2.3 Transport Across Cell Membranes Flashcards
What are the components of the membrane structure?
Phospholipid bilayer Intrinsic protein Extrinsic protein Glyoprotein Glycolipid Cholesterol
What is the function of the phospholipid bilayer?
Prevents water soluble substances entering and leaving the cell
Makes the membrane flexible
Allows lipid soluble substances to enter and leave the cell
What is the function of the:
Intrinsic protein?
Extrinsic protein?
Acts as a channel to allow water soluble substances across the membrane
Provides structural support
Receptor site for cell recognition
What is the function of the cholesterol?
Is cholesterol present in plant cells?
Provides strength to membrane
Prevents loss of water and dissolved ions
Pulls together fatty acids to reduce lateral movement
Cholesterol is not present in plant cells because they have a cell wall which is strengthening enough
What is the function of the Glycoprotein and glycolipid?
What is the difference between the two structures?
Acts as a recognition site
Helps cells to attach to each other to form tissues
Glycoproteins are polysaccharides that are attached to proteins
Glycolipids are polysaccharides that are attached to phospholipids
Define hydrophilic
Define hydrophobic
Attracts water
Repels water
What is the thickness of the cell surface membrane?
7nm
Why do phospholipids align themselves in a bilayer?
Phosphate head is polar and line with extracellular fluid containing water and an inner layer aligns polar phosphate headsets intracellular fluid containing water
The non polar fatty acid tails are tucked Inbetween
Why is the model called the fluid mosaic model?
Proteins and lipids give a mosaic appearance
Proteins and can move around the lipids making it fluid
What property of phospholipids ensure that the membrane remain fluid?
Phospholipids are not bonded together. They are bound by hydrophilic and phobic interactions
What factors effect plasma membrane permeability?
Temperature
pH - wrong pH, proteins denature
Ethanol - dissolves fatty acids and cholesterol, creating gaps in membrane
Define osmosis
When water moves from a high water potential to a low water potential
Define water potential
Concentration of water in a solution
Define hypotonic
What occurs to animal cells and plants cells when it is hypotonic?
Lower concentration of solute molecules outside of cell
Animal cell bursts - cellysis
Plant cell doesn’t burst because of cell wall
Becomes turgid
Define hypertonic
What occurs to animal cells and plants cells when it is hypertonic?
Higher concentration of solute molecules outside cell
Animal cell shrivels
Plant cell membrane shrinks - plasmolysis
Cell wall does not shrink
Define isotonic
What occurs to animal cells and plants cells when it is isotonic
Equal concentration of solute molecules outside cell
Animal cell - nothing
Plant cell - cell membrane is slightly torn away - incipient plasmolysis
Describe the phospholipid structure
What does it do, in terms of its function in the cell?
Phosphate head
Polar hydrophilic
2 fatty acid tails
Hydrophobic
Non polar
Forms a bilayer between extracellular and intracellular fluid
Define simple diffusion
How is diffusion affected by ficks law?
give an example of a molecule that passes a membrane using simple diffusion
Net movement of particles down the concentration gradient from a high concentration to a low concentration
Rate of diffusion increases with increase in SA, decrease in thickness of exchange surface and increase in concentration gradient
Oxygen
Define facilitated diffusion
Movement of particles down concentration gradient using a carrier or channel protein (transport proteins)
How does a carrier protein work?
Give 3 examples of molecules that pass through a carrier protein
- A large molecule attaches to binding site of carrier protein
- Protein changes shape and releases molecule on the other side. It then assumes its original position
Amino acid
Glucose
Testosterone
How does a channel protein work?
What kind of molecule passes through a channel protein? Give an example
Charged particles (ions) diffuse across the channel protein because the pore is lined with polar groups
Channel proteins are specific to one particular ion each
They can open and close
Solute molecule
Sodium
Define active transport
Movement of particles against concentration gradient, moving from a low concentration to a high concentration, through a carrier protein, requiring energy
