biochem test 3
Which of the following lipids is used for energy storage?
- A) glycolipids
- B) glycerophospholipids
- C) sphingolipids
- D) triacylglycerols
Compared to vegetable oil, beef fat is has a higher proportion of
- A) long-chain unsaturated fatty acids
- B) long-chain saturated fatty acids
- C) short-chain unsaturated fatty acids
- D) short-chain saturated fatty acids
Which of the following is true for biological membranes?
- A) membranes are lipid bilayers.
- B) membrane lipids have both hydrophobic and hydrophilic properties.
- C) all of the above.
- D) none of the above.
The fluidity of the lipid in the interior of a bilayer is generally increased by:
- A) a decrease in temperature
- B) an increase in fatty acyl chain length
- C) an increase in the number of double bonds in fatty acids
- D) the binding of water to the fatty acyl side chains
Lipid molecules are said to be amphipathic, when
- A) they have asymmetric carbons and can exist in left- and right-handed forms.
- B) they have a dual nature with part of the molecule being hydrophobic (unpolar) and the
other part hydrophilic (polar).
- C) they are capable of moving out from a lipid bilayer.
Triacylglycerols are NOT found in cell membranes because they are
- A) charged at biological pH
- B) not abundant in cells
- C) not amphipathic
- D) amphipathic
Integral membrane proteins are proteins that
- A) penetrate or span the membrane
- B) loosely associated with the membrane
- C) can be released from the membrane by changing the pH
- D) can be released from the membrane by changing the ionic strength
Facilitated diffusion (passive transport) through a biological membrane is
- A) driven by ATP hydrolysis
- B) driven by the movement of lipids
- C) driven by a concentration gradient
- D) endergonic
Which of the following transport processes requires no energy?
- A) Facilitated diffusion
- B) Primary active transport
- C) Secondary active transport
Which of the following is NOT TRUE regarding the oxidation of fatty acids by the b-
- A) the reactions produce acetyl-CoA.
- B) the reactions DO NOT produce FADH
- C) the reactions produce NADH.
- D) the reactions occur in the mitochondria.
In animal cells, where does fatty acid synthesis occur?
- A) in lysosome
- B) in the nucleus
- C) in mitochondria
- D) in the cytosol
Fatty acids are activated to acyl-CoAs and the acyl group is further transferred to carnitine
- A) acyl-carnitines readily cross the mitochondrial inner membrane, but acyl-CoAs do not.
- B) acyl-CoAs easily cross the mitochondrial membrane, but the fatty acids themselves will
- C) carnitine is required to oxidize NAD
Fatty acids are oxidized in the ______.
- A) mitochondrial matrix
- B) cytosol
- C) endoplasmic reticulum
- D) nucleus
Which of the following compounds serves to transport excess ammonia from muscle to liver
for urea synthesis?
- A) alanine
- B) aspartic acid
- C) glycine
- D) serine
Which of the following best defines an essential amino acid?
- A) an amino acid that cannot be made de novo by humans and must be obtained in the diet
- B) an amino acid that can be made by human
- C) all of the above is correct
- D) both A and B are correct
At the subcellular level where does the urea cycle occur?
- A) mitochondrial matrix only
- B) mitochondrial matrix and the cytosol
- C) cytosol and nucleus
- D) cytosol only
The carbon skeletons for amino acid biosynthesis are derived from intermediates in all of the
- A) citric acid cycle
- B) pentose phosphate pathway
- C) β-oxidation pathways of fatty acids
- D) glycolysis
Urea synthesis in mammals via urea cycle takes place in tissues of the:
- A) brain
- B) muscle
- C) liver
- D) kidney
Early in your chemistry career, you probably spilled some sodium hydroxide on your hands
and noticed that bases feel soapy. The soapy feeling is caused by:
- A) Release of hydrogen from triacylglycerols
- B) Release of calcium from triacylglycerols
- C) Production of soap as a result of the reaction between base and the triacylglycerols in your
Transamination reactions require which coenzyme?
- A) PLP (pyridoxal phosphate)
- B) NADP
- C) FMN
- D) FAD
Alanine is NOT classified among the essential amino acids because:
- A) We consume so much alanine that we don't need to make any.
- B) We can form alanine by transamination of pyruvate.
- C) We can form alanine by cleaving arginine.
- D) Alanine is neutral and no neutral amino acids are essential.
Which of the following lipoprotein particles are indicative of “good” cholesterol?
- A) HDL
- B) LDL
- C) chylomicrons
- D) VLDL
Which of the following lipoprotein particles are indicative of “bad” cholesterol?
- A) HDL
- B) LDL
- C) chylomicrons
- D) VLDL
High levels of cholesterol in the blood can lead to
- A) hyperglycemia
- B) atherosclerosis
- C) hyperammonemia
In order to synthesize fatty acids, acetyl-CoA is shuttled out of mitochondria as
- A) Pyruvate
- B) Malate
- C) Citrate
- D) Oxaloacetate
Which two amino acids serve as the primary nitrogen donors for the biosynthesis of the other
- A) Aspartate and alanine
- B) Aspartate and asparagine
- C) Glutamate and glutamine
- D) Serine and glycine
Enzymes that digest the triacylglycerols into free fatty acids and monoacylglycerol are called
- A) hydrases
- B) glyases
- C) lipases
- D) all of the above
Cholesterol is not oxidized for energy within the body, but you might help eliminate it from
your body if you could increase the formation of:
- A) Triacylglycerols
- B) Bile salts
- C) Mineralocorticoids
- D) Protein hormones
How many rounds of b oxidation would be required for a 16-C fatty acyl chain to be degraded
- A) 16
- B) 8
- C) 7
- D) none of the above
The conversion of palmitoyl-CoA (16:0) to myristoyl-CoA (14:0) and 1 mol of acetyl-CoA by
the beta-oxidation pathway results in the net formation of:
- A) 1 FADH2 and 1 NADH
- B) 1 FADH2 and 1 NADPH
- C) 1 FADH2, 1 NADH, and 1 ATP
- D) 2 FADH2 and 2 NADH
Free fatty acids in the bloodstream are:
- A) bound to hemoglobin
- B) carried by the protein serum albumin
- C) freely soluble in the aqueous phase of the blood
- D) nonexistent; the blood does not contain fatty acids
Cholesterol is synthesized from:
- A) acetyl-CoA
- B) choline
- C) lipoic acid
- D) malate
Which types of amino acids are ketogenic?
- A) those that are degraded to pyruvate.
- B) those that are degraded to acetyl-CoA.
Glutamate can be synthesized directly from:
- A) oxaloacetate
- B) citrate
- C) a-ketoglutarate
Nonessential amino acids:
- A) are synthesized by plants and bacteria, but not by humans.
- B) can be synthesized in humans.
If a person's urine contains unusually high concentrations of urea, which one of the following
diets has he or she probably been eating recently?
A)High carbohydrate, very low protein
- B) Very high fat, very low protein
- C) Very low carbohydrate, very high protein
The drug called lovastatin is now used to decrease plasma cholesterol levels by
inhibiting the rate-limiting step of cholesterol synthesis. This step is catalyzed by:
- A) HMG-CoA synthase
- B) HMG-CoA reductase
- C) thiolase
- D) acetyl-CoA carboxylase
Each of the following statements are true for lipoproteins, EXCEPT.
- A) Lipoproteins are complexes of lipid and protein which are necessary for lipid
transport in the blood.
- B) Atherosclerosis is not linked to high levels of LDL-bound cholesterol.
- C) Low density lipoproteins carry cholesterol and cholesterol esters.
Which of the following statements about cholesterol is FALSE?
- A) Plant-based foods contain cholesterol.
- B) Cholesterol can be metabolized to bile acids.
- C) Cholesterol can be converted to cholesteryl ester for storage.
- D) Cholesterol is an essential component of all animal cell membranes.
Triacylglycerols contain three fatty acid molecules esterified to the three hydroxyl groups of
- A) glycerol
- B) sphingasine
- C) pyruvate
- D) alanine
The principal site of cholesterol synthesis is:
- A) The liver
- B) The ovaries
- C) The testes
- D) The intestines
In steady-state metabolism:
- A) The rates of catabolism far exceed the rates of anabolism
- B) The rate of anabolism exceeds the rate of catabolism
- C) A balance exists between rates of anabolism and catabolism
Unlike water-soluble hormones, steroid hormones act by:
- A) Transport to a target cell, diffusion through the membrane, and controlling genes
- B) Moving to the target organ and binding to a membrane
The Cori cycle is:
- A) the conversion of lactate to pyruvate in skeletal muscle to drive glycogen synthesis
- B) the interconversion between glycogen and glucose l-phosphate
- C) the production of lactate from glucogen in skeletal muscle with the resynthesis of glucose
from lactate in liver
- D) the synthesis of alanine from pyruvate in skeletal muscle and the synthesis of pyruvate
from alanine in liver
- A) are able to enter their target cells.
- B) are water-soluble.
- C) act through binding receptors.
- D) act by changing the expression of specific genes
Which of the following chemicals is NOT a second messenger?
- A) Calcium ions
- B) cyclic AMP (cAMP)
- C) cyclic GMP (cGMP)
- D) insulin
How does the blood glucose level of diabetics tend to compare to "normal?"
- A) Blood glucose levels of diabetics tend to be high.
- B) Blood glucose levels of diabetics tend to be low.
- C) There is little to no difference between the blood glucose of diabetics and normal levels.
Which of the following tissues CANNOT use free fatty acids from blood for energy but can
use ketone bodies as an energy source?
- A) liver
- B) brain
- C) muscle
When blood glucose is abnormally high, the pancreas releases:
- A) epinephrine
- B) glucagon
- C) glucose
- D) insulin
Of the two types of diabetes, which of the following situations is UNIQUE to type II
- A) an inability to take up glucose efficiently from the blood
- B) an inability to respond to insulin
- C) an inability to produce sufficient insulin
- D) high levels of glucose in the urine
lower melting point
at least one double bonds
longer the chain =
less double bonds =
free fatty acids transported by
albumin in blood
membrane interior is
acetyl CoA must be attached to ______
to cross the inner mitochondrial membrane from cytosol
each trip through beta oxidation
looses and gains what?
looses 2 carbons
produces 1 NADH and 1 FADH2
fatty acid synthesis starts with _____ in the ____---
liver cytoplasm from the mitochondria via citrate transporter
cholesterol from diet
transfer of amino group from alpha AA to alpha keto acid
synthesis of AA in cytosol needs
nitrogen intermediates from metabolic pathways
ammonia from glutamate
Most other lipids (e.g. triacylglycerols, and cholesterol) are
transported in the blood as part of complex particles called
Membranes are composed of
1) lipids (amphipathic lipids: have both hydrophilic and hydrophobic
2) proteins (integral and peripheral)
The interior of the membrane is fluid and hydrophobic
Hydrophobic (lipophilic) molecules can pass through a membrane’s
hydrophobic interior by
simple diffusion down the gradient
Polar or charged molecules require proteins to form passages
through the hydrophobic barrier
1) Passive transport (facilitated diffusion) takes place when an
ion or polar molecule moves down its concentration gradient
2) Active transport: energy source is required for moving a
molecule for moves against a concentration gradient e.g. the
Fatty acids are synthesized by the repetitive condensation
of two-carbon units originally derived from
acetyl-CoA in the cytosol that came from the mitochondria