Week 7: Digestion, Energy, And Glycolysis Flashcards
Digestion definition
The set of biochemical reactions that convert food (macronutrients) into bio synthetic building blocks or biologically useful energy
Where does digestion begin
In the mouth
Mouth
Mechanically mixed?
Teeth
Mouth
Chemically mixed?
Saliva
The enzyme that cleaves the olgipeptides
Pepsin
What happens to oligopeptides in low pH
Low pH denatures proteins making them easier to hydrolyze
What does bile do
Helps get lipids in solution where they can more easily be digested
What is proteases linked to
Proteins
What is Lipases linked to
Lipids
What is released from the small intestine when low pH is sensed (food bolus)
Secretin
What increases the pH of the homogenate
NaHCO3
Pre-enzyme Zymogen Pepsinogen
Pepsin
Site of synthesis is stomach
Pre-enzyme Zymogen Chymotrypsinogen
Active enzyme Chymotrypsin
Site of synthesis is Pancreas
Pre-enzyme Zymogen Trypsinogen
Active enzyme is Trypsin
Site of synthesis is Pancreas
Pre-enzyme Zymogen Procarboxypeptidase
Active enzyme is Carboxypeptidase
Site of synthesis is Pancreas
Pre-enzyme Zymogen Proelastase
Active enzyme is Elastase
Site of synthesis is Pancreas
What happens during process of Pepsinogen to Pepsin
Hangs out in zymogen form until food arrives, decreasing pH which converts from inactive to active
What happens during process of Trypsinogen to Trypsin
Trypsinogen has intrinsic proteolytic activity, will spontaneously convert to trypsin. Trypsin then acts on other Trypsinogen molecules in turn
Why are enzymes not just synthesized in their active forms?
They could chew up proteins in the pancreas
Digestion of lipids
Starts with bile - solubilize the lipids
What does bile salts act like
A detergent to help homogenize and disperse fats
What form are most lipids in
Triacylglycerol
Form fat droplets
Bile salts disperse the lipids that that lipases can get to them
What does a high fiber diet do
Lower cholesterol
What is energy metabolism
Catabolism (break down)
Think of a cannibal
Stages in Metabolism
Stage 1: Digestion - breaking down large molecules
Stage 2: Forming Acetyl CoA
Stage 3: Convert molecules to energy
Energy is required to meet 3 fundamental needs
What are they
Power muscle contraction
Active transport of molecules
Biosynthesis
- Metabolic Pathways
Control flow of energy and matter series of enzymatically chemical reactions
- ATP is the energy currency of life
Controlled way to move energy around
Ex. Na+/K+ pump coupled with ATP hydrolysis
- ATP can be formed by the oxidation of carbon fuels
ADP + Pi double arrows ATP
- Limited number of reaction types that involve particular intermediates (pyruvate) are common to all metabolic pathways
Redox, Condensation, Hydrolysis, Addition/Elimination, Isomerization
- Metabolic pathways are highly regulated
By enzymes [s], [enzymes] type of enzyme allosteric effects/effectors
- Enzymes involved are organized into large complexes
Subunits, G-Coupled Receptors
Catabolic
Spontaneous
Combust carbon fuels to synthesize ATP or ion gradients
Anabolic
Non-Spontaneous
Use ATP and reducing power to synthesize large biomolecules
How can thermodynamically unfavorable reactions occur
They can be coupled and driven by a favorable reaction
4 Types of ATP high phosphoryl-transfer potential
- Charge Repulsion-many negative charges close to each other
- Resonance Stabilization - Pi has more resonance
- Increase in Entropy (multiple molecules made)
- Stabilization by hydration - Pi as well
Exercise
ATP can only power muscles for less than a second
Creative phosphate can regenerate ATP
Then, ATP must be generated by metabolic pathways
Substrate-Level-Phosphorylation
3 activated carriers
Carriers are kinetically stable in teh absence of specific catalysts (high activation energy)
The metabolism of activated groups is accomplished with a small number of carriers
Activated carriers exemplify the modular design and economy of metabolism
NAD/P
Nicotinamide Adenine Dinucleotide Phosphate
Can be derived from diet or body can synthesize from tryptophan
NAD+/NaDH
Catabolic
NADP+/NADPH
Anabolic
FAD
Flavin Adenine Dinucleotide
Derivative of Riboflavin
Becomes FADH2
Cosubstrate
CoA or HSCoA to Coenzyme A
Carrier of Acyl groups
Acetyl CoA has a high Acetyl group transfer potential
Transfer of acyl group is exergonic bc thioester is unstable
Big Idea of Glycolysis
Glucose to Pyruvate
Energy Investment
1st Phase
Step 1-5
Energy Generation Phase
Phase 2
Step 6-10
Step 1-Hexokinase
Glut transporter does not recognize G-GP3 once glucose is converted it can no longer leave the cell
Step 2 - Phosphoglucose Isomerase
Aldehyde to Ketone
Sets mlc up to be cleaved in 2
Rings opening of these sugars happens normally
Step 3 - Phosphotructo Kinase
Big Negative DeltaG
Major regulatory enzyme for glycolysis
Allosteric
ATP coupled
Step 4 - Aldolase
Cleaves 6-C sugar into 2
Reversible Reaction
Driven either way based on cellular conditions
Step 5 - Triose Phosphate Isomerasae
This run pushed forward by the disappearance of GAP is consumed in the next step
Step 6 - GAP dehydrogenase Reaction
Redox reaction
Oxidize GAP to 1,3 - BPG
Energy gained from oxidation will be used to add a phosphate from solution onto 3C molecule
2 step process that is not energetically favorable
Step 7 - Phosphoglycerate Kinase
Substrate Level phosphorylation
Energy of oxidation of carbon atom is used to form ATP
1,3-BPG has greater phosphory transfer potential than ADP, Thusm it can be coupled to power the synthesis of ATP
Step 8,9,10
Phosphoglycerate Mutase
Enolase
Pyruvate Kinase
- PO4 from 3C to 2C
- Elimination (Dehydration)
- High Phos. Transfer potential compound
ADP + H+ to ATP
Net Reaction of Glycolysis
Glucose + 2Pi + 2ADP + 2NAD+ to
2 pyruvate + 2ATP + 2NADH +2H+ + 2H20
Reactions of Glycolysis
- Hexokinase
- Phosphoglucose Isomerase
- Phosphofructokinase
- Aldolase
- Triose Phosphate Isomerase
- Glyceraldehye 3-Phosphate dehydrogenase
- Phosphoglycerate Kinase
- Phosphoglycerate Mutase
- Enolase
- Pyruvate Kinase
H
PI
PF
A
TPI
G3PD
PGK
PGM
E
PK
Anaerobic
Without Oxygen
Yeast and certain bacteria pyruvate is used to produce ethanol
In animals pyruvate is transformed into lactate
Aerobic
O2 is present
Pyruvate is broken down into Acetyl CoA and further Oxidation
Citric Acid Cycle
Electron Transport Chain
Oxidative Phosphorylation
What can occur without oxygen
Glycolysis
ETC and OX. Phos cannont
Those two would normally regernate NAD+ but without 02 present the cell turns anaerobic fermentation
Lactic Acid Fermentation
Happens in you, when muscles are lacking in energy
Oxidative ATP generation takes longer, so body defaults to this for quick ATP generation
Ultimate E donor in LAF
G3P
Ult e acceptor, lactic acid
Pyruvate turns into lactic acid
Ult e acceptor, alcohol
Acetaldehyde turns into ethanol
What does excessive fructose lead to
Obesity
Fatty Liver
Type 2 Diabetes
