Chapter 6: Lipids and Membranes Flashcards
What is diffusion and how does it occur?
Movement of any molecule down its concentration gradient. It occurs spontaneously without any energy
What is turgor pressure and why is it important to plans?
The pressure produced by water coming into a cell due to a hypotonic solution. The cell is able to be rigid and retain water
How does facilitated diffusion work?
Channel proteins or carrier provide a doorway for certain polar molecules and ions to pass
How does LDL get increased?
A diet high in saturated fats
What does increased HDL lead to?
More cholesterol excretion
How many sodiums are moved out of the cell and how many potassiums move in the cell in the sodium-potassium pump?
3 sodiums move out and 2 potassiums move in
What type of protein is a GLUT-1 transporter?
Carrier protein
Why are saturated fats solid at room temperature?
They can pack close together due to their linear structure
Which fats are considered “healthy” fats?
Unsaturated fats
How does an unsaturated fat differ from a saturated fat?
Unsaturated fats have one or more double bonds between C; there is one fewer H on each double-bonded carbon
What is active transport?
When energy is required
What characterizes a steroid?
A carbon skeleton with four fused rings
What causes cystic fibrosis?
Mutant CFTR channels (channel proteins). Chloride on inside can’t fill in the holes on the channels and the channels won’t be open so mucus accumulates outside the cell
How do cotransporters work?
They use the power of ions moving down their gradient to move a molecule against its gradient
What molecules can easily cross the selectively permeable membrane?
Small nonpolar molecules like hydrocarbons, CO2, and O2
What happens at equilibrium?
The ions on both sides are balanced and there is no net movement, but the ions still continue to move across
What are peripheral proteins?
Membrane proteins that are loosely bound to the surface of the membrane and often interact with exposed surface of integral proteins
Why are unsaturated fats liquid at room temperature?
They can’t pack as close together due to their bendy structure
What is the key characteristic that all lipids share?
Hydrophobic
What do double bonds between C in unsaturated fats cause the fatty acid chain to do?
Kink and bend in a different direction
What does hypotonic mean?
Less solutes are in the environment
How does a glycerol bind with a fatty acid?
Dehydration
What are aquaporins?
Channel proteins that allow water to flow through at an extremely high rate
How specific are cotransporters?
Very specific. Both molecules must be present for it to work
What is HDL?
High density lipoprotein. Removes LDL from the bloodstream. “Good” cholesterol
How often does the plasma membrane move?
It moves laterally 10^7 times per second
What influences membrane permeability?
Fatty acids of different lengths and saturation
What does isotonic mean?
The environment outside the cell is the same as inside
What are essential fatty acids and how do we get them?
Fatty acids we must get through our diet because our bodies don’t produce them. Omega 3s, Omega 6, Fish oil, etc.
How is it determined what can pass through a channel protein?
What amino acids are expressed
How does soap work?
Soap dissolves in water and orients themselves w the oil/grease, agitation separates oil from surface, and it is washed away in running water. It takes advantage of hydrophilic and hydrophobic
Which fats are solid at room temperature and which are liquid at room temperature?
Saturated are solid and unsaturated are liquid
How does a saturated fat differ from an unsaturated fat?
Saturated fats have no double bonds between C and have the most H atoms as possible
Which fats clog arteries and why?
Saturated fats because they can pack close together
What are trans fats?
Mostly man-made fats that exist naturally in very small amounts. They are created by adding hydrogen atoms to unsaturated fats. They were an attempt to create healthy saturated fats
Are lipids polymers?
No, they are clumped together because they are hydrophobic
Do carrier proteins change shape?
Yes
What happens if the environment is hypertonic to the cell?
Water moves out of the cell
What is cystinuria?
Defect in carrier protein that transports cysteine across membrane of kidney cells leading to bladder stones. Very common in dogs
What are the 3 ways molecules move across the membrane?
Diffusion, facilitated diffusion, and active transport
What types of steroids are made from cholesterol?
Sex hormones (estrogen and testosterone)
What molecules require a membrane protein to cross the selectively permeable membrane?
Ions and polar molecules
Do channel proteins change shape?
No
What does hypertonic mean?
More solutes are in the environment
What are the functions of membrane proteins?
Transport, enzyme activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix (ECM)
Is it easy for the membrane to flip-flop?
No, it is very rare
What are fats more commonly known as?
Triglycerides
What are the three types of lipids that are the most biologically relevant?
Steroids, fats, and phospholipids
What are integral (transmembrane) proteins?
Membrane proteins that span the membrane with segments both inside and outside the cell
How do longer hydrocarbon chains effect membrane permeability?
They decrease permeability because molecules have to travel further when the chains are longer
What is the difference between HDL and LDL?
HDL removes LDL that clumps in the bloodstream. The difference lies in what other proteins are present
What does cholesterol do?
It is a precursor from which other steroids are synthesized. It is also an important component of the cell membrane
What can happen with a mutation to the aquaporin-2 gene?
Nephrogenic diabetes insipidus. Can’t absorb water the way they’re supposed to and have to always have water with them
What does secondary active transport (cotransport) do?
Uses the gradient created by an ATP powered pump to power the transport of a molecule against its gradient
What proteins are used in facilitated diffusion?
Channel proteins and carrier proteins
What type of transport is facilitated diffusion?
Passive transport
How do proteins arrange themselves in the membrane?
Hydrophilic parts are on the outside and the hydrophobic parts and in between the bilayer
What do all different types of cells contain?
Different membrane proteins
When are ion pumps used?
Active transport
What do HDL and LDL stand for?
High density lipoprotein and low density lipoprotein
What does the word hydrogenated indicate?
Trans fats
What is osmosis?
The diffusion of water across a semipermeable membrane
How do viruses infect certain cells?
They need certain receptors to bind to
What happens during active transport?
Energy (ATP) is used to move molecules against their concentration gradient
Why do we use trans fats?
They were designed as a healthy alternative to saturated fats, but they turned out to be worse for us than saturated fats
What types of molecules use facilitated diffusion?
Polar molecules and ions
What does amphipathic mean? What molecule is amphipathic?
It has two different regions with distinct properties (hydrophilic and hydrophobic). Phospholipids are amphipathic
How are trans fats made?
Taking an unsaturated fat and getting rid of the C double bonds or changing the configuration to end with an unsaturated fat with the properties of a saturated fat
What are the two parts of a phospholipid?
Hydrophilic phosphate head and hydrophobic fatty acid tails
Do membranes have the same mosaic everywhere?
No, it is different everywhere
How do phospholipids orient themselves in a membrane?
The tails face in and the heads face out
What do ion pumps do?
Maintain electrochemical gradients and membrane potentials for nerve impulses
Why are phospholipids able to form membranes rapidly?
Because they are amphipathic
What does the fluid mosaic model imply?
The membrane is always moving and made up of more than just phospholipids
What happens if the environment is hypotonic to the cell?
Water moves into the cell
What is LDL?
Low density lipoprotein. It clogs arteries. “Bad” cholesterol
What are the two molecules that fats are made from?
Glycerol and fatty acid
What type of lipid is cholesterol?
Steroid
Is energy used on a cotransporter?
No, it is used to create a build up of charge on one side.
How do carrier proteins work?
Change shape to shuttle molecules across the membrane. They are a doorway with a door. The molecule comes in and the door to the extracellular fluid closes as the one to the interior opens
How do you distinguish between steroids?
Different chemical groups are attached to the four carbon rings
What are the two major types of membrane proteins?
Integral (transmembrane) and peripheral
What is passive transport?
When no energy is required
These macromolecules don’t mix with water
Lipids
Are fats polymers?
No
How do molecules move down their concentration gradients?
From high to low concentration without being effected by other substances
