What are 2 characteristics of the selectively permeable membrane?
Allows nutrient uptake and waste removal.
Allows hydrophilic molecules to pass through the membrane with ease
Phospholipid membranes are described as what?
What does the ‘mosaic’ portion of the membrane refer to?
To the proteins floating within
What does the ‘fluid’ portion refer to?
To the proteins being able to move about in the membrane
Are fatty acids amphipathic?
What do the double bonds between the polar + nonpolar components do to the membrane?
Keeps the membrane fluid
Prevent the fatty acids from packing closely together
How is membrane fluidity maintained?
With decreasing temp.
As temp continues to decrease, the phospholipids continue to solidfy slowly.
In a plasma membrane, what dictates the freezing temp.
Saturated vs. Unsaturated fatty acids
Long chain vs. Short chain fatty acids
What behaves as a temp buffer in the plasma membrane allowing it to be semi-fluid at environmental conditions?
What are the 2 major classes of proteins in the membrane?
Integral and peripheral
What are characteristics of integral membrane proteins?
Penetrate membrane interior
Involved with transporting larger and polar molecules
What are characteristics of peripheral membrane proteins?
Do not go through the membrane, they’re loosely attached
Act as enzymes
Attachment to cytoplasmic side: cytoskeleton
Attachment to the extracelkular side: extracellular matrix
What are the 6 primary functions of membrane proteins?
- Providing a stronger membrane network.
- For cell to cell recognition
- To form tight membrane junctions between different cells
- Function as enzymes
- Function as receptors
- Important for transportation
What are membrane carbs involved in?
What do membrane carbs do?
Remove foreign cells from the body
Covalently attach to lipids, membrane proteins
How can the attached carbs vary?
They vary from cell to cell
Vary from species to species
Vary from different individuals of the same species
Why is the bidirectional movement (in and out) of the plasma membrane important?
Nutrients enter and wastes exit
Important for ion regulation
Maintains selective permeability of the cell
What are the 2 types of transport proteins?
Channel and carrier proteins
How does the diffusion rate across the plasma membrane vary?
Due go size, shape and chemical nature of the material, the diffusion rate vary
How do channel proteins transport molecules?
They form a hydrophilic channel through the membrane.
Only open in response to certain stimuli: Usually electrical, chemical, mechanical
How do carrier proteins transport molecules?
Physically grab and escort the molecules through
They show a high degree of substrate specifity
Interior changes shape to allow movement of materials
Does a passive process requires work or no?
Does this process happen spontaneously or non-spontaneously?
Passive process requires no work, hence it is a spontaneous process
What’s osmosis? Is this a passive or active process?
It’s the movement of water across a semi-permeable membrane?
It’s a passive process
How does the water move in osmosis?
From low to high concentration regions.
Always occurs regardless of the solute identity
Describes the ability of solution to cause a cell to gain or loose water.
Mainly dependent on the concentrations of solute that are unable to cross a membrane
Match the following. (For organisms with a cell wall)
Isotonic, hypotic, hypertonic, plasmolyzed, turgid, flaccid
Plant and animal cells gain/lose water to survive.
Why do organisms that lack a cell wall live in isotonic environments?
To maintain constant internal environment which will prevent cell lysis or shriveling.
What are contractile vacuoles?
Have pumps to force water out of the cell to prevent cell lysis in hypotonic environments
What does a cell wall provide in hypotonic environments?
Cell wall swells in hypotonic environments but it will ONLY swell so much before it exerts a counter force called turgor pressure.
What effect does turgor pressure have on the cell?
It will be more firm (turgor)
Allows mechanical support for small plants
What’s facilitated diffusion? Is this passive or active?
Transport proteins facilitate the movement of polar molecules and ions across membrane
What do transport proteins do to the speed of the polar molecules that move across the membrane?
It speeds up the movement substantially.
Transport protein: Always very specific to certain materials
How does the shape of the carrier proteins change?
A molecule binds triggering rhe shape change.
Allows materials to pass down the concentration gradient
What’s the name of the protein channel that water uses to pass through the membrane?
What’s active transport?
Uses energy to move molecules against its concentration gradient
What’s primary and secondary active transport?
Primary: ATP utilization to move materials against concentration gradient
Secondary: Using another form of energy to move materials
Are all proteins involved in active transport carrier proteins?
What’s the process of active transport?
- Solute to be transported binds to a specific site on the transport protein
- ATP molecule transfers one of its phosphates to the transport protein
- The protein changes shape once ATP binds to it so the solute can be released on the other side of the membrane
- Phosphate detaches and the transport protein changes back to its original shape
What are the 2 forces that drive the movement of the solute?
Concentration difference + charge difference
Is the inside of the cell more positive or negative?
What creates the charge separation of the cell?
Ex: Proton pumps
What are co-transporters?
They couple the movement of one material down it’s concentration gradient to the movement of another material UP its concentration gradient
What’s bulk transport?
When larger molecules require entry into the cell using vesicles
What does bulk transport include,
Exocytosis and endocytosis
How does exocytosis take place?
- Transport vesicle full of the molecule to be exported buds from the golgi apparatus and move towards plasma membrane
- The vesicle fuses with the plasma membrane, expelling the it’s contents with it. (Larger molecules: proteins + sugars)
What are the 3 types of endocytosis?
Phagocytosis, pinocytosis, receptor-mediated endocytosis
Cell engulfs a particle by wrapping it with pseudopods.
- Particle is packages into a vacuole
- Vacuole fuses with lysosome
- Digestive enzymes break down vacuole contents
Droplets of fluid are taken up by tiny vesicles
What’s receptor-mediated endocytosis?
Receptor proteins are specific for a certain molecule
Receptor proteins pick up the specific molecule and plasma membrane pinches inward forming a coated pit.