CM Structure And Function Flashcards
Describe the phospholipid bilayer.
- Make up the cell membrane. PL’s arranged in 2 layers -PB. PL’s have 2 side, one is the hydrophilic head which likes water and the hydrophobic tails which dislike water. Tails are made up of FA’s and point inwards.
- PB allows small, non-polar molecules like oxygen and CO2 to pass whereas larger, charged molecules like ions and glucose must pass through proteins.
- PB isn’t rigid as it has lipids and proteins that can move around allowing the membrane to be flexible.
What is cholesterol?
A lipid that acts as a spacer in the CM. Keeps CM fluid and flexible. Without it the CM would be rigid depending on temperature.
How does cholesterol maintain fluidity at low temperature?
It prevents PL’s from packing too closely which keeps the CM from being to stiff.
How does cholesterol maintain fluidity at high temperature?
It reduces movement of PL’s, preventing CM from becoming too loose and unstable.
What are peripheral proteins?
Proteins which sit on the surface of the CM and help maintain cells shape and transmit signals.
Define passive transport.
Movement of molecules from a low concentration to a high concentration. No energy required.
Name and explain two types of passive transport.
- Simple diffusion- small, non-polar molecules like oxygen ca pass through PB.
- Facilitated diffusion- larger/charged molecules like ions and glucose need transport proteins like channels/carriers to pass through PB.
Define active transport.
Movement of molecules from a low concentration to a high concentration, against the gradient. It requires ATP energy and carrier proteins.
Explain the sodium-potassium pump.
- 3Na+ from inside the cell bind to the protein pump.(antiporter pump).
- ATP attaches to the pump and transfers energy (ATP phosphorylation) causing pump to change shape.
- Pump releases the 3Na+ out of cell.
- 2K+ from outside the cell bind to the pump.
- Pumps goes back to original shape and releases the 2K- into the cell.
Explain the membrane potential and explain how ion channels are involved.
Resting membrane potential is when the cells is negative on the inside and positive on the outside.
Maintained using the sodium-potassium pump.
Some K+ are leaked out of the cell via ion channels which further keeps the inside of the cell more negative.
What is endocytosis and name three types.
Endocytosis is how the cell takes in large particles/fluids by engulfing them.
3 types include; phagocytosis, pinocytosis, and receptor-mediated endocytosis.
Explain phagocytosis.
Cell eats large particles like bacteria. (Engulfing large particles).
Explain pinocytosis.
Cell drinks small droplets of fluid.
(Taking in fluids and dissolving substances).
Explain receptor-mediated endocytosis.
Cell uses receptors to bring in molecules like cholesterol. Specific molecules bind to receptors on cell surface, CM surrounds the molecule forming a pocket which pinches off to forms a vesicle inside the cell.
What is exocytosis?
In animals, cells release materials like hormones and NT into extracellular environment.
Used in plants to export cell wall material. Vesicles fuse with plasma membrane and the contents are released outside the cell.
What is the ECM and what are the contents?
Network outside the cell to support and help cells communicate. Made up of:
- collagen to provide strength and structure to tissues.
- proteoglycans to help tissues resist compression.
- fibronectin to help the cell stick to ECM.
- integrins are proteins that connect the ECM to the cells cytoskeleton.
How does ECM help cells?
- collagen provides scaffolding, giving the tissue strength.
- proteoglycans create a gel like matrix that cushions cells to resist compression.
- integrins transmit signals between ECM and cell, helping cell respond to their environment.
What is cystic fibrosis and explain how it’s caused?
A genetic disease caused by a mutation in the CFTR gene, which codes for a protein that helps move chloride ions across CM.
CFTR protein doesn’t work so the chloride ions don’t leave the cell - without their movement water doesn’t flow out of the cell leading to thick mucus in lungs.
Mucus blocks airway making breathing difficult and clogs ducts in pancreas which affects digestion.
What are the 3 types of carrier proteins used in active transport?
Uniporters - move one molecule at a time
Symporters - move two molecules in the same direction
Antiporters - move two molecules in opposite direction
What is the resting membrane potential in eukaryotic cells?
-40 to -80 mv
