BioS240 Homeostasis: The
Physiology of Plants and Animals
3 hours. Basic concepts of physiological mechanisms
that contribute to survival of multicellular
organisms. Comparison of a variety of organisms.
Prerequisite(s): BIOS 100 and CHEM 112
and CHEM 114. (general bio., Org. and Inorg. Chem.)
NOTE prerequisites are not checked by the
computer system when you register!! First set
of lectures will be review of basic concepts covered
by those courses
Homeostasis
Homeostasis, from the Greek words
for "same" and "steady," refers to
any process that organisms use to
actively maintain fairly stable
conditions necessary for survival,
What is Homeostasis?
• The maintenance of a constant condition in the
internal environment in spite of changes to the
external environment.
• The term homeostasis means, homois = same,
stasis = standing, steady.
• Claude Bernard (1865) was the first to observe
that the body had specific mechanisms that
regulated various physiological processes, within
Claude Bernard
(1813-1877)
Walter B. Cannon
(1871-1945)
Requirements for Homeostasis
• Life has been defined as the ability of a system to
maintain homeostasis. If homeostasis is not
maintained a cell, tissue or organism will perish.
• Sensing the internal and external environment is key
to maintain homeostasis
• Isolation of the internal environment allows for
concentrating chemicals in a regulated manner. Cell
membranes become crucial as cellular homeostasis is
fundamental for organismal level homeostasis
• Feedback mechanisms to control fluctuations in
internal environment.
• Isolation within cell structures in eukaryotes allows
Plant and Animal Cells
mitochondria fig 1.5
peroxisome fig 1.1
chloroplast/amyloplast
Figs 1.1, 1.6, 8.12-13
vacuole fig 1.1
cell wall figs 1.1, 1.8-11
Membrane proteins and the bilayer
hydrophilic
hydrophobic
Integral
The Cell: A molecular approach 12-3.
Peripheral
pp. 330
Membrane function
All organelles within a cell are also isolated by membranes
Thylakoid membrane- Photosynthesis occurs
Inner mitochondrial membrane-ATP synthase
ER and Golgi complex-elaborate systems of proteins
involved in lipid and protein biosynthesis
Vacuole-responsible for water uptake and cell
enlargement therefore has to control molecule
movement.
Why are membranes needed?
Membranes provide structural hydrophobic isolation from other
cells and the external environment. Isolation and barriers
provide resistance to movement of molecules which in biology is
key for regulating what comes in and out.
Membranes contain lots of proteins (transporters, carriers,
channels, receptors, enzymes) that regulate many processes
(membrane potential, transport, bioenergetics, etc…).
Membranes within organelles allow for the compartmentalization
of processes and for their specific regulatory steps.
All these processes need energy, so substrates for energy need
to be acquired (food, light), and energy sources (glucose, ATP,
…) should be able to be transported, stored and used in the
tissues where it is need it. Finding the right balance of demand
Why are Cells Small?
Why are Cells Small?
- Cells must exchange gases & other molecules
among themselves and with environment…
Why are Cells Small?
- Cells must exchange gases & other molecules
among themselves and with environment…
Why are Cells Small?
- Cells must exchange gases & other molecules
among themselves and with environment…
- Need to bring nutrients in and excrete
wastes out
Why are Cells Small?
- Cells must exchange gases & other molecules
among themselves and with environment…
- Need to bring nutrients in and excrete
wastes out
Why are Cells Small?
- Cells must exchange gases & other molecules
among themselves and with environment…
- Need to bring nutrients in and excrete
wastes out
- As size increases, the rate of diffusion for
exchange of molecules and gases becomes
too slow to be efficient.
Why are Cells Small?
- Cells must exchange gases & other molecules
among themselves and with environment…
- Need to bring nutrients in and excrete
wastes out
- As size increases, the rate of diffusion for
exchange of molecules and gases becomes
too slow to be efficient.
Surface Area to Volume
Surface Area to Volume
Surface Area to Volume
Cell surface area is important in taking in
metabolites, ions or nutrients: the more surface
area the more capacity to exchange these gases
and molecules
Surface Area to Volume
Cell surface area is important in taking in
metabolites, ions or nutrients: the more surface
area the more capacity to exchange these gases
and molecules
Surface Area to Volume
Cell surface area is important in taking in
metabolites, ions or nutrients: the more surface
area the more capacity to exchange these gases
and molecules
Surface area increases as the square of cell diameter
Surface Area to Volume
Cell surface area is important in taking in
metabolites, ions or nutrients: the more surface
area the more capacity to exchange these gases
and molecules
Surface area increases as the square of cell diameter
Surface Area to Volume
Cell surface area is important in taking in
metabolites, ions or nutrients: the more surface
area the more capacity to exchange these gases
and molecules
Surface area increases as the square of cell diameter
The bigger the surface area the bigger the entire
cell volume: gases and molecules may need to reach
all parts of the cytoplasm, organelles and nucleus.
Cells cannot be too big.
Surface Area to Volume
Cell surface area is important in taking in
metabolites, ions or nutrients: the more surface
area the more capacity to exchange these gases
and molecules
Surface area increases as the square of cell diameter
The bigger the surface area the bigger the entire
cell volume: gases and molecules may need to reach
all parts of the cytoplasm, organelles and nucleus.
Cells cannot be too big.
Surface Area to Volume
Homeostasis vs changing environment
• The physical world both provides the context
for life and constrains its existence.
•
A world of environmental factors...
– resources (food)
– conditions (temperature)
• Most factors have extremely wide ranges:
Homeostasis vs changing environment
• Organisms typically contrast with their
external environments:
– internal conditions are maintained +/- constant
– fluxes of heat and substances must be regulated
– but organisms are open systems...
• resources must be acquired
• wastes must be eliminated
• How do organisms accomplish this?
– organisms are specialized
– organisms have specific geographic distributions
Examples of Resource Gradients
Homeostasis can be affected by:
• External:
• Internal:
– 1. Temperature
– 1. Temperature
– 2. Water
– 2. Water
– 3. Light
– 3. Gases (PO2, PCO2)
– 4. Food, Nutrients
– 4. Carbon
– 5. Predators
– 5. pH
– 6. Waste
Homeostasis vs changing environment
Limiting Factors
Resource Gradient
Homeostasis vs changing environment
Limiting Factors
Resource Gradient
Homeostasis vs changing environment
Limiting Factors
Resource Gradient
Homeostasis vs changing environment
Limiting Factors
Optimum
Resource Gradient
Homeostasis vs changing environment
Limiting Factors
Zone Of Tolerance
Optimum
Resource Gradient
Homeostasis vs changing environment
Limiting Factors
Zone Of Tolerance
Optimum
Lethal
Minimum
Resource Gradient
Homeostasis vs changing environment
Limiting Factors
Zone Of Tolerance
Optimum
Lethal
Minimum
Lethal
Maximun
Resource Gradient
Homeothermia in Mammals
Homeothermia in Mammals
Tolerance curves in a frog heterotherm
The ability of a frog to jump depends on the ability to
generate energy and efficient muscle fiber contraction as
a function of internal temperature.
Homeostasis
vs changing
environment
Environmental
conditions
Swim faster than your
prey or predator over a
wide temp range and
you will do well
High rates of photosynthesis
over a wide range of temps
increases growing season
length
Environmental conditions can moderate physiological processes
which in turn modulate the gene plasticity that determine
survivorship, growth and reproduction of an organism.
Homeostasis
vs changing
environment
Environmental
conditions
Phenotypic plasticity is necessary for
residence in the homeostasis range that
allows for growth and reproduction
Phenotypic plasticity and homeostasis: Facultative
anaerobes or aerotolerant anaerobic bacteria have largest
range of oxygen levels. Who grows faster?
O2 toxicity
Homeostasis vs changing environment
Homeostasis:
at the cellular level
at the tissue/organ level
at the organismal level
Homeostasis vs changing environment
Homeostasis:
at the cellular level
Ion concentration
transporters
Membrane potential
at the tissue/organ level
pH
pumps
sensors
(direct or indirect)
at the organismal level
Temperature
pCO2
coordinated
sensors & effectors
At the organism level tolerance curves can interact, and affect
fitness. Adaptations to temperature separate aquatic bacteria
by growth temperature. Note that maximum growth
temperature rarely overlap as a result of limited phenotypic
plasticity (tolerance curve) for each temperature adaptation.
Organismal level: Water Regulation by
Terrestrial Plants and Animals
Organismal level: Water Regulation by
Terrestrial Plants and Animals
BASIC REVIEW (ON YOUR OWN)
The Eukaryotic Cell: Components
BASIC REVIEW (ON YOUR OWN)
The Eukaryotic Cell: Components
• Outer cell membrane
composed of lipids and
proteins
• Cytoplasm: interior
region. Composed of
water & dissolved
chemicals…a gel
Organelles
Organelles
• Specialized structures within eukaryotic cells that perform
different functions...
Organelles
• Specialized structures within eukaryotic cells that perform
different functions...
• Analogous to small plastic bags within a larger plastic bag.
Organelles
• Specialized structures within eukaryotic cells that perform
different functions...
• Analogous to small plastic bags within a larger plastic bag.
Perform
functions
such as :
-protein production
(insulin, lactase…)
-Carbohydrates,
lipids…
Organelles of Note:
Organelles of Note:
-Contains the genetic material
(DNA), controls protein
synthesis.
Organelles of Note:
-Contains the genetic material
(DNA), controls protein
synthesis.
DNA --> RNA --> Protein
Organelles of Note:
-Contains the genetic material
(DNA), controls protein
synthesis.
DNA --> RNA --> Protein
Organelles of Note:
-Contains the genetic material
(DNA), controls protein
synthesis.
DNA --> RNA --> Protein
-Surrounded by a double
membrane with pores
Organelles of Note:
-Contains the genetic material
(DNA), controls protein
synthesis.
DNA --> RNA --> Protein
-Surrounded by a double
membrane with pores
Organelles of Note:
-Contains the genetic material
(DNA), controls protein
synthesis.
DNA --> RNA --> Protein
-Surrounded by a double
membrane with pores
-Contains the chromosomes =
fibers of coiled DNA &
protein
Chloroplasts
Chloroplasts
• Found in plants, algae and
some bacteria. Responsible
for capturing sunlight and
converting it to food =
photosynthesis.
Chloroplasts
• Found in plants, algae and
some bacteria. Responsible
for capturing sunlight and
converting it to food =
photosynthesis.
• Surrounded by 2
membranes
Chloroplasts
• Found in plants, algae and
some bacteria. Responsible
for capturing sunlight and
converting it to food =
photosynthesis.
• Surrounded by 2
membranes
• And…contain DNA
Golgi Complex
Golgi Complex
• Stacks of
membranes…
Golgi Complex
• Stacks of
membranes…
• Involved in modifying
proteins and lipids
into final form…
– Adds the sugars to
make glyco-proteins
and glyco-lipids
• Also, makes vesicles
to release stuff from
cell
Microfilaments
Microfilaments
• Thin filaments (7nm diam.)
made of the globular
protein actin.
Microfilaments
• Thin filaments (7nm diam.)
made of the globular
protein actin.
• Actin filaments form a
helical structure
Microfilaments
• Thin filaments (7nm diam.)
made of the globular
protein actin.
• Actin filaments form a
helical structure
• Involved in cell movement
(contraction, crawling, cell
extensions)