This document provides learning objectives about energy transfers in living things and how cells use energy. It discusses how exergonic reactions release energy and endergonic reactions require energy input. ATP is generated through exergonic reactions and provides energy to drive endergonic reactions like active transport. Enzymes lower the activation energy of reactions and influence their rates. Homeostatic control mechanisms like feedback loops regulate reaction rates.

1. Energy and Enzymes

2. Learning Objectives
Enzymes and Energy of Life
1.Describe the energy transfers that are common to life.
2.Describe how cells use energy to do work.
3.Compare and contrast potential and kinetic energy.
4.Explain how physical laws constrain energy use in organisms.
5.Compare and contrast exergonic and endergonic reactions.
6.Explain how oxidation and reduction reactions are linked.
7.Explain how ATP is used in coupled reactions.
8.Explain how enzymes catalyze reactions.
9.Describe how negative and positive feedback regulate reaction rates.
10. Be able to explain homeostasis, feedback loops and their importance to
biology.
11.List the factors that influence enzyme activity.
12.Explain how acids and bases affect pH
13.Explain a gradient (thermal, concentration, etc.)
14.Indicate the direction of energy or material flow under different conditions
15.Predict the permeability of membranes under different conditions

4. 2 Forms of Energy
• Kinetic Energy • Potential energy

6. Sunlight
(kinetic
energy)
Heat
energy
Potential
energy
Chemical energy
(potential energy)
available for
cellular tasks
Heat
energy
Cellular
respiration Sugar
Photosynthesis
H2O
CO2
O2
Figure 4.2

8. 1st Law of Thermodynamics

9. 2nd Law of Thermodynamics

11. Chemical Reactions Sustain Life
• Metabolism
• Endergonic Reactions
• Exergonic Reactions

12. Potential
energy
of
molecules
Potential
energy
of
molecules
Products
Energy must
be supplied
Reactants
Energy
required
Energy in Energy in
Energy
released
Energy out
Energy out
Energy is
released
Products
Reactants
Progress of reaction
Progress of reaction
Carbon
dioxide
Water Glucose Oxygen
Oxygen Glucose Carbon
dioxide
Water
Exergonic reactions release energy; products contain less energy than reactants
Endergonic reactions require energy input; products contain more energy than reactants
Figure 4.4
6CO2 6H2O
+ C6H12O6 6O2
+
6O2 C6H12O6
+ 6CO2 6H2O
+

13. Electrons ( ) are transferred
from donor to acceptor
Electron acceptor
molecule
Electron donor
molecule
Oxidation
Oxidized molecule Reduced molecule
Reduction
e-
e-
Figure 4.5
Redox Reactions

15. Proteins of electron transport chain
Electron donor
(molecule being
oxidized)
Electron acceptor
(molecule being
reduced)
Energy
Energy
Energy Energy
Membrane
High Potential energy
of electrons
Low
Figure 4.6
e−
e−

16. ATP = adenosine triphosphate

17. H2O
Energy
Hydrolysis
Figure 4.8
ADP
ATP
P P P
P
P P
ATP Hydrolysis

19. from exergonic
reactions
Energy
Energy
for endergonic
reactions
ATP hydrolysis
ATP synthesis
Figure 4.9
ADP
ATP H2O
P
+

20. Glucose
E.g., ATP provides the energy to build large molecules out of
small subunits
E.g., ATP binding changes shape of proteins involved in muscle
contraction
ATP energizes target molecule, making it more likely to bond
with other molecules.
ATP donates a phosphate group that changes the shape of
the target molecule.
Glucose
“activated”
by phosphate
group
Figure 4.10
Short polysaccharide Longer polysaccharide
Activated glucose
ATP ADP
P
P
P
P
P
ATP ATP ADP ADP
+ +

22. Enzymes as Catalysts
• Enzymes “speed up”
reactions by lowering
the “activation energy”
of a reaction.
• Enzymes DO NOT
change the overall
energy released in a
reaction.
22
Fig. 4.10
Activation energy
required with enzyme
Net energy
released in
reaction
Potential
energy
of
molecules
Activation energy
required without enzyme
Without enzyme
With enzyme
Reactants
Progress of reaction
Products

24. • Enzymes
• Activation Energy
• Active Site
• Cofactors

25. Products
Activation energy
required with enzyme
Potential
energy
of
molecules
Reactants
Activation energy
required without
enzyme
Net energy
released in
reaction
With enzyme
Without enzyme
Enzyme
Products
Enzyme-substrate complex
Substrate Active site
Enzyme
a.
b.
Figure 4.11

27. Enzyme from
human
Enzyme from
hot springs
bacterium
Low
High
Rate
of
reaction
Temperature (°C)
Human
body
37°C
30 40 50 60 70 80
Temperature

28. 7
pH
pH
reaction
rate
2
0 1 3 4 5 6 8 9 10
stomach
pepsin
intestines
trypsin
11 12 13 14

30. Control of Reaction Rates
• Negative Feedback
• Noncompetitive Inhibition
• Competitive Inhibition
• Positive Feedback*

31. Substrate
Inhibitor
Enzyme
Competitive
inhibition
Noncompetitive
inhibition
Active site
Inhibitor
Normal
binding
Figure 4.14

32. Enzyme
1
Enzyme
2
Enzyme
3
Enzyme
4
Substrate Product
Negative feedback
Enzyme 4’s product inhibits
action of enzyme 1
Figure 4.13

33. 2 Types of Homeostatic Control Mechanisms

34. Section 4.5
This image is a concentration gradient of black pixels, with high
concentration at the top and low concentration at the bottom.
At the top, the black pixels are
abundant and close together.
High concentration
of black pixels
Low concentration
of black pixels
At the bottom, the black pixels
are sparse.
“Gradient” Describes a Difference
Between Neighboring Regions

35. Movement Across Membranes:
A Summary
Table 4.2
Mechanism Characteristics
Passive
transport
Net movement is down concentration
gradient; does not require energy input.
Substance moves across membrane without
assistance from transport proteins.
Simple
diffusion
Water diffuses across a selectively
permeable membrane.
Osmosis
Substance moves across membrane with
assistance from transport proteins.
Facilitated
diffusion
Area of low
concentration
Area of high
concentration

36. Table 4.2 Contd.
Net movement is against concentration
gradient; requires transport protein and
energy input, often from ATP.
Transport in
vesicles
Vesicle carries large particles into or out of a
cell; requires energy input.
Active
transport
Endocytosis Membrane engulfs substance and draws it
into cell.
Exocytosis Vesicle fuses with cell membrane, releasing substances
outside of cell.

37. Membrane Transport Summary
Is the substance
nonpolar?
Yes
No
Is the substance
moving down its
concentration
gradient?
Yes
No
Is the substance
very large?
No
Yes
Is the substance
entering or
leaving the cell?
Exocytosis
Facilitated
diffusion
Simple diffusion
Active
transport
Entering Endocytosis
Leaving

38. Glucose
enters cell
by facilitated
Diffusion.
Enzymes break
starch into
glucose.
ATP is released into
cytosol.
In cellular
respiration, enzymes
in mitochondrion use
energy from glucose
to produce ATP.
ADP returns to
mitochondrion.
Endergonic
processes such as
active transport
use energy from
ATP hydrolysis.
Enzymes break glucose
into two pieces, which
enter mitochondrion.
Cytosol
Outside of cell
Starch
Starch hydrolysis
ATP production: P
P
Figure 4.24
Endergonic processes in this figure Exergonic processes in this figure
ADP + ATP H2O
+
Active transport Facilitated diffusion
Reactions of cellular respiration
ATP hydrolysis: H2O
ATP + ADP +
P
P P
P P P

39. Metabolism
Enzymes
Chemical reactions
Exergonic
Endergonic
Energy
Active
transport Potential
energy
Kinetic
energy
Concentration
gradient
Facilitated
diffusion
Simple
diffusion
ATP
consist of
are proteins
that catalyze
if they require
net input of
if they
release
is a molecule
that stores
requires
exists in two forms
creates
stores
dissipates
are
Figure 4.25