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Biochemistry > Unit 2 - Active Recall > Flashcards

Unit 2 - Active Recall Flashcards

1
Q

What does catalysis do?

A
  • lowers the activation energy for a reaction
  • increase reaction rates by decreasing ΔG ‡
  • A lower ΔG ‡ allows more molecules to react
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2
Q

What is the ‘reaction coordinate’ equation?

A

ΔG° = ΔH° – TΔS° = -RTlnKeq

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3
Q

How do you increase rxn rates?

A

Increasing number of molecules, increasing the temperature, or adding a catalyst will increase reaction rates

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4
Q

List all that you know about protein catalysts (enzymes)?

Note: riboenzymes not included

A
  • Are the largest group of proteins (six families)
  • Have active sites that bind substrate/product
  • Put substrates in proximity, with correct orientation and provide functional groups for catalysis (decrease activation energy)
  • Preferentially bind and stabilize the transition state (induced fit)
  • Do not change the reaction equilibrium (i.e. catalyze reaction in both directions)
  • Are not chemically changed by the reaction
  • Are normally present in low amounts relative
    to the reactants and products
  • have characteristic pH and temperature optima
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5
Q

Enzymes typically increase reaction rates by ___________ fold. And _________ fold maximally.

A

10^8 – 10^12 fold

max of 10^17 fold

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6
Q

What do enzymes stabilize?

A

The enzyme stabilizes the transition state

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7
Q

Enzymes use three types of catalysis. Explain each.

A
  1. Acid-base catalysis: transfer or removal of H+
  2. Covalent catalysis: transient formation of a covalent bond between enzyme and substrate
  3. Metal catalysis: direct or indirect role in catalysis; often oxidation-reduction Rx
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8
Q

Describe how chymotrypsin uses a catalytic triad to
hydrolyze a peptide bond.

A
  • Chymotrypsin uses both covalent and acid-base catalysis to hydrolyze a peptide bond (enhancement of ~ 1010)
  • Triad used: Asp 102, His 57, Ser 195
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9
Q

Explain the chymotrypsin mechanism step by step.

A
  1. His accepts a proton from Ser (base catalysis) allowing the nucleophilic oxygen of serine to attack the carbonyl carbon of the substrate (covalent catalysis)
  2. His donates a proton to the new NH2 of the C-terminal peptide fragment, breaking the peptide bond (Tetrahedral intermediate transition state)
  3. Departure of the Rc leaves the enzyme covalently
    bound to the RN region of the substrate (Acyl-enzyme intermediate - stable & covalent)
  4. Water donates a proton to His 57 and resulting OH- attacks the carbonyl group of substrate (resembles step 1)
  5. His 57 donating a proton leads to collapse of the
    second tetrahedral intermediate (resembles step 2)
  6. N-terminal portion of substrate diffuses away,
    regenerating chymotrypsin
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10
Q

What other information do you recall about chymotrypsin catalysis?

A
  • Even with mutation of Asp 102, His 57, and Ser 195, proximity and orientation still enhance the reaction rate by 10^5
  • Mutants with Ser 195 replaced are at least 106 fold less active
  • Mutants with Asp 102 or His 57 replaced are 1,000 fold less active
  • Gly 193 and a backbone amide stabilizes the transition state
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11
Q

Explain chymotrypsin substrate binding pocket?

A
  • substrate binding pocket complements the substrate
  • lets us know that divergent evolution of chymotrypsin has occurred

Note:
- Catalytic triads are used throughout biology

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12
Q

What is the Michaelis-Menten Equation?

A

V = Vmax[𝑆] / 𝐾m + [𝑆]

note:
-hyperbolic (like hemoglobin)

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13
Q

What is the catalytic rate constant (kcat ) and its equation?

A

kcat = Vmax / [E]total

note:
- kcat = catalytic rate constant or turnover number, when the enzyme is saturated with S (substrate)
- determines how quickly an enzyme can act

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14
Q

Lineweaver-Burk plot linearizes Michaelis-
Menten kinetics data..give the equation.

A

1/V = (Km / Vmax) (1/[S]) + (1/Vmax)

note:
- very similar to y=mx+b
- Vmax and KM are the two most important parameters for an enzyme, and are easy to estimate with a Lineweaver-Burk plot

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15
Q

Give an example of an irreversible enzyme inhibition (ie: irreversible inhibitors)

A

Diisopropylfluorophosphate is an irreversible inhibitor of chymotrypsin

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16
Q

Exceptions to Michaelis-Menten kinetics

A
  • Michaelis-Menten kinetics are only valid for the simplest enzyme reactions
  • Many enzymes require multiple substrates/products and/or require multiple steps
  • For multistep reactions KM is a complicated function of many rate constants
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17
Q

Explain role of allosteric enzymes & effectors

A
  • Allosteric (”other site”) enzymes often have multiple subunits and show cooperativity: (analogous to hemoglobin vs myoglobin)
  • Enzymes can have positive or negative allostery
  • Allosteric (“other site”) effectors may inhibit or activate enzymes and are used to control metabolic pathways
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18
Q

What do you know about lipids?

A
  • Lipids are heterogeneous, hydrophobic (or amphipathic), and thus insoluble
  • Lipids associate into larger structures and are not usually free in solution (due to hydrophobic effect)
  • Due to potential to aggregate, lipid storage and transport is a challenge
  • Cellular structures (membrane bilayers,
    vesicles)
  • Energy storage (fat = triacylglycerols)
  • Bioactivity (messengers, vitamins, hormones)
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19
Q

List types of lipids

A
  • Fatty acids (FAs: aliphatic carboxylic acids)
  • Triacylglycerols (TAGs: 3 FAs esterified to
    glycerol)
  • Phospholipids (PLs: phospho-head group attached to diacylglycerol or ceramide)
  • Isoprenoids/steroids (e.g. cholesterol)
    Glycolipids (glycosphingolipids)
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20
Q

What do you know about fatty acids?

A
  • are amphipathic (hydrophilic carboxyl group and hydrophobic hydrocarbon tail of variable length)
  • FAs may be saturated (no double bonds), mono- or poly-unsaturated
  • Most natural unsaturated FAs have unconjugated cis double bonds (“trans” fats mainly derived artificially)
  • may be saturated (no double bonds), mono- or poly-unsaturated
  • most FAs are found esterified to cholesterol (CE) or to
    glycerol (TAGs or PLs), or are bound to albumin in the blood
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21
Q

What are the two types of nomenclature for FA double bonds?

A
  1. Omega nomenclature: Count the carbons starting from the tail to the first double bond (the tail carbon is always referred to as the ω (omega) carbon, while that next to the carboxy carbon is α)
    - ex: 18:3(n-3) or 18:3ω-3
  2. delta nomenclature: Count the carbons starting from the carboxyl group: list positions of the double bonds (assume cis unless otherwise specified)
    - 18:3(9,12,15) or 18:3Δ 9,12,15
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22
Q

What do you know about triacylglycerols?

A
  • TAGs (also called triglycerides) consist of 3 FAs esterified to glycerol: they are found in circulating lipoproteins or in insoluble cytosolic lipid droplets
  • In adipose tissue, stored TAG in droplets can be hydrolyzed to release FFA and glycerol for delivery to
    the liver and other tissues
  • TAGs are the major energy reserve in the body: oxidation of FAs produce over twice the energy per gram compared to carbohydrates
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23
Q

What do you know about glycerophospholipids?

A
  • Most phospholipids (PLs) are esters of 3- glycerophosphate, two FAs, and a polar headgroup.
  • major component of cellular membranes and vesicles; lyso-PLs have only one FA
  • Headgroups vary by charge, cellular location, and effects on membrane curvature and protein function.
  • PLs are also precursors of lipid second messengers: position specific cleavage of PIP 2 by phospholipases generates bioactive molecules such as diacylglycerol and
    inositol-1,4,5-P
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24
Q

Define sphingomyelin and glycosphingolipids?

A

Sphingomyelin and glycosphingolipids (e.g. cerebrosides, gangliosides) contain a sphingosine backbone; they have signaling or recognition roles and are abundant in the
brain

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25
Q

Genetic disorders of glycosphingolipid
degradation

A

Glycosphingolipids (GSLs) are synthesized and degraded in strictly ordered pathways: genetic defects in lysosomal
GSL degradation causes severe neurodegenerative diseases

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26
Q

What do you know about cholesterol?

A
  • Cholesterol is important for maintaining lipid bilayer fluidity. Derived from diet or made endogenously from isoprene
  • Cholesterol is highly insoluble and must be transported in lipoproteins, imbalances in which cause atherosclerosis and vascular diseases
  • The liver coordinates intercellular transport and regulation of cholesterol; in humans, cholesterol is excreted, not degraded
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27
Q

Lipoproteins allow for __________ and __________ transport. Explain.

A
  • allow for triacylglycerol and cholesterol transport
  • TAG’s and cholesterol are packaged as lipoproteins when in circulation to allow for transport
  • TAG in lipoproteins are used as a fuel source or stored in adipose tissue
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28
Q

Cholesterol derivatives?

A

Cholesterol is a precursor of bile acids, steroid
hormones and vitamin D Isoprenoids (derived from cholesterol intermediates) include dolichol and ubiquinone

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29
Q

Why do lipids spontaneously associate in water? What structures can be formed?

A
  • lipids spontaneously associate in water due to their amphiphilic or hydrophobic nature, but adopt many different structures depending on their size, shape, charge

These structures include:
- droplets (TAGs)
- micelles (FFAs, lyso-PLs)
- vesicles (PLs)
- bilayers (PLs)
- monolayers (air-water interface)

Note:
Micelle-forming lipids can act as detergents: solubilizing membranes, grease, etc., to release components

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30
Q

The hydrophobic effect drives ______________.

A

bilayer formation

31
Q

Describe biological membranes.

A
  • The lipid bilayer consists mainly of lipids (PLs, cholesterol) and proteins, and is fluid in 2D
  • Rotation and lateral diffusion is allowed, but “flip flop” is rare
  • Since lipid ”flip flop” motions are rare, lipid composition is different in the inner vs. outer membrane leaflets
32
Q

Unsaturated fats do not pack together well…why is this?

A
  • cis double bonds “bend” the fatty acid chain, reduces the efficiency by which they can pack together.
  • also true for triacylglycerides
33
Q

Double bonds influence the fluidity of lipids. Give other examples than improve fluidity of membranes?

A
  • Membrane fluidity increases with degree of FA chain unsaturation, and decreases with FA chain length
  • Cholesterol also influences membrane fluidity by “smoothing” the transition between solid and liquid phospholipid phases (it is rigid but does not pack well into the bilayer)

Note:
- Cell membranes must be fluid at body temperature!

34
Q

Membrane proteins are classified based on the nature of their interactions with the lipid bilayer. Give a few examples.

A
  • Integral proteins are associated via non-polar interactions and require detergents to extract
  • Peripheral proteins are associated with the membrane surface via electrostatic contacts
  • Many integral membrane proteins can span the bilayer
    as a-helices or b-barrels
35
Q

How can we predict a-helical membrane proteins by using their sequence?

A

a-helical transmembrane domains can often be recognized as stretches of ~20 non-polar residues (20 x 1.5Å = 30Å, i.e. thickness of bilayer interior)

36
Q

What is the equation for gas law/energy transport?

A

ΔG = RT ln([X]B /[X]A) + ZFΔψ

R= gas constant
T = temperature (in K)
Z = charge of molecule
F = Faraday’s constant
ψ = voltage potential across membrane (due to unequal – and + ions)

37
Q

Bilayers are not permeable to ______ molecules/ions, which require ________ transport

A

polar
protein-mediated (facilitated)

38
Q

Give examples of facilitated transport?

A
  1. Carrier molecules
    - form a hydrophobic shield around polar molecules (often ions)
  2. Pores/channels
    - non-stoichiometric:fast(106/sec)
    - No conformational change during transport
    - always passive, selective
    - may be gated (e.g. by ligand or voltage)
  3. Transporters
    - stoichiometric: slower (103/sec)
    - Conformational changes
    - passive or active (pumps)
    - specific, may be regulated
    - can move multiple ligands through conformational changes
39
Q

Explain the bacteriorhodopsin transport cycle?

A
40
Q

Explain ATP synthase transport?

A
41
Q

Glucose transport in intestinal epithelial cells?

A
42
Q

What do you about Na+ / K+ ATPase pump? Electrochemical gradient?

A
  • Na,K-ATPase changes conformation as it pumps ions (antiport, active transport)
  • The Na+/K+ gradient is maintained by the Na,K-ATPase pump, which uses one-third of our total energy at rest!
43
Q

What do you know about glucose?

A
  • Made of monosaccharides (one) that are reducing units
  • 6- carbon (hexose) compound formed naturally in food or in the body through digestion of more complex carbohydrates
  • after absorption it can oxidize to provide energy, or is stored as fat/glycogen
44
Q

Cyclization generates α and β anomers..why?

A

Unlike other stereoisomers, anomers are biologically identical, because a and b anomers can freely interconvert.

45
Q

i. Is a cyclized hexose or pentose a reducing sugar?
ii. Why does a solution of glucose molecules consist of about 64% β anomer, about 36% α anomer, and only trace amounts of the linear or open-chain form.

A

i. Yes, its freely interchangeable and releases sugars so reducing
ii. When glucose is dissolved in water, the cyclic forms interconvert through a process called mutarotation. In this process, the glycosidic bond between the anomeric carbon and the hydroxyl group on the fifth carbon atom (C5) undergoes rotation, leading to a dynamic equilibrium between the α and β forms. This equilibrium is influenced by various factors such as temperature, pH, and solvent composition.

46
Q

Explain what you know about oligosaccharides (some)?

A
  • form when 2 to 10 monosaccharides bond chemically.
  • major oligosaccharides, the disaccharides, or double sugars, form when two monosaccharide molecules combine.
  • Monosaccharides and disaccharides collectively make up the simple sugars.
47
Q

Explain what you know about polysaccharides (many)?

A
  • describes the linkage of from 10 up to thousands of sugar molecules.
  • Oligo/Polysaccharides form during the chemical process of dehydration synthesis, a water-losing reaction that forms a more complex carbohydrate molecule.
  • Both plant and animal sources contribute to these large chains of linked monosaccharides.
48
Q

Explain what you know about starch and how it exists in two forms?

A
  • storage form of carbohydrate in plants

Forms:
1. Amylose (linear, digest slowly due to 1 reducing end)
2. Amylopectin (branched, digest quickly due to moving of reducing ends)

49
Q

Fiber is made of cellulose…what else can you recall about cellulose?

A
  • major polysaccharide of glucose found in plant.
  • makes up cell wall
  • most abundant
  • unbranched polymers of glucose residues joined by beta-1,4-linkages
  • stabilized by H-bonds
50
Q

What is carbohydrate? What are the functions of carbohydrates?

A
  • Atoms of carbon, hydrogen, and oxygen combine to form a basic carbohydrate (sugar) molecule in the general formula (CH2O)n, where n ranges from 3 to 7 carbon atoms with hydrogen and oxygen atoms attached by single bonds.
  • Can be classified by polymeric state (mono, oligo, poly)
  • has two functional groups aldose (aldehyde) and ketone (keto)
  • primary source of energy, contribute to the structural integrity of cells and tissues, stored in the body as glycogen in the liver and muscles, crucial role in cell recognition and communication
51
Q

What are monosaccharides, oligosaccharides, and polysaccharides? Similarities and differences?

A

OVERALL:
- Monosaccharides are the simplest form of carbohydrates, consisting of single sugar molecules like glucose and fructose.
- Oligosaccharides are made up of a few (typically 2 to 10) monosaccharide units bonded together, such as sucrose (glucose + fructose) or lactose (glucose + galactose).
- Polysaccharides are complex carbohydrates composed of many monosaccharide units joined together in long chains, examples include starch, glycogen, and cellulose.

SIMILARITIES:
- All are carbohydrates, meaning they contain carbon, hydrogen, and oxygen in the ratio of 1:2:1.
- They are composed of monosaccharide units.

DIFFERENCES:
- Monosaccharides consist of single sugar units, while oligosaccharides contain a few (2 to 10) monosaccharide units, and polysaccharides have many monosaccharide units (more than 10).
- Polysaccharides are typically larger and more complex than monosaccharides and oligosaccharides.
Monosaccharides are the building blocks of oligosaccharides and polysaccharides.
- Monosaccharides are usually sweet-tasting, while oligosaccharides and polysaccharides may not necessarily exhibit a sweet taste.
- Polysaccharides often serve as storage or structural compounds in living organisms, while monosaccharides and oligosaccharides may have various metabolic roles.

52
Q

What are the similarities and differences between starch, fiber, and glycogen?

A

SIMILARITIES:
- All three are polysaccharides, meaning they are composed of multiple sugar molecules bonded together.
- They are all important sources of energy in the human diet.
- They are composed of glucose molecules.

DIFFERENCES:
- Starch is a storage polysaccharide found in plants, while glycogen is a storage polysaccharide found in animals, particularly in the liver and muscles.
- Fiber is a type of polysaccharide found in plants that humans cannot digest completely, whereas both starch and glycogen are digestible by humans.
- Starch and glycogen are highly branched polysaccharides, while fiber is often linear or only slightly branched.
- Starch serves as a reserve energy source in plants, while glycogen serves as a reserve energy source in animals.
- Starch is broken down into glucose during digestion and serves as a source of glucose for energy, while fiber contributes to digestive health by aiding in bowel movements and providing bulk to stool without being digested itself.

53
Q

What are the health benefits of fiber?

A
  • improved digestive health, regulation of blood sugar levels, lower cholesterol levels, weight management, and reduced risk of certain diseases like heart disease, diabetes, and colorectal cancer.
54
Q

Why aren’t all carbohydrates physiologically equal?

A

Carbohydrates are not physiologically equal due to differences in their chemical structures, which lead to variations in their digestion, absorption rates, and effects on blood sugar levels. These differences influence how quickly they provide energy, their impact on insulin response, and their potential health effects. Factors such as the type of carbohydrate (simple vs. complex), fiber content, and presence of other nutrients contribute to these distinctions, resulting in varying physiological effects.

55
Q

What is a glycan?

A
  • a generic term to describe molecules with glycosidic bonds, including sugar (polysaccharides or carbohydrates).
  • glycogen = storage molecules within mammalian muscle and liver (1:4 ratio)
  • forms as a large polysaccharide polymer synthesized from glucose in the process of glycogenesis (catalyzed by the enzyme glycogen synthase, more later).
  • so much more branched than amylopectin
56
Q

What are the two types of glycans?

A
  • N-linked glycans: These are oligosaccharides that are attached to the nitrogen atom of asparagine residues in proteins.
  • O-linked glycans: These are oligosaccharides that are attached to the oxygen atom of serine or threonine residues in proteins.
57
Q

What is the role of glycan on erythropoietin?

A
  • Hormone produced by kidney to stimulate bone marrow’s production from RBC.
  • Glycosylation stabilize EPO – no glycosylation, no function.

Note:
- Can be used to treat anemia.
- Can be used as a blood doping agent for endurance sports.

58
Q

What is the role of glycans on red blood cells?

A

The role of glycans on red blood cells is to determine blood type and facilitate immune recognition and cell-cell interactions.

59
Q

What is the digestive process of carbohydrates?

A
  1. Mouth: Salivary amylase begins breaking down starches into smaller polysaccharides and disaccharides.
  2. Stomach: Acidic environment stops carbohydrate digestion temporarily.
  3. Small Intestine: Pancreatic amylase continues breaking down polysaccharides into smaller molecules like disaccharides and oligosaccharides. Then, enzymes from the intestinal lining further break down disaccharides and oligosaccharides into monosaccharides (e.g., glucose, fructose, galactose).
  4. Absorption: Monosaccharides are absorbed into the bloodstream through the intestinal lining and transported to cells for energy.
60
Q

Why is too much glucose toxic?

A

Too much glucose can be toxic to the body because it can lead to a condition called hyperglycemia, which is characterized by abnormally high blood sugar levels. Chronic hyperglycemia can cause damage to various organs and tissues in the body over time.

61
Q

How can you target carbohydrate digestion to treat diabetes?

A
  • eating whole grains in their “whole form” like brown rice or oats can be healthier than eating highly processed whole grain bread.
  • High-fiber foods don’t contain as much digestible carbohydrate, so it slows the rate of digestion and causes a more gradual and lower rise in blood sugar.
62
Q

Review the structure of glycogen

A

Glycogen is a branched polymer made of glucose molecules linked together. It has a highly branched structure, with many glucose chains connected by alpha-1,4-glycosidic bonds and branching points formed by alpha-1,6-glycosidic bonds. This structure allows for rapid release of glucose when energy is needed and efficient storage in cells such as liver and muscle cells.

63
Q

Explain the breakdown of glycogen. What four enzymes are needed?

A
  1. Glycogen phosphorylase
  2. Transferase
  3. alpha 1-6 glucosidase (debranching enzyme)
  4. phosphoglucomutase
64
Q

Explain the regulation of glycogen breakdown

A

The breakdown of glycogen is regulated by hormonal and enzymatic mechanisms. Hormones like glucagon and adrenaline signal for glycogen breakdown in response to low blood glucose levels or stress. These hormones activate enzymes like glycogen phosphorylase, which catalyzes the breakdown of glycogen into glucose. Additionally, enzymes like glycogen synthase are inhibited to prevent glycogen synthesis. This coordinated hormonal and enzymatic regulation ensures that glycogen breakdown occurs when the body needs glucose for energy.

Note:
- In eukaryotes, transferase and glucosidase are present in a single polypeptide

65
Q

What is the importance of glycogen metabolism in glucose homeostasis?

A

Glycogen metabolism plays a crucial role in glucose homeostasis by storing excess glucose as glycogen when blood glucose levels are high and releasing glucose from glycogen when blood glucose levels drop. This process helps maintain a stable supply of glucose to meet the energy needs of various tissues, especially during periods of fasting or physical activity, ensuring proper functioning of the body and preventing hypoglycemia or hyperglycemia.

66
Q

Compare and contrast liver glycogen breakdown and muscle glycogen breakdown

A

Liver glycogen breakdown and muscle glycogen breakdown are similar processes but with distinct purposes and outcomes. Both involve the enzymatic breakdown of glycogen, a storage form of glucose. However, liver cells primarily break down glycogen to release glucose into the bloodstream, regulating blood sugar levels, while muscle cells break down glycogen to provide immediate energy for muscle contraction. Additionally, liver cells can perform gluconeogenesis to synthesize glucose from non-carbohydrate sources, while muscle cells lack this capability. Overall, while both tissues utilize glycogen for energy, the liver prioritizes maintaining blood glucose levels, whereas muscle glycogen breakdown serves more immediate energy needs within the muscle itself.

67
Q

What is the overall structure of glycogen?

A

The overall structure of glycogen is a highly branched polymer made of glucose molecules linked together in chains with both alpha-1,4-linkages (linear chains) and alpha-1,6-linkages (branch points).

68
Q

What is the benefit for glycogen to have such as a structure?

A

The branching structure of glycogen allows for efficient storage and rapid release of glucose when needed, providing quick energy for the body’s cells.

69
Q

How is glycogen synthesized? How is glycogenesis regulated?

A

i. Glycogen is synthesized through glycogenesis, a process where glucose molecules are linked together to form glycogen chains. This synthesis is catalyzed by enzymes like glycogen synthase and branching enzyme, utilizing UDP-glucose as a substrate.

ii. Glycogenesis is regulated primarily by hormones like insulin and glucagon. Insulin stimulates glycogen synthesis by activating enzymes like glycogen synthase, while glucagon inhibits glycogen synthesis and promotes glycogen breakdown to release glucose into the bloodstream. Additionally, intracellular signaling pathways and allosteric regulation also play roles in glycogen synthesis regulation.

70
Q

How is glycogen broken down? How is glycogenolysis regulated?

A

i. Glycogen is broken down through a process called glycogenolysis, which involves the enzymatic cleavage of glucose molecules from the glycogen polymer. This breakdown primarily occurs in the liver and muscle tissues.

ii. Glycogenolysis is regulated by hormonal signals, primarily through the action of glucagon and epinephrine, which stimulate the activation of glycogen phosphorylase, the key enzyme in glycogen breakdown. Conversely, insulin inhibits glycogenolysis by promoting glycogen synthesis and inhibiting glycogen phosphorylase. Additionally, the levels of ATP and glucose within the cell also play a role in regulating glycogenolysis.

71
Q

What are the similarities and differences between liver vs muscle glycogenolysis?

A

SIMILARITIES
- Both liver and muscle glycogenolysis involve breaking down glycogen to release glucose.
- They both occur in response to low blood glucose levels or increased energy demand.

DIFFERENCES
- Liver glycogenolysis primarily supplies glucose to the bloodstream to maintain blood glucose levels, while muscle glycogenolysis provides glucose for energy within the muscle cells.
- Liver glycogenolysis is regulated by hormones like glucagon and epinephrine, whereas muscle glycogenolysis is primarily regulated by local factors like energy demand during muscle contraction.
- Liver glycogenolysis releases glucose-6-phosphate, which can be converted to glucose for release into the bloodstream, while muscle glycogenolysis generates pyruvate or lactate, which can be used for energy production within the muscle or released into the bloodstream for conversion to glucose by the liver.

72
Q

How does glycogen metabolism maintain glucose homeostasis? How does insulin affect type 1 and type 2 diabetes?

A

I. Glycogen metabolism maintains glucose homeostasis by storing excess glucose as glycogen when blood glucose levels are high and releasing glucose from glycogen when blood glucose levels drop.

II. Insulin affects type 1 diabetes by being absent due to autoimmune destruction of insulin-producing cells, leading to unregulated blood glucose levels. In type 2 diabetes, insulin resistance reduces the effectiveness of insulin, causing elevated blood glucose levels.

73
Q

How does glucagon affect diabetes?

A

Glucagon raises blood sugar levels by releasing stored glucose from the liver, which can be problematic for individuals with diabetes, particularly those with insufficient insulin production or sensitivity. In type 1 diabetes, where insulin is lacking, glucagon’s action can exacerbate high blood sugar levels. In type 2 diabetes, where insulin resistance is present, glucagon can further contribute to hyperglycemia by promoting glucose release from the liver.

Biochemistry (13 decks)

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