Generalized Eukaryotic Cells

Question 1

What are the two types of plasma membranes? (in terms of orientation to the membrane)

Answer 1

Intrinsic (integral), such as channels or receptors

Extrinsic (peripheral)

Question 2

True or false? The plasma membrane is permeable to some small charged substances?

Answer 2

False, it is permeable to small ‘uncharged’ substances (eg. CO2, urea etc.)

Question 3

What is the hydrostatic pressure needed to oppose the movement of water called?

Answer 3

Osmotic pressure (ie. when the concentration of solute on both sides of the membrane is equal/isotonic, there is an osmotic pressure of zero).

Question 4

Describe red blood cells in isotonic, hypertonic and hypotonic solutions

Answer 4

Isotonic: Equal rate of water diffusion in and out, normal cell

Hypertonic: Water diffuses out of the RBC into the higher concentrated solute. Shrivelled cell results

Hypotonic: Water diffuses into the RBC, which is more concentrated, resulting in it swelling and/or bursting

Question 5

List the two carrier-mediated transport systems of a plasma membrane

Answer 5

1. Facilitated transport: Solute ‘diffuses’ across a membrane that it could otherwise not traverse due to size or charge, but not concentration/electric gradient
2. Active transport: ATP is used to transport solute against their concentration gradient

Question 6

How do the curves for rate of transport vs. concentration gradient of solute differ for simple diffusion and carrier-mediated transport at a cell membrane?

Answer 6

Simple diffusion: The greater the concentration gradient, the greater the rate of transport across the plasma membrane (linear relationship)

Carrier-mediated transport: Increasing the concentration gradient increases the rate of transport until a maximum rate at which point all membrane carriers are saturated (linear line levels off)

Question 7

What are the components of a cellular cytoskeleton in increasing size?

List a couple roles for each component

Answer 7

• microfilaments (cell movement and contraction, actin and myosin)
• intermediate filaments (structure)
• Microtubules (structure, core of cilia, mitotic spindles and centrioles)

Question 8

What is a basal body?

Answer 8

Two centrioles that form at right angles to each other at the base of cilia/flagellum (for microtubule support)

Question 9

What are the ‘shelf like’ folds inside mitochondria called?

Answer 9

Cristae

Question 10

What is heterolysis?

Answer 10

When a primary (normal) lysosome fuses with an endocytotic vesicle to form a secondary lysosome where the phagocytosed particle can be digested

Question 11

List two functions of smooth ER

Answer 11

• Phospholipid and fatty acid synthesis and metabolism

- Detoxification in the liver

Question 12

Which two organelles are found in abundance in secretory cells?

Answer 12

• The rough ER

- Golgi

Question 13

What are the three components of DNA?

Answer 13

• Five carbon sugar (2-deoxyribose)
• A nitrogen base
• Inorganic phosphate

Question 14

At what cellular stage of life does DNA replication occur?

Answer 14

The S stage of interphase

Question 15

Describe the cell cycle

Answer 15

1. Interphase occupies 90% of cell cycle. The cell prepares for DNA synthesis (G1), synthesizes or replicates DNA (S) and prepares for mitosis (G2)
2. Mitosis: prophase, metaphase, anaphase, telophase, cytokinesis

Question 16

At what stage of a cell’s life do microtubules appear and chromatid condenses into chromosomes?

Answer 16

Prophase

Question 17

If a membrane bound enzyme is activated when a hormone is present, does this refute the hypothesis that this enzyme is activated by a G protein?

Answer 17

No, hormone activation does not deny any G-protein participation in the process.

However, the enzyme cannot be activated in the absence of GTP bound to the G protein (if it is to be classified as a G protein activated enzyme).

Question 18

If an anti-inflammatory drug interferes with DNA replication, in which phase of the cell cycle would cells tend to be arrested?

Answer 18

S phase

S-phase is the part of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase. Precise and accurate DNA replication is necessary to prevent genetic abnormalities which often lead to cell death or disease