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Flashcards in movement of substances Deck (20)
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1
Q

The membrane of cells is made almost entirely of ___ and ___, together with a small amount of ____.
The lipid of membranes is ____ and ____.

A

The membrane of cells is made almost entirely of protein and lipid, together with a small amount of carbohydrate.
The lipid of membranes is phospholipids and cholesterol.

2
Q

What makes up a phospholipid molecule?

A

A glycerol-phosphate hydrophilic “head”, and a hydrophobic tail made out of 2 hydrocarbon chains

3
Q

When mixed with water, phospholipid molecules arrange themselves into a _____ in the ___ ____ _____, in which the hydrophobic tails are _____ to each other.

A

When mixed with water, phospholipid molecules arrange themselves into a bilayer in the cell surface membrane, in which the hydrophobic tails are attracted to each other.

4
Q

What are the two types of proteins in the phospholipid bilayer?

A

Integral proteins: partially/fully buried in the phospholipid bilayer
Peripheral proteins: superficially attached on either surface of the phospholipid bilayer

5
Q

What are the roles of membrane proteins in the phospholipid bilayer?

A
Channel proteins (for passage through the membrane): each channel allows one specific substance to pass
Pump proteins: for active transport across the membrane, energy from ATP is used selectively to move one or two specific substances across
6
Q

Why is it called the fluid mosaic model?

A

The membrane is described as fluid because the components (lipids and proteins) move around within their layers
The word “mosaic” describes the scattered pattern of the proteins

7
Q

Why is the membrane so fluid?

A

Phospholipids of the membrane are a mixture of saturated and unsaturated fatty acid tails. An excess of unsaturated fatty acid tails makes the membrane more fluid.
- Because the kinks in the tails prevent close-packing of the lipids
(presence of cholesterol reduces fluidity by preventing/reducing movements of lipid molecules)

8
Q

Diffusion is…

A

Diffusion is the net movement of molecules from a region of higher concentration to a region a lower concentration, down a concentration gradient, using kinetic energy from the continuous random movement of molecules.

9
Q

What kind of molecules diffuse through simple diffusion?

A
  • Small, non polar molecules (e.g. oxygen/carbon dioxide)
  • Fat-soluble molecules (e.g. vitamin A)
  • Membrane is fully permeable
10
Q

Facilitated diffusion is…

A

Facilitated diffusion is the diffusion of ions and polar molecules through cell surface membranes using specific protein channels or carriers, down a concentration gradient, from a region of high concentration to a region of low concentration.

11
Q

What are channel and carrier proteins?

A
  • Carrier proteins are protein-lined pores that are large enough for a molecule to pass through
  • Channel proteins are globular proteins that can form pores large enough for diffusion. Pores close up when molecules are no longer present
12
Q

What is active transport?

A

Active transport involves the movement of molecules from a region of lower concentration to a region of higher concentration, AGAINST a concentration gradient, using metabolic energy in the form of adenosine triphosphate (ATP) produced by the cell.

13
Q

What are the key/defining features of active transport?

A
  1. It occurs against a concentration gradient
    - for useful molecules and ions
  2. It is a highly selective process
    - only molecules that are very needed will be more likely to be taken in
  3. It involves special molecules of the membrane called “pumps”
    - globular proteins that transverse the lipid bilayer, require ATP, specific to particular molecules (selective), either uni/bidirectional
14
Q

What is bulk transport?

A

Bulk transport occurs by the movement of vesicles of matter (solids/liquids) across the cell surface membrane. This requires ATP

  • Exocytosis (exit) and endocytosis (enter)
  • Phagocytosis (solids) and pinocytosis (fluids)
15
Q

Osmosis is…

A

Osmosis the net movement of water molecules from a region where water is at a higher water potential through a partially/selectively permeable membrane to a region with a lower water potential

16
Q

(PLANTS) When the external water potential is higher than the water potential of the cell,…

A

Cell wall is stretched, cell is said to be turgid

17
Q

When the external water potential is the same as the water potential of the cell,…

A

No net water movement

18
Q

(PLANTS) When the external water potential is lower than the water potential of the cell,…

A

Cytoplasm pulls away from the cell wall, cell is said to be plasmolysed and flaccid

19
Q

(ANIMALS) When the external water potential is higher than the water potential of the cell,…

A

Cell lyses

20
Q

(ANIMAL) When the external water potential is lower than the water potential of the cell,…

A

Cell outline becomes crenated