Things I Don't Know Part 2

Question 1

Where can translation occur?

Answer 1

In the cytoplasm, or on the surface of the endoplasmic reticulum.

Question 2

Describe what causes the neuronal disorder Lishencephaly.

Answer 2

A defect in the gene lis1, a regulator of dyenin.

Question 3

What is the main role of dyenin?

Answer 3

Moves nuclei in humans and fungi.

Question 4

Name the components of the endomembrane system.

Answer 4

• Endoplasmic reticulum
• Golgi
• Lysosomes
• Endosomes (late, early, recycling)
• Peroxisomes
• Lipid droplets

Question 5

What is exocytosis?

Answer 5

The release of material into the extracellular space.

Question 6

What are other names for the Biosynthetic pathway?

Answer 6

• Exocytic pathway

- Secretion pathway

Question 7

Name the organelles/cellular compartments involved in endocytosis.

Answer 7

• Early endosomes
• Late endosomes
• Lysosomes

Question 8

Give a function of lysosomes in specialised cells.

Answer 8

Participate in the secretion of hydrolases.

Question 9

Describe the inner environment of lysosomes.

Answer 9

Acidic (pH 5.0)

Question 10

What is pinocytosis?

Answer 10

The uptake of liquid into a cell.

Question 11

What is phagocytosis?

Answer 11

The uptake of large particles, e.g. prokaryotes

Question 12

Describe the ‘fast recycling pathway’.

Answer 12

1) Endocytic vesicles form at plasma membrane
2) Endocytic vesicles fuse with early endosome
3) Ligands and receptors separate
4) Receptors are recycled

Question 13

Describe the ‘slow recycling pathway’.

Answer 13

1) Material is transported from the early to the recycling endosome
2) Material is transported back into the plasma membrane.

Question 14

What are the roles of the lysosome?

Answer 14

• Receives material from the endocytic pathways

- Fuses with autophagosomes

Question 15

Where are lipid droplets formed?

Answer 15

The smooth endoplasmic reticulum (ER)

Question 16

What are v-SNAREs?

Answer 16

Proteins in transport vesicles that allow the vesicles to fuse with specific target membranes by recognising t-SNAREs on the membrane.

Question 17

What do nuclear pores consist of?

What do they do?

Answer 17

Nuclear pores consist of nucleoporins (proteins).
They form a selective gate, allowing free passage of small molecules (e.g. ions), and restricting transport of larger proteins and complexes.

Question 18

What is the nuclear lamina?

Answer 18

Interaction between the nuclear ropes and intermediate protein filaments.

Question 19

In which organisms is the nuclear lamina found?

Answer 19

In animal cells only.

Question 20

What does the nucleolus make?

Answer 20

Ribosomal subunits

Question 21

Describe heterochromatin.

Answer 21

Densely-packed, transcriptionally inactive DNA form.

Question 22

Describe euchromatin.

Answer 22

Loosely organised, transcriptionally active DNA form.

Question 23

Name the enzyme that transcribes DNA into mRNA.

Answer 23

RNA polymerase II

Question 24

What is the role of RNA polymerase I?

Answer 24

Makes up ribosomal RNA (rRNA).

Question 25

What is meant by ‘amphiphatic’?

Answer 25

Molecules that are polar/hydrophilic at one end, and hydrophobic at the other.

Question 26

Give two lipids found in animal plasma membranes.

Answer 26

Steroids (e.g. cholesterol) and phosphoinositides.

Question 27

How can cells detect their extracellular environment?

Answer 27

Using receptors that bind to ligands.

Question 28

Explain how H-proteins work.

Answer 28

• They hydrolyse their bound GTP (cleave off a phosphate group) and go into an inactive state.
• Guanine-nucleotide exchange factor (GEF) replaces the GDP+phosphate with a fresh GTP.
• This activates the G-protein and results in the transmission of a signal.

Question 29

What inactivates G-proteins?

Answer 29

GTP-ase activating proteins.

Question 30

How are kinases and phosphatases used in signalling?

Answer 30

• Kinases add phosphates, and phosphatases remove a phosphate from proteins.
• This alters the protein’s conformation (shape), thus activating or deactivating the protein.