Cells and the Internal environment Flashcards
What is the average human (70kg) made up of?
18% protein
15% fat
7% minerals
60% water
What is the volume total body water of an average human in L and in ml/100g?
42L, which equates to 71ml/100g
What tissue holds less water?
fat (adipose tissue)
How does body water change with age?
decreases
What are the two body fluid compartments and what proportion of the body fluid do they hold?
- extracellular fluid: 1/3
- intracellular fluid: 2/3
What percentage of body weight do these groups take up?
1) blood plasma
2) interstitial fluid
3) intracellular fluid
1) 5%
2) 15%
3) 50%
How do we gain water into the body from the external environment?
- blood vessels (clinically eg. transfusions, drip)
- stomach & intestine (food and drinks)
How do we lose water from the body to the external environment?
- blood vessels (haemorrhage)
- skin (sweating)
- intestine & stomach (faeces, increased water loss with diarrhoea and vomiting)
- lungs via respiration
- kidneys via excretion
Roles of transmembrane proteins?
- holes/pores in membrane
- transport of molecules
- receptors
What do phospholipids form in water?
liposomes
What are the functions of the cell membrane?
- provide structure
- acts as a barrier
- selective transport of substances in and out of the cell
what is the composition of blood plasma, describing concentration of Na+, Cl-, K+ and proteins?
Na+ -> 152 mM
Cl- -> 113 mM
K+ -> 5 mM
proteins -> low but higher than interstitial fluid
what is the composition of interstitial fluid, describing concentration of Na+, Cl-, K+ and proteins?
Na+ -> 143 mM
Cl- -> 117 mM
K+ -> 4 mM
proteins -> very low
what is the composition of intracellular fluid, describing concentration of Na+, Cl-, K+ and proteins?
Na+ -> 14 mM
Cl- -> 9 mM
K+ -> 157 mM
proteins -> high due to high enzyme concentration
Define chemical disequilibrium
different composition due to cell membranes varying permeability to different molecules
What factors affect movement across a cell membrane?
- size
- lipid solubility
- charge (most important factor)
How does size affect permeability?
high size (>3nM) decreases passage through membrane
How does lipid solubility affect permeability?
molecules with higher lipid solubility pass more readily thought the membrane due to ability to dissolve in fatty acid tails
How does charge affect permeability?
charged molecules are less able to cross the cell membrane
Which molecules easily diffuse across the cell membrane?
- small, chargeless, lipid soluble molecules
- eg. O2 and N2
Describe (simple) diffusion
random movement of molecules (due to collisions) causing net movement down a concentration gradient in a fluid
What is the speed and distance between water molecules?
- 2,500 km/hr
- 0.3 nm
Describe filtration
- high pressure forces liquid out of small pores in capillaries
- dependent on size of molecules
Describe osmosis
passive movement of water across a membrane in response to a solute gradient (low to high)
- OR water potential gradient (high to low)
Define osmotic pressure (P)
pressure at which would prevent H2O moving
define protein mediated transport
facilitated diffusion and active transport
define facilitated diffusion
- down concentration gradient and passive
- using carrier or channel proteins
How do carrier proteins work?
combine with molecule to carry it across the membrane
highly specific
eg. GLUT1 transporter
give an example of channel proteins
aquaporins
Na+ channel proteins
describe active transport
- against concentration gradient
- using energy from ATP
- using ATPase enzyme
Give an example of active transport
secretion of H+ from parietal cells lining the stomach into the gastric acid in the stomach lumen
using H+ATPase
Describe endocytosis
mass transport of molecules from outside the cell to inside the cell by engulfing within cell membrane
- moves proteins and very large molecules
Describe pinocytosis
invaginated membrane pinches off pockets (used in fat uptake)
Describe phagocytosis
arms of cytoplasm encapsulate foreign bodies and destroy them
part of immune response
describe exocytosis
bulk movement of molecules out of the cell by fusion of vesicle with cell membrane
