Other biochemistry molecules

Question 1

Keq effects on Gibbs free energy

Answer 1

ΔG= ΔG ° + RT lnKeq

Q> Keq: non spontaneous
Q

Question 2

Lipid structure built from fatty acids

Answer 2

Backbone: e.g sphingosine, glycerol
Head group: charged or neutral
Fatty acid side chain

Question 3

Digestion of fats

Answer 3

Lipids enter small intestine nearly fully intact.

Emulsification occurs in duodenum

• aided by bile
• increases surface area.

Pancreas secretes lipase, colipase, cholesterol esterase

It hydrolyses lipids into lipid components: cholesterol, free fatty acids

Micelles formed from these components.

Question 4

Absorption of fats

Answer 4

Micelles absorbed into mucosal cells of small intestine.

Digested lipids re-esterified into triacylglycerols and cholesterols esters.
- lipids packaged into chylomicrons.

They are more water soluble and can diffuse directly into bloodstream

Question 5

Transport of lipids

Answer 5

Albumin: carrier protein
- protein binds to lipids and carries around bloodstream

Lipoproteins: aggregation of apolipoproteins and lipids
- bond to lipids and transport around bloodstream and lymph

Types of lipoproteins (picture)

Question 6

Apolipoproteins

Answer 6

Receptor proteins involved in signaling that attach to lipids and help transport them around the body.

Question 7

Cholesterol metabolism

Answer 7

From diet or synthesized in liver

HMG-CoA reductase key enzyme in cholesterol biosynthesis

Question 8

Anabolism of fatty acids

Answer 8

Occurs in liver

Major enzymes: acetyl-CoA caboxylase, fatty acid synthase

Stimulated by insulin

Major products: palmetic acid

The Citrate/ Malate Shuttle

• acetyl-CoA accumulates in mitochondrial matrix.
• Major enzymes:
  
  1. Citrate synthase
  2. Citrate lease (cytosol)

Acetyl-CoA Carboxylase (happens in cytoplasm)

• substrate: acetyl-CoA.
• activated by citrate and insulin
• requires biotin and ATP
• product is malonyl-CoA

Fatty Acid Synthase ( happens in cytoplasm)

• substrate: malonyl-CoA
• activated by insulin
• requires vitamin B5 and NADPH
• product is palliatif acid.

Question 9

Oxidation of Fatty Acids

Answer 9

Reverse of fatty acid synthesis

Occurs in mitochondria

Activated by fatty-acyl-CoA synthetase and attached of CoA to fatty acid.

Repetition of four steps oxidizing and releasing acetyl-CoA. Each cycle produces:

• 1 acetyl-CoA
• 1 NADH
• 1 FADH2

Question 10

Ketogenesis

Answer 10

Synthesis of ketones

Occurs in the mitochondria

2 important enzymes:

• HMG-CoA synthase forms HMG- CoA
• HMG-CoA lyase breaks HMG-CoA into acetoacetate

Question 11

Ketolysis

Answer 11

Breakdown of Ketones

Occurs in mitochondria

Thiophorase activates acetoacetate to acetoacetyl-CoA

Question 12

Ketoacidosis

Answer 12

High ketone concentration leads to low blood pH. Caused by:

• type 1 diabetes ( low insuline conc.)
• starvation ( low blood sugar, glycogen stored maxed)
• alcohol excess ( low insulin production, malnourishment)

Question 13

Carbohydrate structure

Answer 13

General formula: CnH2nOn

Suffix: ose

Most carbohydrate are D carbohydrates E.g D-glucose

Question 14

Isomeric forms (carbohydrate structure)

Answer 14

Classes of Diastereomers

• Epimers: differ at one chiral carbon
• Anomers: differ at new chiral carbon formed by ring closure.

Question 15

Cyclic conformations

Answer 15

Anything on the left side of Fischer project= top of Hawthorne projection

Anything on the right side of Fischer project= bottom of Hawthorne projection

α- D- glucose: functional group attached to anomeric carbon pointing downwards

β- D- glucose: functional group attached to anomeric carbon pointing upwards

Question 16

Glycosidic Linkage

Answer 16

Dehydration reaction:

OH group of anomeric carbon with acetyl group, between sugars.

Question 17

Fermentation

Answer 17

Pyruvate reduced to:

• Ethanol in alcoholic fermentation.
  
  1. done by yeast and some bacteria
• Lactic acid in lactic acid fermentation.
  
  1. Some fungi and bacteria
  2. Muscle cells

Replenishes NAD+

Question 18

Gluconeogenesis

Answer 18

Opposite of glycolysis

Changing 2 pyruvate back into glucose

Important substrates

• G3P
• Lactate
• Glucogenic amino acids

Since some steps irreversible in glycolysis some enzymes undo these changes.

• pyruvate —> oxaloacetate (via pyruvate carboxylase) (step 10)
• phosphoenolpyruvate carboxylase (step 10)
• Fructose-1,6- Bisphophatase (step 3)
• Glucose-6-Phosphatase (step 1)

Question 19

Pentose Phosphate Pathway

Answer 19

Occurs in cytoplasm

Parallel to glycolysis and alternate path for glucose.

Forms ribulose-5- phosphate which then forms nucleotides

Rate limiting enzyme: glucose-6- phosphate dehydrogenase

Question 20

Tissue specific metabolism

Answer 20

Absorptive state: fed state

Post absorptive state: fasting state

Question 21

Regulation and integration of metabolism

Answer 21

Insulin: liver, muscles, adipose

• decreases glucose
• increases lipids

Glucagon: liver, muscle, adipose

• increases glucose
• decreases lipids (doesn’t affect muscle)

Glucocorticoids (cortisol)
- promotes mobilization of energy stores.

Catecholamines

• increase activity of liver and muscle glycogen phosphorylase
• increase lipolysis in adipose tissue.

Thyroid hormones

• T3 and T4
• increase Catecholamine effect and also increase basal metabolic rate.

Question 22

Analysis of metabolism

Answer 22

Measure metabolism using respiratory measures (respiratory quotient)

Question 23

Citric Acid Cycle Preparation

Answer 23

Pyruvate —> Acetyl CoA

Enzyme: Pyruvate Dehydrogenase Complex (PDC)

Net result: 2 NADH—> 5 ATP

Question 24

Citric Acid Cycle

Answer 24

1. Pyruvate —> Citrate
2. Citrate—> Isocitrate
3. Isocitrate—> 𝛼 ketoglutarate (NADH and CO₂)
4. 𝛼 ketoglutarate—> Succinyl-CoA (NADH and CO₂)
5. Succinyl-CoA—> Succinate (GTP)
6. Succinate—> fumurate (FADH ₂)
7. fumurate—> malate
8. malate—> oxaloacetate (NADH)

Step 1,3 and 4 are irreversible.

Question 25

Biosignaling

Answer 25

Communication within and between cells

Question 26

Gated Ion channels

Answer 26

Moves ions across them via facilitated diffusion. Close under certain circumstances.

Question 27

Voltage Gated Ion Channels.

Answer 27

Closes when there is a change in the membrane voltage

Question 28

Ligand Gated Ion Channels

Answer 28

Ligand binds to channel at ligand binding domain. Once ligand attaches, Transmembrane Domain will open up and allow the ions to go through.

Question 29

G-protein Coupled Receptors

Answer 29

Have characteristic 7 transmembrane domain - amino side is extra cellular and carboxylic side intracellular Cellular signal transduction. Detect molecules outside cell. Bind ligand and activate G-protein. G-protein interacts with ion channel or an enzyme. Types: Gs: stimulates adenylate cyclase Gi: inhibits adenylate cyclase Gq: activates phospholipids C

Question 30

Oncogenes

Answer 30

Proto-oncogenes: positive cell cycle regulators ( cell cycle progresses and cell growing). - a mutation causes them to become oncogenes which makes the cell become cancerous. Tumor suppressor genes: negative cell cycle regulators (cell doesn’t grow too much)

Question 31

Electron transport chain

Answer 31

What: Major energy producing pathway. Electron Carriers from Krebs Cycle pass electrons to e- transport chain generated an electrochemical gradient. H+ ions flow down gradient through ATP synthase protein yielding ATP. Where: within the mitochondria. H+ ions in the inter membrane space and e- transport chain proteins + ATP synthase in inner mitochondrial membrane. ATP produced in mitochondrial matrix. When: process yields high amount of energy, BUT only when O2 is present as final electron acceptor. This is why aerobic organisms need to breathe.