Biochem - Chapter 8 [Lipids and Proteins Are Associated in Biological Membranes]

Which protein would likely be involved in a channel? [exhibit 8A]

1

Which of the following four fatty acids has the highest melting point? 1. CH3CH2CH2CH2CH2COOH 2. CH3CH2CH2CH2CH2CH2CH2CH2 CH2COOH 3. CH3CH2CH2CH2CH2CH2CH2COOH 4. CH3CH=CHCH2CH2COOH

2

How many hydroxyl groups does a molecule of glycerol have?

3

Which of the following four fatty acids has the lowest melting point? 1. CH3CH2CH2CH2CH2COOH 2. CH3CH2CH2CH2CH2CH2CH2CH2 CH2COOH 3. CH3CH2CH2CH2CH2CH2CH2COOH 4. CH3CH=CHCH2CH2COOH

4

These two lipid vitamins are often found in membranes:

A and E

Which of the following statements concerning active transport is true?

A membrane-associate protein must be involved.

Which property has not been observed for membrane proteins?

A. energy storage [correct] B. transport of substances into and out of the cell C. catalysis (enzymatic activity) D. acting as a receptor

Which of the following lipids is not found in biological membranes?

A. triacylglycerols [correct] B. phosphoacylglycerols C. glycolipids D. cholesterol

Which of the following treatments would be most useful in separating an integral membrane protein from the lipid component of a cell membrane?

Add a detergent.

How do the membranes of plant and animal cells compare?

Animal cell membranes tend to be more rigid than those of plant cells.

Which of the following is not a lipid-soluble vitamin? A. Ascorbic Acid B. Cholicalciferol C. Vitamin K D. Retinol E. Tocopherol

Ascorbic Acid [Lipid soluble] B. Cholicalciferol C. Vitamin K D. Retinol E. Tocopherol

Which of the following is not true? A. Receptors are often invaginated into the cell after binding to their specific molecule. B. A given receptor type is present at a constant level on the outside of a cell C. In certain disease states, the level of a given receptor is increased or decreased D. Binding of receptors to ligands sometimes shows hyperbolic binding curves

B. A given receptor type is present at a constant level on the outside of a cell [correct] A. Receptors are often invaginated into the cell after binding to their specific molecule. C. In certain disease states, the level of a given receptor is increased or decreased D. Binding of receptors to ligands sometimes shows hyperbolic binding curves

Vitamin E has all of the following properties, except:

B. It can be made in the sunshine. [correct] A. It is an antioxidant. C. It is essential for at least some mammal's fertility. D. It is often a component of membranes. E. All of these describe vitamin E.

Which of the following is not a function or characteristic of membrane proteins? A. Transport B. Catalytic activity C. Blood clotting D. Receptor sites

C. Blood clotting [true] A. Transport B. Catalytic activity D. Receptor sites

Protein #2 would most likely function as a: exhibit 8A]

Carrier

Which of the following does not belong in the list? A. Retinol B. Vitamin A C. beta-carotene D. Cholesterol

Cholesterol

Which of the following lipid molecules possess a different fundamental structural make-up from the others?

Cholesterol

Which of the following groups is not present in a phosphatidic acid?

Choline

Which of the following methods of transport across a membrane does not require a protein? A. Passive transport B. Facilitated transport C. Active Transport D. Simple diffusion

D. Simple diffusion [DOES require a protein] A. Passive transport B. Facilitated transport C. Active Transport

Which of the following is not true? A. Plant oils are favored in the diet because they generally contain more unsaturated fats than found in animal fats. B. Unsaturated fatty acids are healthier for humans than saturated ones C. Heart disease can be correlated with diets high in saturated fatty acids D. Unsaturated fatty acids lead to higher levels of LDL than saturated fatty acids do

D. Unsaturated fatty acids lead to higher levels of LDL than saturated fatty acids do [correct] A. Plant oils are favored in the diet because they generally contain more unsaturated fats than found in animal fats. B. Unsaturated fatty acids are healthier for humans than saturated ones C. Heart disease can be correlated with diets high in saturated fatty acids

The following lipid vitamin is often used to preserve foods from spoiling:

E

Fatty acids with multiple double bonds are usually conjugated.

False

Membranes are generally symmetrical, i.e., the outer face is composed of the same number and types of phospholipids as the inner face.

False

Plants need cholesterol in their membranes to counteract the rigidity of the cell wall.

False

When a membrane reaches its transition temperature, integral membrane proteins dissociate from the bilayer.

False

Which of the following is true? A. All fatty acids have an even number of carbons B. Most fatty acids have an odd number of carbons C. Fatty acids are equally likely to have an even number of carbons as they are an odd number D. Fatty acids with an odd number of carbons are more rare than those with an even number

Fatty acids with an odd number of carbons are more rare than those with an even number

How does cholesterol affect membrane fluidity?

It tends to decrease the fluidity. [decreases at high temperatures] [increases at low temperatures]

Which of the following is not a product of saponification of a triglyceride? A. Long chain fatty alcohols. B. The salt of the fatty acids. C. Soaps. D. Glycerol. E. All of these are products of saponification.

Long chain fatty alcohols.

Which of the following is the best phrase to describe the modern view of membrane structure? A. Membranes are lipid-lipid bilayers. B. Membranes are lipid-lipid bilayers with associated proteins. C. Membranes are composed solely of lipids and proteins. D. Membranes are a fluid mosaic of lipids and proteins. E. Membranes are found only in eukaryotic cells.

Membranes are a fluid mosaic of lipids and proteins.

Sphingolipids are particularly important in these structures:

Membranes, the brain and the nervous system. [incorrect] Lipoproteins.

Glycolipids are particularly important in these structures:

Membranes, the brain and the nervous system. [incorrect] Lipoproteins.

Which protein might help to identify the cell type? [exhibit 8A]

More than one could help identify the cell type.

The following lipid vitamin has important involvement with calcium ions: A. A B. D C. E D. K E. More than one reacts with calcium ion.

More than one reacts with calcium ion.

Which of the following groups is not present in a cerebroside?

Phosphate

Which of the following would not be enriched on the outer side of the lipid bilayer compared to the inner side?

Phosphoacylglyerol

Which of the following is not a characteristic of most fatty acids? A. Presence of trans double bonds. B. Even number of carbon atoms. C. Only one carboxyl (-COOH) group. D. Absence of conjugated double bonds. E. All of these characterize lipids.

Presence of trans double bonds. [correct] B. Even number of carbon atoms. C. Only one carboxyl (-COOH) group. D. Absence of conjugated double bonds.

Which of the following groups is not present in sphingomyelin?

Sugar [present] A. Sphingosine B. Fatty acid C. Phosphate

Glycolipids are characterized by containing the following non-lipid component:

Sugars

Which of the following statements is true? A. All triacylglycerols and all phosphoacylglycerols have the same fatty acids in them. B. All triacylglycerols have the same fatty acids, but the fatty acids in phosphoacylglycerols vary. C. The fatty acids in triacylglycerols vary, but all phosphoacylglycerols have the same fatty acids in them. D. The fatty acids in both triacylglycerols and in phosphoacylglycerols vary.

The fatty acids in both triacylglycerols and in phosphoacylglycerols vary.

Cell membranes typically display asymmetry. What does this mean?

The two leaves of a bilayer contain different collections of lipids and proteins.

What distinguishes primary from secondary active transport?

The type of linkage to ATP hydrolysis

Which of the following best describes lipids' insolubility in water?

They are typically insoluble.

How does the presence of cis double bonds in fatty acids affect membrane fluidity?

They tend to increase the fluidity.

I find that briefly washing cells in a buffered solution at pH 11 is effective for isolating a cell membrane-associated hormone receptor. (A standard growth solution for the cells is pH 7.) Which of following best fits this description?

This is a peripheral membrane protein that probably interacts with membrane phospholipids using lysine-mediated salt bridges.

Cholesterol is particularly important as a component of animal membranes.

True

Glycolipids on the surface of cells are especially important as cell markers.

True

Lipids differ from most other biomolecules because they are defined on the basis of solubility, rather than on their chemical structure.

True

Multiple sclerosis is characterized by destruction of the myelin sheath.

True

The HDL class of lipoprotein is generally believed to be preventative of heart disease.

True

There are likely to be huge stores of lipid vitamins in healthy animals.

True

The mechanism of membrane transport may involve the following:

[All of these are correct.] A. ATP hydrolysis. B. Conformation change of membrane proteins. C. Phosphorylation or dephosphorylation of membrane proteins. D. ATP hydrolysis and conformation change of membrane proteins.

Phospholipids are particularly important in these structures:

[All of these are correct.] A. Membranes. B. Lipoproteins. C. The brain and nervous system. D. Membranes, the brain and the nervous system.

Which of the following is true? A. Fatty acids with trans double bonds may be particularly unhealthy because they increase the ratio of LDLs to HDLs. B. A fatty acid with 14 carbons and one trans double bond will behave more like a saturated fatty acid with 14 carbons than will an unsaturated fatty acid with a cis double bond. C. Fatty acids with trans double bonds can be formed by hydrogenation reaction of polyunsaturated fatty acids D. fatty acids with trans double bonds tend to have higher melting points than those with cis double bonds all else being equal

[All of these are correct] A. Fatty acids with trans double bonds may be particularly unhealthy because they increase the ratio of LDLs to HDLs. B. A fatty acid with 14 carbons and one trans double bond will behave more like a saturated fatty acid with 14 carbons than will an unsaturated fatty acid with a cis double bond. C. Fatty acids with trans double bonds can be formed by hydrogenation reaction of polyunsaturated fatty acids D. fatty acids with trans double bonds tend to have higher melting points than those with cis double bonds all else being equal

Which of the following alcohols is never found in phosphatides?

[All of these can be components of phosphatides.] A. Ethanolamine B. Serine C. Inositol D. Sugars

The key reaction of eyesight (in dim light) involving vitamin A is:

[All of these.] A. Reaction of the protein complex called Rhodopsin. B. A cis-trans isomerization of a double bond. C. Bleaching of a pigment in the retina. D. Reaction of Rhodopsin and cis-trans isomerization of a double bond.

Which of the following groups is not present in lecithin?

[all of these are components of lecithin.] A. Choline B. Fatty acids C. Glycerol D. Phosphate

Glycoproteins on the cell surface are involved in this type of function:

[all of these are correct.] A. Cell identification B. Receptor sites C. Immune function D. Cell identification and receptor sites

The order-disorder transition (melting) in membranes

[all of these] A. is cooperative B. can be monitored by fluorescence techniques C. can be monitored by spin labeling

A major difficulty in extracting receptor proteins from membranes is that

[all of these] A. it is difficult to remove the proteins from the membrane without denaturation B. there may be very few molecules of the protein in a cell C. receptor proteins tend to have high molecular weights

Where can membrane proteins be located?

[in either position] A. entirely within the membrane B. on the surface of the membrane

Facilitated diffusion requires

a carrier protein to which the transported substance binds

Biological waxes are composed of

a fatty acid and a long-chain alcohol.

In the operation of the sodium-potassium pump

a membrane protein is phosphorylated with ATP as the source of the phosphate group

Which of the following cell types contains cholesterol?

animal

Which of the following is a metabolic precursor of prostaglandins & leukotrienes? A. vitamin A. B. arachidonic acid. C. sphingomyelin. D. cholesterol.

arachidonic acid.

Liposomes are

artificial membrane-bounded structures used to deliver medications.

Unsaturated fatty acids usually have ____ double bonds.

cis

Saponification is the hydrolysis of a(n)

ester bond

What kinds of bonds do lipase break in order to release fatty acids from triacylglycerols?

esters

Passive transport is the same as:

facilitated diffusion

Transport of a compound across a cell membrane (down a concentration gradient) was measured at several concentrations. The presence or absence of ATP had no effect on the transport of this compound. Which best describes the mechanism of transport? Concentration Difference, µM Transport Rate, µmol/min 2.5 30 5 60 10 100 25 175 50 200

facilitated diffusion

Which of the following molecules is not amphipathic?

glucose

With what compound are fatty acids reacted to make a fat or oil?

glycerol

What does amphipathic mean?

having both hydrophilic and hydrophobic regions

Membrane lipids in a lipid bilayer are held together by

hydrophobic interactions

The association of membrane proteins with lipids in the membrane bilayer always involves

hydrophobic interactions

Aspirin produces most of its analgesic effects by

inhibiting the synthesis of prostaglandins

The freeze-fracture technique of electron microscopy is useful in studying membrane structure because

integral membrane proteins can be seen in association with one leaflet of the lipid bilayer

A useful method for studying membrane proteins in place in the membrane is

nuclear magnetic resonance

The difference between active transport and passive transport is that

one requires expenditure of energy by the cell and the other does not.

In the sodium-potassium pump

sodium is transported out of the cell and potassium into the cell, both against concentration gradients

What characteristic is most used to define lipids?

solubility

The myelin sheaths of neurons typically contain large amounts of

sphingolipids

The degree of membrane fluidity depends on

the percentage of unsaturated fatty acids

In the fluid mosaic model of membrane structure

the proteins "float" in the lipid bilayer

Which of the following compounds yields the most energy per gram?

triacylglycerols

The distribution of lipids in membranes is

uneven, with bulkier molecules on the exterior

The vitamin classified as fat soluble rather than water soluble is

vitamin A [Water soluble] B. vitamin B1 C. vitamin B6 D. vitamin C

Rickets is caused by a deficiency in

vitamin D.

The vitamin needed for blood coagulation is

vitamin K