Cell Membranes and Exchange Across Membranes Flashcards
Why can’t sodium ions just diffuse across the membrane of a cell [1]
Because it is charged
Which part of the phospholipid is polar? [1]
The phosphate group
What model is used when describing the cell surface membrane? [1]
The fluid mosaic model
What is the function of cholesterol in the cell membrane? [2]
To provide stability to the membrane by fitting between phospholipid molecules and causing them to pack more closely together which prevents them from moving around too much which is why at warm temperatures we don’t just melt.
What structure do phospholipids arrange themselves into? [1]
Bilayer
Proteins which have a polysaccharide attached to them are called what? [1]
Glycoprotein
Proteins that run throughout the entire membrane are called what? [1]
Intrinsic
What is the function of receptor proteins? [1]
To detect chemicals released from other cells
Why does increasing the temperature increase the fluidity of the membrane? [1]
Because the phospholipids have more energy so can move around more
What does passive mean? [1]
That no energy is required
What does an active process require in order to work? [1]
Energy usually in the form of ATP
What is the definition of simple diffusion? [1]
The random net movement of particles from an area of high concentration to an area of lower concentration
Diffusion continues until what is reached? [1]
Equilibrium
What is the difference between simple and facilitated diffusion? [1]
Facilitated involves the use of channel or carrier proteins
What type of molecules may rely on facilitated diffusion? [1]
Large ones eg. Amino Acids
Polar molecules
Describe how a carried protein works? [3]
1) Large molecule attaches to the carrier protein
2) Protein changes its shape
3) This releases the molecule onto the other side of the membrane
Describe how a channel protein works? [2]
They form pores in the cell surface membrane so allow charged particles to diffuse through them, not they are specific to a certain charged particle
Describe 3 factors that affect the rate of simple diffusion? [3]
- The concentration gradient
- Surface area
- Diffusion pathway
What affects the rate of facilitated diffusion but not the rate of simple diffusion? [1]
The number of carrier proteins available for exchange
Name one way in which a cell is adapted to increase the rate of diffusion? [1]
- Microvilli
What is osmosis? [2]
The random net movement of water molecules from areas of higher water potential to areas of lower water potential
What is the water potential of pure water? [1]
0
The more solute added to a solution the more ___________ the water potential gets? [1]
Negative / Lower
If two solutions have the same water potential then they are? [1]
Isotonic
Name three factors that affect the rate of osmosis? [3]
- Surface area
- Water potential gradient
- Thickness of exchange area
What groups are required to make ATP? [3]
Adenine (organic base)
Ribose
3 phosphate groups
What type of reaction forms ATP from ADP? [1]
Condensation
What part of ATP is ‘high in energy’ [1]
The inorganic phosphate group
Active transport require what? [1]
Energy in the form of ATP
What type of process is active transport? [1]
Active
What type of proteins are required for active transport to happen? [1]
Carrier
Describe the co-transport of glucose in the ileum [5]
- Sodium ions are actively transported out of the cell to create a gradient in the ileum and the epithelial cell
- Sodium will now diffuse down this gradient back into the cell and will do this via the sodium co-transporter protein
- The co-transporter protein will also carry in glucose so the concentration of glucose in the cell increases
- The glucose then diffuses down its concentration gradient back into the blood
