form a double helix (shape).

Replication:
8- DNA/double helix is unwound /unzipped.
9- A primer is needed at the start of replication/attaches to DNA strand.
10- DNA polymerase adds nucleotides to the 3’ end (of a new/growing strand/primer).
11- One strand is replicated continuously and the other strand is replicated in fragments discontinuously.
12- The strand replicated in fragments is joined together by ligase.

Question 9

Describe the structure of RNA and the process of transcription (9)

Answer 9

Structure:
1- RNA is single stranded.
2- It is composed of nucleotides containing ribose (sugar), phosphate and base.
3- The four bases are uracil, adenine, cytosine and guanine.
4- Groups of three bases/nucleotides form codons in mRNA/anticodons in tRNA.
5- Start/stop codons exist.
6- tRNA folds due to base pairing/has an attachment site for a specific amino acid.
7- rRNA (and protein) forms a ribosome.

Transcription:
8- Transcription occurs in the nucleus.
9- RNA polymerase forms mRNA/ unwinds and unzips DNA.
10- (Complementary) base pairing occurs - adenine with uracil, guanine with cytosine.
11- The primary transcript/mRNA contains introns and exons.
12- Introns are removed/ exons remain after (RNA) splicing.
13- (Splicing)forms the mature transcript/mRNA.