IB Biology- Cell Membrane/Transport

What is the plasma membrane?

A selectively permeable membrane which is made up by a phospholipid bi-layer which includes polar heads and non-polar fatty acid tails. It is able to regulate what goes in and out of the cell.

Six functions of membrane proteins...

Transport things in and out of cell

Enzymatic activities

Attachment to cytoskeleton and extracellular matrix

Communication with other cells (identification)

Adhesion to other cells

Receptor proteins

Why is the plasma membrane described as a fluid mosaic model?

Has many parts that come together to make a whole and those parts constantly move.

What are glycoproteins? What is their function?

Membrane carbohydrates that are covalently bonded to proteins. Serve as "chemical ID" for the cell.

What are glycolipids? What is their function?

Membrane carbohydrates that are covalently bonded to lipids. Serve as "chemical ID" for the cell.

What is cholesterol? What is its function?

Cholesterol is a steroid and is mostly hydrophobic. It makes sure the plasma membrane is not too fluid, but fluid enough. It also prevents crystallization and restricts cellular motion.

Function of channel/carrier proteins

Passive transport across the membrane

Function of protein pumps

Active transport across the membrane

Function of enzymes

Used in cell surface reactions

Function of Adhesion proteins

Binding cells together

Function of receptor proteins

Hormone binding and recognition

How do the hydrophobic and hydrophilic properties of the phospholipid bilayer allow the membrane to maintain its structure?

Since the cell membranes are phospholipid bilayers, a double layer of molecules exist as a stable boundary between two aqueous compartments because the molecular arrangement shelters the hydrophobic tails of the phospholipids from water while exposing the hydrophilic heads to water.

What does selectively permeable (in the context of the plasma membrane) mean?

Some substances can cross the membrane, while others can't.

What is diffusion?

The spreading out of particles in liquids and gases that happens because the particles are in continuous random motion.

What is osmosis?

The diffusion of water across a selectively permeable membrane.

Distinguish between solute, solvent, and solution.

solute-

solvent-

solution-

Simple diffusion

1. Does it go with the concentration gradient?

2. Does it use a selectively permeable membrane?

3. Does it use membrane proteins?

4. Does it need ATP?

1. Yes

2. No/Yes

3. Yes

4. No

Osmosis

1. Does it go with the concentration gradient?

2. Does it use a selectively permeable membrane?

3. Does it use membrane proteins?

4. Does it need ATP?

1. Yes

2. Yes

3. Yes

4. No

Facilitated Diffusion

1. Does it go with the concentration gradient?

2. Does it use a selectively permeable membrane?

3. Does it use membrane proteins?

4. Does it need ATP?

1. Yes

2. Yes

3. Yes

4. No

Active Transport

1. Does it go with or against the concentration gradient?

2. Does it use a selectively permeable membrane?

3. Does it use membrane proteins?

4. Does it need ATP?

1. Against

2. Yes

3. Yes

4. Yes

What are the four types of membrane transport?

Simple diffusion, osmosis, facilitated diffusion, active transport

What method of membrane transport is used by water?

Osmosis through aquaporins

What method of membrane transport is used by non-polar molecules?

diffusion

What method of membrane transport is used by polar molecules?

facilitated diffusion

What method of membrane transport is used by any molecule against the concentration gradient?

active transport

What method of membrane transport is used by macromolecules?

endocytosis or exotycosis

What is a vesicle?

Vesicles are tiny sacs made of membranes, which are used to transport items around the cell.

What is the process of vesicle transport of a protein molecule through a eukaryote cell? Begin with protein synthesis in the Rough ER and finish with exocytosis through the plasma membrane.

Proteins are synthesized by ribosomes on the Rough ER. The protein then gets transported to the golgi apparatus, where it will get further modified and packaged for secretion. When it gets packaged, phospholipids from the golgi membrane will pinch off to form a vesicle around the protein. The vesicle will move to the plasma membrane, fuse with it, and then the protein will get released from the cell.

Exocytosis vs. Endocytosis...

In endocytosis, the cell takes IN biological membranes and particulate matter by forming new vesicles from the plasma membrane. Plasma membrane temporarily shrinks in size.

In exocytosis, the cell SECRETES certain biological molecules by the fusion of vesicles with the plasma membrane. Plasma membrane temporarily increases in size.

Compare and contrast facilitated diffusion and active transport.

Compare: Both types of transport use integral membranes to move molecules.

Contrast: Facilitated diffusion is a form of passive transport: no energy required because molecules are moving with their concentration gradient. Active transport requires energy because molecules are being moves against their concentration gradient.

Since carbs are big, the cell uses facilitated diffusion to help move them into the cell. What factors will increase the rate of carbohydrate uptake by the cell? Can the rate of carbohydrate uptake continually increase or will the rate eventually level out? Explain your reasoning.

The rate of carb uptake by the cell will be increased as the concentration of carbs on the outside of the cell increases. It adds to the concentration gradient and more carbs will be moved into the cell. However, the rate of uptake will NOT continually increase because there are only so many integral proteins that can facilitate the movement into the cell before they're all occupied. The rate will level out.