2.3 Plasma membrane: composition and surface area, and 2.4 Transport across the plasma membrane Flashcards
What is the environment of living cells?
A layer of fluid in contact with the outer plasma membrane.
What is the plasma membrane?
Controls the movement of substance between the extracellular fluid outside and the intracellular fluid (cytosol) inside the cell.
What conditions can unicellular organisms regulate and give an example for each:
- Temperature (pant, shiver, lose fur)
- Oxygen concentration (breathing in)
- Carbon dioxide concentration (breathing out)
- pH (acidity or alkalinity)
- Osmotic pressure (concentration of salts/ions)
- Nitrogen waste concentration
- Glucose concentration (store it in the body for when it is needed)
What is the phospholipid bilayer?
A double layer of phospholipids which makes up the plasma membrane.
What are the 2 functions of the phospholipid bilayer?
Acts as a flexible boundary of the cell
-Restricts what chemicals/substances can come in and out of the cell
What are the 2 types of membrane proteins?
- Integral proteins (permanents part of the membrane)
- Peripheral proteins (temporary)
List the 6 functions of membrane proteins:
- Transport substances across the membrane
- Secure the cytoskeleton to the membrane
- Enzymes (catalysts for reactions by lowering energy)
- Receptors
- Cell to cell adhesion
- Identity markers
What is a solute?
A substance dissolved into a liquid
What is a solvent?
A liquid
What is a solution?
A solute and a solvent
What is a concentration?
The amount of solute dissolved in an amount of solvent or solution
What is diffusion?
The passive net movement of a substance from an area of high concentration to an area of low concentration.
-Diffusion is very fast over small distances, while it is very slow over long distances.
What is a concentration gradient?
The difference between solute concentrations
When is diffusion fastest?
- There is a high concentration difference
- Heat is applied
What are the 2 molecules which cannot readily cross the phospholipid bilayer?
- Non-polar, uncharged hydrophobic molecules
- Small, polar uncharged hydrophilic molecules
What are the 2 molecules which cannot diffuse across the phospholipid bilayer?
- Larger (> 5 carbon atoms) uncharged polar molecules
- Ions (charged)
What is the function of channels in the phospholipid bilayer?
Provide a route for diffusion of substance that cannot penetrate the lipid bilayer
What are the principles of diffusion?
- The smaller the object, the greater the diffusion (large SA:V)
- The larger the object, the lower the diffusion (small SA:V)
What is osmosis?
The movement of free-water molecules through a semi-permeable membrane from an area of high water concentration to low water concentration across a select semi-permeable membrane.
What is a hypertonic solution?
A solution that contains a high concentration of solute compared to the other side of a semi-permeable membrane.
What is an isotonic solution?
A solution that has an equal solute concentration compared to the other side of a semi-permeable membrane.
What is a hypotonic solution?
A solution that contains a lower concentration of solute compared to the other side of the semi-permeable membrane.
What is exocytosis in bulk transport?
Transport out of a cell, where vesicles transporting molecules fuse to the membrane to release their contents.
What is endocytosis in bulk transport?
Transport into the cell, which has 3 types.
What is active transport?
The active net movement of a substance from an area of low concentration to an area of high concentration through a membrane via a carrier protein.
What is facilitated diffusion?
The passive net movement of a substance from an area of high solute concentration to an area of low solute concentration through a membrane via a specific protein channel.
