USF PCB 3023 Exam 2 Questions And Answers With 100% Correct Answers
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Course
USF PCB 3023
Institution
USF PCB 3023
Composition of Lipid Bilayer - 50% lipids (outnumber all other molecules 50:1), proteins (50% of
mass of membranes), cholesterol
Plasma Membrane (Function) - Enclose Cells, Organelles
1. Defines Boundaries to regulate chemical composition and environment
2. Define malleable borders
Saturated -...
1. Defines Boundaries to regulate chemical composition and environment
2. Define malleable borders
Saturated - Single Bonded
Unsaturated - Double Bonded
Fatty Acids - Monomers for Lipids
Function of Lipids - 1. energy storage
2. cell membranes
Why Do Mitochondria have a double membrane? - Prehistoric cells absorbed mitochondria (as a
bacteria)
Why do lipids self-assemble in water? - To prevent hydrophobic tails from touching water.
Hydrophillic heads protect. This lowers free energy (delta G).
If hydrophillic heads are exposed... - Delta G will increase
Glycolipids - lipid with glycosidic bond to glucose in hydrophillic head.
Antigens on Red Blood Cells are..? - Glycolipids
,Cholesterol - A lipid steroid ring attached to glycerol. Fills gaps in Plasma Membrane left by
unsaturated hydrocarbon tails. Rigid.
How many pints of Blood are in the body? - 10 pints, on average. When you donate blood you
donate a pint. 7,000,000,000 RBCs in a single liter. Body has trillions of cells
What is Fluidity? - How easily lipids can move within a membrane
Are cells symmetrical or asymmetrical? - Asymmetrical. Asymmetry established at 'birth' of the
cell
What is flipase? - Specific catalyzed Transfer. Uses fatty acids from cytosolic monolayer to add new
membrane. Responsible for 'flip-flop' of lipids
What is scramblase? - Random Catalyzed Transfer.
Where are lipids synthesized? - Endoplasmic Reticulum.
How are lipids synthesized in the ER transported across the cell? - Via vesicles.
(EXCEPTION: Lipids for Mitochondrial Membrane and Plasmid Membrane)
Why are cells asymmetrical? - 1. To distinguish living and dead cells (Phosphatadylserine (-) is
transferred across membrane during apoptosis)
2. Signal Transduction. So that extracellular signals can be relayed through cell membrane
Types of Movement in Membrane Lipids - 1. Lateral Diffusion (~10^8 cm^2/sec at 310K)
2. Transverse Fluctuation
3. Rotation
4. Flexion
, 5. Flip-Flop (RARE for lipids. Common for cholesterol)
Planar (Black) Membrane - Technique to study a lipid bilayer
Liposome - Organelle. Good for studying lipid bilayers
FRAP- fluorescence recovery after photo-bleaching - FRAP measures membrane fluidity- the
ability of a cell to shuffle lipids laterally to replace the photo bleached portion. Revealed that cells are
typically consistency of olive oil
Transmembrane Proteins - Have hydrophillic and hydrophobic regions
Types of Transmembrane Proteins - 1. Single Alpha Helixes
2. Multiple Alpha Helixes
3. Rolled up Beta Sheets
Lipid-Anchored Proteins - Simply anchored to lipids in one layer of the membrane
Types of Lipid-Anchored Proteins - 1. Lipid Anchored via Non-Covalent Interaction
2. Covalently Attached to Lipid Chain
3. Covalently Attached to Oligosaccharide link
Types of Periphreal proteins - Attach to other membrane proteins non-covalently
Function of Membrane Proteins - 1. Transport (protons, ions, small molecules, proteins, RNA)
2. Signal Transduction (Chemical to Mechanical) or (Chemical to Chemical)
3. Cell to Cell Recognition
4. Cytoskeletal and ECM attachment
5. Catalysis
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