Topic 3: Membranes Flashcards
Describe fatty acids
Long chain of carbon atoms with a carboxyl group at one end
Average number of carbons in a fatty acid chain
12-20
Describe triacylclylcerols
3 fatty acids bound to a glycerol anchor
Describe a phospholipid
a glycerol head at the top, attached to two fatty acid tails
What are triacylglycerols used for?
to store energy
‘Amphipathic’ means…
having both hydrophilic (polar) and hydrophobic (non-polar) properties
A micelle is…
a formation of phospholipids, like an oil drop in water. Glycerols face outwards.
A liposome is…
a formation of phospholipids, used in medicine to deliver needed substances. Hollow ball of phospholipids, with hydrophilic properties facing outwards, but also inwards in a second layer
Which type of proteins go all the way through the membrane?
Integral Proteins
Peripheral proteins never touch….
the hydrophobic core
Amphipathic proteins are…
integral proteins
Four functions of membrane proteins
Transport, enzymatic activity, signal transduction, and attachment recognition
Sterols can prevent freezing in the bilayer by…
embedding themselves between the phospholipids, preventing them from packing too tightly
Sterols can prevent melting in the bilayer by…
embedding themselves between the phospholipids to fill in the gaps.
Four ways to increase membrane fluidity
1) short chain fatty acids
2) unsaturated fatty acids
3) sterols
4) higher temperatures
Four ways to decrease membrane fluidity
1) long chain fatty acids
2) saturated fatty acids
3) sterols
4) lower temperatures
True or False: Sterols are amphipathic
True
Order the following from best to worst for crossing the cell membrane:
Ions, small uncharged polar molecules, large uncharged polar molecules, non-polar molecules
1) non-polar molecules
2) small, uncharged polar molecules
3) large uncharged polar molecules
4) ions
True or False: facilitated diffusion is active transport
False
Aquaporins are…
narrow channel proteins that allow the passage of water across the membrane
A Gated channel is…
a channel protein that can switch between open, closed, and intermediate states to transport most ions across the cell membrane
Carrier proteins…
passively transport larger molecules across the cell membrane using diffusion and facilitated transport
Why do cells need a selective barrier?
To maintain homeostasis in dynamic environments
How does diffusion work in relation to the concentration gradient of a solute
works with the concentration gradient to reach equilibrium, does not require ATP
Osmosis vs Diffusion
Osmosis is specifically the diffusion of water. If the solute can’t diffuse to reach equal concentrations, water will diffuse to do so
Type of diffusion represented with a linear function
Simple diffusion (rate of reaction increases steadily with concentration)
Type of diffusion represented with a logarithmic function
Facilitated diffusion (rate of reaction increases drastically at first, but levels out and reaches a plateau)
A 5M liposome placed in a 10M solute, solution is….
hypertonic. water diffuses outwards
4.2M liposome placed in a 4.2M solute, solution is….
isotonic. At equilibrium
9.2M liposome placed in 4.2M solute, solution is….
hypotonic, water diffuses inwards
Secondary Active Symport…
a solute is transported against it’s own concentration gradient with the help of a driving ion in the same direction
Secondary Active Antiport
a solute is transported against its own concentration gradient with the help of a driving ion in the opposite direction
Secondary Active Transport…
indirectly uses ATP, taking energy released by other reactions
Primary Active Transport…
requires ATP
Which of the following is NOT found in a triglyceride?
Saturated fatty acids, unsaturated fatty acids, charged organic group, or glycerol anchor.
Charged organic group
A larg epolar molecule moves through a protein against its concentration gradient, and hydrolyzes ATP during the process. What is this?
Primary active transport
What could a cell do to prevent its membrane from becoming too viscous?
Increase sterols, increase unsaturated phospholipids
Which of the following can most easily diffuse across a lipid bilayer?
Methane, water, glucose, or H+
Methane
(non-polar small molecule)
How does preserving olives in brine (20-30% salt solution) help prevent it from spoiling or being contaminated by microorganisms?
Bacteria can’t survive in a hypertonic solution because their cytoplasm loses wate
Which of the following is NOT a component of a phospholipid?
A 3-carbon glycerol backbone
A phosphate group
A core of four fused carbon rings
Two fatty acid tails
A core of four fused carbon rings
A cell wanting to move Magnesium ions across a lipid bilayer down its concentration gradient would use…
a protein channel
Unsaturated fatty acids cause a membrane to be fluid at lower temperatures. Why?
The double bonds form a kink in the fatty acid tails, forcing adjacent lipids to be spaced further apart
In the fluid mosaic model, what does ‘fluid’ refer to?
The movement and exchange of phospholipids and proteins within the two layers of phospholipids
What is the difference between simple diffusion and facilitated transport?
Facilitated transport requires a transport protein, while simple diffusion does not
What 2 terms can refer to the movement of water across a membrane from an area of lower solute concentration to an area of higher solute concentration?
Diffusion & Osmosis
