Cell Membranes and Transport Flashcards Preview

AS Biology > Cell Membranes and Transport > Flashcards

Flashcards in Cell Membranes and Transport Deck (24):
1

What the two functions of ORGANELLE membranes?

-isolate organelles from cytoplasm, allowing cellular processes to occur separately
-site of biochemical reactions

2

How does the plasma membrane appear under an electron microscope?

A double line 7-8nm wide

3

What three things are cell membranes mainly composed of? (Use PPC)

Phospholipids
Proteins
Cholesterol (animal cells)

4

How did Singer and Nicholson describe a cell membrane's structure in 1972 and why?

'Fluid mosaic model'
Proteins scattered like a mosaic throughout phospholipids and membrane components can move (fluid)

5

What are the main component of membranes?

Phospholipids

6

What mass on average do proteins make up of a cell membrane?

45%

7

What are the two surfaces of a membrane?

Extracellular (facing outside)
Cytosolic (facing inside)

8

What three proteins can be found in the membrane?

Intrinsic
Extrinsic
Glycoproteins

9

What are the 5 functions of CELL SURFACE membranes?

-allow take up of selected nutrients
-allows secretion of chemicals
-enables cell recognition
-allows cell to change shape
-keep cellular components inside cell

10

Incipient plasmolysis:-

The point at which the protoplast is just about to pull away from the cell wall

11

Hypertonic:-

Higher water potential in cell, water flows out down a water potential gradient

12

Isotonic:-

Water potential equal inside and outside the cell

13

Hypotonic:-

Lower water potential inside the cell= water flowing in by osmosis down a water potential gradient

14

What does cholesterol do in membranes?

Maintain fluidity, increasing stabilty

15

Highest water potential (pure water)?

0kPa

16

What is water potential measured in?

kPa (kilopascals)

17

Solute potential:-

Conc of dissolved substances inside the cell. Always negative. "Measure of the reduction in water pot due to the presence of solute molecules."

18

Pressure pot:-

Pressure exerted on the cell contents by the cell wall and cell membrane.

19

Haemolysis:-

Red blood cells have a low water pot. In water, water flows in down water pot grad. No cell wall to stop cell expansion so continues until it bursts (haemolysis).

20

Red blood cells in hypertonic solution:-

Water will flow out, cells will be crinkled (crenated).

21

Exocytosis:-

Secretory vesicles carry their contents to the cell surface membrane, merge with it and the secretion is released.

22

Two types of endocytosis:-

Phagocytosis and pinocytosis

23

Phagoxytosis:-

Solid material taken into cell in a vesicle. Lysosomes fuse w/ vesicle and empty their enzymes into it. Enzymes digest material and producta are absorbed into cytoplasm.

24

Pinocytosis;-

Similar to phago but with liquid material. Vesicles formed can be very small.