Biology 101 Module 5

1. 5-1
Chapter 5
The Dynamic Cell
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McGraw-Hill Education.

2. • In this section, the following objective will be covered:
• Summarize the laws of thermodynamics and how they relate to
living organisms.
5.1What Is Energy?

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5-3
What Is Energy?
•Energy is the capacity to do work.
•Our biosphere gets its energy from the sun.
•Two basic forms of energy
• Potential energy—stored energy
• Kinetic energy—energy of motion
• Two forms are converted back and forth
• During conversions, some lost as heat

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5-4
Potential Energy Versus Kinetic Energy
(left and center): © Patrik Giardino/Corbis;(right):© Joe McBride/Corbis

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5-5
Calorie and
Kilocalorie
•Measuring energy
• Food energy measured in calories
• Calorie—amount of heat required to raise
temperature of 1 gram of water by 1°C
• Kilocalorie or Calorie = 1,000 calories
• Value listed on food packages

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5-6
Energy Laws
•Two energy laws
• First law—conservation of energy
• Energy cannot be created or destroyed, but it
can be changed from one form to another.
• Second law
• Energy cannot be changed from one form to
another without a loss of usable energy.
• Heat is the least usable form of energy.

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5-7
Entropy
• Every energy transformation leads to an increase in
the amount of disorganization or disorder.
• Entropy—relative amount of disorganization
• Only way to maintain or bring about order is to add
energy
• Our universe is a closed system.
• All energy transformations increase the total
entropy of the universe.
• Energy provided by the sun allows plants to make
glucose from the more disorganized water and
carbon dioxide.
• Some of sun’s energy is lost as heat

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5-8
Cells and Entropy
Unequal distribution
of hydrogen ions
• more organized
• more potential energy
• less stable
• less entropy
Equal distribution
of hydrogen ions
• less organized
• less potential energy
• more stable
• more entropy

9. • In this section, the following objective will be covered:
• Explain the role of adenosine triphosphate (ATP) in a
cell.
• Describe the flow of energy between photosynthesis and
cellular respiration.
5.2 ATP: Energy for Cells

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5-10
ATP: Energy for Cells
• Adenosine triphosphate
• Energy currency of cells
• Cells use ATP to carry out nearly all activities.
• One nucleotide along with 3 phosphate groups
makes it unstable.
• Easily loses a phosphate group to become ADP
(adenosine diphosphate)
• Continual cycle of breakdown and regeneration

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5-11
ATP

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5-12
The ATP Cycle
• ATP releases energy
quickly.
• Amount of energy
released is usually just
enough for a biological
purpose
• Breakdown can be easily
coupled to an energy-
requiring reaction.

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5-13
Coupled
Reactions
• Energy-releasing reaction can
drive an energy-requiring
reaction
• Usually energy-releasing
reaction is ATP breakdown

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5-14
Coupled Reaction
ATP breakdown provides the energy for muscle
movement.
• Myosin combines with ATP.
• ATP breaks down.
• Release of ADP + P causes myosin to change shape and pull
on the actin filament.
(photo): © CNRI/ScienceSource

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5-15
The Flow of
Energy
• Activities of chloroplasts and
mitochondria enable energy to flow
from the sun through all living things.
• Photosynthesis—solar energy used
to convert water and carbon dioxide
into carbohydrates
• Food for plants and other
organisms
• Cellular respiration—carbohydrates
broken down and energy used to
build ATP
• Useful energy is lost with each
transformation.
• Living things dependent on constant
in/out of solar energy

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5-16
Flow of Energy
(leaves): © Comstock/PunchStock RF; (woman): © Karl Weatherly/Getty RF

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5-17
Humans and Energy
•Humans are also involved in the cycling of
molecules between plants and animals and
in the flow of energy from the sun.
• Inhale oxygen, eat plants and animals
• Energy rich foods allow us to produce the ATP
required to maintain our bodies and carry on
activities.

18. • In this section, the following objective will be covered:
• Identify the role that enzymes play in metabolic pathways and the
ways they can be inhibited.
5.3 Metabolic Pathways and Enzymes

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5-19
Metabolic Pathways and Enzymes
Metabolic pathway—series of linked reactions
• The letters E1–E6 represent enzymes.
• Protein molecules that function as organic catalysts speed up reactions.
• Can only speed up possible reactions
a. Active enzyme and active pathway
b. Feedback inhibition
c. Inactive enzyme and inactive pathway

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5-20
Enzymatic
Action
• Enzymes act on substrates
• May facilitate breakdown or synthesis
reactions

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5-21
Enzyme’s
Active Site
• Accommodates substrate
• Like a lock and key—specific to one
substrate
• Induced fit model—undergoes slight
shape change to accommodate substrate
• Change in shape facilitates reaction
• Active site returns to original shape after
releasing product(s)
• Enzymes are not used up by the reaction.

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5-22
Enzyme
Inhibition
• Occurs when an active enzyme is prevented
from combining with its substrate
• Cyanide is a poison because it binds to and
inhibits cytochrome c oxidase.
• Penicillin interferes with a bacterial enzyme that
kills the bacteria.
• Feedback inhibition
• When a product is in abundance, it competes
with substrate for active site
• An end product of a pathway can inhibit the
first enzyme in the pathway—binds to site
other than active site to cause shape
change—which shuts the entire pathway
down

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5-23
Active Enzyme and Active Pathway
a. Active enzyme and active pathway

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5-24
Feedback Inhibition
When a product builds up—the body doesn’t
need more
• Product binds to enzyme and changes its shape
• Loss of shape = loss of function
b. Feedback inhibition

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5-25
Feedback Inhibition, Concluded
Now the substrate can’t bind to enzyme and the reaction
stops
• When the product gets low, enzyme will go back to original
shape
• Enzyme starts working again
c. Inactive enzyme and inactive pathway

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5-26
Energy of Activation
• Molecules frequently do not react with each other unless activated.
• Energy of activation (Ea)—energy needed to cause molecules to react
with one another
• Enzymes lower the amount of energy required.
• Enzymes bring substrates into contact and even sometimes
participate in the reaction.

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5-27
Energy of
Activation (𝐄 𝐚)
• A LOWER hurdle is
easier/ faster to
get over
• A LOWER energy
of activation
makes a reaction
easier/ faster

28. • In this section, the following objective will be covered:
• Compare and contrast passive versus active transport, and list the
types of each.
• Explain osmosis and the effect it has on cells in environments of
varying tonicity.
5.4 CellTransport

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5-29
Cell
Transport
•Plasma membrane regulates traffic in and
out of cell.
•Selectively permeable—some substances
pass freely, some transported, some
prohibited
•3 ways to enter
• Passive transport—substances move
from higher to lower concentration, no
additional energy required
• Active transport—substances move from
lower to higher concentration, additional
energy is required
• Bulk transport—movement independent
of gradients, additional energy required

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PassiveTransport
• No energy required for simple diffusion
• Molecules move down their concentration gradient
until equilibrium is reached.
• Cell does not expend additional energy—molecules
already in motion
• Some molecules slip between phospholipids.
• Facilitated diffusion—others use transport protein
specific to molecule
• Water uses aquaporins—this explains faster than expected
transport rate

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5-31
Simple Diffusion Demonstration
a.Crystal of dye is placed in the water b. Diffusion of water and dye molecules c. Equal distribution of molecules results

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Facilitated
Diffusion

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5-33
Osmosis Demonstration

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5-34
Osmosis in Animal and Plant
Cells – Isotonic Environment
• Isotonic solution
• No net gain or loss of water
• Concentration of water same on both sides of
the membrane
• 0.9% saline isotonic to red blood cells

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5-35
Osmosis in Animal and Plant
Cells – Hypotonic Environment
•Hypotonic solution
• Concentration of water outside cell greater than
inside cell
• Cell gains water
• Animal cells may lyse or burst
• Plant cells use this to remain turgid

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Osmosis in Animal and Plant
Cells – Hypertonic Environment
•Hypertonic solution
• Concentration of water outside cell less than
inside cell
• Cell loses water
• Animal cells shrink
• Plant cells undergo plasmolysis and may wilt.

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5-37
Active
Transport
• Cells expend energy to move molecules
against a concentration gradient.
• Requires transport protein
• Sodium-potassium pump important in
maintaining gradient of ions used in nerve
impulse conduction

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5-38
Bulk
Transport
• Macromolecules are often too large
to be moved by transport proteins.
• Vesicle formation takes them in or
out of cell.
• Exocytosis—movement out of cell
• Endocytosis—movement into cell
• Phagocytosis—cell surrounds, engulfs, and
digests particle
• Pinocytosis—vesicle forms around liquid or
small particles
• Receptor-mediated endocytosis—
receptors for particular substances found in
coated pit—selective and more efficient

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5-39
BulkTransport –
Exocytosis

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BulkTransport –
Endocytosis

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5-41
Receptor-Mediated
Endocytosis

42. Chapter 5
Objective
Summary
• You should now be able to:
• Summarize the laws of thermodynamics
and how they relate to living organisms.
• Explain the role of adenosine
triphosphate (ATP) in a cell.
• Describe the flow of energy between
photosynthesis and cellular respiration.
• Identify the role that enzymes play in
metabolic pathways and the ways they can
be inhibited.
• Compare and contrast passive versus
active transport, and list the types of each.
• Explain osmosis and the effect it has on
cells in environments of varying tonicity.