Other biochemistry molecules Flashcards
Keq effects on Gibbs free energy
ΔG= ΔG ° + RT lnKeq
Q> Keq: non spontaneous
Q
Lipid structure built from fatty acids
Backbone: e.g sphingosine, glycerol
Head group: charged or neutral
Fatty acid side chain
Digestion of fats
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.
Absorption of fats
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
Transport of lipids
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)
Apolipoproteins
Receptor proteins involved in signaling that attach to lipids and help transport them around the body.
Cholesterol metabolism
From diet or synthesized in liver
HMG-CoA reductase key enzyme in cholesterol biosynthesis
Anabolism of fatty acids
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:
- Citrate synthase
- 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.
Oxidation of Fatty Acids
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
Ketogenesis
Synthesis of ketones
Occurs in the mitochondria
2 important enzymes:
- HMG-CoA synthase forms HMG- CoA
- HMG-CoA lyase breaks HMG-CoA into acetoacetate
Ketolysis
Breakdown of Ketones
Occurs in mitochondria
Thiophorase activates acetoacetate to acetoacetyl-CoA
Ketoacidosis
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)
Carbohydrate structure
General formula: CnH2nOn
Suffix: ose
Most carbohydrate are D carbohydrates E.g D-glucose
Isomeric forms (carbohydrate structure)
Classes of Diastereomers
- Epimers: differ at one chiral carbon
- Anomers: differ at new chiral carbon formed by ring closure.
Cyclic conformations
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
Glycosidic Linkage
Dehydration reaction:
OH group of anomeric carbon with acetyl group, between sugars.
Fermentation
Pyruvate reduced to:
- Ethanol in alcoholic fermentation.
- done by yeast and some bacteria
- Lactic acid in lactic acid fermentation.
- Some fungi and bacteria
- Muscle cells
Replenishes NAD+
Gluconeogenesis
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)
Pentose Phosphate Pathway
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
Tissue specific metabolism
Absorptive state: fed state
Post absorptive state: fasting state
Regulation and integration of metabolism
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.
Analysis of metabolism
Measure metabolism using respiratory measures (respiratory quotient)
Citric Acid Cycle Preparation
Pyruvate —> Acetyl CoA
Enzyme: Pyruvate Dehydrogenase Complex (PDC)
Net result: 2 NADH—> 5 ATP
Citric Acid Cycle
- Pyruvate —> Citrate
- Citrate—> Isocitrate
- Isocitrate—> 𝛼 ketoglutarate (NADH and CO₂)
- 𝛼 ketoglutarate—> Succinyl-CoA (NADH and CO₂)
- Succinyl-CoA—> Succinate (GTP)
- Succinate—> fumurate (FADH ₂)
- fumurate—> malate
- malate—> oxaloacetate (NADH)
Step 1,3 and 4 are irreversible.
Biosignaling
Communication within and between cells
Gated Ion channels
Moves ions across them via facilitated diffusion.
Close under certain circumstances.
Voltage Gated Ion Channels.
Closes when there is a change in the membrane voltage
Ligand Gated Ion Channels
Ligand binds to channel at ligand binding domain.
Once ligand attaches, Transmembrane Domain will open up and allow the ions to go through.
G-protein Coupled Receptors
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
Oncogenes
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)
Electron transport chain
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.
