Cell Membrane

Question 1

What is the cell membrane?

Answer 1

Thin barrier separating the inside of the cell (cytoplasm and organelles) from the outside environment

Question 2

What is the cell membrane for?

Answer 2

Protection, transport, shape/structure and for communicating and signalling

Question 2

What is the fluid mosaic model?

Answer 2

The cell membrane consists of embedded proteins that shift and flow with a layer of phospholipids.

Question 3

What are the 5 types of cell membrane proteins?

Answer 3

1) Receptor
2) Recognition
3) Enzymes
4) Attachment
5) Transport

Question 4

What do receptor proteins do?

Answer 4

Trigger cell activity when a molecule outside binds to a protein

Question 5

What do recognition proteins do?

Answer 5

Allow cells to recognise one another

Question 6

What do enzyme proteins do?

Answer 6

They catalyze chemical reactions on the inner surface of membranes

Question 7

What do attachment proteins do?

Answer 7

They anchor membrane to internal framework and external surface of neighbouring cells

Question 8

What do transport proteins do?

Answer 8

Regulate the movement of hydrophilic molecules via membrane

Question 9

How many routes are there for movement across membranes and what are they?

Answer 9

4
1) Passive Transport
2) Active Transport
3) Endocytosis
4) Exocytosis

Question 10

How many types of passive transport are there? What are they?

Answer 10

Three
1) Diffusion
2) Facilitated Diffusion
3) Osmosis

Question 11

What is diffusion?

Answer 11

A form of passive transport involving movement of molecules from high to low concentration.

Question 12

What is facilitated diffusion?

Answer 12

A form of passive transport. Require assistance of transport or channels that form pores or carrier proteins that require shape changes like glucose.

Question 13

What is Osmosis?

Answer 13

Movement of water from high to low concentration over a semi-permeable membrane.

Question 14

What can affect osmosis?

Answer 14

Tonicity - relative solute concentration of two environments separated by a semi-permeable membrane.
1) Isotonic Solution - Retains shape as salt and water content are equal
2) Hypertonic Solution - water leaves = shrinks
3) Hypotonic Solution - water comes in = bursts

Question 15

What is active transport?

Answer 15

Movement of substances against the concentration gradient aka pumps

Question 16

Whats an example of active transport?

Answer 16

The sodium-potassium pump (more potassium inside the cell, less sodium outside). Requires energy,

Question 17

What is endocytosis?

Answer 17

The movement of large volumes into cells via vesicle formation and it requires ATP

Question 18

How many types of endocytosis are there and what are they called?

Answer 18

Three;
1) Pinocytosis
2) Receptor-Mediated Endocytosis
3) Phagocytosis

Question 19

What is Pinocytosis?

Answer 19

A form of endocytosis. Cell drinking.

Question 20

How does pinocytosis occur?

Answer 20

The cell membrane invaginates enclosing extracellular fluid and then the vesicle pinches off and brings its contents into the cell

Question 21

How does receptor-mediated endocytosis occur?

Answer 21

A form of endocytosis where ligand binds to a receptor protein in the cell membrane, the ligand-receptor complex moves into a clathrin-coated pit invaginates and the vesicle pinches off.

Question 22

What is receptor-mediated endocytosis?

Answer 22

The uptake of molecules vias coated pits

Question 23

What is phagocytosis?

Answer 23

A form of endocytosis. “Cell eating” - uptake of large particles. Bacteria or cell debris bind to cell receptors that form a phagosome vesicle and pinch off.

Question 24

What is exocytosis?

Answer 24

Regulates biological events like neurotransmitter and hormone release delivering proteins etc to the plasma membrane.

Question 25

What can easily pass through cell membranes?

Answer 25

Lipids