Name: ___________________________ Period: ______ Date: ______________

A&P 12 – Chapter 5 – Metabolism and Enzyme Notes

Review: Flow of Energy

• Energy (defn) = the capacity to do work

• Why do we need energy?

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Forms of Energy

• There are two basic types of energy:

– Kinetic energy = energy of ___________

• Mechanical energy= type of kinetic energy

• Eg. _______________________________

– Potential energy = __________ energy

• Chemical energy= type of potential energy

• E. g. ___________________

5.1 Energy Transformations & Metabolism (p. 158)

• In living organisms, the topic of energy focuses on _________________.

Metabolism (def’n): The sum of the ___________________ that occur in a cell.

• Recall: Chemistry: A + B -> C + D

• Reactants Products

• A + B are the reactants, the substances that react together to form the _____________ (C + D)

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

In cells of all organisms, two types of metabolic reactions occur:

Anabolic Reactions

• building up (____________) of molecules.

• Simple molecules are linked together to make complex ones.

• are energy-storing reactions.

• E.g. _______________________from amino acids

Catabolic Reactions

• breaking down complex molecules into _______________________.

• are energy-releasing reactions.

• E.g.___________________________ where the sugar glucose in the presence of O2 is broken down into CO2 and H2O

Sketch diagram/graph here of Anabolic and Catabolic Reactions:

Free Energy =

• the amount of energy available.

• energy that is still “free” to do work after a reaction has occurred = ________________

– Given the symbol G

– G = change in free energy after a reaction has occurred

• Free Energy (G) = Gproducts - Greactants

Energy and Reactions

EXERGONIC REACTIONS (exothermic)

• DG is negative (–)

• Products have less free energy than ______________

• free energy is released

• catabolic ______________

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

ENDERGONIC REACTIONS (endothermic)

• DG is positive (+)

• Products have more free energy than reactants

• free energy is required for the reaction to occur

• anabolic reactions (e.g. _____________________, ______________ contractions)

ATP (Adenosine Triphosphate)

• The energy molecule for cells

• mitochondria produces ATP in the chemical reaction called ______________________

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Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

Functions of ATP

1) Chemical Work: ATP supplies the energy to _______________________________

2) Transport Work: ATP supplies the energy for _______________________________

3) Mechanical Work: ATP supplies the energy to contract muscles, beat cilia and flagella, etc.

Coupled Reactions = The energy released by an exergonic reaction is used to drive an endergonic reaction

• These reactions are closely tied together or “coupled”

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

5.2 Metabolic Pathways & Enzymes (p 159)• Metabolic Pathway = series of linked reactions

– Starts with a particular reactant and stops with an end product– Some pathways are cyclical, often one step leads to another– An example is pictured below

A B C D

₋ They are rarely this simple as this .... more like this:

An Enzyme

• Is a _____________ that acts as a biological _______________.

• It functions to speed up chemical reactions

• Catalyst = a re-usable chemical that helps speed up a chemical reaction. It does not get used up itself during the reaction.

WHY are enzymes so important to living things?

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– So, Nature’s solution … = Enzymes for everything … as enzymes turn unlikely reactions into common, easy processes

So, how do enzymes speed up chemical reactions?

Activation energy (EA) = Energy required for the reaction to go from __________ products

Enzymes speed up chemical reactions by lowering the activation energy (EA) needed for a reaction to occur

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

– Much less energy is required when an enzyme is present

– The result of the reaction does not change, it will still happen

– (DG is negative), but it occurs much faster!

How do enzymes work?Enzyme work a bit like a Lock and Key Mechanism, where the

Enzyme = Lock and the Substrate (or reactant) = Key

E + S ES complex E + P

Note:

• the enzyme is both reactant and product. It doesn’t get used up

• enzymes are only needed in very small amounts

Enzyme Function is very much tied to Enzyme Specificity

• Enzymes are VERY SPECIFIC … and the specificity is based upon SHAPE.

• When the substrate binds with the active site, the enzyme changes shape slightly to optimize the fit. = Induced fit model

• IMPORTANT – read pages 160-161 in textbook and look at figures 5.3 and 5.4 carefully

• Every reaction in a cell requires a specific enzyme

• Enzymes end in “________”

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

5 Factors Affect Enzyme Speed

1) Substrate concentration 4) Enzyme inhibition

2) Temperature and pH 5) Enzyme cofactors

3) Enzyme activation

1. Substrate Concentration

• Enzyme activity increases as substrate concentration increases

• Because more collisions occur between substrate and enzyme

• Until there are too many “keys” and not enough “locks”

• enzyme saturation

2) Temperature and pH

• As temperature increases, reaction rate will increase

• Because higher temperature causes more effective collisions between enzyme and substrate

• Until the temperature becomes too high and the enzyme denatures

• Enzymes have an optimal pH range. Changes in pH can change the tertiary shape of the protein/enzyme … Key won’t fit!

3) Enzyme Activation

• Cells regulate metabolism by regulating the presence and activity of enzymes• Genes controlling protein synthesis and enzyme production can be turned on or off • Phosphorylation can activate enzymes

– the addition of a phosphate molecule on the enzyme makes it active (requires kinase) (p 162)

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)

4) Enzyme Inhibition

Occurs when the substrate is unable to bind to the active site of the enzyme (can happen several ways, 4 are listed here):

a) Competitive Inhibition- both the product and substrate can bind to the active site sets up a competition.

b) Non-Competitive Inhibition- the product binds to a different site (allosteric site) which causes a change of shape to the active site.

c) Feedback Inhibition

d) Poisons permanently block the active site of an enzyme stopping activity

Bio 12 - Chap 5 – Enzyme Notes (Day 2017/18)