Download Chapter 6: Energy Flow in the Life of a Cell What is Energy? Answer

Chapter 6: Energy Flow in Cells
Chapter 6:
Energy Flow in the Life of a Cell
What is Energy?
Answer: The capacity to do work
Types of Energy:
1) Potential Energy = Stored energy
• Positional (stored in location of object)
• Chemical (stored in bonds)
• Electrical (stored in batteries)
Potential energy can be converted
to kinetic energy (& vice versa)
2) Kinetic Energy = Energy by movement
• Light (movement of photons)
• Heat (movement of particles)
• Electricity (movement of charged particles)
Chapter 6: Energy Flow in Cells
Chapter 6: Energy Flow in Cells
Laws of Thermodynamics: Describe the “quantity” (total amount) and “quality”
(usefulness) of energy
Chemical Reaction: Process that forms or breaks the chemical bonds holding
atoms together
1st Law of Thermodynamics: (Law of Conservation of Energy)
• Amount of energy in universe remains constant
• Energy is neither created or destroyed
• Energy can be converted (e.g., Chemical
Figure 6.3 / 6.4 – Audesirk2 & Byers
 Heat)
+
+
Reactants
Products
Types of Chemical Reactions:
2nd Law of Thermodynamics:
• When energy converted, the amount of “useful” energy is decreased
• No process is 100% efficient
Figure 6.2 –
Audesirk2
Exergonic:
Reaction liberates energy
Endergonic:
Reaction requires energy to proceed
& Byers
Chapter 6: Energy Flow in Cells
Chapter 6: Energy Flow in Cells
All chemical reactions require activation energy to begin:
Cellular Respiration:
(Exergonic)
Energy required to “jumpstart”
a chemical reaction
• Must overcome repulsion of atoms due to negative charged electrons
Energy in reactants > Energy in products
Activation
Energy
Activation
Energy
Repel
Nucleus
Nucleus
Photosynthesis:
(Endergonic)
Energy in reactants < Energy in products
Figure 6.5 / 6.7 – Audesirk2 & Byers
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Chapter 6: Energy Flow in Cells
Chapter 6: Energy Flow in Cells
Exergonic Reactions:
Endergonic Reactions:
(“Downhill Reactions”)
(“Uphill Reactions”)
Chapter 6: Energy Flow in Cells
Chapter 6: Energy Flow in Cells
Coupled Reaction: An exergonic reaction supplies the energy needed to
drive an endergonic reaction
How is Cellular Energy Carried Between Reactions?
Answer: Energy-Carrier Molecules
Types of Energy-Carrier Molecules:
1) Adenosine Triphosphate (ATP)
• Most common energy-carrier molecule
• Synthesized from adenosine diphosphate (ADP)
Coupled ATP Reactions:
Characteristics of Energy-Carrier Molecules:
• Rechargeable
Pick up energy
Transport energy
(Exogonic reaction)
Drop off energy
(Entergonic reaction)
• Unstable (Short-term energy storage)
• Function within a single cell
Figure 6.8 / 6.9 / 6.10 / 6.11 – Audesirk2 & Byers
Chapter 6: Energy Flow in Cells
Chapter 6: Energy Flow in Cells
Figure 6.13 – Audesirk2 & Byers
Metabolism: Sum of all chemical reactions in a cell
Types of Energy-Carrier Molecules:
2) Electron carriers (e.g., Nicotinamide Adenine Dinucleotide – NADH))
• Donate high-energy electrons to other molecules
Reactions are linked in Metabolic Pathways
Coupled Electron Carrier Reactions:
Photosynthesis
(Chloroplast)
Cellular Respiration
(Mitochondria)
How do Cells Regulate Metabolic Reactions?
1) Couple exogonic / endergonic reactions together
2) Synthesize energy-carrier molecules
3) Regulate enzyme production / activity
Figure 6.12 – Audesirk2 & Byers
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Figure 6.14 – Audesirk2 & Byers
Chapter 6: Energy Flow in Cells
What are Enzymes?
Chapter 6: Energy Flow in Cells
Figure 6.15 – Audesirk2 & Byers
Enzymes = Biological Catalysts
Answer: Molecules (proteins) that catalyze chemical reactions
What are Catalysts?
Answer: Molecules that speed up chemical reactions
Lower activation energy
Important Features:
Unique Properties of Enzymes (compared to other catalysts):
1) Enzymes are specific (High Specificity)
• Catalyze only one, or a few, chemical reactions
• Structure dictates specificity
Active Site:
Location where substrate(s) can bind
• Catalysts only speed up reactions
that would occur spontaneously
• Catalysts are not destroyed or
altered in the reaction
Chapter 6: Energy Flow in Cells
Chapter 6: Energy Flow in Cells
Enzymes = Biological Catalysts
Enzymes = Biological Catalysts
Unique Properties of Enzymes (compared to other catalysts):
2) Enzymes activity is regulated
A) Regulate synthesis of enzyme
B) Regulate active state of enzyme (inactive vs. active form)
Unique Properties of Enzymes (compared to other catalysts):
2) Enzymes activity is regulated
A) Regulate synthesis of enzyme
B) Regulate active state of enzyme (inactive vs. active form)
C) Feedback Inhibition: Regulate enzyme activity by [product]
C) Feedback Inhibition: Regulate enzyme activity by [product]
D) Allosteric Regulation: Regulate active site shape via small molecules
Figure 6.17 – Audesirk2 & Byers
Chapter 6: Energy Flow in Cells
Figure 6.16 – Audesirk2 & Byers
Chapter 6: Energy Flow in Cells
Enzymes = Biological Catalysts
Enzyme Activity can be Influenced by the Environment:
A) 3 - Dimensional structure of enzymes due to hydrogen bonding
• Factors affecting hydrogen bonding
Unique Properties of Enzymes (compared to other catalysts):
2) Enzymes activity is regulated
A) Regulate synthesis of enzyme
B) Regulate active state of enzyme (inactive vs. active form)
• pH (optimal = 6 – 8)
C) Feedback Inhibition: Regulate enzyme activity by [product]
D) Allosteric Regulation: Regulate active site shape via small molecules
E) Competitive Inhibition: Regulate active site via molecular competition
• Salt concentration
• Temperature
B) Some enzymes require helper molecules
• Co-enzymes (bind with enzyme; assist in reaction)
Example:
B - vitamins (e.g., Vitamin B12)
necessary for DNA synthesis
Figure 6.18 – Audesirk2 & Byers
Figure 6.19 – Audesirk2 & Byers
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