Midterm 2: Quizzes

what is the velocity of a reaction at the conc defined by Km? a) Vmax b) none of the answers c) 1/2Vmax d) V0

c) 1/2Vmax

true or false: triacylglycerols are the most prevalent type of fat seen in membranes?

false

which is the rate-limiting step of a michaelis-menten enzymatic reaction? a) k2 b) k1 c) k-1 d) k-2

a) k2

ATP is a donor molecule for what type of covalent modification of enzymes? a) phosphorylation b) ubiquination c) sulfation d) acetylation

a) phosphorylation

active transport must occur when the delta G value of associated with crossing a membrane is? a) positive b) zero c) negative

a) positive

why do cells need to have the mechanism to synthesize glucose? a) to supply glucose to brain and RBCs during fasting, starvation or extended exercise b) because glucose isn't readily available in our diet c) because glucose needs to be made into fructose to go through glycolysis d) because only glucose made inside the body can be used for fuel

a) to supply glucose to brain and RBCs during fasting, starvation or extended exercise

which of the following statements about metabolism are true? 1) catabolism is the process in which complex substances are broken down, yielding a net output of energy 2) metabolism is an integrated system in which many of the same reactions participate in degradative (catabolic) and biosynthetic (anabolic) pathways 3) anabolism involves the synthesis of polymeric biomolecules and complex lipids from monomers such as fatty acids and nucleotides 4) all organisms require an external source of energy, such as glucose or sunlight, for metabolic energy

all four statements are correct

which of these molecules might be an enzyme's cofactor? a) NAD b) all might be cofactors c) Mg d) Fe e) Biotin

b) all might be cofactors

a trans fatty acid: a) has a tail that resembles a cis fatty acid in conformation b) has a tail that resembles a saturated fatty acid in conformation c) is the most prevalent type of unsaturated fat found in nature d) has a kinked tail structure

b) has a tail that resembles a saturated fatty acid in conformation

if a person is missing the enzyme lactase, what disaccharide do they have difficulty metabolizing? a) tetrahalose b) lactose c) sucrose d) maltose

b) lactose

what is the first reaction that begins metabolism of fructose in the liver? a) aldol cleavage b) phosphorylation c) isomerization d) hydrolysis

b) phosphorylation

which one of the following describes how an uncompetitive inhibitor effects on enzyme's Km and Vmax? a) Km is higher and Vmax is lower b) Km is lower and Vmax is the same c) Km and Vmax are both lower d) Km is higher and Vmax is the same

c) Km and Vmax are both lower

how are zymogens activated? a) phosphorylation b) acetylation c) protease cleavage (peptide bond cleavage) d) dephosphorylation

c) protease cleavage (peptide bond cleavage)

how many molecules of reduced NADPH are produced per glucose-6-phosphate proceeding through the oxidative phase of the PPP? a) 1 b) 0 c) 4 d) 2

d) 2

the reverse of the reaction carried out by pyruvate kinase in glycolysis is carried out by which enzyme(s) in gluconeogenesis? a) fructose-1,6-bisphosphatase b) phosphoenolpyruvate carboxykinase c) pyruvate carboxylase d) both pyruvate carboxylase and phosphoenolpyruvate carboxykinase

d) both pyruvate carboxylase and phosphoenolpyruvate carboxykinase

which enzyme catalyzes the SECOND phosphorylation event in glycolysis? a) hexokinase b) aldolase c) glucose-6-phosphate isomerase d) phosphofructokinase

d) phosphofructokinase

which is true of the potassium ion channel? a) it uses active transport b) it can transport sodium ions c) water and potassium move together through the channel d) polar backbones atoms of the channel replace water interactions as potassium moves through the channel

d) polar backbones atoms of the channel replace water interactions as potassium moves through the channel

what is the purpose of the PPP in a human cell? a) all of the answers are correct b) to generate NADPH for reductive biosynthetic reactions c) to generate NADH that will enter the e- transport chain d) to generate NADPH for reductive biosynthetic reactions and to generate ribulose-5-phosphate/ribose-5-phosphate e) to generate ribulose-5-phosphate/rbose-5-phosphate

d) to generate NADPH for reductive biosynthetic reactions and to generate ribulose-5-phosphate/ribose-5-phosphate

what is the purpose of the first stage of glycolysis? a) producing acetyl co-A b) harvesting ATP energy c) maintaining redox balance in the cell d) trapping glucose in the cell and priming it to become a high transfer phosphate donor

d) trapping glucose in the cell and priming it to become a high transfer phosphate donor

which of the following statements are accurate with respect to glycolysis? 1) glycolysis involves the conversion of monosaccharides into glucose 2) glycolysis involves the breakdown of glucose into glyceraldehyde-3-phosphate 3) glycolysis involves the conversion of pyruvate into glucose to glycerladehyde-3-phosphate 4) glycolysis involves the conversion of acetyl Co-A to carbon dioxide

only statement 2 is correct 2) glycolysis involves the breakdown of glucose into glyceraldehyde-3-phosphate