the smaller the cell, the greater the SA:V ratio, allowing substances to diffuse into and out of the cell more efficiently
how organisms increase SA:V ratio:
fish- gills to increase oxygen intake
elephants- elephant ears to increase heat diffusion (get heat OUT of body)
mitochondria- cristae, inner folds to produce more energy at a faster rate
intestines- villi on the outside to absorb nutrients in the small intestine
why are marine mammals so huge in terms of SA:V ratio:
marine mammals are warm-blooded
ocean water is cold
increased size decreases SA:V ratio, therefore causing LESS HEAT lost to environment (good)
compartmentalization in prokaryotic vs. eukaryotic cells:
prokaryotic: few compartments
eukaryotic: many compartments that divide lysosomes, the ER, the golgi complex, and vacuoles
endomembrane system organelles:
nuclear membrane
rough ER
smooth ER
golgi
lysosomes
vesicles
DOES NOT include:
mitochondria
chloroplasts
peroxisomes
endosymbiotic theory:
eukaryotic cells arose from a prokaryote engulfing another prokaryote cell
endosymbiotic theory evidence:
have their own circular DNA
replicate themselves through binaryfission
use their own ribosomes to produce their own proteins (go through transcription and translation)
have 2 membranes (outer one is a vestige of an endocytotic vesicle)
nucleus: stores and protects genetic information/DNA
DNA is wrapped around histone proteins to form chromosomes
chromatin are the spread out version of DNA
nucleolus: assembles ribosomes
nuclear membrane: separates chromosomes from cytoplasm
nuclear pores: allow molecules to enter/leave nucleus
ribosomes: particles composed of ribosomalRNA and protein
functions:
read a genetic message encoded in a sequence of mRNA
translate that message into a sequence of amino acids that make up the primary structure of a protein
free ribosomes float in the cytoplasm
bound ribosomes are connected to the rough ER
all ribosomes start out as free, but through protein targeting, they migrate to the ER to become bound and get transported to the lysosome, golgi, or membrane
mitochondria: converts food energy into ATP
key structures:
chromosome/DNA (also ribosomes)
inner membrane: highly folded (increases SA), has membrane-embedded enzymes and proteins that make ATP
matrix (cytoplasm): enzymes for the krebs cycle
intermembrane space: electron transport chain
outermembrane space: vestige of endosymbiosis
ER: an interconnected series of channels found between the nuclear membrane and golgi body in eukaryotic cells
the liver contains LOTS of smooth ER because it is responsible for alcoholdetoxification
golgi complex: series of membrane-bound flattened sacs (flattening increases SA)
receives vesicles through the cis face from the rough and smooth ER, and chemically modifies the contents (usually proteins)
packages modified proteins into vesicles that are sent out through the trans face to lysosomes, the cell membrane, or exported from the cell
lysosomes: membrane-bound organelles that contain hydrolytic enzymes
only found in animal cells
carry out intracellular digestion
recycle damaged, worn-out, or excess organelles and molecules
play a key role in apoptosis (programmed cell death)
cytoskeleton: dynamic network of protein fibers
enables cells to move materials and organelles
enables cells to move their membranes (endocytosis, amoeboid movement)
microfilaments: made of protein actin, muscle contraction, helps form cleavage furrow during animal cell division
intermediate filaments: made of protein keratin, reinforcement of shape and position of organelles in cell
microtubules: made of protein tubulin, assist in the separation of chromosomes during cell division, important components of cilia and flagella (structures that aid the movement of particles)
centrosome: the organelle (with 2 centrioles)
function:
creating spindle fibers for separating chromosomes during mitosis and meiosis
central vacuole: only in PLANT cells
functions as water storage
storing and releasing needed macromolecules
isolating waste products
maintaining turgor pressure
plant cell wall: composed primarily of cellulose (polysaccharide)
major function:
pressure vessel that prevents over-expansion in response to inward water flow (osmotic pressure, the minimum amount of pressure needed to stop a solution from allowing pure solvent to flow through a semipermeable membrane)
primary component of wood and water-conducting tubes in plant stems
phospholipid structure (amphiphatic):
hydrophobic/nonpolar tail
hydrophilic/polar head
held together by glycerol
hydrophobic tails face inward toward nonpolar environments
hydrophilic heads face outward toward polar environments
stabilized by weak bonds (van der waal bonds) between the tails
fluid mosaic model:
fluid because components are moving laterally within the plane of the phospholipid bilayer
mosaic because it is composed of a variety of pieces such as proteins, cholesterol, and carbs (glycoproteins and glycolipids)
diffusion: the movement of molecules from an area of high concentration to an area of low concentration
happens spontaneously (relies on the KINETIC energy in the diffusing molecules)
molecules flow DOWN their concentrationgradients
two forms of passive transport:
simple diffusion: small nonpolar molecules like CO2, N2, and O2
steroid hormones and fats
facilitated diffusion: polar molecules and ions can't diffuse across a phospholipid bilayer
requires protein channels: transmembrane proteins that only let specific molecules or ions pass
active transport:
pumping a molecule or ion up its concentration gradient
lower concentration to higher concentration
requires energy on the part of the cell (usually ATP to ADP to power the pumping process, but also the electron flow)
bulk transport:
endocytosis: cells taking in substances from the outside by engulfing them in a vesicle derived from the membrane
exocytosis: cells dump the contents of vesicles (waste products) outside of the cell
both require ENERGY and the involvement of the cytoskeleton
membrane potential: an electrical charge across a membrane that creates voltage differences
is created by pumping ions across their membranes
ex. chloroplasts and mitochondria create electrochemical gradients that generate ATP (creates the -70 mV charge across nerve cell membranes)
osmosis: diffusion of WATER from low to high solute concentration (from hypotonic to hypertonic)
hypotonic: higher percentage of water, less solute
hypertonic: lower percentage water, more solute
osmosis in plants:
in hypertonic solutions: water leaves the cell, loses turgor pressure (pressure exerted by fluid in cell that presses the cell membrane against the cell wall), membrane peels away from wall (plasmolysis), vacuole shrinks, plant wilts
in hypotonic solutions: water flows into the cell, turgor pressure increases, vacuole expands
osmosis in animal cells:
in hypertonic solutions: water leaves the cell, cell shrinks
in hypotonic solutions: water flows into the cell, cell bursts
plant cells can survive hypotonic and isotonic solutions, while animal cells can only survive isotonic solutions
structure of leaf stomata:
stomata (plural) are pores on the underside of leaves
each stoma (singular) is formed by 2 guardcells
with sufficient water, they buckle outward, creating a pore that allows CO2 to enter the leaf for photosynthesis, but which also allows water vapor to escape
stomata can close in response to environmental cues such as waterstress
water potential: a measurement of water's tendency to move from one place to another
adding solute decreases water potential
pressure increases water potential
water flows from areas of higher to lower water potential
hypotonic = high water potential
formula for water potential:
water potential = solute potential (adding solute to water DECREASES water potential) + pressure potential (adding pressure INCREASES water potential
water moves from HIGH water potential to LOW water potential (hypotonic to hypertonic)
cholesterol, a type of lipid that is embedded in the membrane, helps minimize the effects of temperature on fluidity
at low temperatures, it increases fluidity
at high temperatures, it decreases fluidity
phagocytosis: form of endocytosis in which large particles are transported INTO the cell
used by a macrophage to engulf a pathogen
the food vacuole will later fuse with the lysosome to break that engulfed particle down to its basic components
pinocytosis: form of endocytosis in which the cell takes in small amounts of extracellular fluid
receptor-mediated endocytosis: form of endocytosis in which receptor proteins are used to capture a specific target molecule that comes in low concentrations
flu viruses, diphtheria, and cholera toxin all use this type of endocytosis
Suppose a certain type of molecule were to be removed from the blood by receptor-mediated endocytosis. What would happen if the receptor protein for that molecule were missing or defective?
The target molecule would no longer be pulled out of the blood, so it might start building up to abnormally high levels. In fact, this is exactly what happens in the disease known as familial hypercholesterolemia
peroxisomes: houses enzymes involved in oxidation reactions, which produce hydrogen peroxide (H2O2) as a by-product
DOES NOT receive vesicles from the golgi
chloroplasts: thylakoids are in stacks called grana (singular = granum)
photosynthesis location
glycoprotein: protein with carb attached
glycolipid: lipid with carb attached
integral membrane proteins: at least one hydrophobic region that anchors them to the core of the phospholipid bilayer
transmembrane proteins: extends all the way across the membrane