Energy, Enzymes, and Respiration

Energy Types

Light

Heat

Mechanical

Chemical

Potential/ion gradient

What is an exergonic reaction? Does an exergonic reaction have a positive or negative

G?

Exergonic reaction: reaction proceeding spontaneously to the right

G = negative, energy is released

What is an endergonic reaction? Does an endergonic reaction have a positive or

negative G?

Endergonic reaction: reaction not proceeding

G = pos, energy is retained

Does a spontaneous reaction have a positive or negative G?

Negative, because there is a release of energy

Does a reaction that is not spontaneous have a positive or negative G?

Positive, nothing is happening with the energy

What is the G of a chemical reaction that has reached equilibrium?

0, because the rate of forward and backward reaction is the same

How can cells use ATP to drive endergonic reactions? What are ATP coupled reactions? Explain

how ATP coupled reactions function.

ATP is used as an energy source

ATP coupled reactions are exergonic reactions linked to endergonic reactions

What are the functions of enzymes in biological reactions?

Enzymes are biological catalysts = increase the rate of reactions to sustain life

What is activation energy? How do enzymes affect the activation energy of reactions?

Explain why enzymes have this effect.

Activation energy: initial input of energy, enzymes help bring the rate of reaction down for life to be sustained

Describe the ways in which enzymes lower the activation energy of a chemical reaction.

Straining reactions: easier for reaction to occur

Positioning reactions: right position for reaction to occur

Changing local environments: reaction site created environment conducive to life

How can the activity of enzymes be regulated?

Through Competitive inhibition and Non-Competitive inhibition

Describe competitive inhibition and how it functions to regulate enzyme activity.

Competitive inhibition: Similar looking substance blocks the active site

Describe non-competitive inhibition and how it functions to regulate enzyme activity.

Non-Competitive inhibition: inhibitor attaches at allosteric site

Describe the difference between reversible and non-reversible non-competitive

inhibition.

Reversible: can leave/unbind when wanted

Non-reversible: can’t unbind

What are prosthetic groups and how do they influence enzyme activity?

Prosthetic groups: small molecules attached to enzymes that aid function

What are cofactors and how do they influence enzyme activity?

Cofactors: in organic molecules that promote reaction, near active site for enzyme activity

What are coenzymes and how do they influence enzyme activity?

Coenzymes: organic molecules that promote reactions, NAD; coenzymes that associate with enzymes and to facilitate activity

How can temperature and pH influence enzyme activity?

pH: too high or too low of pH causes protein to denature, needs pH around 7

Temperature: at a higher temperature it will become easier to bend, but too high or too low will cause denaturing

Define metabolism.

Metabolism: the sum total of all chemical reactions in a cell/organism

What is catabolism? What is anabolism?

How are catabolism and anabolism linked?*************

Catabolism: breaking down of molecules

Anabolism: Building of molecules

What is a metabolic pathway? How do enzymes function in metabolic pathways?

Metabolic pathway: series of chemical reactions where each step of the pathway is catalzyes by an enzyme, goal is to create an end product

Describe how metabolic pathways can be regulated through gene regulation.

Gene regulation: turn on gene for making enzymes, turn off to stop enzyme production

Describe how metabolic pathways can be regulated through signal transduction.

Signal Pathways: Sense what happens outside of cell, translates that, then alters the rate

What enzyme is usually targeted when regulating a metabolic pathway?

Explain why this enzyme is targeted.

Rate limiting step: controls speed of pathway/sets the speed (typically slow)

Describe how metabolic pathways can be regulated through biochemical

regulation.

Biochemical regulation= feedback inhibition

Describe how feedback inhibition functions.

end product goes back to inhibit enzyme from creating more

What is an allosteric enzyme? Describe how allosteric enzymes can be used to

regulate metabolic pathways through feedback inhibition.

Allosteric enzyme: an enzyme with an allosteric site

Describe the three ways in which ATP can be produced.

Phosphophorilation - energy of photon to ATP

Substrate level Phosphorylation - organic molecule with phosphate transfer to ATP

Oxidative Phosphorylation - organic molecules, el- out, run through ETC makes electrochemical gradient, uses that energy for ATP

Describe how electrons are transferred in redox reactions

el transfers between donor and accepter molecules

Does the electron donor become oxidized or reduced when it donates electrons

in redox reactions?

The Election donor becomes oxidized when donating

Does the electron acceptor become oxidized or reduced when it accepts

electrons in redox reactions?

The Election acceptor become reduced when accepting

How do electron carriers function in biological redox reactions?

Electron carriers: carry electron through cell

What type of pathways produce precursor metabolites and what type of

pathways use precursor metabolites?

Catabolic pathways produce precursor metabolites (Intermediates)

Anabolic pathways use precursor metabolites ad a starting point

What is reducing power? Describe the functions of reducing power in cells.

Reducing power: reduced electron carriers carrying energy rich electrons

Describe the electron carriers that are used in biological reactions.

NAD

FAD

NADP

Be able to recognize the difference between the oxidized and reduced forms of the

electrons carriers used in biological reactions.

Oxidixed:                                    Reduced:

NAD + 2el + 2H+                        NADH + H

FAD + 2el + 2H+                         FADH2

NADP + 2el + 2H+                      NADPH + H

Be able to describe the functions of the reduced forms of the electrons carriers used in

biological reactions.

Reduced:

NADH + H and FADH2 = Donates to electron transport chain

NADPH + H = Donates to metabolic pathways

Describe, in general, what is happening in aerobic respiration.

Aerobic respiration = in eukaryotes, start with glucose because its highly reduced, able to eventually make ATP

Describe the function of glycolysis in aerobic respiration.

Glycolysis: begin process of taking out el- out of glucose

What is the beginning substrate for glycolysis?

glucose

What is occurring during the energy investment phase of glycolysis?

ATP molecuel’s used to add phosphate groups to glucose, glucose is then phosphorylated into fructose of other molecules

What is occurring during the cleavage phase of glycolysis

splitting the products from the energy investment phase into 3 carbon molecules: G3P (2 of them were DHAP)

What is occurring during the energy liberation phase of glycolysis?

G3P is then split into two pyruvates

Where do the reactions of glycolysis occur in eukaryotes? In prokaryotes?

Eukaryotes: cytoplasm

Prokaryotes: cytoplasm

Is ATP produced in glycolysis? If so, by what process is it produced?

Yes, it is produced its done via substrate phosphorylation

What form of reducing power is produced during glycolysis? How will this reducing

power be used by the cell in aerobic respiration?

Formed: NADH

This feeds into ETC to make more ATP

Into what organic compound is glucose converted after glycolysis is complete?

2 pyruvates

Describe how ATP can be used to regulate glycolysis.

ATP can function as a feedback inhibitor

What is the function of the transition step? How would aerobic respiration be

affected if the transition step could not occur?

The Transition step is from the end of glycolysis to the beginning of CAC

Where does the transition step occur in eukaryotes? In prokaryotes?

Eukaryotes: Lumen of mitochondria

Prokaryotes: all over cell

Describe how pyruvate enters the mitochondria in eukaryotes. What form of

energy is used to drive the transport of pyruvate into the mitochondrial matrix?

Electrochemical gradient is used to power the transport proteins to transport pyruvates into the mitochondrial matrix

What enzyme catalyzes the transition step? What are the products of this

enzymatic reaction? Describe how the enzyme that catalyzes the transition step

is regulated. *************

Pyruvate dehydrogenase catalyzes the transition step

Where do the reactions of the CAC occur in eukaryotes? In prokaryotes?

Prokaryotes: Cytoplasm

Eukaryotes: Mitochondrial matrix

What is the function of the CAC?

1. completes oxidation of glucose

2. makes ATP through substituent level box correlation

3. precursor metabolites

What is the beginning substrate of the CAC?

AcCoA

What is occurring during the reactions of the CAC?

Carbon atoms from acetyl-CoA are released as CO₂.

High-energy electrons are captured in NADH and FADH₂.

A small amount of ATP is made directly.

What products are produced by the reactions of the CAC?

NADH, ATP, FADH

How many turns of the CAC are required to complete the oxidation of glucose?

Explain why.

2, that what’s needed to fully complete oxidation

Describe how the CAC can be regulated. Specifically, describe how regulating

the isocitrate dehydrogenase enzyme can be used to regulate the CAC.

• Citric synthesis

• Isocitrate dehydrogenase

• (some symbl) - ketoglutarate dehydrogenase

What are the products produced by glycolysis and the CAC for every molecule of

glucose that enters glycolysis and completes the CAC?

Glycolysis: NADH, ATP

CAC: Oxidized glucose, ATP, NADH, FADH

Where is the energy that was stored in glucose being stored after glucose is

oxidized using glycolysis and the CAC?

Stored in ATP and high energy electron carriers

What pathways produce ATP directly? By what process is the ATP

produced by these pathways synthesized?

Glycolysis and CAC

By Substrate level phosphorylation

Describe how cells use the reducing power produced during the oxidation of glucose.

Electrons from NADH and FADH can be used to make ATP

What is proton motive force? How does the reducing power produced during the

oxidation of glucose create proton motive force?

Proton motvie force: electrochemical gradient, energy source used to do work

As reducing powers move down each step in the ETC is looses energy which powers proton motive force

What is proton motive force used for in eukaryotic cells? In prokaryotic cells?

Eukaryotes: Synthesis ATP, symport of pyruvate

Prokaryotes: power flagella, transport across membrane

Why can prokaryotes use proton motive force as a source of energy to power

transport across the cell membrane and power movement of flagella while

eukaryotes can’t use proton motive force for these purposes?

PMF had access to the whole cell

Where are the components of the electron transport chain located in

eukaryotes? In prokaryotes?

Eukaryotes: PMF restricted to mitochondria

What happens to NADH and FADH2 when they donate electrons to the ETC?

They become redoxized and go back to glycolysis in CAC

What happens as electrons are passed down the ETC?

They release energy which creates Proton mechanical gradient

What is the terminal electron acceptor in aerobic respiration? In anaerobic respiration?

Aerobic: Oxygen

Anaerobic: inorganic molecules

Describe how ATP synthase functions to produce ATP using proton motive force.

Proton squeezes between C subunit and ‘a’ subunit causing the ‘b’ arm to change position. Globular subunit to rotate, ATP synthesis

If the “a” protein was missing from the ATP synthase complex, would it still

function to produce ATP? Explain why or why not.

Yes because C subunits are still there

What do we call the synthesis of ATP using proton motive force in non-

photosynthetic organisms?

Oxidative phosphorylation

Why is the theoretical yield of oxidative phosphorylation rarely achieved in living cells?

some energy is lost

What is fermentation? How can fermentation be used to help cells produce ATP when

oxygen is not present?

Fermentation (Biochemical process): obtains energy from carbohydrates without oxygen, recycles NADH back into NAD+

Describe how nutrients other than glucose can be catabolized and used as energy sources.

by breaking down other organic molecules to go through glycolysis or CAC to make ATP

What are precursor metabolites?

Precursor metabolites: intermediates in catabolic pathways, can be used in anabolic pathways

In general, what components are required for anabolic pathways?

They require: precursor metabolites, ATP, and reducing power