Cells And Internal Environment Flashcards
Describe how solutes can enter the cell against their concentration gradient using protein-mediated transport
Active Transport.
Requires energy derived from the breaking down of ATP to ADP
Describe the process of exocytosis
Vesicles compromise of membrane and encapsulates substances (eg hormones and neuro transporters)
Vesicles fuse to plasma cell membrane and release molecules out of cells
Describe the structure of the cell membrane
- Phospholipid bilayer
- Phosphate head with two fatty acid tails. Two layers with heads facing outwards.
- Proteins embedded which can span bilayer or sit partially within it
- Cholesterol for structure
Describe the two types of endocytosis
Pinocytosis: membrane invaginates and pinches off pockets (eg uptakes of fats)
Phagocytosis: arms of cytoplasm reach out and encapsulates foreign body to bring into cells (eg immune response)
Explain the process of facilitated diffusion via protein-mediated transport.
Molecules move down concentration gradient (high -> low conc)
Proteins act as carriers.
Solute combines with transport molecule and is carried and released on other side of membrane.
Transport molecule is free to recycle and take up more solute from outside of cell.
Explain the process of filtration using the kidney as an example.
Filtration. Is the means by which some substances can move across a partition from the blood into tubular fluid of kidney nephron.
There is high pressure in glomerulus (region of kidney).
This causes small molecules (especially positively charged molecules) to be forced through pores in filtration barrier.
Some molecules that are too big to pass are retained by blood.
Explain why molecules diffuse from an area of high concentration to low concentration (Use H2O as an example)
Molecules collide when moving rapidly. H2O moves at 2500km/h and are 0.3nm apart.
Collisions result in random movement of molecules.
Number of collisions increase when molecules are closer together (at a higher concentration).
The random movement of the molecules causes molecules to move from an area of more frequent collisions (high conc) to less frequent collisions (low conc).
Explain the process of osmosis
Movement of water across a partially permeable membrane in response to a solute concentration gradient.
Water will diffuse from an area of low solute concentration to high solute concentration.
This causes an increase in volume in the area of high conc.
How are the phospholipid molecules held together in the cell membrane?
Van-der-waal forces
How can water enter the body from its external environment?
- Ingesting (eating and drinking via intestines)
- Blood Transfusion (via blood vessels)
How can water leave the body?
- Vomiting (via stomach/intestines)
- Bleeding (via blood vessels)
- Urination (via kidneys)
- Perspiration (via skin)
How do the concentration of Na+ and Cl- in fluid compartments differ?
High mM in extracellular and low in intracellular
How does lipid solubility affect permeability of molecule through membrane?
More lipid soluble, more permeable and better crossing
How does the charge/ionisation of a molecule affect its permeability across the cell membrane?
The bigger the charge, the less well molecules are able to pass membrane
How does the charge/ionisation of a molecule affect its permeability across the membrane?
Bigger charge means molecules able to pass membrane less well. This is the factor that effects permeability the most.
How does the concentration of K+ differ between compartments?
Low mM in extracellular and high in intracellular
How does the size of a molecule affect the permeability through the membrane?
(Above 3nm) Increasing size, lower permeability
How does the volume of protein differ between the three compartments and why?
Low in extracellular (especially low in interstitial compared to blood plasma) and high in intracellular.
Enzymes are proteins, so high in cells so they can catalyse chemical reactions
