Transport across Membranes Flashcards
What is a cell membrane?
A phospholipid bilayer
What molecules can diffuse through the phospholipid bilayer?
Small non-polar ones e.g. CO2 and O2 and lipid soluble
What is the role of cholesterol in the phospholipid bilayer?
It adds strength and support by making the membrane more rigid and less flexible. This is useful because animal cells have no cell wall and cells like haemoglobin nneed more strength as they travel alone
What is diffusion?
The net movement of molecules from an area of high concentration to low concentration along a concentration gradient
What type of movement is diffusion?
Passive
Does diffusion require ATP?
No
What are the three features that increase the rate of diffusion?
Short diffusion pathway- Large surface area- Concentration gradient
Give examples of the body increasing surface area
Villi- Microvilli- Alveoli- Cristae- Thylakoids
What is facilitated diffusion?
The passive movement of molecules across the cell membrane via a specific membrane transport protein
How does active transport work?
Using a carrier protein and energy from ATP, against conc. gradient
How does co-transport work?
Via a carrier protein which moves 2 molecules at once, one along the concentration gradient and one against the concentration gradient
What is osmosis?
The passive movement of water molecules from an area of less negative water potential to a more negative water potential
Within active transport, which proteins are not involved?
Channel
What is a solution called which has the same water potential as the cell?
Isotonic
If a cell is placed into a hypotonic solution, what will the net direction of water be?
Into the cells
