1. Flashcards
What are the different levels of organization?
- cells are organized into tissues
- tissues are organized into organs
- organs are organized into systems
- systems form an organism
Exceptions to level of organization
- There are animals who don’t have any tissues (sponges)
- organisms that have tissues but no organs (jellyfish)
- some will have organs but no systems (all vertebrates have systems)
Cellular Variation and Function
Why do cells look different and how does this affect their function at the tissue level? At the organ level?
Epithelial - smooth and compact set up
Nervous - multiple dendrites from cell body, not as compact
Muscle - will look at with respect to cardiac - striations, each band is the motor proteins which cause contraction
Organ and System Variation (ex. Lungs)
- why does lung structure vary in different animals? How might this affect their function at the system level? Or the whole animal?
Systems optimize the oxygen intake in whatever environment they are in.
Human - pair of lungs
Birds - pair of lungs and sacs
Insects - side openings allow diffusion of oxygen into their system
Ecological and Evolutionary Levels of Organization
Bird trying to escape:
1. Lives, passes on genes, possibly good ones
2. Dies, no genes passed on, helps predator live
- the bird has many cellular tissue organizations which help them fly/escape
(the ability to fly is dependent on the skeletal muscle, the breakdown of energy in those cells - different levels effect survival) - it is also dependent on how the predator is built
For a pheasant, all-out exertion to escape a predator is crucial at the ecological and evolutionary levels of organization
The structure and contractile properties of the pheasant’s muscle cells help determine how fast the pheasant can escape
The Krebs cycle, which is an important process in making ATP for use in muscle contraction, also helps determine how fast the pheasant can escape
4 Unifying Themes/Principles
- despite diversity in physiological design there are 4 unifying themes/principles
- Physiological processes obey laws of physics and chemistry
- Physiological processes are usually regulated
- Physiological phenotype is a product of the genotype and environment
- Genotype is the product of evolution
- Physical and Chemical Law
(4 Unifying Themes)
Mechanical and engineering rules apply to physical properties of animals (ex. collagen in aorta)
Chemical laws govern molecular interactions (ex. effects of temp.)
- emphasizing things from the molecular level (how things like oxygen pass through cell, need for transport, etc.)
Body size influences biochemical and physical patterns
- ex. Giraffe - due to its tallness and long neck in a cardiovascular perspective the heart needs to pump blood efficiently up to the head opposite of gravity, blood goes down to extremities wanted by giraffe, with gravity, its tight skin and thin legs help the blood go back up to heart
- Processes are Regulated
(4 unifying themes)
Animals must deal with constantly changing environment
- regulate body or change physiology as temperature/environment changes
EXTERNAL - changes with external changes
ENDOGENOUS - self-imposed, ex. control over body temperature
The organism must maintain a suitable internal environment
homeo stasis
Control of Homeostasis
Control by feedback loops (usually negative) or reflex control pathways, using ANTAGONISTIC CONTROLS (induce and reduce effects - bc the body knows how to promote a reaction and stop reactions at the same time
FEEDBACK LOOP - when the body returns to normal range the pathways shut down
ex. Exposure to cold, Tb reduced
Antagonistic
1. induces activations of pathways in the body that cause heat production
2. reduces/stops the activity of the pathways that cause heat loss
Strategies for coping with changing conditions: conformers
Allow internal conditions to change with external conditions
ex. ectotherms
as temperature increases externally, temperature increases internally with it
Strategies for coping with changing conditions: regulators
Maintain relatively constant internal conditions regardless of external conditions
REQUIRES METABOLIC ENERGY
as temperature increases externally, temperature remains constant internally [-]
Strategies for coping with changing conditions: Salmon
When a salmon enters a river from the sea…
Conformers:
- its body temp. (including blood temp.) changes if the river water is warmer or cooler than the ocean water
Regulators:
- its blood CL^- concentration remains almost constant, even through river water is very dilute Cl- and seawater is very concentrated in Cl-
therefore:
- organisms can be conformers and regulators for different exponents of life
animals take on environmental ques for many different things
Likely Locations of Conformers/Regulators
The number of species of terrestrial temperature conformers usually declines toward the poles
- the closer the poles the less likely terrestrial temp. conformers will occur
ex. the Canadian tiger swallowtail is one of the species of butterflies that lives farthest from the equator
- Phenotype is product of genotype and environment
(4 Unifying Themes)
GENOTYPE - genetic make-up, genetic code
PHENOTYPE - morphology, physiology, and behavior
- how the genetic code is read/interpreted - change depending on gene expression and environment
PHENOTYPIC PLASTICITY - single genotype generates more than one phenotype depending on environment (ex. twins)
- similar genomes can be dependent on the environments for how they express morphology, physiology, and behavior
- Genotype is product of evolution
(4 Unifying Themes)
- genotype is made during conception
- Organism develops based on genotype and environment
- Environment impacts different levels of organization (order, molecules - cell - tissue, etc.) and physiology and behavior
- Does the increased behavior lead to increased reproduction, decreased reproduction, or no reproduction
- Depending on reproduction of traits evolution occurs
- Genotype is a product of evolution
Cell Membrane Structure
The membrane is composed of:
- Lipids
- phospholipids
- glycolipids
- sterols - Proteins
- integral
- peripheral - do not necessarily span the membrane, anchored to, if removed it does not form hole in membrane - Carbohydrates
- glycolipids
- glycoproteins
- carbohydrate chains bone to cell-membrane proteins (forming glycoproteins) or to membrane lipids (forming glycolipids) project into the extracellular fluid on the outside face of the cell membrane
Phospholipid Bilayer
- phospholipid molecules assemble into a bilayer with water on either side
Found:
- plasma membrane
- vesicles
- organelles
Structure of Membrane Phospholipid Molecules
Hydrophilic Heads: exposed to the aquatic environment, can have different head groups by chemical modification of R
Hydrocarbon Hydrophobic Tail: changes orientation in water to get away
PHOS - phosphate (negative charge, polar, hydrophilic)
LIPID - 2 lipid chains (carbon nature, hydrophobic)
GLYCEROL BACKBONE - connects tail and head
R Group - alters function - can be swapped for other chemical groups
- R is any addition group added to the phospholipid, change in R changes name
2 types of lipid chains
SATURATED - no double bond, stiffer membrane, phospholipids more compact
UNSATURATED - double bond, more fluid membrane, have more room to move in comparison to each other - introduces kink into the shape of the tail
MC:
Temperature effects fluidity fo membranes. Which type of animal has to worry about this the most?
* Temperature conformers
* Temperature regulators
* Both
* Neither
TEMPERATURE CONFORMERS
temp. conformers must worry because the temperature will affect the fluidity of their cell (as external temp. changes, the internal temp, changes, changing fluidity) and this will affect their physiology and behavior
temp. regulators do not need to worry because their body regulates their temperature to remain constant thus fluidity remains constant
Ex. Temperature Conformers Fluidity
COLD TEMP.:
- risk of cells being too stiff
- their phospholipids have more double bonds to increase fluidity, to ensure the proper fluidity of membrane/cells
TROPICAL TEMP.:
- risk too much fluidity
- their phospholipids have less double bonds to decrease fluidity, to ensure the proper fluidity of membrane/cells
the colder the climate the more double bonds, and warmer less
Integral Proteins
(cell membrane proteins)
- are embedded in the phospholipid bilayer
- signal, responds to external ques
ex. transporter and channel
Peripheral proteins
(cell membrane proteins)
- are non-covalently bonded to integral proteins or lipids but are not within the bilayer
- some peripheral proteins help anchor the cell membrane to filaments of the cytoskeleton
- do not span membrane
- ex. G-protein, respond to g-receptor
Types of cell membrane proteins
- Channel
- Transporter (carrier)
- Enzyme
- Receptor
- Structural protein
Channel Proteins
(cell membrane protein)
DIFFUSION & OSMOSIS, PASSIVE MOVEMENT
- permits simple diffusion of solutes in aqueous solutions or osmosis of water through a membrane
- typically always open, may have certain ways to block opening
Transporter Protein
(cell membrane protein)
(carrier protein)
BINDS MOLECULES ON ONE SIDE OF MEMBRANE, FLIPS/TRANSFORMS AND MOVES MOLECULE TO OTHER SIDE
- bind non-covalently and reversible with specific molecules or ions to move them across a membrane intact
Active transport and facilitated diffusion
Active Transport
Transport through the membrane requires metabolic energy
- normally ATP
- typically against the concentration gradient
Facilitated Diffusion
Transport through the membrane does not require metabolic energy
- works with concentration gradient
Enzyme
(cell membrane protein)
Catalyzes a chemical reaction in which covalent bonds are made or broken
- chem rxn, can receive direct or indirect ques
Receptor
(cell membrane protein)
Binds non-covalently with specific molecules and, because of this bind, initiates a change in membrane permeability or cell metabolism
- mediate the response of a cell to chemical messages (signals) arriving at the outside face of the cell membrane
- usually phosphorylation vent (energy consumed, and produced in some ay) induces and changes in the cell
Structural Protein
(cell membrane transport)
Attaches to other molecules (ex. other proteins) to anchor intracellular elements (ex. cytoskeleton filaments) to the cell membrane
- creates junctions between adjacent cells, or established other structural relations
- provides stabilization, structure to tissues
Membrane Transport
Transport could be across cell membrane, tissue layer, organ membrane
- there are different membrane layers
A. Intracellular and extracellular molecules vary
a) take into account concentration
b) take into account charge
B. Water, epithelial wall, blood
a) takes advantage of salt differences to breath/perspire - ultimately take on oxygen
C. Intestine
a) glucose moves through epithelial cells before moving into bloodstream, have different concentrations, may require active transport
Molecules Moving Across Membranes
(4 types)
- membranes are barriers to movement of water soluble molecules
- the hydrophobicity of liid bilayers is a barrier to movement of hydrated ions across cell membrane
a) small uncharged molecules - move through with relative ease
b) Lipid-soluble substances - able to pass through relatively easy (ex. hormones)
c) Water soluble substances - transport due to hydrophilic, require protein, large molecules - too large, require protein
d) ions - carry a charge, require transport/protein
Lipid soluble molecules through membranes
Cross membranes by diffusion
- diffusion through random movements until finds way through membrane
Hydrophilic flow across membranes
HYDROPHILIC NEED TO CROSS HYDROPHOBIC
Hydrophilic molecules must be transported by:
- Facilitated diffusion
- no energy
- need channel to get through - Active Transport
- energy consumed to move against the concentration gradient
Facilitated Diffusion Channels
- Voltage-gated channel
- Phosphorylation-gated channel
- Stretch-gated (tension-gated channel)
- Ligand-gated channel
Voltage-gated channel
(facilitated diffusion channels)
OPEN WITH CHANGE OF MEMBRANE POTENTIAL
- use polarity of cell (difference ion concentrations across membrane - cell usually more negative at membrane)
- ex. inside of cell becomes more positive
- resting state - closed
Phosphorylation-gated channel
(facilitated diffusion channel)
BINDING OF PHOSPHATE CHANGES THE BEHAVIOR OF DIFFERENT PROTEINS
- changes channels chemical structure, thus its shape
Stretch-gated channel
(facilitated diffusion channel)
(tension-gated channel)
- channel is attached to cytoskeleton of cell
- cell stretches
- cytoskeleton becomes taught
- channels open
Ligand-gated channel
(facilitated diffusion channel)
Opens in response to binding of chemical messenger
- extracellular signal makes contact with channel
- ligand binds to receptor site on channel
Intro to Membrane Potentials
All living cells have a MEMBRANE POTENTIAL
- voltage differences between the inside/outside of cell (cell usually more negative)
- exists because concentrations of ions differ
- voltage is relative to outside of cell
Membrane potential is a source of potential energy fro cells to use to move molecules across membranes
Excitable cells (neurones, muscle cells, etc.) use electrical signals for communication
Cells move down electrochemical gradient
- charge and concentration play factors
Cross-membrane attraction & Bulk Solution
CROSS MEMBRANE ATTRACTION
The membrane is small enough that net positive and negative charges can sense and be attracted to polar charges across the membrane
- opposite charges align on opposite sides of membrane
- cell membrane can maintain separation of oppositely charged ions
- what gives cell negative charge compared to extracellular at membrane
BULK SOLUTION
Farther away from membrane, positive and negative ions are mixed at random
- the net charge in any given region of bulk solution is zero
Is the gradient electrical or chemical or both?
- [Na+] is higher outside the cell
- positive charge is higher outside of the cell
- thus, there is an electrical and chemical gradient
3 Scenarios with various chemical and electrical forces:
(0/0)
(+/-)
(-/+)
(+/-)
- what drives movement of molecules outside to inside
ex. * concentration of positive moleculles is always higher outside, electrical gradient changes
- Electrochemical gradient with no membrane potential (0/0)
- moving down concentration gradient - diffusion - Electrochemical gradient with membrane potential negative inside (+/-)
- all cells have negative charge - positive ions move because of concentration AND electrical gradients both wanting to move down
- results in movement into cell faster/more readily - Electrochemical gradient with membrane potential positive inside (-/+)
- cell becomes more positive relative to others
- wants to move down its concentration gradient into the cell but the electrochemical gradient repels the charges, thus the movement in is reduced
Directions of Gradients
an electrical gradient may move an ion in the same direction as is favoured by the concentration gradients, thereby promoting a high rate of diffusion
an electrical gradient may oppose diffusion on the direction favoured by the concentration gradient, thereby slowing diffusion or even reversing its reaction
- counteractive force affecting how it moves
Concentration Gradients Give Rise to Electrical Gradients
- If no permeability
- If permeability to K+
- If permeability to Na+
UNIVERSAL PRINCIPLE - molecules move DOWN their concentration gradient
- If no permeability to any ion –> concentrations do not change
Many membranes are selectively permeanve
- If permeability to K+
–> K+ moves down concentration gradient and leaves cell
–> a net loss of a + charge and the inside of the cell becomes more negative - If permeability to Na+
–> Na+ moves down concentration gradient and enters the cell
–> a net gain of + charge, and the inside of the cell becomes more +
SIMPLY:
K+ moving down concentration gradient, makes cell more negative
Na+ moving down concentration gradient, makes cell less negative
What keeps the interior of the cell negative?
Intracellular K+ > Extracellular K+
Intracellular Na+ < Extracellular Na+
Na+ and K+ concentrations ^ is maintained by Na+/K+ ATPase:
- moves against their concentration gradients - requires ATP
- maintains homeostasis of the cell, overall negative change
The purpose of moving K+ into the cell and Na+ out of the cell against their concentration gradients is to MAINTAIN OVERALL NEGATIVE CHAGRE OF CELL
Pump sends 2 K+ in, and 3 Na+ out: NET CHARGE -1 in cell
MAINTAINS OVERALL NEGATIVE MEMBRANE POTENTIAL
Ligand
An extracellular signalling molecule that binds specifically to a receptor protein
- signals to cell to induce a reaction
extracellular signals initiate their effects by binding to receptors
Receptor Types
- Ligand-gated channel
- G protein-coupled receptor
- Enzyme/enzyme-linked
- Intracellular
- typically seen with steroid hormones (signal molecule can move through membrane)
1-3 are in the cell membrane
Ligand-gated Channel
- in cell membrane
- acts as receptor and channel
- passageway typically for inorganic ions
- ligand has to bind to the receptor in the extracellular space for the channel to open
- Function primarily in transmission of nerve impulses
ex. acetylcholine is ligand at synapses
Ligand-gated channels and poisons
many poisons are receptor antagonists
- alpha-conotoxin from the cone snail
- binds to muscle acetylcholine receptor
- prevents receptors from binding to acetylcholine = paralysis, muscle can’t retract
- normal - neuron communicates to muscle by the released of acetylcholine which binds to receptor channel, resulting in change of membrane voltage
G protein-couple receptor
Steps:
1. Ligand binds to G protein-coupled receptor
2. Receptor activates G protein
3. G-protein activates another protein
(usually has kinase activity, or activates further downstream)
4. G protein has intracellular effects or more commonly interacts with another membrane protein
ex. epinephrine/adrenaline
ex. activates protein that has catalytic activity that induces the production of a second messenger (ex. cAMP from ATP)
Enzyme-linked Receptors
Simple Steps:
1. Bind with the ligand
2. Activates catalytic site on the same membrane
3. Results in internal
ex. activation of the catalytic site inside the cell causes production of the second messenger (cGMP from GTP)
ex. insulin
Intracellular Receptor
- receptor in cytoplasm or nucleus
- ligands must be small and hydrophobic as it diffuses through cell membrane, and at times nuclear envelope (typically hormones)
- finds intracellular receptor and activates it
- usually interact with DNA response elements which may then regulate other genes, (transcription factors/cofactors)
- move into nucleus and cause downstream effects in gene
ex. steroid hormones
Amplification by Signal Transduction Pathways
- each step within pathway activates a cascade of reactions
- why see proteins so fast
- activates plural of the next protein
- A activates Bs, Bs actives Cs (proteins)