BIOL 3151: Principles of Animal

Physiology

ANIMAL PHYSIOLOGY

Dr. Tyler EvansEmail: tyler.evans@csueastbay.eduPhone: 510-885-3475Office Hours: M,W 10:30-12:00 or appointmentWebsite: http://evanslabcsueb.weebly.com/

• chemical and biochemical processes occurring at the molecular level ultimately influence higher levels of function such as physiology

PREVIOUS LECTUREENERGETICS

PREVIOUS LECTUREENERGETICS

• energy is the ability to do work, thus obtaining energy is of fundamental importance for animals

• In the context of biological systems, energy comes in several forms:

1.) RADIANT ENERGY2.) MECHANICAL ENERGY3.) ELECTRICAL ENERGY4.) THERMAL (HEAT) ENERGY5.) CHEMICAL ENERGY

• Different animals have evolved different strategies for acquiring and using energy

textbook pg 23

PREVIOUS LECTURE4.) THERMAL (HEAT) ENERGY• every enzyme has a characteristic optimal activity under

certain temperatures:

Enzyme activity curve for unknown marine animal

PREVIOUS LECTUREENERGETICS

3.) ELECTRICAL ENERGY• biological systems invest energy to move molecules out of a random distribution• this resting diffusion gradient is a form of stored energy that the cell can use for

other purposesENERGY

ENERGETICSAcquiring, Storing and Using Energy

3.) ELECTRICAL ENERGY• of particular importance to living systems are chemical gradients that form across

cell membranes

• ensuring that more negatively charged molecules are present inside cells than outside creates a chemical gradient or stored electrical energy

• this electrical energy can be released to create electric signals that drive physiological processes

• for example, muscle contraction

textbook Fig 2.2 pg 24

PREVIOUS LECTURE

TODAY’S LECTUREMEMBRANE PHYSIOLOGY

• establishing chemical or electrical gradients within cells is dependent upon properties of CELL MEMBRANES

• typical animal cell consists of several internal structures surrounded by a cellular membrane

MEMBRANE PHYSIOLOGY

Fig 2.43 pg 65

PLASMA MEMBRANE: the outer boundary of the cell that separates the two major fluid compartments: INTRACELLULAR (inside of cells) and EXTRACELLULAR (outside of cells)• the plasma membrane is not a passive envelope, instead its structure is

described by the FLUID MOSAIC MODEL

PLASMA MEMBRANE

• the membrane is composed of a double layer of lipids (the LIPID BILAYER), in which proteins are inserted

• protein components are constantly changing, hence the term fluid mosaic

MEMBRANE PHYSIOLOGY• many cellular processes, including the formation of

chemical or electrical gradients, are dependent on the ability to move molecules across membranes.

• transport of molecules across membranes can occur in two ways:1. WITHOUT the assistance of membrane proteins• PASSIVE DIFFUSION

2. WITH the assistance of membrane proteins• FACILITATED DIFFUSION• ACTIVE TRANSPORT

MEMBRANE PHYSIOLOGYPASSIVE DIFFUSION• although membranes are barriers to the movement of many molecules, some

molecules cross membranes without the help of membrane proteins• movement of molecules is from high concentration to low concentration• no specific transporter proteins are required and no energy is required• this type of transport is called PASSIVE DIFFUSION

MEMBRANE PHYSIOLOGYPASSIVE DIFFUSION• direction of diffusion depends on concentration gradient, but the rate of

diffusion depends on additional factors.• steep concentrations gradients diffusion occurs quickly• large molecules diffuse slower than small molecules• charge• solubility

• The FICK EQUATION describes the rate of diffusion:

dQs

dt=

Ds x A x dCdX

Diffusion area

Rate of diffusion

Diffusion coefficient

concentrationgradient

textbook pg 29

PASSIVE DIFFUSION• lipid soluble molecules can pass across cell membranes via passive diffusion

• e.g. steroid hormones like ESTROGEN and TESTOSTERONE

MEMBRANE PHYSIOLOGY

• these molecules can dissolve into the lipid bilayer and escape the other side

• testosterone supplements are applied under the arms like deodorant because can easily pass across membranes in the skin to enter the blood

PASSIVE DIFFUSION• lipid soluble molecules can pass across cell membranes via passive diffusion

• e.g. steroid hormones like ESTROGEN and TESTOSTERONE

MEMBRANE PHYSIOLOGY

• hormones are also very stable and work at low concentrations. As a result they are causing environmental problems:• e.g. environmental estrogens

• many human chemicals (e.g. contraceptives) mimic the structure of steroids hormones and can cause physiological and developmental problems in animals

• amphibians are especially susceptible because their skin is very permeable

MEMBRANE PHYSIOLOGYPASSIVE DIFFUSION• WATER is another molecule able to pass across cell membranes via passive

diffusion (most other ions cannot cross)• the passive diffusion of water across cell membranes is called OSMOSIS• controlling the movement of water via osmosis is essential for cells to operate

properly• here’s why: ions and other molecules in cells must be in specific concentrations

(i.e. dissolved in the correct amount of water) both inside and outside of cells if animals are to function normally

• virtually every cell in every animal has a total intracellular and extracellular concentration of 300 mOsm.

MEMBRANE PHYSIOLOGYPASSIVE DIFFUSION• if the intra- or extracellular concentration changes, it causes water to move via

osmosis

textbook Fig 2.8 pg 29

• cell membranes are permeable to water but not Na+ or Cl-, so water will diffuse across membrane when Na+ or Cl- is added

• leads to an increase in water volume on one side of the membrane relative to the other

MEMBRANE PHYSIOLOGYWhy is the passive diffusion of water a

problem for physiology?

• movement of water in and out of cells causes changes in CELL VOLUME

• changes in cell volume are problematic for physiological function

• swollen cells can disrupt tissue structure or occlude blood vessels and with too much swelling cells can burst

• shrinking cells can deform the plasma membrane and cytoskeleton

textbook Fig 2.9 pg 31

MEMBRANE PHYSIOLOGYPASSIVE DIFFUSION• the ability of solutions to induce water to cross a membrane is termed

OSMOLARITY, essentially the concentration of particles in a solution• if a cell is placed in a solution with greater osmolarity (i.e. more

particles) then the solution is considered HYPEROSMOTIC relative to the cell

• if a cell is placed in a solution with less osmolarity (i.e. less particles) then the solution is considered HYPOSMOTIC relative to the cell

• When osmolarity is equal on both side of the cell membrane, the solution is termed ISOSMOTIC

textbook Fig 2.9 pg 31

MEMBRANE PHYSIOLOGYPASSIVE DIFFUSION• the effect of the passive diffusion of water on cell volume is easily tested using

isolated red blood cells.• and you will get to do it in lab!

SWELL(IF BURSTS CALLED

HEMOLYSIS)

CRENATE(SHRINK)

NO VOLUME CHANGE

MEMBRANE PHYSIOLOGY• cells work hard to make sure intra- and extracellular concentration are

maintained around 300 mOsm to avoid osmosis and changes in cell volume • cells will transport molecules from one side of the plasma membrane to the

other to in order to maintain these concentrations (called ION TRANSPORT)• ion transport occurs with the help of membrane proteins

textbook Fig 2.43 pg 65

• some INTEGRAL MEMBRANE PROTEINS span the entire membrane and provide a way for molecules to move from one side of the membrane to the other

MEMBRANE PHYSIOLOGY• many cellular processes, including the formation of

chemical or electrical gradients, are dependent on the ability to move molecules across membranes.

• transport of molecules across membranes can occur in two ways:1. WITHOUT the assistance of membrane proteins• PASSIVE DIFFUSION

2. WITH the assistance of membrane proteins• FACILITATED DIFFUSION• ACTIVE TRANSPORT

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION• as with passive diffusion, no energy beyond that of the concentration

gradient is required to drive movement across membrane• but with facilitated diffusion a protein is required to carry the molecule

across the membrane• three main types of protein carry out facilitated diffusion:

textbook Fig 2.48 pg 67

1. ION CHANNELS

2. PORINS

3. PERMEASES

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION

1. ION CHANNELS• ion channels are membrane proteins that form pores through which

molecules can pass• ion channels are specific to one or sometimes two molecules

textbook Fig 2.48 pg 67

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION

1. ION CHANNELS• ion channels are opened or closed in response to specific cellular

conditionsa. LIGAND GATED ION CHANNELS: are open or closed when specific regulatory molecules are present

e.g. IP3-sensitive calcium channel

• this channel induces the release of calcium stores when inositol triphosphate (IP3) is present

textbook Fig 2.49 pg 68

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION

1. ION CHANNELS• ion channels are opened or closed in response to specific cellular

conditionsb. VOLTAGE GATED ION CHANNELS: are open or closed in response to membrane potentials

e.g. potassium (K+) channel in muscles and neurons

• this channel opens when the net charge across the membrane changes

• these type of channels are involved in forming action potential

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION

1. ION CHANNELS• ion channels are opened or closed in response to specific cellular

conditionsc. MECHANO-GATED ION CHANNELS: are open or closed by interactions with proteins in the cytoskeleton

e.g. Transient receptor potential (TRP) ion channel

• changes in cell shape and volume, such as swelling, alter the arrangement of the cytoskeleton and may trigger opening or closing of mechano-gated ion channels to regulate cell volume

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION

2. PORINS• large channels that function in a similar way to ion channels but

permit the passage of larger molecules.

e.g. mitochondrial porins• function in the exchange of

ions and small molecules, including ATP, across the mitochondrial outer membrane.

• much of the transport that occurs across mitochondrial membranes occurs via porins

MEMBRANE PHYSIOLOGYFACILITATED DIFFUSION

3. PERMEASES• rather than creating a pore for a molecule to pass membrane, permeases

act more like enzymes• when molecules bind to permeases, the permease undergoes a

conformational (i.e. shape) change that cause the permease to release the carried molecule on the other side of the membrane

= molecule

MEMBRANE PHYSIOLOGYACTIVE TRANSPORT• in passive and facilitated diffusion, molecules can move only from high

concentration to low concentration• in contrast, cells use ACTIVE TRANSPORT to move molecules against

concentration gradients, but require energy to do so (i.e. ATP)• three general classes of ATP-dependent transporters or ATPases

a. P-Type ATPase (involved in ion/water balance)• use ATP to pump ions across cell membranes• e.g. sodium/potassium ATPase

b. F-Type ATPase (involved in energetics)• uses hydrogen ion gradients to provide the energy for ATP synthesis

c. ABC Transporter (involved in detoxification)• carry large organic molecules across the cell membrane• cells often use ABC transporters to remove toxins

MEMBRANE PHYSIOLOGYACTIVE TRANSPORT

a. P-Type ATPase• P-type ATPases, such as the SODIUM-POTASSIUM ATPASE, are involved in

controlling ion balance and are extremely important in fish• fish gills have a high surface area to volume ratio (i.e. most of the total area

of gill is in direct contact with water) to maximize oxygen exchange• but creates a strong chemical gradient between gills and environment

CHEMICAL GRADIENTS IN AQUATIC ENVIRONMENTS

FRESHWATER FISH LIVE IN HYPOOSMOTIC WORLD

e.g. goldfish• higher concentration of solutes in

cells relative to external environment

• lower concentration of water in cells relative to external environment

• lower concentration of solutes in cells relative to external environment

• higher concentration of water in cells relative to external environment

e.g. tuna

MEMBRANE PHYSIOLOGY

MARINE FISH LIVE IN HYPEROSMOTIC WORLD

CHEMICAL GRADIENTS ARE A PROBLEM FOR FISH

ions

water

OH H

K+Na+

Ions

water

K+Na+

OH H

• Ions will enter cells• Water will exit cells

• Water will enter cells• Ions will exit cells

FRESHWATER FISH LIVE IN HYPOOSMOTIC WORLD

MARINE FISH LIVE IN HYPEROSMOTIC WORLD

Eggs

AlevinFry

Growth phase

Adult

FRESHWATER-lakes-rivers

MARINE-oceans

SALMON EXPERIENCE BOTH PROBLEMS!

FISH ARE AWESOME OSMOREGULATORS!

• lives in desert pools that can become extremely salty as water in these pools evaporate

• 4x as much salt as seawater!!!

LECTURE SUMMARYtransport of molecules across membranes can occur in two ways:• without the assistance of membrane proteins: PASSIVE DIFFUSION

• water can diffuse across cell membranes and alter cell volume• diffusion rate is described by FICK’S EQUATION

• with the assistance of membrane proteins: • 1. FACILITATED DIFFUSION (no energy required)

a. Ion Channelsb. Porinsc. Permeases

• 2. ACTIVE TRANSPORT (energy required)a. P-Type ATPaseb. F-Type ATPasec. ABC Transporter

• fish are constantly challenged by strong chemical gradients formed between gills and freshwater or marine environments• marine fish gain ions and lose water• freshwater fish gain water and lose ions

• fish are awesome osmoregulators

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