Cell membrane

Question 1

Plasma membrane

Answer 1

-provides support
-assists signalling
-regulates inbound and outbound traffic
-supports metabolic activities
-consist of a bilayer of phospholipids with various proteins attached to it

Question 2

Fluid mosaic model

Answer 2

-not in a fixed place
-composed of different things
-cellular membranes are fluid mosaics of lipids and proteins
-phospholipids are amphipathic molecules

Question 3

Amphipathic phospholipids

Answer 3

-Hydrophilic - polar or charged
-Hydrophobic -nonpolar fatty acids
-having both hydrophobic and hydrophilic ends, able to interact with both polar and nonpolar substances

Question 4

Functions of the cell membrane

Answer 4

1. Encloses and protects the cell contents
2. provides and supports mechanical structure
3. Transport in and out of the cell
4. Markers and signalling
5. Metabolic activities

Question 5

1. Encloses and protects the cell contents

Answer 5

-cell membrane is selectively permeable
-allows certain molecules through and block movement of others
-forms a barrier between inside and outside of the cell
-different chemical environments can exist on each side of the membrane

Question 6

2. Provides and supports mechanical structure

Answer 6

EXTRACELLULAR MATRIX: in plant and animal tissues the cell membrane interacts with the cell membrane of adjacent cells
-membrane allows the cell to control the internal pressure and conc. of intracellular components

Question 7

3. Transport in and out of the cell

Answer 7

Passive transport
active transport
bulk transport
transport proteins -> span membrane, specific in transporting e.g ions, sugars, amino acids

Question 8

passive transport

Answer 8

-molecules diffuse across the membrane with the conc. gradient (high to low conc)
-no energy is required
-diffusion, facilitated diffusion, osmosis

Question 9

active transport

Answer 9

-molecules are ‘pumped’ across the membrane against a conc. gradient (low to high conc)
-energy required, and transport protein
-protein pumps, endocytosis, exocytosis

Question 10

bulk transport

Answer 10

exocytosis and endocytosis move items in and out of the cell via secretory vesicles
-move large molecules

Question 11

4. Markers and signalling

Answer 11

-cell can recognise and process signals from the environment
-often include receptor proteins for interaction with specific chemicals (e.g. hormones)
-surface protein markers embedded in the cell membrane identify the cell, making nearby cells to communicate

Question 12

5. Metabolic activities

Answer 12

-enzymes/specialised proteins that perform some metabolic activities are in the membrane

Question 13

Exocytosis

Answer 13

-Hormones or wastes released from cell
-large molecules are secreted when a vesicle fuses with the plasma membrane
-forces material out of the cell in bulk

Question 14

Endocytosis

Answer 14

-forms food vacuole and digests food
-large molecules are taken in when the plasma membrane pinches inwards, forming a vesicle
- ‘cell-eating’, taking bulky material into cell

Question 15

Passing through membrane

Answer 15

-small hydrophobic molecules (e.g. O, CO2) ass through easily
-hydrophilic molecules (e.g. sugars, ions) struggles -> even water needs assistance to cross

-small molecules move across membranes due to diffusion
-through diffusion, molecules pass through pores in the membrane
-diffusion stops when conc. is equal on both sides of membrane