Plasma Membrane + Organelles

Question 1

What must a cell do:

Answer 1

• Generate required energy
• Manufacture cellular materials
• Obtain raw materials
• Remove waste
• Control all of the obove

Question 2

Cells being bound in a plasma membrane results in:

Answer 2

1. A semipermeable barrier
2. A passage of oxygen, nutrients, waste
3. Controlled movement of substances in and out of the cell

Question 3

Phospholipid bilayer (plasma membrane)

Answer 3

Double layer of phospholipids with various embedded or attached proteins

(Hydrophilic head, hydrophobic tailS)

Question 4

Why the plasma membrane isn’t static: What controls fluidity of the membrane.

Answer 4

Saturation:
- Saurated - packed tightly together, less fluidity
- Unsaturated - tails prevent tight packing, more fluidity

Temperature:
- High temp - more fluidity
- Low temp - less fluidity

Cholesterol:
- Stabilises membrane fluidity

Question 5

Membrane proteins are involved in:

Answer 5

Signal Transduction: Relay messages from the body (or environment) into the cell

Cell recognition: Often involves glycoproteins (proteins with added sugar)

Intercellular Joining: Some proteins form long-lasting connections between cells

Linking cytoskeleton + extracellular matrix: allows a cell to physically connect with protein structures outside the cell (extracellular matrix)

Membrane transport: Allows small amounts or molecules to move across the membrane - can be positive or active

Question 6

Diffusion

Answer 6

• movement across membrane
• passive transport - no energy
• membrane are permeable to lipid soluble molecules (hydrophobic) such as steroid hormones + gasses
• move down concentration gradient thus no energy requires
• membranes restricts movement of water soluble and charged molecules such as glucose,ions and water

Question 7

Facilitated diffusion

Answer 7

• passive, no energy - (some channels open in response to signals)
• movement of hydrophilic molecules requires membrane proteins (carriers + channels) which said movement down conc graideint
• carries change shape to help guide molecule

Question 8

Osmosis (facilitated diffusion)

Answer 8

• movement from high water (low solute) concentration to low water (high solute) concentration
• movement of water across a cell membrane requires channels called aquiporins
• cells osmoregulate to prevent swelling or shrinking under varying conditions

Question 9

Active transport

Answer 9

• requires transport proteins which are carriers that use energy (ATP)
• move specific substances against their concentration gradient
• allows a cell to have an internal concentration of a substance that is different from its surroundings ( sodium potassium pump)

Question 10

Co-transport

Answer 10

• in direct active transport
• one substance is pumped across the membrane and its concentration gradient is used to power the movement of a second substance against its concentration gradient.

Question 11

How different parts of the cell do different things:

Answer 11

Different processes —-> different conditions —> separate compartments.

Organelles:
- Provide special conditions for specific processes
- Form concentration gradients
- Package substances for transport or export
- Allow specific substances to be concentrated
- Keep incomparable processes apart

Question 12

Cellular organelles are also bounded by membranes:

Answer 12

• each organelle provides its own special conditions
• endoplasmic reticulum
• lysosomes
• mitochondria
• nucleus
• all cellular membranes are composed of a phospholipid bilayer

Question 13

How membrane limits max size of cell, Ratio?

Answer 13

4. The interaction with the environment limiting the maximum size of a cell
5. A smaller cell having a greater surface to volume ratio than a larger cell

Question 14

Function of the cell membrane

Question 15

Cholesterol and fluidity

Answer 15

At high temp it doesn’t help with fluidity
At low lump it restricts fluidity

Question 16

Constitutive and regulative exocytosis examples