2.3 Transport across cells Flashcards
Cholesterol function in cell membranes
- Provides stability
- Fits between phospholipids, binding to tails
- Causes phospholipids to bind more closely and restricts movement
- Less fluid more rigid, maintain shape of animal cells
- Impermeable
Simple diffusion definition
Net movement of particles down a conc. gradient from an area of high conc. to an area of low conc. directly through a cell membrane
What types of protein does facilitated diffusion use?
Carrier proteins + Protein channels
What types of protein does active transport use?
Carrier proteins
What is facilitated diffusion?
Movement of large molecules or charged molecules through proteins across a membrane
Is diffusion an active process?
No - always passive ∴ no ATP required
What is Fick’s law?
Rate of diffusion ∝ S.A x conc. difference / membrane thickness
Osmosis definition
Net movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane
What are the stages of plant cells being plasmolysed?
Turgid - Incipient plasmolysis - Flaccid/plasmolysed
Protoplasm and cell wall being detached/ connected
Is active transport active?
Yes - its in the name dumbass
Active transport definition
Net movement of particles from areas of low conc. to areas of high conc. against the conc. gradient through carrier proteins across a membrane
How do co-transporters work?
Bind two molecules at a time
- Conc. gradient of one molecule used to move other against its’
What factors affect active transport rate?
- ATP production (respiration)
- No. carrier proteins
- Speed of carrier proteins
What are aquaporins?
Integral channel proteins for water movement
Describe the co-transport of glucose
1) Na+ actively pumped out of epithelial cells into blood by Na+/K+ pump
- High conc. of Na+ in lumen, low in cells
2) Na+ diffuses from lumen into epithelial cells down conc. gradient through Na+/ glucose co-transporter protein
3) Co-transporter also carries glucose into cell
4) Glucose diffuses into blood via facilitated diffusion through channel protein
