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Biological Hierarchy of
Organization, Homeostasis &
Overview of Organ Systems
What Is Energy?
• Capacity to do work
• Forms of energy
– Potential energy
– Kinetic energy
– Chemical energy
First Law of Thermodynamics
• The total amount of energy in the
universe remains constant
• Energy can undergo conversions from
one form to another, but it cannot be
created or destroyed
What Can Cells Do
with Energy?
• Energy inputs become coupled to
energy-requiring processes
• Cells use energy for:
– Chemical work
– Mechanical work
– Electrochemical work
Second Law of Thermodynamics
• No energy conversion is ever 100
percent efficient
• The total amount of energy is flowing
from high-energy forms to forms
lower in energy
Enzyme Structure
and Function
• Enzymes are catalytic protein
molecules
• They speed the rate at which
reactions approach equilibrium
Four Features of Enzymes
1) Enzymes do not make anything
happen that could not happen on its
own. They just make it happen much
faster.
2) Reactions do not alter or use up
enzyme molecules.
Four Features of Enzymes
3) The same enzyme usually works for
both the forward and reverse
reactions.
4) Each type of enzyme recognizes and
binds to only certain substrates.
Activation Energy
• For a reaction to
occur, an energy
barrier must be
surmounted
• Enzymes make
the energy barrier
smaller
activation energy
without enzyme
starting
substance
activation energy
with enzyme
energy
released
by the
reaction
products
Some Factors Influencing
Enzyme Activity
Temperature
pH
Salt concentration
Coenzymes and cofactors
Metabolic Pathways
• Defined as enzymemediated sequences of
reactions in cells
– Biosynthetic (anabolic) –
ex: photosynthesis
– Degradative (catabolic) –
ex: aerobic respiration
ENERGY IN
ENERGY IN
photosynthesis
organic
compounds,
oxygen
carbon
dioxide,
water
aerobic
respiration
ENERGY OUT
Main Types of
Energy-Releasing Pathways
Anaerobic pathways
Aerobic pathways
• Evolved first
• Evolved later
• Don’t require oxygen
• Require oxygen
• Start with glycolysis in
cytoplasm & completed • Start with glycolysis in
cytoplasm & completed
in cytoplasm
in mitochondria
• Very inefficient – most
of energy lost as heat • More efficient – less
energy lost as heat
Summary Equation for Aerobic
Respiration
C6H1206 + 6O2
6CO2 + 6H20
glucose
carbon
oxygen
dioxide
water
Summary Equation for
Photosynthesis
C6H1206 + 6O2
glucose
oxygen
6CO2 + 6H20
carbon
dioxide
water
Processes Are Linked
sunlight energy
PHOTOSYNTHESIS
water
+
carbon
dioxide
sugar
molecules
AEROBIC
RESPIRATION
oxygen
Efficiency of
Aerobic Respiration
• 686 kcal of energy are released
• 7.5 kcal are conserved in each ATP
• When 36 ATP form, 270 kcal (36 X 7.5) are
captured in ATP
• Efficiency is 270 / 686 X 100 = 39 percent
• Most of the energy is lost as heat, but still
less than with anaerobic processes
Body Organization
• Tissue
– Group of cells performing same task
• Organ
– Two or more tissues performing same task
• Organ system
– Two or more organs performing same task
Tissues
• Groups of cells and intercellular
substances that interact in one or more
tasks
• Example: muscle tissue
Organs
• Group of tissues organized to perform a
task or tasks
• Example: Heart is an organ that pumps
blood through body
• Heart consists of muscle tissue, nervous
tissue, connective tissue, and epithelial
tissue
Organ Systems
• Groups of organs that interact physically
and/or chemically to perform a common
task
• Example: Circulatory system includes
heart, arteries, and other vessels that
transport blood through the body
Homeostasis
• Stable operating conditions in the
internal environment
• Brought about by coordinated activities
of cells, tissues, organs, and organ
systems
Homeostatic Mechanisms
22
4 Types of Tissues
• Epithelial tissues
• Connective tissues
• Muscle tissues
• Nervous tissues
Epithelial Tissues
• Line body surfaces, cavities, ducts,
and tubes
• One free surface faces a body fluid or
the environment
basement
membrane
simple
squamous
epithelium
connective tissue
free surface of
epithelium
Epithelium
simple epithelium
basement membrane
connective tissue
Epithelial
Structure of an epithelium
Connective Tissues
• Most abundant tissues in the body
• Fibroblasts secrete
– polysaccharide “ground substance” that
surrounds and supports cells
– fibers of collagen and/or elastin
Soft Connective Tissues
• Loose connective tissue
• Dense, irregular connective tissue
• Dense, regular connective tissue
Soft Connective Tissues
Soft connective tissue
Specialized Connective Tissues
• Cartilage
• Bone tissue
• Adipose tissue
• Blood
Specialized
Connective Tissues
Specialized connective tissue
white blood cell
platelet
red blood cell
cells and platelets of
blood
Fig. 20-3g, p.342
Muscle Tissue
• Cells contract when stimulated
• Moves body and specific body parts
• 3 types
– Skeletal
– Cardiac
– Smooth
Skeletal Muscle
• Attaches to and moves
bones
• Long, cylindrical cells
• Striated cells
• Voluntary control
nucleus
Smooth Muscle
• Located in soft internal
organs and blood vessels
• Cells taper at ends
• Cells not striated
• Not under voluntary
control
where abutting cells meet
Cardiac Muscle
• Present only in heart
• Cells are branching
– ends of cells joined by
communication junctions
• Cells striated
• Not under voluntary control
cell nucleus
Muscle Tissues
Muscle tissues
Nervous Tissue
• Detects stimuli, integrates information,
and relays commands for response
• Consists of excitable neurons and
supporting neuroglial cells
Neurons
• Excitable cells
• Stimulus sends electrical impulse along
plasma membrane
• Transmits information to other neurons,
muscles or glands
Neuroglia
• Neuroglial cells make up more than
half of nervous tissue
• Protect and support neurons
11 Major Organ Systems
• Integumentary
• Nervous
• Muscular
• Skeletal
• Circulatory
• Endocrine
11 Major Organ Systems
Integumentary
System
Nervous
System
Muscular
System
Skeletal
System
Circulatory
System
Endocrine
System
Fig. 20-6, p.344a1
11 Major Organ Systems
• Lymphatic
• Respiratory
• Digestive
• Urinary
• Reproductive
11 Major Organ Systems
Lymphatic
System
Respiratory
System
Digestive
System
Urinary
System
Reproductive
System
Fig. 20-6a2, p.344
Major Organ Systems
Human organ systems