dalton exam iii review2

8/7/2019 Dalton exam III review2

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Biochemistry 3100 Exam Review Dalton

Dalton Exam Question Sheet I What is the name of the enzyme that breaks

down fat in the small intestine? Lipase

A lipase is a water soluble enzyme that catalyzes the hydrolysis of ester chemical bonds in water insoluble lipid substrates


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Dalton Exam Question Sheet I Where are bile salts made?

Bile salts are made in the liver Where are bile salts stored?

Bile salts are stored in the gallbladder. What type of molecules are found in bile salts, and how do

they function? Bile Salts: amphipathic cholesterol derivatives After neutral acids are converted to glycerol and fatty acids,

fatty acids are assembled into bile salt micelles which emulsify (cause the formation of small lipid droplets within water).

The emulsified bile salts can be absorbed into the intestine.

Dalton Exam Question Sheet I What types of enzymes are secreted from the

pancreas. Proteases

Trypsin Chymotrypsin Elastin

Lipases Amylases


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Dalton Exam Question Sheet I

Describe the process through which proteins and carbohydrates are digested and absorbed by the body following a meal. Mouth: Food is consumed in the mouth where it is

initially masticated and small amounts of carbohydrates (starch) are broken down via enzymes in the saliva (ex. Amylase).

Stomach: Food is further broken down via stomach acid (Hydrochloric Acid HCl). Specifically, proteins are denatured and through hydrolysis and pepsin activity,

producing chyme . (carbohydrates are not further degrated in the stomach because the high pH inactivates amylases)

Dalton Exam Question Sheet I Describe the process through which proteins and

carbohydrates are digested and absorbed by the body following a meal. Small Intestine: When chyme enters the small intestine,

the low pH results in the release of the hormones secretin and cholecystokinin into the blood; this stimulates the production of pancreatic juices.

Pancreatic Juices: Alkaline solution that neutralizes chymeand contains enzymes such as proteases and

glucosidsases. Proteases: convert proteins into free amino acids. Glucosidsases: enzymes which cleave glycosidic bonds of

carbohydartes, producing monosacharrides.


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How are amino acids and carbohydrates released into the lining of the intestine? Both free amino acids and carbohydrates are

absorbed into intestinal epithelial brush cells via ion pump transport proteins (secondary active transport).

Dalton Exam Question Sheet I How are amino acids and carbohydrates

released into the bloodstream? Once transported into the epithelial cells of the

intestine, glucose and amino acids are passively transported into the blood stream through transport proteins.


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Dalton Exam Question Sheet I Ion Pump Transport Proteins:

A transport protein which spans the membrane wall, and uses ATP, to transport three eq. of sodium across the membrane wall while at the same time, allowing 2 eq of potassium to flow into the cell (antiport).

The transport of sodium across the membrane wall is an uphill process which requires energy (ATP) and creates a Na+ concentration gradient across the epithelial membrane.

The concentration gradient created by Na+ allows for the flow of Na+ back into the cell, through passive transport

(symport). This process is coupled by the transport of carbohydrates or amino acids into the cell.

BCMB 3100 Dalton Exam III


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Explain the difference between insulin independent and insulin dependent glucose uptake by cells. Function of Insulin:

Insulin functions to control the concentration of glucose in the blood.

When blood glucose levels are high, insulin is released into the blood stream and causes insulin dependent tissue to absorb sugar in the blood.

The absorbed sugar enters glycolysis in the cytosol of the insulin dependent cells and is broken down.

Insulin dependent glucose uptake: Glucose uptake in the muscle and adipose tissue is insulin

dependent.

Dalton Exam Question Sheet I Explain the difference between insulin

independent and insulin dependent glucose uptake by cells. Insulin dependent glucose uptake explained:

Glucose uptake in the muscle and adipose tissue is insulin dependent.

Glucose in the muscle and adipose tissue is insulin dependent because these tissues utilize glucose by converting it into energy (muscle tissue) or other metabolites for energy storage such as acetyl CoA (adipose tissue)

Neither muscle tissue or adipose tissue directly stores glucose.


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Explain the difference between insulin independent and insulin dependent glucose uptake by cells. Insulin independent glucose uptake:

Glucose levels within these tissues are not regulated by insulin.

In liver, brain and red blood cells, glucose uptake through transporter is insulin independent.

Explain

the

difference

between

insulin

independent

and insulin dependent glucose uptake by cells. The Need for Insulin Independent Glucose uptake in the

Brain, Red Blood Cells and Liver Explained: Brain: Brain function is required for life thus, a steady flow of

glucose must always be available, otherwise the body will begin to shut down.

Red Blood Cells: Red blood cells, as glucose transporters do not undergo oxidative phosphorylation (no mitochondria). Insulin regulation of glucose uptake in the red blood cells would inhibit the flow of glucose throughout during times when the bodys glucose levels were high, this would inhibit glucose from reaching the brain.

Liver: One of the livers primary functions is to store glucose in the form of glycogen when glucose levels are high and to produce glucose through gluconeogenesis when glucose levels are low. Insulin regulation of glucose uptake in the liver would prevent liver from releasing glucose formed through gluconeogenesis into the bloodstream when blood glucose levels are low.


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What is the significance of glucosekinase being found in the liver as and hexokinases being found in other tissues? Glucosekinase: Found in the liver.

The liver is used for the storage of glucose (fed state) and for glucose production (starvation).

At low concentrations of blood glucose, the activity of glucosekinase, in the liver, is low. This means that the liver will not store much glucose

The decrease in glucokinase activity at low blood glucose concentrations prevents the liver from storing glucose, making glucose more readily available for tissues.

Dalton Exam Question Sheet I Hexokinase: Found in other tissues.

In the brain, hexokinases can still phosphorylate glucose at low concentrations which allows for glucose retention in the brain at low blood glucose concentrations.


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What is the difference between G and G0

The difference between G and G0 is simply that G0

measures the energy change in a reaction conducted under standard conditions, 1 atm and 25 0C.

The prime of G0 means that the reaction is conducted at pH 7.

In contrast, G corresponds to the energy change between a reactant and a product is the amount of energy released or consumed during a reaction at constant temperature and pressure.

Dalton Exam Question Sheet I Why is it difficult to know the actual G for a

biochemical reaction? Because the concentrations of products and

reactants are likely never near 1M in the cell It is challenging to determine exactly what cellular

concentrations of all products and reactants are within the cell.

Measurement of change in enthalpy within a cell cannot be measured because cellular temperatures are generally observed as constant.


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BCMB 3100 Dalton Exam III

What is NAD+

NAD+ stands for nicotinamide adenine inucleotide.

NADH stands for nicotinamide adenine dinucleotide hydride.

What is the function of NAD+ in catabolic

pathways such as glycolysis. NAD+ is an enzymatic cofactor which functions as

an oxidizing agent.

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In glycolysis, the conversion of fructose 6phosphate to 1,6 fructose bisphoshate requires ATP and has a G value of 14.2 KJ/mol. Is this reaction likely to be reversible? Reversibility: Reversibility in biochemical reactions

result when the G0 of a reaction is near zero. Because the G0 of the phosphofructokinase reaction

is highly negative (more than two orders of magnitude away from equilibrium), the reaction is irreversible.

Dalton Exam Question Sheet I Key Step linking glycolysis to the citric acid

cycle

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Dalton Review Sheet II

The TCA cycle and electron transport chain are coupled at two places.

Reducing equivalents of NADH formed from the TCA cycle begin the electron transport chain at Complex I.

Reducing equivalents are obtained from succinate to via succinate dehydrogenase in Complex II to form QH2 .

Complex IIComplex I

Dalton Review Sheet II The electron transport chain consists of how many complexes?

Five: Complex I [NADH Dehydrogenase], Complex II [Succinate Dehydrogenase Complex], Complex III [Ubiquinol Cytochrome c Oxidoreductase], Complex IV [cytochrome c oxidase], & Complex V [ATP Synthase].

The complexes have allow electrons to flow from high reduction potential to low reduction potential. The complexes contain nonmobile electron carriers that have different reduction potentials.

Increasing Reduction Potential


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Dalton Review Sheet II What else is required to pass electrons down

an electrochemical gradient? Electrochemical Gradient: The ability to pass

electrons from high free energy (high reduction potential) compounds to low free energy compounds.

Dalton Review Sheet II What else is required to pass electrons down

an electrochemical gradient? Terminal electron acceptor. This is O2 for the

electron transport chain.


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What else is required to pass electrons down an electrochemical gradient? Mobile electron carriers to permit transfer of

electrons between complexes.

Ubiquinone Cytochrome c

Dalton Review Sheet II What is protonmotive force and how is it generated across the inner mitochondrial

membrane? Protons are ejected out of the mitochondrial matrix, the process of which is coupled to

the electron transport chain. The flux or protons into the intermembrane space is produced by complex I, II, and III of

the electron transport chain. The protons ejected from the matrix acidify the intermembrane space, generating an electrochemical gradient across the membrane.

The electrochemical gradient is called protonmotive force. Protons then flow down the electrochemical gradient. The electrochemical energy is converted to mechanical energy which drives the ATP synthase complex.


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Describe the structure and function of ATP synthase. Flow of H+ down an electrochemical gradient through a proton

conducting channel Electrochemical energy is converted to F0 mechanical energy and

rotation of the stalk occurs. Rotation of the stalk is lined to rotation of ATP synthase catalytic

subunits which drives ATP synthesis.

Proton conducting

channel

Stalk Matrix

Intermembrane Space

F0 Complex

F1 Complex

Dalton Review Sheet II What is it meant by fatty acid activation?

Fatty acid activation refers to the conversion of fatty acids into fatty acid acyl CoA molecules via acyl CoA synthase.


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Once activated, the fatty acid acyl CoA is converted ito acylcarnitine in a reaction catalyzed by carnitine acyl transferase I.

Acylcarnitine then enters the mitochondrial matrix in exchange for free carnitine via carnitine:acylcarnitine translocase.

In the mitochondrial matrix the isozyme carnitine acyltransferase II catalyzes the reverse reaction converting aclycarnitine into carnitine and fatty acid acyl CoA.

Dalton Review Sheet II What are the major products of the fatty acid

oxidation cycle? Acetyl CoA NADH FADH2


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Explain why gluconeogenesis cannot occur through a simple reversal of glycolytic reactions. There are three irreversible reactions which are associated

with glycolysis. Hexokinase: Conversion of glucose to glucose 6phosphate.

[consumes ATP] Phosphofrutokinase I: Conversion of fructose 6phosphate to 1,6

fructose bisphosphate. [consumes ATP] Pyruvate kinase: Conversion of phosphoenol pyruvate to pyruvate.

[Produces ATP] (the phosphoenol pyruvate product has higher energy than ATP and thus cannot be produced from ATP)

Because these three reactions are irreversible, the reverse reactions must be carried out via other enzymes.

Dalton Review Sheet II What is the major source of pyruvate used for

the generation of glucose in the liver? Amino acid catabolism Alanine can undergo transamination to form

pyruvate


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What is lactic acidosis? Occurs when lactic acid is released into the body

and body pH levels drop.

How does the Liver help prevent lactic acidosis? The liver converts lactic acid into pyruvate which

can subsequently enter into gluconeogenesis.

Dalton Review Sheet II Photosynthesis can be broken down into two

broad series of reactions. What are they?What are the products of the two stages Light reactions

2 ATP & 2 NADPH

Dark Reactions 3phosphoglycerate (sugar)


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PhA

PQ A

Cytochrome bf complex

FB

NADP+ NADPH

P680

P700*

P700 +

P700

P680 +

P680*

Electron EvolvingComplex

2H2O O2 + 4H+

8 H+

hv

hv

Plastocyanin

PQ B

e e

e

e

e

e

e e

e

e

e

e

e

A1

A0

Fx

FA

Photosystem II Photosystem I

e

e Reduction Potential

FdNADPoxidoreductase

Fd

PhotophosphorylationCyclic Electron Flow

Dalton Review Sheet II In the context of photosynthetic reactions, what

is it meant by carbon fixation? Carbon fixation refers to the capture and subsequent

reduction of CO2 gas to form sugars by the Calvin cycle using ATP and NADPH produced in the light reactions of photosynthesis.

What is the role of carbon fixation in the electron transport process? Carbon fixation function to accept electrons from the

electron transport process, and store the energy generated in the form of carbohydrates, amino acids, and fatty acids.


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Dalton Sample Questions Glucosekinase and hexokinase are two enzymes that

perfom identical reactions folloing the import of glucose into a cell. In what cell types are these enzymes found?

Glucosekinase: Liver Hexokinase: Brain

What reaction do these enyzmes catalyze? Glucose Glucose 6phosphate

Why doe some cells use glucosekinase and why do some use hexokinase?

The brain depends on glucose as an energy source, and hexokinase is active at low concentrations of glucose, unlike glucokinase.

Hexokinase can effectively utilize glucose under starvation conditions as opposed to glucokinase.

Dalton Sample Questions Where in the cell do the following occur?

Oxidatin of pyruvate to acetyl CoA. Cytoplasm

Generation of Pyruvate. Cytoplasm

Converstion of 2phosphoglycerate to phosphenol pyruvate. Cytoplasm

Conversion of glucose to glucose 6phosphate Cytoplasm

Conversion of succinate to fumarate. Inner mitochondrial membrane Accumulation of H+ as a consequence of the electron transport

chain. Inter mitochondrial membrane space.


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Dalton Sample Questions

What key metabolic step needs to occur before the products of glycolysis can be fed into the TCA cycle? Name the enzyme and coenzyme involved in this reaction.

Dalton Sample Questions Describe the major steps involved in the TCA cycle including

the major products and reactants. Include a description of the initial step involving the formation of citrate and the relative amounts of major products generated.


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Citric Acid Cycle

COO -

C

CH 2

COO -

O

CH 2

C

CH 2

COO -

COO -

COO -

HO

Oxaloacetate

Citrate

H 3 C

O

SCoAH2O

HS CoA H+

CitrateSynthase

NAD +

NADH CO 2

NAD +NADH

CO 2Pi

GDP (or ADP)

GTP (or ATP)

FADH 2

NAD +NADH

FAD

Dalton Sample Questions Name two Coenzymes required for the TCA

cylce and their oxidized and reduced states. Indicate which his oxidized and which is reduced. NAD+ (oxidized) NADH (Reduced) FAD+ (Oxidized) FADH2 (Reduced)


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Dalton Sample Questions What is protonmotive force and how is it generated

across the inner mitochondrial membrane? Protons are ejected out of the mitochondrial matrix, the

process of which is coupled to the electron transport chain.

The flux or protons into the intermembrane space is produced by complex I, II, and III of the electron transport chain. The protons ejected from the matrix acidify the intermembrane space, generating an electrochemical gradient across the membrane.

The electrochemical gradient is called protonmotive force.

Protons then flow down the electrochemical gradient. The electrochemical energy is converted to mechanical energy which drives the ATP synthase complex.

Dalton Sample Questions Name two types of mobile electron carriers

that participate in the electron transport chain. Cytochrome c Ubiquinone


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Describe the structure and function of ATP synthase complex. Flow of H+ down an electrochemical gradient through a proton

conducting channel Electrochemical energy is converted to F0 mechanical energy and

rotation of the stalk occurs. Rotation of the stalk is lined to rotation of ATP synthase catalytic

subunits which drives ATP synthesis.

Proton conducting

channel

Stalk Matrix

Intermembrane Space

F0 Complex

F1 Complex

Describe how acetyl CoA is produced from fatty acyl CoA as part of fatty acid oxidation and how ATP is eventually generated.

Fatty acid oxidation is a 4 step process Each cycle of fatty acid oxidation produces

One Acetyl CoA One NADH One FADH2

Each turn shortens fatty acyl CoA by 2 carbons forming acetyl CoA NADH, FADH2 fed into the e transport chain to generate ATP. Acetyl CoA is fed into the TCA cycle for energy production.

Fatty acyl CoA reenters the cycle multiple times to maximize oxidation and energy production. Each time the fatty acyl CoA is introduced, Acetyl CoA must be added.


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Dalton Sample Questions

Draw the reaction involving the conversion of glucose to glucose 6phosphate, name the enzyme involve.

Dalton Sample Questions Draw the reaction catalyzed by glycogen

synthase involving the incorporation of UDP glucose into an unbranched molecule of glycogen.


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Dalton Sample Questions Where in the cell does glucose 6phosphate isomerase particpate in the oxidation of glucose?

Cytoplasm Pyruvate is generated from the oxidation of acetyl CoA (true or false)

False Where in the cell is 2phosphoglycerate converted to phosphoenol pyruvate?

Cytoplasm How many molecules of acetyl CoA are produced from one turn of the fatty acid oxidation cycle?

One Trans amination of amino acids in the liver result in the generation of a 3 carbon molecule starting

point for gluconeogenesis. What is this molecule? Pyruvate

How many net molecules of ATP are generated from the oxidation of one glucose? Two

Where in the chloroplast does plastocyanin perform its function? Thylakoid membarane

Which compartment of theh chloroplast becomes acidified as a consequence of H+ accumulation during electron transport.

Thlakoid Space (lumen)

Dalton Sample Questions The conversion of phosphoenol pyruvate to

pyruvate is shown below What pathway is this a part of?

Glycolysis What is the role of pyruvate kinase in this reaction?

Catalyzes the formation of pyruvate from phosphoenolpyruvate

Transfers the phosphoryl group from phosphoenolpyruvateto ADP generating ATP.

In terms of metabolic fluxes, what is important about this reaction?

It is irreversible.

dalton exam iii review2

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