Energy From Food/Mitochondria

What happens in stage 1 of cellular metabolism

Breakdown of food into simple subunits; mostly occurs outside of cells (lysosomes can digest large molecules in the cell interior

What happens in stage 2 of cellular metabolism

Breakdown of simple subunits into Acetyl CoA; occurs mainly in cytosol (except for final step of conversion from pyruvate to acetyl coA, which occurs in the mitochondria)

What happens in stage 3 of cellular metabolism

Complete oxidation of acteyl coA and CO2; occurs entirely in mitochondria

What are oxidations

Series of small steps in which free energy is transferred to carrier molecules (most commonly ATP and NADH)

What catalyses oxidations

enzymes

Controlled oxidation of sugar versus direct burning of sugar

Controlled oxidation (or stepwise oxidation) allows for some free energy to be storeed in activated carrier molecules

Direct burning causes all the free energy to be released as heat and none of it is stored

how does the oxidation of sugars begin

glycolysis

Net products of glycolysis

2 pyruvate, 2 ATP (2 used to start, 4 released), 2 NADH

What is needed to initiate glycolysis and why?

2 ATP is needed to provide the energy to start glycolysis because glucose is not a reactive molecules

Summary of process of glycolysis

fructose 1, 6 biphosphate is cleaved into glyceraldehyde 3-phosphate, which then yields 2 pyruvate, 4 ATP, and 2 NADH

Which steps are irreversible in glycolysis

Step 1, 4, 10

Enzyme that catalyzes Step 1 of glycolysis

hexokinase

Enzyme that catalyzes Step 2 of glycolysis

Phosphofructokinase

Enzyme that catalyzes Step 3 of glycolysis

isomerase

What do steps 1-3 of glycolysis do

convert glucose to glucose 1, 6-biphosphate

What does step 4 of glycolysis do

Converts fructose 1, 6-biphosphate into glyceraldehyde 3-phosphate and hihydroxy-acetone phosphate (requires 2 ATP)

What does step 5 of glycolysis do

Converts dihydroxy-acetone phosphate to glyceraldehyde 3-phosphate through cleavage of 6-carbon sugar into two 3-carbon sugars

Enzyme that catalyzes Step 4 of glycolysis

aldolase

Enzyme that catalyzes Step 5 of glycolysis

triose phosphate isomerase

What do steps 6-9 of glycolysis do

Generates energy (step 6 reduces NAD+ into NADH) (step 7 uses substrate-level phosphorylation to transfer a phosphate to ADP to make ATP)

Enzyme that catalyzes Step 6 of glycolysis

glyceraldehyde 3-phosphate dehydrogenase

Enzyme that catalyzes Step 7 of glycolysis

phosphoglycerate kinase

What does step 10 of glycolysis do

Pyruvate is created and the phosphate on phosphoenolpyruvate generated in step 9 is transferred to ADP to create ATP

Enzyme that catalyzes Step 10 of glycolysis

pyruvate kinase

What’s a kinase

Enzyme that transfers phosphate groups from high-energy donor molecules (like ATP_ to specific substrates through a process called phosphorylation

What is substrate-level phosphorylation and what is an example of it in glycolysis

It is the transfer of a phosphate group directly from substrate molecule (ex: synthesis of ATP in glycolysis

What happens to pyruvate in the absence of oxygen (in animals and humans)

Pyruvate is converted to lactate (lactic acid fermentation)

Example of lactic acid fermentation

Muscle cell undergoing vigorous contraction when there’s inadequate oxygen

What happens to NADH in fermentation

NAD+ regeneration

What’s NAD+ regeneration

In glycolysis, NAD+ is used to produce NADH, and then when pyruvate is converted to lactate or ethanol, NADH is turned back into NAD+ (which is then fed back into glycolysis) —> a loop

Does fermentation yield more or less energy than complete oxidation

less energy

Whats fermentation

An anaerobic energy-yielding pathway

What happens to pyruvate in organisms that grow anaerobically (like yeast)

pyruvate is converted into acetaldehyde, which releases carbon dioxide, and the converted to ethanol

Products of ethanol fermentation

CO2 and ethanol

Where is pyruvate broken down into acetyl CoA

Mitochondrial matrix

What does breakdown of pyruvate yield

Acetyl CoA

What enzyme converts pyruvate into Acetyl CoA

pyruvate dehydrogenase

What else is released when pyruvate is converted to acetyl CoA

NADH and CO2

What’s the structure of the pyruvate dehydrogenase comlex

It has multiple copies of 3 enzymes

What’s unique about the enzymes organized in pyruvate dehydrogenase complex

The product of one reaction becomes the substrate of the next reaction

Go through substrates and products of each reaction in the pyruvate dehydrogenase complex

Enzyme 1: decarboxylates pyruvate + releases CO2 to form hydroxyethyl-TPP intermediate

Enzyme 2: uses Coenzyme A to make acetyl CoA

Enzyme 3: transfer electron to NAD+ to make NADH and H+

what does the citric acid cycle do

converts acetyl CoA into a bunch of activated carriers, ATP, NADH, and FADH2

What are the high energy electrons used to produce

ATP through oxidative phosphorylation (in ETC)

What happens to much of the energy released in the oxidation reactions of the Citric acid cycle

Stored as high-energy electrons in the activated carriers NADH and FADH2

Whats oxidative phosphorylation

metabolic pathway producing ATP comprising of 2 main processes: Electron Transport Chain and chemiosmosis

Whats chemiosmosis

Movement of ions (protons) down electrochemical gradients across selectively permeable membrane to generate energy to make ATP.

Net products of citric acid cycle

3 NADH, 1 FADH2, 1 GTP, 2 CO2

What does oxaloacetate do in citric acid cycle

Accepts acetyl CoA and is regenerated in the cycle

What happens to the 2 carbons of the acetyl group in acetyl CoA in citric acid cycle

They are released as CO2

What helps make CO2 in citric acid cycle

Water, which supplies the oxygen

How is GTP (guanosine triphosphate) produced in the citric acid cycle

substrate-level phosphorylation

What happens in the breakdown of fatty acids

fatty acids are imported into the mitochondrial matrix and enzymes there remove 2-carbon units from the fatty acids, which forms 1 molecule of acetyl CoA + NADH + FADH2

Whats FADH

reduced flavin adenin dinucleotide

Cycle from fatty acid to Acetyl CoA

Fatty acid (which is in the form of fatty acyl CoA) is broken down by cycle of reactions that trims two carbons at a time from its carboxyl end. (One cycle yields 1 Acetyl CoA, 1 NADH, 1 FADH2)

Oxidized forms of electron carriers

FAD, NAD+

Reduced forms of electron carriers

FADH2, NADH

What are intermediates formed in glycolylsis and citric acid cycle used for

biosynthetic (anabolic) pathways

What do biosynthetic(anabolic) pathways do

convert intermediates from glycolysis and the citric acid cycle into amino acids, nucleotides, lipids, and other small organic molecules

What’s gluconeogenesis

process by which blood glucose is synthesized from small non-carbohydrate organic molecules like lactate, pyruvate, or amino acids

Gluconeogenesis versus glycolysis regarding favorability

Glycolysis as a whole is energetically favorable, but the synthetic reactions carried out in gluconeogenesis need an input of energy

Key control point of gluconeogenesis

Step 3 of glycolysis: fructose 6-phosphate → fructorse 1, 6-biphosphate by phosphofructokinase and ATP

Gluconeogenesis: fructose 1,6-biphosphate → fructose 6-phosphate by fructose 1, 6-bisphosphotase and H20

What does fructose 1, 6-bisphosphatase

regulates reverse reaction for gluconeogenesis

What is phosphofructokinase activated by

AMP, ADP, and inorganic phosphate (byproduct of ATP hydrolysis)

What is phosphofructokinase inhibited by

ATP, citrate, and fatty acids

What is fructose 1,6-bisphosphatase activated by

ATP, citrate, and fatty acids

What is fructose 1,6-bisphosphatase inhibited by

byproducts of ATP hydrolysis

Balance between glycolysis and gluconeogenesis

highly regulated:

when energy reserve is running low → glucose broken down rapidly

when cell has sufficient energy reserves (in form of pyruvate, citrate, or ATP) → glucose is synthesized and exported to other issues

What do animals do to provide energy while fasting and why

store glycogen because the structure of glycogen in animal cells is very similar to starch in plants as branched polymer of glucose

What does glycogen phosphorylase do

Catalyzes breakdown of reaction of glycogen to glucose 1-phosphate in liver cells

What is glucose 1-phosphate converted to

glucose 6-phosphate (which then feedds into glycolytic pathway)

What is regulated by glucose 6-phosphate

Glycogen synthetic and degradation pathways

What is activated by glucose 6-phsophate in the synthetic pathway of glycogen

glycogen synthase

What is inhibited by glucose 6-phsophate and ATP in the breakdown of glycogen

Glycogen phosphorylase

Storage material thats more important than glycogen

Fat

What does oxidation of a gram of fat release

2x the energy than oxidation of a gra of glycogen

Does adult human store more glycogen or fat

Fat (can last nearly a month while glycogen storage may only last a day)