Cellular Energy: ATP & Enzymes

What is it? Where do organism’s get it? How do they use it?

Where does Energy come

from? • Ultimately, from the

sun. • It is transferred

between organisms in the earth’s lithosphere, but is slowly lost with every transfer

Energy • The capacity to perform work; to

rearrange matter • 2 forms:

– Potential Energy (PE): stored energy, due to position or structure

– Kinetic Energy (KE): Energy of motion • Heat is KE associated with the movement of

molecules/atoms

Energy is transferred not created

• Total amount of Energy in Universe is constant (1st Law) – Nothing created or destroyed, only transformed

• One result of ALL energy transfers is the production of heat (2nd Law) – Heat = disordered, unharnessed KE. This KE

is LOST; cannot be used to perform work

Heat loss during rxns

Chemical Reactions • Reactants (Substrates): The starting

materials that are consumed during a chemical reaction.

• Products: The ending materials of a chemical reaction.

• Endergonic (energy input): Store Energy – products have higher energy than reactants.

• Exergonic (energy output): Release Energy – products have lower energy.

Endergonic

• Products have more energy than reactants

• Photosynthesis: – Reactants = CO2 &

H2O + light energy – Products = sugar

molecules

Exergonic • Reactants have more

energy than products • Bonfire

– Reactants: Cellulose (glucose), O2

– Products: light, heat, CO2, H2O

• Cellular respiration “burns” glucose to harness energy for work

Anabolic and Catabolic Reactions

Protein Glycogen

Glucose

Glucose

Amino acids

ANABOLIC REACTIONS

CATABOLIC REACTIONS

Glycerol

Uses energy

Uses energy

Uses energy

Yields energy

Yields energy

Yields energy

Yields energy

Triglycerides

Protein Glycogen Triglycerides

Fatty acids Amino acids Amino acids

Fatty acids

Glycerol Glucose + + +

Cellular metabolism • The sum of all cellular endergonic and

exergonic reactions. • The ATP molecule delivers and transfers

energy to parts of a cell that are conducting these reactions.

ATP

• Sugar, base, and… • 3 phosphates

groups • Covalent bonds +

negatively charged phosphates groups = high PE!

Energy Transfer • Some freed energy is lost as heat • The rest is transferred via the phosphate

group when it binds to another molecule (phosphorylation)

ATP fuels ALL cellular work

ATP is continually regenerated

Enzymes are also required to drive reactions

Exergonic Reaction without Enzyme

Enzymes lower Activation Energy • Some energy (EA) must be applied to begin a rxn

– Sometimes the energy barrier is prohibitively large – Enzymes reduce that barrier, allowing rxn to

proceed with LESS energy input

Enzyme are not consumed, they are recycled

1. Available enzyme w/ active site

2. Substrate binds 3. Conversion to

products 4. Products

released

Enzymes possess:

• Ideal temperature regimes • Ideal pH ranges • Cofactors (inorganic molecules & ions)

and coenzymes (organic molecules)

Competition & Inhibition • Some molecules may

“mimic” enzymes (competitive inhibition) – Either shutdown OR

accelerate reaction • Others change enzyme

conformation (noncompetitive inhibition) – Always shuts down

reaction

Concept Check • Enzymes catalyze reactions in a cell.

There are hundreds of different enzymes in a cell—each with a unique three-dimensional shape. Why do cells have so many different enzymes?

a) Each enzyme molecule can only be used once.

b) The shape of enzyme’s active site generally fits a specific substrate.

c) The substrate molecules react with enzymes to create new enzymes.

d) Enzymes are randomly produced. With thousands of different shapes—one is likely to work.

What molecules provide energy to bodies?

1. Adenosine triphosphate (ATP) 2. Creatine Phosphate (CP) 3. Carbohydrates (Glucose) 4. Fats

What molecules provide energy to organisms?

• Adenosine triphosphate (ATP) – THE energy carrying molecule in the body

• Muscles store only enough ATP for 1 – 3 seconds of activity – ATP is generated continuously

• Usually via carbohydrate catabolism with or without O2

ATP structure

Substrates for producing ATP

• After depleting stored ATP, cells turn to other sources of stored energy to regenerate ATP: – Creatine phosphate (CP) – Carbohydrates (Glucose) – Triglycerides

CP transfers P to make ATP

Glucose metabolism

In cytoplasm

In mitochondria

Fats as fuel • Stored triglycerides (storage form of fats) are

metabolized to generate ATP for: – Low intensity exercise – Exercise of long duration

• Ex: 10 hr. hike + moderate climb

• Abundant energy source, even in lean people

• Provides 2x more energy per gram as carbohydrate

Distribution – ATP/CP

– Carbohydrates

– Fats

– Protein

Energy use over time: Increasing intensity

Interpreting Data • This graph illustrates how

an enzyme catalyzes reactions in biological systems. From an energy standpoint is this reaction an endergonic or exergonic reaction? a) Endergonic b) Exergonic c) There is not enough

information in this graph to decide the type of reaction.

Interpreting Data

•Which of the following represents the energy of activation after modification by an enzyme?

– A. – B. – C.

Answer

•Which of the following represents the energy of activation after modification by an enzyme?

– A.

Energy