(Lectures 1-3) Intro Flashcards
Physiology
Study of an organism’s functions
Levels of organization in the body (6)
Chemical < Cellular < Tissue < Organ < System < Organismal
Components of chemical level
Atoms, molecules
Examples of elements essential to maintaining life
Carbon, hydrogen, oxygen, nitrogen, phosphorus, calcium, sulfur
Def. of cell
- Basic structural/functional units of an organism
- Smallest unit capable of supporting life
6 life processes
- Metabolism
- Reproduction
- Differentiation
- Growth
- Movement
- Responsiveness
Metabolism
Sum of all reactions in the body; catabolism (breakdown) + anabolism (synthesis)
Responsiveness
Body’s ability to detect and respond to internal/external environmental changes
Movement
Motion of the body, organs, cells, and intercellular structures
Growth
Increase in body size due to
- An increase in the number of cells
- An increase in the size of existing cells
- An increase in material between cells
Differentiation
Development of a cell from an unspecialized to a specialized state
Reproduction
Formation of new cells for tissue growth/repair/replacement, or the production of a new individual
What is homeostasis?
The maintenance of relatively stable conditions in the body’s internal environment despite changes to the external environment
It’s dynamic, and maintained by the processes that control and regulate the body.
T/F: Homeostasis in the body is only maintained at the cellular level
False; it’s maintained at all levels
Compartmentalization
- Body is divided into compartments that contain fluids and are separated by semipermeable membranes
- Transport occurs between the compartments
- Exchange between internal/external environments helps maintain homeostasis
Feedback Loop
A cycle of events where a parameter of the internal environment is repeatedly monitored, evaluated, and changed
Feedforward
Mechanism used by our bodies in anticipation of a change in a controlled variable (e.g. mouth watering in anticipation of food)
T/F: homeostasis is fixed at a certain point
False
Homeostatic set point
Value around which the normal range of a variable fluctuates; serves as an error-sensing function
T/F: there are always minor adjustments being made to maintain a normal operating range
True
Negative feedback
Reverses a change in a controlled variable
Positive feedback
Strengthen/reinforce a change in a controlled variable
Stimulus
Disrupts homeostasis by either increasing or decreasing a controlled variable
Receptors
Sense changes to controlled variables and send input (action potentials) to the control center
Control center
- Determines the set point
- Evaluates input from receptors
- Generates output when necessary
Effectors
Receive output from the control center, produce a response that changes the controlled variable
3 main components of a cell
- Plasma membrane (outer surface)
- Cytoplasm (cellular contents between membrane and nucleus)
- Nucleus (contains most of the cell’s DNA)
Structure of the plasma membrane
- Lipid bilayer; polar/hydrophilic heads face the ECF and cytosol, with the nonpolar/hydrophobic tails between them
- Contains phospholipids, cholesterol, glycolipids
Peripheral proteins
Found on the surface of the membrane (either internal or external)
Integral proteins
Found within the lipid bilayer; known as transmembrane proteins if they span the lipid bilayer
Functions of membrane proteins
- Anchoring proteins
- Recognition proteins
- Enzymes
- Receptor proteins
- Carrier proteins
- Channels
What is the cytosol?
Cytoplasm - organelles
- Site of many chemical reactions
- Mostly water w/many dissolved particles (ions, glucose, amino acids, etc.)
What are organelles?
Specialized structures in the cell with specific functions
Ribosomes
- Site of protein synthesis
- High rRNA content
- Each one includes ~80 proteins
Endoplasmic Reticulum
Network of membranes; flattened sacs, tubules
- Rough ER has ribosomes
- Smooth ER extends from rough ER; site of lipid synthesis, does not have ribosomes
Mitochondria
Powerhouse of the cell! Make ATP
Cytoskeleton - what are the 3 types?
Network of protein filaments that extends through the cytosol
- Microfilaments (thinnest)
- Intermediate filaments
- Microtubules (thickest)
Microfilaments
- Made of actin
- Mostly found at the edge of the cell
- Help generate movement
- Provide mechanical support
- Form microvilli
Intermediate Filaments
- Found where cells experience stress
- Help position organelles
- Attach cells to each other
Microtubules
- Hollow tubes, consist mostly of tubulin
- Determine cell shape
- Move organelles
- Found in cilia, flagella
4 primary types of tissue
- Nervous
- Epithelial
- Connective
- Muscle
Neural Tissue
- Detects/responds to changes in the body’s external and internal environment
- Consists of neurons and neuroglia
Muscle Tissue
- Convert electrical signals into mechanical force; contract to generate movement
- Can be voluntary or involuntary
Epithelial Tissue
- Covers body surfaces, lines internal body surfaces/cavities
- Forms glands
- Main function is as a protective barrier
Connective Tissue
- Binds tissue together
- Supports/strengthens
- Protects/insulates internal organs
- Major transport system in the body
Cell Junctions
Specialized components in the plasma membrane that hold cells together and help form tissues.
Tight Junctions
- Web-like strands of transmembrane proteins that connect the outer surfaces of adjacent plasma membranes.
- Prevent substances from passing between cells
Desmosomes
- Form filament-like junctions between cells
- Bind cells together, providing additional strength (important where cells are under high mechanical stress!)
- Contain the transmembrane protein cadherin
Gap Junctions
- Form tunnels between cells so they can exchange materials (cytosol, ions, etc.); i.e. directly communicate with each other
Hemidesmosomes
- Anchor cells to the basement membrane
- Contain the transmembrane protein integrin
Adherens Junctions
- Help epithelial surfaces resist separation during contractile movements
- Contain plaque that attaches to membrane proteins and microfilaments
- Encircle a cell, forming zones called adhesion belts
What substances can pass through the plasma membrane?
- Nonpolar molecules
- Small, uncharged polar molecules
What substances can’t passively move through the plasma membrane?
- Ions
- Large, uncharged polar molecules
What features of the membrane affect permeability?
- Transmembrane proteins (carriers, channels)
- Lipids (form vesicles)
- Cholesterol (can make membrane impermeable)
What is a concentration gradient?
The different in concentration between two areas (e.g. either side of a plasma membrane)
What is an electrical gradient?
The difference in electrical charge between two areas (e.g. either side of a plasma membrane - created by ions)
What is an electrochemical gradient?
Electrical gradient + concentration gradient
Passive Transport
Substances move down their concentration/chemical gradient without the expenditure of energy
Active Transport
Substances move against their concentration; energy is required
What process is linked to other reactions so they can easily use the energy it releases?
ATP hydrolysis
Factors that affect diffusion
- Steepness of concentration gradient
- Temperature
- Mass of diffusing particle
- Surface area
- Diffusion distance
Simple diffusion
Movement of substances directly through the plasma membrane
Facilitated diffusion
Movement of substances through carriers/channels down their concentration gradient
T/F: Channels (for facilitated diffusion) are not ion-specific
False
Which two ion channels are more common in plasma membranes?
K+ and Cl-
Between simple and facilitated diffusion, which is faster?
Simple diffusion
Channel-mediated facilitated diffusion
Solutes move down their concentration/electrochemical gradient through a membrane channel
Carrier-mediated facilitated diffusion
Solutes move down their concentration/electrochemical gradient by binding to a carrier protein. A change in the protein’s shape allows the solute to enter or exit the cell.
Osmosis
Net movement of a solvent through a selectively permeable membrane.
Occurs by simple diffusion and through aquaporins (channels)
Hydrostatic Pressure
Pressure exerted by a liquid
Osmotic Pressure
The amount of pressure needed to completely stop the osmotic movement of water
Osmolarity
Measure of the total number of dissolved particles per litre of solution
If HCl and estrogen were each placed in water, which solution would have a higher osmolarity?
HCl, because it would dissolve into H+ and Cl- ions. Estrogen does not dissolve.
Tonicity
Effect of osmolarity on cell shape; affects cell volume, which then affects shape
3 levels (?) of tonicity and effect on a cell
Isotonic: equal concentrations of nonpenetrating solutes on either side of a membrane, cell is unaffected
Hypertonic: higher concentration of nonpenetrating solutes outside a membrane, net decrease in solvent entering cell
Hypotonic: higher concentration of nonpenetrating solutes inside a membrane, net increase in solvent entering cell
Primary vs. Secondary Active Transport
Primary: uses energy from hydrolysis of ATP to change the shape of a pump
Secondary: uses energy from an ion’s electrochemical gradient to transport other solutes via a pump
Symport vs Antiport
Symport: secondary active transport where both solutes move in the same direction
Antiport: secondary active transport where both solutes move in different directions
Vesicular Transport
Lipids form vesicles, which engulf solutes to move them across the plasma membrane.
Exocytosis
Vesicles move substances out of the cell
Endocytosis
Vesicles bring substances into the cell.
Receptor-Mediated Endocytosis
Ligand binds to a receptor on the plasma membrane, and a vesicle forms to bring the ligand into the cell
Phagocytosis
Cells engulf large solids (e.g. worn-out cells, bacteria, viruses); protects body from disease
Pinocytosis
Cells intake small droplets of ECF; no receptors involved!
Peroxisomes
- Similar structure to lysosomes
- Contain enzymes that use molecular oxygen to oxidize organic compounds and produce H2O2
- Abundant in liver cells
