Cells and the Internal Environment

Question 1

Average human components %

Answer 1

18% protein
15% fat
7% minerals
60% water

Question 2

Total body water %

Answer 2

5% blood plasma (extracellular)
15% interstitial fluid (extracellular)
40% intracellular fluid
1/3 extracellular fluid
2/3 intracellular fluid

Question 3

Cell membrane = Phospholipid Bilayer components

Answer 3

7.5nm
Phosphate head (H2O soluble = hydrophilic)
2 fatty acid chains (H2O insoluble = hydrophobic)
Transmembrane protein ( Forms holes or pores in membrane to allow molecules to cross, also receptors)

Question 4

Cell membrane provides:

Answer 4

Structure
Acts as a barrier to keep constituents in (and out)
Allows selective transport of substances into and out of cell

Question 5

Chemical disequilibrium

Answer 5

Different composition due to cell membranes permeability to molecules which varies greatly

Question 6

Cell membrane factor and effects

Answer 6

Increased size (above 3nm) = less passage
Increased lipid solubility (fat) = more passage
Increased charge (ionisation) = decreased permeability

Question 7

Diffusion

Answer 7

H2O molecules move at 2,500 km/h only 0.3nm apart.
Collisions cause random movement (high to low) down concentration gradient
<3nm H2O soluble molecule cross membrane by diffusion
Diffusion can take place in open system or across partition that separates two systems

Question 8

Osmosis

Answer 8

movement of water across a membrane in response to a solute concentration gradient ( moves from low to high solute gradient)

Question 9

Osmotic pressure

Answer 9

pressure which would prevent H2O moving.
all compartments normally at osmotic equilibrium.

Question 10

Protein-mediated transport

Answer 10

Proteins act as carriers and channels to facilitate flow of substances that cannot permeate lipid bilayer - ions and large unionised molecules.
High to low = facilitated diffusion down concentration gradient, no energy needed

Question 11

Active transport

Answer 11

Low to high concentration gradient
Against concentration gradient
Uses energy:
ATP to ADP
ATPase = enzyme = energy

Question 12

Endocytosis

Answer 12

Into cells (proteins and large molecules)

Question 13

Exocytosis

Answer 13

Out of cells (hormones and neurotransmitters)

Question 14

Pinocytosis

Answer 14

Invaginate membrane pinches off pockets
e.g. fat uptake

Question 15

Phagocytosis

Answer 15

Arms of cytoplasm encapsulate
e.g. immune response