Organelles And Cell Membrane

Question 1

What are the characteristics of the cell membrane?

Answer 1

1) flexible
2) strong
3) permeable (partially)
4) thin (12nm)
5) outermost limit of cell
6) protection
7) not inert (engage in reactions)

Question 2

How is the phospholipid bilayer arranged?

Answer 2

Hydrophobic tails face inwards while hydrophobic heads face outwards

Question 3

What are the 8 functions of the cell membrane?

Answer 3

1) encloses the contents of the cell
2) barrier
3) controls movement of molecules in and out of cell
4) separation of sub-cellular compartments
5) communication
6) chemical reactions
7) cellular identity
8) cell movement

Question 4

What is diffusion?

Answer 4

The passive movement of molecules down the conc. gradient (high concentration region to low concentration region) through a partially permeable membrane

Question 5

What is osmosis?

Answer 5

Movement of water across a selectively permeable membrane from a region of high conc. to low conc. (high water potential to low water potential)

Only small dissolved molecules can move across, not larger molecules

Question 6

What is facilitated diffusion?

Answer 6

Carrier proteins binding with and helping/facilitating the diffusion of some kinds of particles across cell membrane

Movement through protein pore

Question 7

What is active transport?

Answer 7

Energy (ATP) required to move particles across cell membrane against conc. gradient

ATP produced during cell respiration occurring in mitochondria

Question 8

What is endocytosis?

Answer 8

General term used for a group of processes that bring substances into cells

E.g. phagocytosis and pinocytosis

Question 9

What is exocytosis?

Answer 9

Process by which materials are exported out of the cell via secretory vesicles

Question 10

What is pinocytosis?

Answer 10

Cell drinking

Tiny pockets form to carry small droplets containing dissolved/suspended substances inside the cell

Question 11

What do cell adhesion molecules do?

Answer 11

Proteins enabling cells to adhere to one another

Important in preventing cells wandering of during development and ending up in the wrong place

Question 12

What is the function of tight junctions?

Answer 12

Cells required to stick together in a continuous sheet

Snap fasteners

Question 13

Why do some proteins act as receptors?

Answer 13

For hormones

Question 14

What is the function of ‘cell markers’

Answer 14

Let other cells in the body know that they are self and not foreign

Question 15

What is the function of Glycoproteins

Answer 15

Carbohydrate molecules connected to some proteins

Establish cellular identity, important in the immune response