BIO 205 Chapter 6 Part 1 Lecture

8/14/2019 BIO 205 Chapter 6 Part 1 Lecture

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Chapter 6, Part 1

BIO 205


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Metabolism of Prokaryotic Cells


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Enzymes act on substrates

Enzyme activity is highly specific

Enzymes are not changed by the reactions,and can be reused

Enzymes increase the probability thatchemical reactions will occur

Enzymes Catalyze All Cellular Reactions

Enzymes in Metabolism


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Substrates bind to the enzyme at the active site, which isspecific to the substrate

Enzymes align substrate molecules in such a way that areaction is energetically favorable

Enzymes Act through Enzyme-Substrate Complexes


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The enzyme surface contains the active site.

The enzyme is a rigid three-dimensional body.

Lock-and-key model of enzyme mechanism.

Mechanism of Enzyme Action


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The active site becomes modified to accommodatethe substrate.

Induced-fit model

Mechanism of Enzyme Action


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The inhibitor fits into the active site, thereby

preventing the substrate from entering.

The mechanism of competitive inhibition.

Inhibitors of Enzyme Action


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Inhibitors of Enzyme Action

Mechanism of noncompetitive

The inhibitor binds to a site other than the active site, thereby

changing the conformation of the active site.The substrate nolonger fits.


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Blocking an active site (competitiveinhibition)

Changing the shape of an active site

(noncompetitive inhibition)

It inhibits an enzyme in the pathway so noproduct is available to feed the next reaction.

Enzyme Activity Is Regulated and Can Be Inhibited

Other types of inhibition

Feedback inhibition hinders metabolic pathways


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The product of one reaction

serves as the substrate for thenext

Each reaction is catalyzed by adifferent enzyme

A metabolic pathway is asequence of chemical reactions.

Enzymes Often Team Up in

Metabolic Pathways


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Protein synthesis, etc.

Cell division

Movement

ATP (adenosine triphosphate) is thecellular energy currency, providingenergy for:

Energy in the Form of ATP is Required for Metabolism

Energy in Metabolism


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A free phosphate group

Energy is released from ATPwhen the bond holding thelast phosphate group onthe molecule is broken,

producing:

Adenosine diphosphate(ADP)


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Energy must be stored in more stable forms likeglycogen or lipids (in prokaryotes)

ATP cannot be stored because it is relativelyunstable.

Adding a phosphate group to a molecule iscalled phosphorylation.


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A metabolic pathway coupled to the ATP/ADP cycle


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The Catabolism of Glucose


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If not, it is anaerobic respiration.

If oxygen is consumed while making ATP, it is aerobicrespiration.

Cells make ATP by harvesting energy through cellularrespiration.

Cellular Respiration Is a Series of Catabolic Pathways forthe Production of ATP.

Energy in glucose is released slowly by converting toATP through metabolic pathways.

Glucose Contains Stored Energy That Can Be Extracted

The Catabolism of Glucose


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This releases 4 ATP and 2 NADH molecules

Glycolysis is the splitting of 1 glucose molecule into 2pyruvate molecules

Glycolysis Is the First Stage of Energy Extraction.

Glycolysis


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Glycolysis


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End of Chapter 6, Part 1

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BIO 205 Chapter 6 Part 1 Lecture