Exams Flashcards
When an individual has a respiratory quotient of 1 they are oxidizing glucose over protein and lipids.
True
The __________________ allows for pyruvate to be decarboxylated to form acetyl CoA.
pyruvate dehydrogenase complex
Which of the following downregulates the pyruvate dehydrogenase complex?
Acetyl CoA
The citric acid cycle generates 3 NADH and 1 FADH2 as reducing equivalents and 1 GTP (or ATP) by substrate level phosphorylation.
True
NADH forms more ATP than FADH2 during oxidative phosphorylation because NADH donates its electrons to Complex 3 allowing for larger generation of the electrochemical gradient.
False
Amphibolic reactions serve both anabolic and catabolic functions.
True
The major fuels used by the body during the postabsorptive phase (between meals or at an overnight fast) include all of the following except
liver glycogen, non-esterified FA from adipose tissue, glycerol from adipose tissue, MUSCLE GLYCOGEN
Non-esterified fatty acids are higher during starvation than the fed state.
True
Which of the following is false regarding glucokinase (or hexokinase 2)?
IT IS SUBJECT OF FEEDBACK INHIBITION BY ITS PRODUCTS, It responds to a high influx of glucose, It traps glucose in the cell , It has a high Michalis Menton constant
Digestive enzymes are secreted from which cells in the pancreas?
acinar cells
Which of the following is not a function of insulin?
increases lipogenesis
increases glycogen storage
increases net protein synthesis
INCREASES HORMONE SENSITIVE LIPASE
The presence of cyclic AMP in the cell upregulates all of the following except
glycogenolysis, gluconeogenesis,
beta-oxidation, CHOLESTEROL BIOSYNTHESIS
Malonyl CoA is an important regulator of lipid metabolism. Which of the following is not true about malonyl CoA?
It can be used for ketone body synthesis
Which of the following is a key stimulator of muscle protein synthesis?
mechanistic target of rapamycin complexes
Glucose metabolism can be regulated in the liver by sequestering glucokinase (hexokinase 2) into the nucleus when glucose concentrations are elevated (~5 mmol/L)
FALSE
Which is not a gluconeogenic precursor?
ACETYL COA
alanine
glycerol
lactate
The monosaccharides galactose and fructose from the diet are converted into glucose in the small intestine.
FALSE
In the pancreas, hexokinase 4 “senses” glucose which facilitates insulin release in the blood.
TRUE
Which glucose transporter (GLUT) requires insulin before glucose can enter the cell?
4
Which glucose transporter (GLUT) requires insulin before glucose can enter the cell?
erythrocytes
The direct fate of glucose 6 phosphate in the liver includes all of the following except
-removal of the phosphate to enter the blood
-enter the pentose phosphate pathway
-form glucose 1 phosphate for glycogen synthesis
**form glycerol 3 phosphate for triacylglycerol synthesis
The step the “commits” glucose to glycolysis is
6 phosphofructo-1 kinase
The formation of 2-fructo-6-bisphosphate (or fructose 2,6 bisphosphate) by insulin stimulates the activity of 6-phosphofructo-1-kinase (or phosphofructokinase 1 or PFK-1) to keep glycolysis active.
True
The formation of pyruvate to lactate via lactate dehydrogenase is important to maintain NAD+ concentrations in the cell to be used by glyceraldehyde-3-phosphate dehydrogenase in glycolysis.
True
The liver can store more glycogen by weight than muscle, but whole-body muscle content is greater than the liver, thus provides more glycogen stores.
true
Which of the following stimulates glycogen synthase?
Insulin
List the 2 main functions of the pentose phosphate pathway.
- Generate ribulose 5 phosphate (or ribose 5 phosphate) for ribonucleotide synthesis
- Generate NADPH as a reducing agent for anabolic processes
Glycogen phosphorylase is inactive when phosphorylated.
False
To form new glucose via gluconeogenesis,
_________
, ___________
, and
____________________
in glycolysis are irreversible and must be bypassed.
hexokinase
PFK-1
pyruvate kinase
Gluconeogenesis can occur in which 2 tissues?
liver and kidney
What transports long chain fatty acids into the cell from the blood?
cluster of differentiation 36
What is necessary for long chain fatty acids to be transported from the mitochondrial intermembrane space to the matrix for beta-oxidation?
carnitine
The oxidation of saturated fatty acids produces less ATP than monounsaturated fatty acids with the same number of carbons.
False, Saturated fatty acids produce more ATP than MUFA of the same carbon length.
Methylmalonyl CoA mutase requires _________________ to form succinyl CoA from propionyl CoA.
Correct!
vitamin B12
Describe in 2-3 sentences how acetyl CoA moves from the mitochondria matrix to the cytosol for fatty acid synthesis.
In the matrix, Acetyl CoA combines with oxaloacetate (OAA) to form citrate. Citrate is then transported from the matrix to the cytosol via the citrate transporter. Then, citrate lyase (ATP-dependent) cleaves citrate to re-form OAA + Acetyl CoA. Now Acetyl CoA can be carboxylated by Acetyl CoA Carboxylase (ACC) the regulated enzyme for fatty acid synthesis.
Which of the following serves as a negative or down-regulator for acetyl CoA carboxylase (ACC)?
AMPK
Ketone bodies are made in the liver and can be oxidized by all tissues except the liver.
True
The predominant ketone body made is
3-hydroxybutyrate
In 1-2 sentences describe the primary purpose of using ketone bodies as a fuel source during starvation.
The main purpose is to reduce the brain’s dependence on glucose for energy. Another answer may include to reduce protein break down in the muscle, in which the AA would be used as gluconeogenic precursors.
The product of fatty acid synthesis is
palmitic acid
Catecholamines stimulate the de-phosphorylation of both perilipin and hormone sensitive lipase to break down triacylglycerol to fatty acids + glycerol in adipose tissue.
False
Which of the following is false regarding eicosanoids.
they have long half-lives
Proinflammatory eicosanoids are usually derived from arachidonic acid while anti-inflammatory eicosanoids are usually derived from eicosapentaenoic acid.
False - the anti inflammatory eicosanoids are derived from docosahexaenoic acid (DHA).
Chylomicrons are absorbed from the small intestine into the lymph because they are too large to enter the portal blood.
True
Which lipoprotein is the major source of cholesterol transport to the cells?
LDL
In the blood, HDL exchanges cholesterol esters for triacylglycerol (TAG) with other lipoproteins.
True
Describe in detail how cholesterol is regulated at the gene level in the cell when:
a) endoplasmic reticulum (ER) cholesterol concentrations are at 0% mol. (4 points)
b) endoplasmic reticulum (ER) cholesterol concentrations are at 100% mol. (3 points)
a) When ER cholesterol concentrations are DEPLETED, cholesterol is not associated with SCAPs cholesterol sensing domain (because levels are low). Thus, SCAP is associated with SREBP, and is transported from the ER via COP2 vesicles to the Golgi. In the Golgi, SREBP2 is cleaved, and the transcription factor is released. The transcription factor enters the nucleus and binds to the promotor region of the genes that transcribe enzymes to increase cholesterol synthesis (e.g., HMG-CoA reductase)
b) When ER cholesterol concentrations are ADEQUATE, cholesterol binds to the SCAP/SREBP2 complex which associates with INSIG. INSIG prevents the complex from being transported from the ER to the Golgi for further processing. INSIG also binds to the reductase and tags it for ubiquination.
Which apolipoprotein activates the enzyme that cleaves fatty acids from triacylglycerol so they can be taken up by tissues?
Apo C2
After eating a high-fat meal, chylomicrons will peak in the blood
at 4 hours
HDL cholesterol is formed by which apolipoprotein?
Apo A1
7-dehydrocholesterol in the skin is a precursor to which steroid hormone?
1,25 di-hydroxyvitamin D3
List 2 reasons why cholesterol is esterified in the cell.
Maintain cholesterol homeostasis in the cell
Free cholesterol is toxic
Provides cholesterol to the cell when needed
Can be incorporated into lipid droplets that eventually donates to lipoproteins for secretion
Why are bile acids conjugated in the liver?
To make them more amphipathic and able to act as an emulsifier and more soluble in the micelle.
Bile acids serve as a nuclear receptor so it can regulate the amount of bile that is synthesized and excreted.
True
Describe in 2-3 sentences how excreting bile acids in the feces lowers blood cholesterol levels.
Bile acids are efficiently reabsorbed in the ileum and returns to the liver for re-circulation (enterohepatic circulation). When less bile is absorbed, more must be made in the liver. Cholesterol is used to make new bile in the liver, thus, lowering blood cholesterol levels.
HDL can cross the arterial wall and provoke an inflammatory response, which can lead to plaque formation.
False
Ketone bodies can provide all of the brain’s requirement for glucose.
False
Long-chain fatty acids that cross the blood brain barrier are used for the generation of ATP in the brain.
False
The minimum amount of glucose consumed by the brain in energy-balanced individuals is
100 g/d
The Acceptable Macronutrient Distribution Range (AMDR) for carbohydrate is
45-65%
and lipids is
20-35%
.
Which of the following is not a reason to limit added sugars?
they can replenish glycogen stores for athletes after a long workout
The Adequate Intake (AI) for dietary fiber is
14 g/1,000 kcal/d
According to research by Miketinas and Patterson, 2021, US adults with diabetes consume more fiber than healthy adults.
True
One-third of the brain’s essential fatty acid content consists of _________ and _________.
docosahexaenoic acid + arachidonic acid
Aspirin modifies the cyclooxygenase 2 enzyme; therefore, pro-inflammatory leukotrienes are epimerized to pro-resolving leukotrienes.
True
Saturated fatty acids intake should be replaced with the following:
polyunsaturated fatty acids
The conversion rate of alpha-linoleic acid to eicosapentaenoic acid and docosahexaenoic acid in our bodies is very efficient; therefore, the need to supplement eicosapentaenoic acid to docosahexaenoic acid in some populations is not necessary.
False
The majority of added sugars in the US diet come from which of the following?
sugar-sweetened beverages
Glucose is the preferred fuel for enterocytes.
Glutamine is the preferred fuel for enterocytes.
The recommended intake of dietary fiber is 15 g per 1,000 kcal daily.
False
Fructose is absorbed from the small intestinal lumen into the enterocyte by
GLUT 5
Highly fermented fibers include all of the following except
*cellulose
pectin
oat bran
inulin
Digestion of starch by amylase begins in the mouth by hydrolysis of what type of linkage?
alpha (1–>4)
The function of fiber in the large intestine depends on which of the following
degree of fermentation
type of fiber
resident microflora
- all of the above
Which of the following is NOT true when describing cholecystokinin (CCK)?
- it is released into the lumen of the small intestine
it stimulates digestive enzyme release from the pancreas
it functions as a hormone in the GI tract
it stimulates bile release from the gallbladder
Which of the following is NOT a function of gel forming fibers?
binding bile and removing it from the body
improved satiety
attenuate nutrient absorption
*increase gastric emptying
Which of the following sugars is NOT a disaccharide?
sucrose
*amylose
maltose
lactose
Resistant starch escapes digestion in the small intestine and enters the large intestine to be fermented by microbiota.
True
Which of the following is not absorbed in the stomach?
AMINO ACIDS, alcohol, salts, butyrate
The duodenum absorbs most nutrients except Fe and Ca
False
Bile acids can be ______ with glycine and taurine making them more polar prior to form micelles that aid in emulsifying dietary fat
true
Major functions of stomach
secretion of HCl, zmogens, endocrine hormones, and intrinic factor
regulation of chyme entry into SI
temporarily storing food and liquid
Which stomach cells release HCL and intrinsic factor?
Parietal
Leptin is released from the stomach during fasting and stimulates food intake
false
The ileum absorbs ______ and _____
vitamin b12 and bile acids
zwitterion
AA has a net charge of zero
Type of reaction that occurs when two amino acids form a peptide bond
condensation
The primary structure of a protein directs the folding of the protein in its 3D shape
true
Vitamin C and zinc are necessary for the hydroxylation of lysine and proline so collagen can mature
false
Which of the following can lead to the impairment of starch digestion and cause GI distress?
Alpha-glucosidase inhibitors
Incretins do all of the following except
stimulate insulin release
INHIBIT DIPEPTIDYL PEPTIDASE-4
proliferate pancreatic beta cells
effect food intake via the vagus nerve
What is required for pancreatic lipase to break down triacylglycerides in the presence of bile acid
colipase
30% of phytosterols are absorbed in the enterocyte
false
apolipoprotein associated with chylomicrons
APO B48
The most appropriate way to classify dietary fiber by physiological function is by solubility
false
During the fed state, the brain uses _____ percent of glucose for energy
10
which of the following is not a gluconeogenic substrate
glycerol
alanine
lactate
ACETYL COA
adipose tissue has glycerol kinase
false
which glut is expressed in the brain
GLUT3
Hexokinase primarily acts as a glucose sensor in which tissue
pancreas
gluconeogenisis occurs in which two tissues
liver, kidney
primary regulator of glycolysis
fructose 2-6 bisphosphate
glycogen synthase is activated when phosphorylated
false
glycogen contains amylose and amylopectin
false, contains 1-4 and 1-6 branches but not called amylose and amylopectin
glycogen synthase adds glucose to the non-reducing end of existing glycogen molecule
true
net ATP from glucose alanine cycle
4
