Lecture 3 Flashcards
Why are organelles membrane-bound?
Organelles are membrane-bound because it allows for the separation and regulation of different cellular processes within a cell. Ensures separation of incompatible processes and optimizes efficiency by creating special environments and concentrations.
What molecule stabilises membrane fluidity?
Cholesterol stabilizes membrane fluidity.
The rigid rings of the cholesterol molecule interact with the hydrophobic tails of the phospholipids. This stabilizes them and makes them more rigid as well. This makes the cell membrane less permeable to small molecules. Cholesterol is especially important for regulating membrane fluidity in changing temperatures.
What is the difference between passive and active transport?
Passive transport does not require ATP and instead, substances can simply move down their concentration gradient
How does temperature affect the plasma membrane
High temperatures result in more fluidity (and vice versa)
What sort of molecules can passively diffuse across the plasma membrane?
Lipid soluble (hydrophobic) molecules
What happens during co-transport of molecules?
Substances are pumped out of the membrane. The concentration gradient of this substance is then used to power the movement of a second substance against its concentration.
What are the key functions of membrane proteins?
- Signal Transduction, relay messages from enviroment or body to cell
- Cell recognition (often involves glycoproteins)
- Intercellular joining, some form long lasting connections between cells
- Linking cytoskeleton and extracellular matrix*
- Membrane transport (transporting molecules, this can be passive or active)
What is facilitated diffusion
Facilitated diffusion is a form of passive transport. Proteins called channels or carriers aid movement of specific substances down their concentration gradient without the use of energy.
Carriers undergo a shape change to help guide molecule
What are aquaporins?
They are channels that allow movement of water across a cell membrane.
This relates to osmosis
What is the sodium-potassium pump an example of?
It is an example of active transport. It requires ATP to move molecules in and out of the cell membrane
Explain Co-Transport
This is indirect active transport. This is when one substance is pumped across the membrane and its conc. gradient is used to power the movement of a second substance
T or F: Cellular organelles are also bounded by membranes
True
What are some of the functions of organelles in a cell
Provide special conditions for specific
processes.
Keep incompatible processes apart.
Allow specific substances to be
concentrated.
Form concentration gradients.
Package substances for transport or export.
what are all cellular membranes composed of?
A phospholipid bilayer.
Hydrophilic heads, hydrophobic tails
Relaying messages from
the external environment
into the cell can best be
described as:
Signal transduction
Why are organelles membrane bound?
To maintain their environment. For protection and separation
Organelles are membrane-bound because it allows for the separation and regulation of different cellular processes within a cell. Ensures separation of incompatible processes and optimizes efficiency by creating special environments and concentrations.
What is the plasma membrane made of?
Phosphophilid Bilayer
What sort of molecules can passively diffuse across the plasma membrane?
Lipid soluble (hydrophobic) molecules
What happens during co-transport of molecules?
Substances are pumped out of the membrane. The concentration gradient of this substance is then used to power the movement of a second substance against its concentration.
What are the key functions of membrane proteins?
Transportation of substances
Controling the transportation of these substances
Transduction (passing signals/information into the cell)
Recognition of other cells and proteins
Membrane transport
Linking cytoskeleton to extracellular matrix
Connecting cells to other cells (sometimes long lasting connections
