Unit 3: Membrane Structures and Transport Flashcards
(35 cards)
Generally speaking, what is a membrane structure composed of?
a. Lipids (usually phospholipids)
b. sterol lipids
c. proteins
Describe phospholipids.
Phospholipids form a bilayer due to their construction. They have a hydrophilic head and a hydrophobic tail (composed of fatty acids).
True or False: Lipid membranes are stationary.
False. They move constantly in the same plane.
What is cholesterol?
A sterol lipid found between fatty acid chains. They keep membranes fluid and stabilize them.
What is cholesterol’s equivalent in plants?
Phytosterols.
What is the approximate ratio of proteins in the cell? Why?
Approximately 50 lipid molecules to 1 protein. This is due to the larger size of a protein.
What are two main points about proteins with regards to the cell membrane?
a. There are many different types.
b. They are specific to each cell type.
What are the 7 membrane functions?
- Define the cell–contains and separates.
- Selective transport.
- Enzyme activity.
- Signal transduction–protein receptors
- Cell adhesion– cell-to-cell link
- Cell recognition
- Attachment to cytoskeleton
What do protein receptors do?
They transfer messages from the outside of the cell to the inside of the cell. The reverse is also possible.
What allows cell membranes to have their 7 functions?
Membrane Proteins.
Where is most of our cholesterol used?
To make bile.
What re the 3 types of membrane proteins?
Peripheral membrane proteins, integral membrane proteins, trans-membrane proteins.
What is diffusion?
The movement of particles down concentration gradient examples of molecules that can diffuse thru membrane.
What can diffuse thru a membrane?
Water, EtOH, oxygen, carbon dioxide, nitrogen gas, hydrophobic molecules and lipid-soluble molecules.
What is osmosis?
The passive transport of water through aquaporin channels ad through membranes.
What are the three “main types” of solutions?
Hypotonic, isotonic and hypertonic.
What are some examples of osmosis?
Turgor pressure (plants), using salt or sugar as preservatives, water moving into the stomach after the addition of H and Cl ions, and contractile vacuoles (some protists).
What is facilitated diffusion?
The transport of solutes across membrane down concentration gradient via specific transport proteins (channel proteins).
What does down concentration gradient mean?
To move from an area of high concentration to one of low concentration.
What are two examples of facilitated diffusion?
Glucose transporter and gated ion channels in membranes of neurons.
What is active transport?
It is transport against concentration gradient. It requires energy and transmembrane proteins.
What are other terms for transmembrane proteins?
Pumps or exchangers.
What are the 4 types of active transport?
a. Ion pumps
b. Co-transport
c. Exocytosis
d. Endocytosis
What are ion pumps?
They move ions across the membrane against their concentration gradient.
