Passage Of Substances Across Them Question:membrane

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AP Biology Unit 2 Questions with

Detailed Verified Answers

Question: Fluid Mosaic Model

Answer: The currently accepted model of cell membrane structure, which

envisions the membrane as a mosaic of protein molecules drifting laterally

(Move continually and form changing patterns) in a fluid bilayer of

phospholipids (Molecules are not attached side to side and are free to slide

next to each other)

Question:Methods that Keep Cell Membranes Fluid

Answer: Phospholipid changes or shifts; Cold hardening of plants: Shift to

unsaturated fatty acids; Hibernating Animals: Increase cholesterol (Decreases

fluidity)

Question:Methods for Transporting Small Molecules Across the Cell

Membrane

Answer: If hydrophobic, can cross phospholipid bilayer

Question:Methods for Transporting Large Molecules Across the Cell

Membrane

Answer: Can cross through certain transport proteins; Exo/endocytosis

Question:Selective Permeability

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Answer: A property of biological membranes that allows them to regulate the

passage of substances across them

Question:Membrane Composition of Plant in Hot Climates

Answer: Membrane might contain phospholipids with more saturated

hydrocarbons and contain more cholesterol to decrease the fluidity of the

membrane

Question:Membrane Protein Functions

Answer: Transport, enzymes, signal transduction, cell to cell recognition,

intercellular joining, attachment to the cytoskeleton

Question:Glycolipid and Glycoprotein

Answer: Membrane carbohydrates that vary from cell to cell, which enable

membrane carbohydrates to function as markers that distinguish one cell

from another; Attach cells, cell-cell recognition, cell communication

Question:Integral Proteins

Answer: A transmembrane protein with hydrophobic regions that extend into

and often completely span the hydrophobic interior in contact with the

aqueous solution on one or both sides of the membrane (or lining the channel

in the case of a channel protein); Pass through the phospholipid bilayer; Act as

enzymes, help in communication and structure; Act as transport proteins;

Have polar amino acids to match the head areas and non-polar amino acids in

the fatty acid area

Question:Peripheral Proteins

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Answer: A protein loosely bound to the surface of a membrane or to part of

an integral protein and not embedded in the lipid bilayer; On cytoplasmic side

of the membrane; Act as enzymes, help in communication and structure

Question:Outer Membrane vs. Inner Membrane

Answer: Outer membrane has oligosaccharides attached while the inner

membrane does not, the ECM or cytoskeleton are only found on one side of

the membrane

Question:Cholesterol

Answer: Helps to regulate membrane fluidity; Makes membrane less fluid by

restraining phospholipid movement; Also lowers temperature required for

membrane to solidify; Helps resist changes in fluidity as temperature changes;

Decreases fluidity

Question:Membrane Carbohydrates

Answer: Branched oligosaccharides form glycophospholipids and

glycoproteins on external surface; Recognition of “self” vs. “other”

Question:Phospholipid Bilayer

Answer: O2 and CO2 are small molecules that can diffuse across; Hydrophilic

molecules (polar), large molecules, and ions can’t cross the phospholipid

bilayer

Question:Transport Proteins

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Answer: A transmembrane protein that helps a certain substance or class of

closely related substances to cross the membrane; Provides a polar

(hydrophilic) environment for ions and polar molecules to diffuse through

Question:Aquaporins

Answer: Facilitated diffusion channels that allow water to cross membranes

Question:Diffusion

Answer: The random thermal motion of particles of liquids, gases, or solids. In

the presence of a concentration or electrochemical gradient, diffusion results

in the net movement of a substance from a region where it is more

concentrated to a region where it is less concentrated; Affected by

concentration, temperature, pressure, particle size, and mixing (stirring)

Question:Passive Transport

Answer: The diffusion of a substance across a biological membrane with no

expenditure of energy; Diffusion, osmosis, facilitated diffusion

Question:Concentration Gradient

Answer: A region along which the density of a chemical substance increases

or decreases; In passive transport, substances move down the concentration

gradient

Question:Osmosis

Answer: The diffusion of free water molecules across a selectively permeable

membrane