Lecture 2 - Body fluids and membrane transport

Question 1

Average body mass distribution of a 30-year-old 70kg male

Answer 1

18% fat
22% lean body muscle
60% water (42 litres)

Question 2

Breakdown of the 42 litres in body water

Answer 2

Intracellular fluid (ICF) = 25L
Extracellular fluid (ECF) = 17L

ECF is split into 3 places:
1L transcellular fluid
3L blood plasma
13L interstitial fluid

Question 3

Transcellular fluids

Answer 3

Cerebrospinal fluid (brain)
Urine (kidney and bladder)
Gastrointestinal fluids (saliva, bile etc)
Aqueous and vitreous fluids (eye)
Synovial fluids (joints)
etc

Question 4

Plasma membrane: how permeable is it, what does it contain, and what does it do?

Answer 4

Highly selective permeability

Lots of transport proteins for uptake and removal of specific solutes

Vital for the regulation of the intracellular environment

Question 5

Plasma membrane permeability: what things are impermeable and what facilitates movement through the membrane?

Answer 5

The phospholipid bilayer is impermeable to ions and polar molecules

Permeability is provided by membrane proteins:
channels
carriers
pumps

Question 6

Carrier proteins in the membrane

Answer 6

Facilitator - uniport (one molecule moving)
Cotransporter - symport (two molecules moving the same direction)
Exchanger - antiport (two molecules moving in opposite directions)

Question 7

Water and solutes in ICF:
K⁺
Na⁺
Ca²⁺
Cl⁻
Organic solutes⁻
Proteins⁻

Answer 7

⠀
High
Low
Very low
Low
High
High

Question 8

Water and solutes in ECF:
K⁺
Na⁺
Ca²⁺
Cl⁻
Organic solutes⁻
Proteins⁻

Answer 8

⠀
Low
High
Low
High
Low
Low

Question 9

Damari is a loser.

Answer 9

TRUE

Question 10

Capillary endothelium

Answer 10

A very thin layer of cells lining blood vessels

Highly permeable in some organs, not in others (e.g. brain)

An important role in the regulation of the interstitial fluid

Question 11

Epithelia: where are they located and what do they do?

Answer 11

layers of cells covering the internal and external surfaces of organs and tissues

• protective/barrier function
• important roles in absorption and secretion

Question 11

Epithelial transport into the cell from the gastrointestinal tract

Answer 11

Glucose passes from the gut lumen, through the apical membrane, and the basolateral membrane and then into the cells.

Question 12

Epithelial transport out of the cell into the gastrointestinal tract

Answer 12

Na⁺, K⁺, and Cl⁻ pass from inside the cells, through the basolateral membrane, through the apical membrane, and then outside of the cell into the gut lumen.