Study Terms Exam 1 Flashcards
Homeostasis
-maintenance of relatively stable internal conditions despite continuous changes in environment
-a dynamic state of equilibrium (conditions vary, but within limits)
Positive feedback
-not as common (usually controls infrequent events that do not require continuous adjustment)
-response enhances original stimulus= amplifying effect
-ex: enhancement of labor contractions by oxytocin
Negative feedback
-most common feedback mechanism
-response reduces original stimulus
-ex: regulation of body temperature
Macromolecules
-larger molecules built out of individual units called monomers
-includes; lipids, carbohydrates, nucleic acids, and proteins
Lipids
-built from fatty acids
-functions:
–energy storage
–signaling (steroid hormones)
–building cell membrane (phospholipids)
Cell membrane
-built primarily from phospholipids (bilayer and amphipathic)
-selectively permeable (what can and cannot pass through)
-fluid (fluid mosaic model)
Phospholipids
have a hydrophobic tail and hydrophilic head group
Cytoplasm
-~70-80% water
-dissolved and suspended chemicals
-ions
Potential energy
-energy stored in position or configuration
-includes energy in chemical bonds
Kinetic energy
-energy of motion
-includes sound, thermal energy, electricity, electromagnetic radiation
Cellular respiration
-occurs in mitochondria-begins in cytoplasm
-starts with 1 molecule of glucose
-undergoes 4 step process: glycolysis, pyruvate processing, Krebs cycle, electron transport/ chemiosmosis
-requires oxygen
-produces ~30 ATP/glucose, also CO2 and H2O
ATP
-adenosine triphosphate
-stores potential energy
–phosphate groups are negatively charged, covalent bond linking them carries potential energy due to the strong repulsive forces
Passive transport
-AKA diffusion
-down a concentration gradient ([high]->[low])
-does not require cellular energy
-may or may not use membrane proteins
Active transport
-up a concentration gradient ([low]->[high])
-requires cellular energy (ATP)
-uses membrane proteins
Concentration Gradient
-Down a concentration gradient: high to low
-up a concentration gradient: low to high
Diffusion
-the passive movement of molecules (no energy)
-molecules move from areas of high concentration to areas of low concentration
Simple Diffusion
-movement through intermolecular spaces or membrane openings (between phospholipids)
-no interactions with carrier proteins
-molecules must be lipid soluble
ex: O2, nitrogen, CO2, and alcohols
Facilitated diffusion
-interaction with carrier proteins
-movement through tubular proteins that span entire membrane
-selective: size and electrical charges
-may be gated
-carrier protein changes shape during transport + specific
ex: aquaporins: allow passage of water through cell membranes
transport of amino acids and glucose
Protein channel
selective on size and electrical charges; can be voltage gated or chemical(ligand)-gated
gated channel
-Voltage gated: open/close in response to changes in electrical potential across cell membrane (ex Na+ and K+ channels)
-Chemical (ligand)-gated: open/close in response to binding of chemical (ex. acetylcholine channel)
osmosis
-diffusion of water through a semipermeable membrane
-uses aquaporins (channels)
-travels down concentration gradient
-H2O moves from where it is in high concentration to where it is low in concentration
-net movement of water caused by a concentration difference of water
solvent
a fluid substances dissolve in
ex: water
solute
a substance dissolved in a solvent
ex: salts, sugars
isotonic
-solution and cell have same solute concentration
-no net movement of water
hypotonic
-solution has lower solute concentration than inside the cell
-water moves into the cell
-leads to swelling and bursting (lysis)
hypertonic
-solution has greater solute concentration than inside the cell
-water moves out of the cell
-cell shrivels and becomes crenate
osmotic pressure
-the pressure needed to counter osmosis
-the more solutes inside a cell, the higher its osmotic pressure
-water wants to move down its concentration gradient towards the hypertonic solution
-sucks
hydrostatic pressure
-pressure exerted by water against the plasma membrane
-due to fluid pressing against boundary
-HP pushed fluid across the boundary
-in blood vessels, due to blood pressure
primary active transport
-carrier protein uses ATP directly to move molecules against their concentration gradient
sodium-potassium pump
-located in plasma membrane
-1 ATP powers pump to transport:
3 Na+ ions out of the cell
2 K+ ions into the cell
both against their concentration gradient
-establishes negative electrical voltage inside cell
-regulates volume of cell
–activated by increase in cell volume
secondary active transport
-uses the energy of one molecule (driver) moving down its concentration gradient to power movement of another molecule up its concentration gradient
-ATP used indirectly to create concentration gradient of “driver”
symporter
transport substance in same direction as driver
antiporter
transport substance in the opposite direction as driver
vesicular trafficking
transport from one area or organelle in cell to another
endocytosis
transport into cell:
Phagocytosis: cell eating, pseudopods form and flow around solid particles, forms a vesicle which is pulled into cell
Pinocytosis: cell drinking or fluid phase endocytosis, brings in extracellular fluid and dissolved solutes, fuses with endosome
exocytosis
transport out of cell
-substance being ejected is enclosed in secretory vesicle
-commonly exocytosed substances: hormones, neurotransmitters, mucus, cellular wastes
Membrane potential
the voltage across the plasma membrane
-voltage (electrical potential) is the difference in electrical charge between two points
-exists in nearly all cells
neuron
(nerve cells); excitable cells that conduct electrical signals
-extreme longevity
-no mitosis, with free exceptions
-high metabolic rate (requires continuous supply of oxygen and glucose
-all have similar structure
polarized
producing positive electrical charge and a negative electrical charge
graded potential
short-lived, localized changes in membrane potential
-can be depolarizations or hyperpolarizations
-triggered by a change that opens gated ion channels
(chemical signals binding to receptors, changes in charge across memrbane)
-spread as opposite charges attract each other
-magnitude declines with distance
depolarization
potential difference becomes smaller
hyper polarization
potential difference becomes greater
action potential
graded potentials are generated in the dendrites and cell body of a neuron, they can trigger action potentials
-rapid changes in membrane potential
responsible for transmission of nerve signals and do not decay over distance
repolarization
where negative membrane potential begins to be restored
propagation
AP transmitted from origin down entire axon length
occurs in one direction
refractory period
time in which neuron cannot trigger another AP
absolute refractory period
time from opening Na+ channels until resetting of the channels
Purpose:
-ensures that AP is an all-or-none event
-enforces one-way transmission of nerve impulses
relative refractory period
most Na+ channels in resting rate, some K+ channels still open
-repolarization is occurring
-threshold for AP generation is elevated
myelinated
Schwann cells wrap around axon in paper towel roll fashion
continuous conduction
in nonmyelinated axons
slow
saltatory conduction
in myelinated axons
30x faster than continuous conduction
jump gap to gap
intensity
all action potentials are alike in magnitude, regardless of stimulus intensity
magnitude
declines with distance (graded potential)
current is lost due to leakage channels
frequency
number APs received per second
