UIUC ANSC 221, Exam II Questions With
Verified Answers
Biological Membranes
Framework of the membrane is the phospholipid bilayer
Hydrophobic
water fearing region, faces in
Hydrophilic
water living region, faces out
Fluid-mosaic model
membrane is considered a mosaic of lipid, protein, and carbohydrate molecules
Integral/Intrinsic membrane proteins
transmembrane and lipid-anchored proteins
Transmembrane proteins
One or more regions that are physically embedded in the hydrophobic region of the phospholipid
bilayer
Lipid-anchored proteins
Covalent attachment of a lipid to an amino acid side chain within a protein
Peripheral membrane/extrinsic proteins
Noncovalent bound to regions of integral membrane proteins that project out from the membrane, or
they are bound to the polar head groups of phospholipids
Fluidity
individual molecules remain in close association yet have the ability to readily move within the
membrane
Semifluid- most lipids can rotate freely around their long axes and move laterally within the
membrane leaflet
Length of fatty acyl tails & fluidity
Shorter acyl tails are less likely to interact, which makes the membrane more fluid
Double bonds in acyl tails & fluidity
Double bond creates a kink in the fatty acyl tail, making it more difficult for neighboring tails to
interact and making the bilayer more fluid
Cholesterol & fluidity
Cholesterol tends to stabilize membranes (effects depend on temp.)
, Depending on the cell type, _____% of membrane proteins may be restricted in their movement.
10-70%
Integral membrane proteins may be bound to components of the cytoskeleton, which restricts the
proteins from moving _____.
laterally
Cytosol and endomembrane system work together to synthesize most _____.
lipids
Cytosolic leaflet
located in smooth ER
Fatty acid building blocks
made via enzymes in cytosol or taken in from food
Most transmembrane proteins are directed to ____
ER membrane
From ER membrane bound proteins can be transferred via _____ to other regions of the cell
vesicles
Glycosylation
Process of covalently attaching a carbohydrate to a protein or lipid
Glycolipid
carbohydrate to lipid
Glycoprotein
carbohydrate to protein
N-linked
attachment of carbohydrate to nitrogen atom of asparagine side chain
O-linked
occurs only in Golgi, addition of sugars to oxygen atom of serine or threonine side chains
_____ permeable plasma membrane
selectively
Structure and selectivity ensure
essential molecules enter, metabolic intermediates remain, waste products exit
Verified Answers
Biological Membranes
Framework of the membrane is the phospholipid bilayer
Hydrophobic
water fearing region, faces in
Hydrophilic
water living region, faces out
Fluid-mosaic model
membrane is considered a mosaic of lipid, protein, and carbohydrate molecules
Integral/Intrinsic membrane proteins
transmembrane and lipid-anchored proteins
Transmembrane proteins
One or more regions that are physically embedded in the hydrophobic region of the phospholipid
bilayer
Lipid-anchored proteins
Covalent attachment of a lipid to an amino acid side chain within a protein
Peripheral membrane/extrinsic proteins
Noncovalent bound to regions of integral membrane proteins that project out from the membrane, or
they are bound to the polar head groups of phospholipids
Fluidity
individual molecules remain in close association yet have the ability to readily move within the
membrane
Semifluid- most lipids can rotate freely around their long axes and move laterally within the
membrane leaflet
Length of fatty acyl tails & fluidity
Shorter acyl tails are less likely to interact, which makes the membrane more fluid
Double bonds in acyl tails & fluidity
Double bond creates a kink in the fatty acyl tail, making it more difficult for neighboring tails to
interact and making the bilayer more fluid
Cholesterol & fluidity
Cholesterol tends to stabilize membranes (effects depend on temp.)
, Depending on the cell type, _____% of membrane proteins may be restricted in their movement.
10-70%
Integral membrane proteins may be bound to components of the cytoskeleton, which restricts the
proteins from moving _____.
laterally
Cytosol and endomembrane system work together to synthesize most _____.
lipids
Cytosolic leaflet
located in smooth ER
Fatty acid building blocks
made via enzymes in cytosol or taken in from food
Most transmembrane proteins are directed to ____
ER membrane
From ER membrane bound proteins can be transferred via _____ to other regions of the cell
vesicles
Glycosylation
Process of covalently attaching a carbohydrate to a protein or lipid
Glycolipid
carbohydrate to lipid
Glycoprotein
carbohydrate to protein
N-linked
attachment of carbohydrate to nitrogen atom of asparagine side chain
O-linked
occurs only in Golgi, addition of sugars to oxygen atom of serine or threonine side chains
_____ permeable plasma membrane
selectively
Structure and selectivity ensure
essential molecules enter, metabolic intermediates remain, waste products exit
