Cell/Plasma Membranes

Question 0

Plasma Membrane Structure

Answer 0

The plasma membrane is composed of two layers of phosolipids.
O - hydrophilic (water loving)
|| - hydrophobic (water hating) ⬆️ phospholipid
|| ⬇️ Bi layer
O

Question 1

Biological Membranes

Answer 1

• part of cell structure
• living cells-> small compartments surrounded by a plasma membrane
• organelles of eukaryotes-> formed from membranes
• biological membranes selectively regulate the movement of substances across them (ATP, diffusion, osmosis)

Question 2

Components of Plasma Membrane Structure

Answer 2

• Carbohydrate Chains
• Glycolipid
• Phospholipid ↔️ phospholipid bilayer
• Glycoprotein
• Cholesterol

Question 3

The Plasma Membrane Structure

• Proteins
• Carbohydrates
• Cholesterol

Answer 3

• Proteins embedded in the phospholipid bilayer
• Carbohydrates- outer surface, linked to protein (Glycoproteins) or the phospholipid (Glycolipids) molecules
• Cholesterol- between the phospholipid molecules

Question 4

Fluid Mosaic Model

Answer 4

Fluid- phospholipid molecules and some protein molecules are capable of sideways movement within the bilayer (movement)

Mosaic- presence of proteins interspersed throughout the membrane (colour)

Question 5

Crossing the membrane

• Partially Permeable
• Impermeable

Answer 5

• Plasma membrane is partially permeable (allows some materials to pass through, but not others)
• impermeability of membranes-> water soluble molecules-> phospholipid bilayer
• Partially permeable membranes-> Selectively permeable -> Differentially permeable -> Semi permeable

Question 6

Can/Cannot cross phospholipid bilayer

• Charge
• Size
• Solubility

Answer 6

CAN:
- Lipid soluble (lipophillic) substances - (eg. Chloroform & alcohol)
- Small uncharged molecules - (eg. Oxygen & carbon dioxide)
CANNOT:
- Ions - small charged molecules
- Large water soluble substances (polar) - (eg. Amino acids & monosaccharides)

Question 7

Transport Proteins

• Carrier Proteins
• Protein Channels

Answer 7

2 major classes
Carrier proteins: bind to molecules to be transported

Channel proteins: form hydrophilic pores in membrane (pores: open & close)

Question 8

Diffusion

Answer 8

DEFINITION: Passive movement of a substance from a region of high concentration to a region of low concentration along the concentration gradient.

• net movement
• movement will continue until equilibrium is reached
• diffusion occurs in gases and lipids overtime

Question 9

Equilibrium

Answer 9

DEFINITION: A state of balance (equality of distribution)

Question 10

Facilitated Diffusion

Answer 10

DIFINITION: Passive movement of a substance down the concentration gradient with the assistance of protein carriers or channels.

Involves protein carriers in the plasma membrane
Movement is by the process of diffusion

Question 11

Osmosis

Answer 11

DIFINITION: Passive movement of water through a partially permeable membrane, from a region where there are more free water molecules to a region where there are fewer free water molecules.
(High concentration of water to a high concentration of solute)
Special form of diffusion
Water moves across the membrane to ‘dilute’ the solute

Question 12

Active Transport

Answer 12

DEFINITION: Movement of substances across membranes that requires the expenditure (use) of energy; occurs through selective protein carriers.
Net movement of dissolved substances into or out of a cell against the concentration gradient.

Question 13

Bulk Transport

• Endocytosis
• Exocytosis

Answer 13

Movement of solid molecules
Endocytosis
-movement into a cell
- Phagocytosis - movement of a solid 
- Pinocytosis - movement of a liquid
Exocytosis
- movement out of a cell

Question 14

Solute/Solvent

Answer 14

DEFINITION: salt water

Solute: the substance that is dissolved eg.salt

Solvent: the substance doing the dissolving eg. Water

Question 15

Hypertonic
Hypotonic
Isotonic

Answer 15

DEFINITION: more solute on the outside of the cell
-Net movement=out, cell shrinks
DEFINITION: less solute outside the cell than the inside
-Net movement=in, cell expands
DEFINITION: equal concentration of solutes inside the cell, relative to the outside
- no net movement

Question 16

Experimental Method

FINISH

Answer 16

experimental method - the use of controlled observations and measurements to test hypotheses

Experimental Method: hypothesis-> variables-> experimental error-> interpretation of results-> drawing conclusions-> safety in the laboratory.