Carbs: Homework and Tophat Flashcards

1
Q

P1: Be able to identify different carbohydrates (i.e., di- vs. oligosaccharide, homo- vs. heteropolysaccharide, etc.) in images and/or descriptions.

A
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2
Q

P1: A1C is formed via non-enzymatic glycosylation. What does that mean?

A

Glucose can non-enzymatically attach to hemoglobin
Via N-terminus or Positively- charged AA residues
Interferes with protein’s oxygen delivery to tissues (poor release)
Glucose also scavenges nitric oxide, altering blood pressure

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3
Q

P1: How do simple carbohydrates differ from complex carbohydrates?

A

Simple carbohydrates = monosaccharides, disaccharides (sucrose)
Also includes high-fructose corn syrup
Fewer glycosidic bonds so monomers enter glycolysis faster: “quick energy”

Complex carbohydrates = oligosaccharides and larger polysaccharides
Also includes dietary fiber
More glycosidic bonds so monomers enter glycolysis slower

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4
Q

P1: Why is glycogen storage limited within the human body?

A

-This is due to glycogen’s polarity, and the amount of water that ends up bound to each residue. We couldn’t store all that water alongside the glycogen, but triacylglycerols don’t have this issue, so it is way more efficient!
- Mechanism underlying the hydration process
not entirely understood

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5
Q

P1: Know which conjugated molecule(s) (i.e., glycoprotein, glycolipid and glycoRNA) have O-glycosidic bonds versus N-glycosidic bonds.

A
  • O-glycosidic bond is between carbon-1 and OH group’s oxygen
  • N-glycosidic bond is between carbon-1 and NH2 group’s nitrogen

*All three have carbohydrates attached to their exterior surface
*Glycoproteins are both N and O linked, Glycolipids are N linked, and GlycoRNA’s are O linked.

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6
Q

P2: Understand how dietary carbohydrates are digested.

A

Dietary carbohydrate digestion begins in the mouth as an amylase present

Found within many foods like bread, pasta, fruits and vegetables

Added sugars in many condiments, like ketchup and BBQ sauce

Table sugar (an inorganic food additive) also contains this biomolecule
Brown sugar has sucrose and molasses (with glucose, fructose, etc)

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7
Q

P2: If dietary fiber is indigestible, why is it important we regularly consume it? Be sure to clarify the role of soluble versus insoluble fiber.

A

enters large intestine mostly intact
Has low-viscosity and is non-fermentable (i.e., metabolically inert)
- Evidence also suggests INsoluble fiber helps improve the bioavailability of water-soluble vitamins within large intestine
- Recall soluble fiber has high-viscosity and is fermentable (good source for bacteria in LI)

– Resulting short chain fatty acids
mostly absorbed through colonic
lumen

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8
Q

P2: Does insulin stimulate the liver to synthesize or metabolize glycogen?

A

Insulin triggers insulin signal transduction pathway in muscle and fat cells
Also stimulates liver activity

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9
Q

P2: Know the four metabolic pathways involved in cellular respiration.

A

Glycolysis: glucose (primary input); pyruvate and NADH (outputs)

Pyruvate oxidation: pyruvate (primary input); acetyl CoA and NADH
(outputs)

Citric acid cycle: acetyl CoA (primary input); NADH and FADH2 (outputs)

Oxidative phosphorylation: NADH and FADH2 are the primary inputs

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10
Q

P2: During starvation, how does the brain obtain glucose?

A

only fuel the mammalian brain uses under non-starvation conditions is glucose.

Body cannibalizes muscle (protein) and fat (triacylglycerol), gluconeogenesis synthesizes glucose from non-carbohydrate sources

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11
Q

P2: If you’re on a low-carb diet, how does the brain obtain glucose?

A

Brain still requires glucose

Non-carbohydrate precursors for gluconeogenesis obtained from dietary lipids and proteins

Consumed fats also source of acetyl CoA used for ketone body synthesis

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12
Q

P3: Where does glycolysis occur in prokaryotes? What about in eukaryotes?

A

Both prokaryotes and eukaryotes within the cytoplasm

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13
Q

P3: Define the term “isozyme”. How do isozymes differ from isomers?

A

enzyme with different primary structure but catalyzes same reaction
they’re different atoms making up composition

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14
Q

P3: Understand how each of the allosteric enzymes involved in glycolysis is regulated in the muscle versus in the liver.

A

Muscle -
Hexokinase: feedback inhibition by glucose-6-phosphate, but glucose 6-phosphate not solely a glycolytic intermediate. Impacted by phosphofructrokinase activity
Phosphofructokinase: most important control site in mammalian glycolytic pathway, allosterically inhibited by ATP, changes in pH, and citrate. Stimulated by AMP - signal for low- energy state
Pyruvate kinase: allosterically inhibited by ATP, alanine and phosphorylation of select serine residues. stimulated by fructose 1,6-biphosphate- product of reaction catalyzed by phosphofructokinase
Liver -
Hexokinase: enzyme not present in the liver; reaction performed BY glucokinase (isozyme, with low glucose affinity), not subject to feedback inhibition by glucose 6-phosphate
Glucokinase: only phosphorylates glucose when blood-glucose levels high, ensures brain has priority for the monosaccharide. Regulated via interaction with glucokinase regulatory protein, when bound it’s inactivated and localized to nucleus
phosphofructokinase: different isozyme in liver than in muscle, allosteric inhibition in liver due to citrate not ATP or pH. Nucleotide levels don’t fluctuate as much in liver as in other tissues. lactate not produced in the liver, so remains physiologically neutral.
pyruvate kinase: different isozymes in different tissues. L isozyme allosterically inhibited by phosphorylation by PKA. dephosphorylation by a protein phosphatase

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15
Q

P3: Where does pyruvate oxidation occur in prokaryotes vs. in eukaryotes?

A

Cytoplasm for Prokaryotes
Mitochondria for Eukaryotes

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16
Q

P3: Understand how pyruvate oxidation is regulated.

A

allosterically inhibited by phosphorylation of select serine residues, PDH phosphatase stimulated by calcium and insulin. Also regulated by NADH, acetyl CoA and ATP

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17
Q

P4: Where does the CAC occur in prokaryotes? What about in eukaryotes?

A

Cytoplasm for prokaryotes
Mitochondria for eukaryotes

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18
Q

P4: How do the α-ketoglutarate dehydrogenase complex and the pyruvate dehydrogenase complex differ? How are they similar?

A

α-ketoglutarate dehydrogenase - reaction removes carboxyl group containing carbon-1 and forms thioester linkage with CoA. Allosteric enzyme with 3 distinct enzyme; each has own active site, same structure and mechanism as pyruvate dehydrogenase complex

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19
Q

P4: ATP is generated via substrate-level phosphorylation in glycolysis and the CAC. Why is the reaction in the CAC considered unusual?

A

No kinase or donor molecule with phosphoryl-transfer potential (substrate-level phosphorylation)

only example of substrate-level phosphorylation within mitochondria

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20
Q

P4: Understand how each of the allosteric enzymes involved in the citric acid cycle is regulated. Do certain effectors regulate both enzymes?

A

Isocitrate dehydrogenase - (IDH1, IDH2, IDH3), IDH1 and IDH2 both reduce NADP+ while IDH3 reduces NAD+, IDH1 in cytoplasm and peroxisomes; IDH2 and IDH3 in mitochondria. IDH3 involved in CAC; requires a metal cofactor for activity
regulation- allosterically inhibited by ATP and NADH, muscle unique in hwo much its metabolic rate varies, stimulated by ADP, citrate and calcium (muscle only)

α-ketoglutarate dehydrogenase complex- allosteric enzyme with 3 distinct enzymes; each has own active site, same structure and catalytic mechanism as pyruvate dehydrogenase complex
regulation - different α-KGDH isozyme in brain than in muscle and liver, allosteric inhibition from ATP, NADH, succinyl CoA, reactive oxygen species

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21
Q

P5: Where does oxidative phosphorylation occur in prokaryotes? What about in eukaryotes?

A

Plasma membrane for prokaryotes
Inner mitochondrial membrane for eukaryotes

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22
Q

P5: NADH and FADH2 are the primary inputs for the ETC. Which complex in the ETC accepts electrons from NADH? What about from FADH2?

A

Complex 1

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23
Q

P5: Understand how electrons flow within the ETC.

A

Complex 2

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24
Q

P5: Which amino acid must be neutralized for ATP synthase’s c ring to turn?

A

amino acid gluatmate

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25
Q

P5: Understand how oxidative phosphorylation is regulated.

A

activity of ETC and ATP synthase tightly coupled, NADH and FADH2 oxidation linked with ADP phosphorylation, known as acceptor control or respiratory control

when ADP concentration low, NADH and FADH2 produced by earlier parts of cellular respiration not oxidized back to NAD+ or FAD

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26
Q

Does the monosaccharide shown below contain all six of the major elements required for life?

A

No, it does not. (only had CHO in the aromatic ring)

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27
Q

The polysaccharide shown below contains 4 sugar residues connected by:

A

O-glycosidic bonds (-O-)

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28
Q

Below is glycosylated hemoglobin, with glucose in blue and hemoglobin in black. The monosaccharide is attached to the protein via:

A

the side chain of an amino acid residue

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29
Q

Unlike standard monosaccharides, amino sugars also contain the chemical element:

A

nitrogen

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30
Q

A carbohydrate is comprised of 7 sugar residues: 3 galactosamine (GalN) and 4 mannose (Man). Based on this information, the carbohydrate would be categorized as a/an:

A

heteropolysaccharide

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31
Q

Which statement about dietary fiber is incorrect?

A

Dietary fiber includes cellulose (from plants) and gristle (from animals).

correct
-dietary fiber includes both water-soluble and water-insoluble types
-soluble fiber can be fermented by gut bacteria
-insoluble fiver cannot be fermented by gut bacteria

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32
Q

True or false: The glycoprotein shown contains a compound sugar.

A

This is false. (compound sugar: also known as disaccharides or double sugars, are molecules made of two bonded monosaccharides)

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33
Q

In the glycoglycerolipid shown below, select the oxygen participating in the O-glycosidic bond.

A

(on O connecting ring and side chain)

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34
Q

The amylase present in your saliva cleaves:

A

alpha-1,4-glycosidic bonds

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35
Q

True or false: In the small intestine, alpha-dextrinase cleaves alpha-1,4-glycosidic bonds.

A

This is false.

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36
Q

Bacteria in the large intestine convert soluble fiber into short chain fatty acids. This process would likely involve:

A

fatty acid synthesis

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37
Q

A redox reaction involving glucose is shown below. The electrons being transferred are associated with hydrogen. Glucose is a reducing sugar, which means it:

A

loses electrons and is oxidized in the reaction

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38
Q

True or false: The brain only uses glucose as a fuel source under non-starvation conditions.

A

This is false.

39
Q

Glycolysis happens in the <blank> which is why all cells (including mature red blood cells) can perform the pathway.</blank>

A

cytoplasm

40
Q

What do hexokinase and phosphofructokinase have in common?

A

Both of these enzymes hydrolyze ATP and transfer a phosphoryl group.

41
Q

What do phosphofructokinase and pyruvate kinase have in common?

A

Both of these enzymes transfer a phosphoryl group to an acceptor molecule.

42
Q

True or false: If two proteins are isozymes, then they also have identical chemical formulas (i.e., are isomers).

A

This is false.

43
Q

People with acute liver failure are unable to fully metabolize citrate. Consequently, citrate enters systemic circulation and accumulates within the liver. Would this impact glycolysis?

A

Yes, liver phosphofructokinase would be suppressed due to high citrate levels.

44
Q

In what way do glycolysis and pyruvate oxidation differ?

A

Glycolysis can occur anaerobically, but pyruvate oxidation cannot.

45
Q

Under aerobic conditions, NAD+ is regenerated via <blank> of the electron-transport chain.</blank>

A

complex I

46
Q

Below is an image of the citric acid cycle. Select the rate-limiting step.

A

(On isocitrate)

47
Q

True or false: A coenzyme (either NAD+ or FAD) is reduced in each of the four redox reactions in the citric acid cycle.

A

true

48
Q

Succinate dehydrogenase is unusual because it participates in the citric acid cycle as well as:

A

oxidative phosphorylation

49
Q

Both isocitrate dehydrogenase and the α-ketoglutarate dehydrogenase complex can be suppressed by high levels of:

A

ATP and NADH

50
Q

HW 7: True or false: Digestive enzymes break covalent bonds in carbohydrate-containing foods.

A

true

51
Q

Dietary carbohydrate digestion involves: alpha-dextrinase, pancreatic alpha-amylase and saliva alpha-amylase. For each molecule listed, indicate where in the human body it participates in digestion.

-alpha-dextrinase:
-pancreatic alpha-amylase:
-saliva alpha-amylase:

A

-alpha-dextrinase: SI
-pancreatic alpha-amylase: SI
-saliva alpha-amylase: mouth

52
Q

High blood sugar prompts the pancreatic beta-cells to release insulin. This hormone stimulates the liver to
[ Select ] and stimulates the fat cells / adipose tissue to
[ Select ]

A

synthesize glycogen and uptake glucose

53
Q

Saliva alpha-amylase and pancreatic alpha-amylase have 94% amino acid similarity. This helps explain why they:

A

catalyze very similar reactions

54
Q

_____ dietary fiber can be metabolized by bacteria within the human ___________.

A

soluble and Large intestine

55
Q

All of the following statements about glucose are correct except:

A

Glucose is metabolized in the mitochondria of mature red blood cells.

56
Q

In the diagram below, we see a redox reaction from a metabolic pathway. The electrons being transferred are associated with the hydrogen atoms (shown in red font). Identify the molecule being reduced and the molecule being oxidized.

A

molecule being reduced: acetophenone (gaining electrons from another molecule)
molecule being oxidized: NADPH (loss of electrons; donating to the acetophenone)

57
Q

NADH is a primary input for oxidative phosphorylation. Which other pathway(s) have we talked about in the lipid section and/or protein section that involved this coenzyme (either NAD+ or NADH)? Select all that apply.

A

amino acid synthesis and the beta-oxidation pathway

58
Q

All of the following statements about glycolysis are true except:

A

Glycolysis consists primarily of irreversible reactions.

59
Q

Glycolysis consists of 10 reactions, 3 of which will be used to regulate the pathway. Match the (almost) irreversible reaction with the allosteric enzyme that catalyzes it within the muscle.
reaction 1 :
reaction 3:
reaction 10:

A

reaction 1: hexokinase (1 glucose to G6P)
reaction 3: phosphofructokinase (fructose 6 phosphate to fructose 1,6 biphosphate)
reaction 10: pyruvate kinase (phosphoenolpyruvate to pyruvate)

60
Q

Glyceraldehyde 3-phosphate is an intermediate of glycolysis. This molecule was also generated during the metabolism of:

A

glycerol

61
Q

In the image below, you see the primary protein structure for Human A, Human B, and Human C. Each molecule is able to cleave an aldol functional group using covalent catalysis and a Schiff base intermediate. Based on this information, the molecules are:

A

isozymes of one another

62
Q

True or false: The human body can metabolize glucose, but not other monosaccharides.

A

This is false! We can metabolize other monosaccharides so long as they are converted into an intermediate of glycolysis.

63
Q

Carbohydrates have a variety of roles. Which role is shared with lipids?

A

Serving as fuel (energy) sources in people.

64
Q

What do amino acids and monosaccharides have in common?

A

Both are water-soluble, carbon-based molecules.

65
Q

The sulfated oligosaccharide shown below contains
[ Select ]
bonds and would be classified as a/an
[ Select ]

A

O-glycosidic and heteropolysaccharide

66
Q

Glucose and sucrose were both subjected to Fehling’s test. What happened in the YouTube video shown in class?

A

Glucose reacted but sucrose didn’t react. Glucose is a reducing sugar.

67
Q

True or false: All dietary fiber is metabolically inert.

A

false

68
Q

Why are disaccharides like maltose considered a “quick energy” source?

A

Because they have very few glycosidic bonds to cleave.

69
Q

Cats can have one of three blood types: A, B or AB. Type A has N-glycolylneuraminic acid (NeuGc), while type B has N-acetylneuraminic acid (NeuAc). Based on your knowledge of human blood types, what monosaccharide(s) - if any - would you expect on the AB blood type in cats?

A

Both N-glycolylneuraminic acid (NeuGc) and N-acetylneuraminic acid (NeuAc)

70
Q

What do saliva α-amylase and lingual lipase have in common?

A

Both enzymes are catalytically active within the mouth.

71
Q

Phosphorylation can be used to regulate which allosteric enzymes involved in glycolysis? Select all that apply

A

liver pyruvate kinase and muscle pyruvate kinase

72
Q

Dimethoate is a commonly used agrochemical. However, chronic exposure to it can cause an individual to develop hyper-β-alaninemia (i.e., excessive alanine) in the muscles. Would hyper-β-alaninemia impact glycolysis?

A

Yes, muscle pyruvate kinase would be suppressed as a consequence of hyper-β-alaninemia.

73
Q

All of the following statements about pyruvate oxidation are true except:

A

Pyruvate oxidation can occur with or without oxygen present.

TRUE
-Pyruvate oxidation converts pyruvate into acetyl CoA.
-Pyruvate oxidation is part of cellular respiration.
-Pyruvate oxidation consists primarily of irreversible reactions.

74
Q

True or false: Phosphorylation can be used to regulate the pyruvate dehydrogenase complex

A

True

75
Q

Both glycolysis and pyruvate oxidation:

A

include one or more redox reactions

76
Q

Generally speaking, glycolysis and pyruvate oxidation are both suppressed by:

A

high levels of ATP

77
Q

All of the following statements about the citric acid cycle are true except:

A

The citric acid cycle regenerates NAD+ and FAD.

TRUE
-The citric acid cycle involves one or more redox reactions.
-The citric acid cycle is part of cellular respiration.
-The citric acid cycle occurs in the cytoplasm of prokaryotes.

78
Q

What do the pyruvate dehydrogenase complex and the α-ketoglutarate dehydrogenase complex have in common?

A

Both complexes perform oxidative decarboxylation reactions.

79
Q

Match each major metabolic intermediate with where it can enter cellular respiration as an input or intermediate.

Fumarate
pyruvate
oxaloacetate
succinyl Coa

A

Fumarate: CAC
pyruvate : pyruvate oxidation
oxaloacetate: CAC
succinyl Coa: CAC

80
Q

Electrons from complex I are passed to

A

Complex 3

81
Q

Electrons from complex II are passed to

A

Complex 3

82
Q

Electrons from complex III are passed to

A

Complex IV

83
Q

Electrons from complex IV are passed to

A

oxygen

84
Q

Which complexes in the electron-transport chain pump protons, contributing to the proton gradient? Select all that apply.

A

complex 3,4,1

85
Q

True or false: ATP is directly generated by complexes I through IV of the electron-transport chain.

A

False

86
Q

Atovaquone is an antifungal used to treat fungal pneumonia. It is a structural analog of coenzyme Q and competes with coenzyme Q for binding. Which complex in the electron-transport chain does NOT involve coenzyme Q, and therefore, would not be directly impacted by atovaquone?

A

Complex 4

87
Q

True or false: The proton-motive force consists of two gradients - a chemical gradient and a charge gradient.

A

This is true! The chemical gradient reflects the uneven distribution of protons. The charge gradient reflects the inherent positive-charge of those protons.

88
Q

L9 Top Hat: True or false: Each complex within the electron-transport chain interacts with multiple, different electron carriers.

A

True

89
Q

Complex III accepts electrons from coenzyme Q. Coenzyme Q acquired these electrons from electron carriers at:

A

both complex I and II

90
Q

In both the electron-transport chain and light-dependent photosynthetic reactions

A

electrons are transferred between protein complexes

91
Q

L10: In order to get ATP synthase’s c ring to turn, protons must neutralize glutamate. This amino acid is characterized as a:

A

negatively-charged amino acid

92
Q

True or false: NADH generates more ATP than FADH2 does because NADH is carrying more electrons than FADH2 is.

A

false

93
Q

All of the following are sources of precursors for gluconeogenesis EXCEPT:

A

acetyl CoA from a ketone body

ARE
-glycerol from triacylglycerol metabolism
-lactate from lactic acid fermentation
-oxaloacetate from a glucogenic amino acid