Biochem Exam 3

Which of he following is NOT correct concerning the structure given? A) it is a component of biological membranes B) it is amphipathic C) it is a sphingolipid D) it is a phosphoglyceride E) it is phosphatidyl choline

C) it is a sphingolipid

Which of the following in NOT a main function of lipids? A) cell signaling B) fuel source C) structural rigidity of the cytoskeleton D) membrane component E) all of the above

C) structural rigidity of the cytoskeleton

The polar head group of phospholipids is found at which carbon of glycerol?

C3

Cholesterol and other steroids are not soluble in blood, and therefore must be transported. Predict what chemical modifications must occur for cholesterol to move through the circulatory system.

Cholesterol is esterfied to a fatty acid for transport by lipoprotein particles, the surface of which is hydrophilic and the interior is hydrophobic

Which of the following membranes would be the most fluid? A) all membrane proteins are integral and associate with the hydrophobic region of the membrane B) both proteins and lipids readily undergo transverse ("flip-flop") diffusion from the inside to the outside of the membrane C) membranes are synmmetric D) the membrane lipids self-assemble to form the lipid bilayer E) a biological membrane consists of proteins sandwiched between two layers of lipids, which is reffered to as a lipid bilayer

D) the membrane lipids self-assemble to form the lipid bilayer

Carbohydrates are: A) aldehydes with two or more hydroxyl groups B) ketones with two or more hydroxyl groups C) acids with two or more hydroxyl groups D) alcohols with two or more hydroxyl groups E) A and B

E) A and B

What force(s) stabilize(s) the lipid bilayers? A) Van der Waals interactions B) electrostatic and hydrogen bonding between the polar heads and surrounding water C) covalent bonds between the lipid tails D) covalent bonds between the lipids and the membrane proteins E) A and B

E) A and B

What evidence exists to show that membrane asymmetry can be preserved for long periods?

Lateral diffusion from fluorescence recovery after photo-bleaching experiments

The most common motif found in membrane spanning proteins is:

alpha helices of nonpolar AA that pass through the membrane

Which digestive enzyme digests amylopectin?

alpha-amylase

The flourescence recovery after photobleaching (FRAP) technique has been used to study:

lateral diffusion in membranes

The low incidence of protein or lipid flip-flop in a membrane preserves:

membrane asymmetry

Would you agree that a peripheral membrane protein can act as Na+, K+-ATPase and why?

no, because a peripheral protein does not form a transporter across the entire membrane

The energy for ________________ transport comes from the gradient itself

passive

An anti-porter and a symporter are examples of ___________________.

secondary transporter

To which AA residues in glycoproteins are the sugars commonly linked?

serine, threonine, and asparagine

Palmitate has how many carbons in its chain?

16

How many molecules thick are membranes?

2

Biochemists organize proteins wit carbs attached into 3 classes. Below is a list of structural differences in these 3 classes, one of which is assigned to the wrong class. Identify the incorrect structural correlation. A) unlike glycoproteins and proteoglycans, in mucopolysaccharides, carbs are attached via ester bonds to Asp and Glu B) The glycosaminoglycan component of proteoglycans determines their properties C) The defining feature of the mucopolysaccharide is a region of the protein backbone called the variable number of tandum repeats region D) the carb portion of glycoproteins such as erythropoietin are thought to make it more soluble in blood E) glycosaminglycans often have repeating units of disaccharides containing a negatively charge carboxylate or sulfate group

A) unlike glycoproteins and proteoglycans, in mucopolysaccharides, carbs are attached via ester bonds to Asp and Glu

Which of the following helps regulate membrane fluidity in animals? A) protein B) cholesterol C) ATP D) magnesium ion E) none of the above

B) cholesterol

If you wanted to show how membranes regulate their curvature and budding processes, which of the following membrane structures would you study? A) presence of lipid rafts B) degree of fatty acid unsaturation C) presence of active transport proteins D) presence of prostoglandin H2 synthase-1 E) none of the above

B) degree of fatty acid unsaturation

Which is the proper order of permeability of molecules across a membrane, from the most permeable to the least? A) water, glucose, urea, sodium ion B) water, indole, glucose, sodium ion C) water, indole, sodium ion, glucose D) indole, glucose, urea, sodium ion E) indole, water, glucose, sodium ion

B) water, indole, glucose, sodium ion

Glycoproteins are normally: A) found on the outside of membranes B) secreted as extracellular proteins C)found inside organelles D) A and B E) all of the above

D) A and B

The nutritional storage form(s) of glucose in plants: A) glycogen B) amylose C) amylopectin D) B and C E) all of the above

D) B and C

Which of the following describes the role of a protein in the selective permeability of a membrane? A) the polar heads of phospholipis in allowing polar molecules to cross membranes B) the binding of steroid to an extracellular peripheral membrane proteins C) The insertion of a porin with polar AA forming B-strands D) Na+, K+-ATPase activity that sets up an electrical potential across the membrane E) all of the above

D) Na+, K+-ATPase activity that sets up an electrical potential across the membrane

Which of the following membranes would be the most fluid? A) a bilayer made of lipids with polyunsaturated 18 carbon-fatty acids B) a bilayer made of lipids with saturated 18 carbon-fatty acids C) a bilayer made of lipids with saturated 16 carbon-fatty acids D) a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids E) all of the above are equivalent in fluidity

D) a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids

What are lectins? A) proteins that bind the carbs on glycoproteins and other macromolecules B) proteins that promote cell-cell interaction C) proteins found in animal, plants, and microorganisms D) all of the above E) none of the above

D) all of the above

Which of the following id true? A) membranes are lipid bilayers B) membrane lipids have both hydrophobic and hydrophilic properties C) many membranes are electrically polarized D) all of the above E) none of the above

D) all of the above

Membrane lipids are primarily composed of: A) phospholipids B) glycolipids C) cholesterol D) A and B E) A, B, and C

E) A, B, and C

A phosphate lipid (phosphatidic acid) has which of the following components? A) phosphate B) glycerol C) ester linkage D) acyl chain E) all of the above

E) all of the above

All of the following are repeating units of glycosaminoglycans except: A) chondroitin 6-sulfate B) keratin sulfate C) hyaluronate D) heparin E) all of these form glycosaminoglycans

E) all of these form glycosaminoglycans

The backbone of a phospholipid is which of the following? A) glucose B) cholesterol C) fatty acid chain D) triacylglycerol E) glycerol

E) glycerol

An w-3 fatty acid_________________. A) has a methyl group at the carboxyl end of the fatty acid B) has a methyl group on the third carbon of the chain C) has a double bond on the third carbon in from the carboxyl group D) has a triple bond on the third carbon from the methyl end of the fatty acid E) none of the above

E) none of the above

Polar-head groups of phospholipids are estrified to what functional group?

Phosphate

Identify the differences in archea membrane lipids compared to those of eukaryates or bacteria and how these differences help them withstand extreme environmental conditions.

The fatty acid chains are branched, allowing them to pack more tightly, thereby protecting membrane integrity

The notion 12:2 indicates which of the following about a fatty acid?

There are 12 carbons in the chain with 2 double bonds

Selectins are proteins that:

bind immune-system cells as part of the inflammatory response

How do some viruses gain entry into specific cells?

by binding to glycoproteins on the cell surface that are unique to specific cells

Double bonds ________________ melting points of fatty acids and their derivatives

decrease

The simplest carbohydrates are:

dihydroxyacetone and D- and L- glyceraldehyde

Which phospholipid is enriched in neural sheath membranes?

diphophatidylglycerol (cardiolipin)

Carb residues attached to the membrane lipids are always positioned on the _____________________ side of the membrane

extracellular

Eating ______________________ increases the w-3 fatty acids decreasing _______________________

fatty fish; cardiovascular disease

An aldehyde and an alcohol can react to form a ______________

hemiacetal

The longer the fatty acid, the ___________ the fatty acid.

higher the melting point of

The degree of membrane fluidity depends on...

the % of unsaturated fatty acids

Digitalis is a cardiotoinic steroid that does not act like a steroid. Instead, its function is to inhibit __________________.

the Na+-K+ pump