BMS1011 Lecture Notes - Lecture 1: Pyruvate Dehydrogenase, Acetyl Group, Mitochondrion
24 Aug 2018
School
Department
Course
Professor
WEEK 8
LECTURE 14 (C2) & 15 (C3) – Carbohydrate Oxidation I&II
CARBOHYDRATES
Discuss the digestion, absorption and transport of dietary carbohydrates
Digestion
:
-
Diet is mostly consumed as disaccharides and polysaccharides
Disaccharides: Sucrose, lactose, maltose
Polysaccharides: Starch, glycogen, cellulose
Absorption
:
-
Only monosaccharides can be absorbed from lumen → blood
-
Enzymes are used to break down these carbohydrates to glucose (monosaccharide) subunits
-
Brush-boarder enzymes are found on the microvilli
Transport:
1.
PRIMARY ACTIVE TRANSPORT
•
Na+ pumped from low concentration to high concentration
•
K+ pumped from a low concentration to high concentration
2.
SODIUM-GLUCOSE CO-TRANSPORT (secondary active transport)
•
Na+ going from high concentration in lumen to low concentration in
cytoplasm
•
Glucose is going from low concentration in lumen to high
concentration in cytoplasm
•
An ion going along the gradient is releasing indirect energy to drive
second solute against gradient
IMPORTANCE/CHARACTERISTICS OF GLUCOSE
ACTS AS AN EXCELLENT FUEL
•
Yields a lot of energy when oxidised (02480kJ/mol)
•
Efficiently stored in polymeric form
•
Can be used widely by organisms and tissues
Discuss the function of the glycolytic pathway
•
Breakdown of glucose to 2 molecules of 3C pyruvate
•
Free energy is released in form of: 2 ATP, 2 NADH
Identify the key features of this pathway
•
TWO Phases:
i.
Preparatory Phase
GLUCOSE
→
GLYCERALDEHYDE-3-PHOSPHATE
ii.
Payoff Phase
GLYCERALDEHYDE-3-PHOSPHATE
→
PYRUVATE
•
THREE Irreversible steps:
-
Step 1, 3, 10
-
Regulating these points prevents ‘futile cycling’ → two metabolic pathways run simultaneously cause no overall effect as they cancel out
-
By-pass steps are required
1
HEXOKINASE
GLUCOSE + ATP < ---------------------------- > GLUCOSE-6-PHOSPHATE
GLUCOSE-6-PHOSPHATASE
2
PFK-1
FRUCTOSE-6-PHOSPHATE < ---------------------------- > FRUTOSE 1,6-BISPHOSPHATE
FRUC-1,6, BISPHOSPHATASE
3
PYRUVATE KINASE
PHOSPHOENOLPYRUVATE < ---------------------------- > PYRUVATE
PYRUVATE CARBOXYLASE & PEP CARBOXYKINASE
3.
•
FACILITATED DIFFUSION
Glucose going from high to low concentration using carrier protein
4.
•
FACILITATED DIFFUSION
K+ going from high to low concentration through a channel
IS A VERSATILE BIOCHEMICAL PRECURSOR
•
Synthesis of complex polysaccharides
•
Stored in cells as polysaccharide
•
Oxidised to produce ATP and metabolic intermediates
•
Oxidised to yield 5C sugars and NADPH
OVERALL EQUATION
:
Glucose + 2NAD
+
+ 2ATP + 2P
i
→
2 Pyruvate + 2NADH + 2ATP + 2H
+
+ 2H
2
O
INPUTS = 1 GLUCOSE, 2 ATP, 2 NAD+
OUTPUS = 2 PYRUVATE, 2 ATP (4 total but 2 was used), 2 NADH
GLYCOLYSIS
GLYCOLYSIS: 10 step-pathway to breakdown glucose to 2 molecules of pyruvate in aerobic conditions
•
LOCATION: Cytosol
Document Summary
Lecture 14 (c2) & 15 (c3) carbohydrate oxidation i&ii. Discuss the digestion, absorption and transport of dietary carbohydrates. Diet is mostly consumed as disaccharides and polysaccharides. Only monosaccharides can be absorbed from lumen blood. Enzymes are used to break down these carbohydrates to glucose (monosaccharide) subunits. Na+ pumped from low concentration to high concentration. K+ pumped from a low concentration to high concentration. Na+ going from high concentration in lumen to low concentration in cytoplasm concentration in cytoplasm second solute against gradient. Glucose is going from low concentration in lumen to high. An ion going along the gradient is releasing indirect energy to drive. Yields a lot of energy when oxidised (02480kj/mol) Can be used widely by organisms and tissues. Breakdown of glucose to 2 molecules of 3c pyruvate. Free energy is released in form of: 2 atp, 2 nadh. Glucose going from high to low concentration using carrier protein. K+ going from high to low concentration through a channel.
