Bio CH. 8+9

How does energy flow into an ecosystem?

sunlight

How does energy leave an ecosystem?

heat

What is exergonic?

- reactions that release energy

- breakdown of organic molecules

Fermentation

a partial degradation of sugars that occurs without O2

Aerobic Respiration

consumes organic molecules and O2 and yields ATP

Anaerobic Respiration (fermentation)

similar to aerobic respiration but does not use O2

Cellular Respiration

aerobic and anaerobic respiration, often more for aerobic respiration

C6H12O6 + 6 O2 --------

6 CO2 + 6 H2O + Energy (ATP + heat)

redox reactions

When there is a transfer of one or more electrons from one reactant to another.

oxidation

a substance loses electrons

reduction

substance gains electrons

During cellular respiration what happens to fuel and O2

fuel is oxidized and O2 is reduced

Organic molecules with an abundance of hydrogen, like carbohydrates and fats, are excellent ...

fuels

Electrons in cell respiration from organic compounds are usually first transferred to was coenzyme?

NAD+

NAD+ functions as a what during cellular respiration

oxidizing agent

NADH represents stored energy that is tapped to synthesize ______

ATP

Electron transport chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.

How does the electron transport chain work?

Electrons are passed down the chain in a sequential and orderly fashion. Energy is released from the flow of electrons down the chain. This release of energy is coupled to the generation of ATP by oxidative phosphorylation

Glycolysis

breaks down glucose into two molecules of pyruvate

Pyruvat Ox. and CAC

completes breakdown of glucose

Ox. Phosphorylation

accounts for most of atp synthesis (powered by redox reactions)

What is substrate level phosphorylation?

ATP synthesis when the phosphate donor is a substrate with high phosphoryl transfer potential

For each molecule of glucose degraded to CO2 and water by respiration. How many ATP molecules are made?

32 or 38

Where does Glycolysis occur?

Cytoplasm

Glycolysis has two major phases:

- energy investment phase

- energy payoff phase

Does glycolysis occur whether or not O2 is present?

Yes

What are the products of the glycolysis phase?

2 pyruvate + 2 H2O

2 ATP

2 NADH +2 H+

Hexokinase

The enzymes that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the first step of glycolysis. This is one of the main regulatory steps of this pathway. Hexokinase is feedback-inhibited by glucose-6-P.

phosphoglucoisomerase

glucose-6-phosphate to fructose-6-phosphate (isomerization)

Phosphofructokinase

The enzyme that catalyzes the phosphorylation of fructose-6-phosphate to form fructose-1-6-bisphosphate in the third step of glycolysis. This is the 1st committed step

Aldolase

fructose 1,6-bisphosphate to dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (G3P)

triose phosphate dehydrogenase

oxidized by trasfer of electrons to NAD TO NADH

- (G3P is oxidized and NAD+ is reduced)

Phosphoglycerokinase

enzyme that converts two 1, 3-bisphosphoglycerate to two 3-phosphoglycerate and yields 2 ATP (3-phosphoglycerate is dephosphorylated)

Phosphoglyceromutase

3-phosphoglycerate to 2-phosphoglycerate (isomerizaton)

Enolase

2-phosphoglycerate to phosphoenolpyruvate (PEP)

- releases water which makes it a dehydration reaction

Pyruvate kinase

Enzyme converting phosphoenolpyruvate to pyruvate.

- releases 2 ATP

First step of pyruvate oxidation

Pyruvate goes through protein and gets modified,while also losing a carboxyl group to produce CO2

Second step of pyruvate oxidation

NAD+ is reduced to NADH

Third step of pyruvate oxidation

An acetyl group is transferred to coenzyme A, resulting in acetyl CoA

Citric Acid Cycle

Completes the breakdown of glucose by oxidizing a derivative of pyruvate to carbon dioxide.

Product of citric acid cycle per glucose

1 ATP, 3 NADH, 1 FADH2

How is the citric acid cycle and glycolysis linked to

Pyruvate is converted to Acetyl coenzyme A

What level of phosphorylation is glycolysis and CAC

Substrate level phosphorylation

first step of citric acid cycle

The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate

- releases CoA

What type of reaction is the second step in citric Acid cycle?

Isomerization

third step of the Citric Acid Cycle

Isocitrate is oxidised to alpha ketoglutarate and a molecule of NADH (reduced) is formed from NAD+. A CO2 is also lost

Fourth step of Citric Acid cycle

alpha ketoglutarate is made into succinyl CoA by alpha ketoglutarate dehydrogenase; another CO2 is lost and resulting compound is oxidized forming NADH (reduced) ; remaining molecule has CoA attached to is by unstable bond

Fifth step of Citric Acid Cycle

The CoA is removed from Succinyl CoA to form succinate. When the dehydrogenase enzymes cleave the CoA off from the succinyl CoA the energy that is produced from doing this is used to convert GDP into GTP. This GTP then combines with ADP to produce ATP

Eighth step of the Citric Acid Cycle

The substrate is oxidized, reducing NAD+ to NADH and regenerating oxaloacetate from Malate (loses two hydrogen)

For every one molecule of glucose,how many turns of the citric acid cycle occur?

2

The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain

Just know

Where is the electron transport chain

The inner membrane of the mitochondria (cristae)

The carries of electron transport alternate reduced and oxidized states as they accept and donate electrons.

Just know

What happens to the free energy as they go down the chain?

It drops and is finally passed to O2 forming H2O

Cytochromes

An iron-containing protein that is a component of electron transport chains in the mitochondria

What happens with H+ when electron transfer in the electron transport chain occurs.

The H+ are pumped from the mitochondrial matrix into the intermembrane space

ATP synthase

Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP

How does ATP work

uses the exergonic flow of H+ to drive phosphorylation of ATP

- the H+ from the gradient goes through the rotor which powers it and adds another phosphorous to ADP

What is the H+ gradient referred to as?

proton motive force

About how much percent of the energy in a glucose molecule is transferred to ATP during cellular respiration?

34%

What does glycolysis couple with when O2 is not present

Fermentation or anaerobic respiration to produce ATP

Anaerobic Respiration

Uses an electron transport chain with a final electron acceptor other than O2 like sulfate (something electronegative)

How does fermentation work

uses substrate-level phosphorylation instead of an electron transport chain to generate ATP

Two forms of fermentation

alcoholic and lactic acid

Alcohol fermentation

pyruvate is converted to ethanol in two steps

- first step releases CO2

- second step reduces acetaldehyde to ethanol

lactic acid fermentation

Pyruvate in reduced by NADH, forming lactate as an end product, with no release of CO2

Obligate anaerobes

carry out fermentation or anaerobic respiration and cannot survive in the presence of O2

Facultative anaerobes

can live with or without oxygen

- like yeast and many bacteria

Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration

- glycolysis accepts many carbohydrates

- proteins must be digested to amino acids and amino groups must be removed before amino acids can feed glycolysis or the citric acid cycle

Just know

Fats are digested to what?

Glycerol

Fatty acids are broken down by what?

Beta oxidation which yields acetyl CoA

An oxidized gram of fat produces how much more ATP than an oxidized gram of carbohydrate

More than 2 times

Metabolism

The totality of an organisms chemical reactions

Metabolic pathway

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.

- starting molecule - product

Catabolic pathways

release energy by breaking down complex molecules into simpler compounds

Anabolic pathways

Metabolic pathways that consume energy to build complicated molecules from simpler ones.

Free energy

energy that is available to do work when temperature and pressure are uniform

The change in free energy (delta G)

The difference between he free energy of the final state and the free energy of the initial state

- only processes with a - delta G are spontaneous

Exergonic reaction

proceeds with a net release of free energy and is spontaneous

- delta G is negative

Endergonic reaction

absorbs free energy from its surroundings and is nonspontaneous

- delta G is positive

Cells are not in equilibrium

they are open systems experiencing a constant flow of materials

Catabolic pathways do what with free energy?

Release it