prokaryotes and eukaryotes

Question 1

Both animal and plant cells contain cell surface membranes.

Describe the roles of the cell surface membrane within these cells.

Answer 1

acts as a) barrier between the cytoplasm and the external environment.

Protection:
protects the organelles from damage/pathogens

Question 2

Describe the structure of RER

Answer 2

made up of flattened sacs/cisternae

(which are) covered with ribosomes

Question 3

Proteins are synthesised during translation at the ribosomes.

Explain what happens to proteins following this process until they are secreted from the cell.

Answer 3

proteins folded in the rough endoplasmic reticulum

proteins are packaged into OR transported in vesicles

proteins are modified in the Golgi apparatus/body/complex

exocytosis

Question 4

The endosymbiosis theory suggests that mitochondria may have evolved from bacteria that were taken
inside other cells.
These cells then evolved into eukaryotes.
i. Give two structural features of mitochondria that support this theory.

Answer 4

contain (circular) DNA ✓
have double membrane ✓

Question 5

Humans use the enzyme α-amylase to break down polysaccharides in food for absorption into the
blood.
The gene for human α-amylase is found on chromosome 1.
The gene is transcribed in the nucleus and translation occurs on the rough endoplasmic reticulum in
cells of the salivary gland.
Describe how the molecule is prepared and secreted by cells of the salivary gland after translation
has taken place.

Answer 5

transport vesicle from RER ✔

modification / processing / folding ✔

in / at, Golgi (body / apparatus) ✔

(packaged into) secretory vesicle ✔

vesicles move along the cytoskeleton ✔

(vesicle) fuses with, cell surface / plasma,
membrane

(secretion occurs by) exocytosis ✔

Question 6

DNA is a polymer of nucleotides that contains the genetic code needed for a protein to be made.
Tubulin is a protein that is found in all eukaryotes and some prokaryotes.
i.
Explain how the genetic code in the gene for tubulin codes for the protein tubulin.

Answer 6

The sequence of bases in the DNA determines the sequence of amino acids in tubulin (✓).
Each triplet of bases (codon) codes for a specific amino acid (✓).

Question 7

. Epithelial cells in the airways of mammals play an essential role in defences against pathogens.
Explain the function of epithelial cells in the airways of mammals in the defence against pathogens
and suggest the importance of the cytoskeleton in carrying out this function.

Answer 7

In the airways, goblet cells secrete mucus, which traps pathogens such as bacteria.
Ciliated epithelial cells then move this mucus up and out of the airway.
The cytoskeleton, made of microtubules, is important for this because it allows the cilia to move.

✅ Boom — full marks (4 or 5 depending on the question