unit two Flashcards
prokaryotes
NO nucleus DNA in a nucleoid cytosol no organelles other than ribosomes small size primitive Bacteria and Archaea
Eukaryotes
Has nucleus and nuclear envelope cytosol membrane bound organelles much larger in size Plant and animal size
cells must be small to maintain a large…
surface area to volume ratio
ex) small intestine is highly folded to increase absorption of nutrients
ex) root hairs expansion of root epidermal cells; increase surface area for water and mineral absorption
Nucleus
control center of the cell
contains DNA and is surrounded by nuclear envelope
nuclear pores control what enters and leaves
chromatin: complex of DNA and proteins. make up chromosomes
nucleolus: region where ribosomal subunits form
Ribosomes
protein synthesis/creation
made of rRNA and protein
large subunit and small subunits
free: float in cytosol and produce cell used proteins
bound: attached to ER make proteins for export
Endomembrane System
regulates protein traffic and performs metabolic functions
ER: network of membranes and sacs
rough has ribosomes on surface
smooth packages proteins for secretion, send transport to Golgi and make replacement
synthesize lipids, metabolize carbs detox drugs and poison and store Ca
Golgi Apparatus
series of flattened membrane sacs (cisternal)
synthesis and packaging of materials (small molecules) for transport in vesicles protein to produce lysosome
cis face- receives vesicles
trans face- ships vesicles
lysosomes
intracelular digestión that recycle cells materials. programmed cell death
contains hydrolytic enzymes
vacuoles
storage of materials (food, water, minerals, pigments, poison)
membrane bound vesicle
plants have large and central vacuoles
mitochondria
site of cellular respiration
double membrane: outer and inner
cristae- folds of inner membrane; contains enzymes for ATP production; increased SA to increase ATP
matrix: fluid filled inner compartment
chloroplasts
site of photosynthesis
double membrane
thylakoid disks in stacks (grams) stroma (fluid)
contains chlorophyll (pigments) for capturing
endosymbiont theory
mitochondria and chloroplasts share similar origin
eukaryotes engulfed prokaryotes .
evidence: double membrane, own ribosomes and DNA and reproduce independently
peroxisomes
breaks down fatty acid; detox alcohol
involves production of hydrogen peroxide
cytoskeleton
network of protein fibers
support, mobility regulate biochemical activities
extracellular matrix
outside plasma membrane
composed of glycoproteins (ex. collagen)
strengthens tissues and transmits external signals to cell
intercellular junctions (animal cells)
tight junctions- 2 cells are fused to form watertight seal
desmosomes- rivets that fasten into strong sheets
gap sheets- channels through which ions, sugar, small molecules can pass
plant cells organelles
cell wall- protect plant, maintain shape
composed of cellulose
plasmodesmata- channels between cells that let molecules pass
cell membrane-
selective permeability
fluid mosaic model (membrane of phospholipids and proteins and carbs held together by weak interactions)
phospholipids
amphipathis- hydrophilic phosphate head and hydrophobic fatty acid tails
hydrophobic barrier keeps hydrophilic molecules out
membrane fluidity
low temps: phospholipids with unsaturated tails (kinks prevent close packaging)
cholesterol- limits fluidity at high temps, also hinder close packing at low temps
integral proteins
embedded in membrane
determined by freeze fracture
transmembrane with hydrophilic heads and hydrophobic middles
peripheral proteins
extracellular or cytoplasmic sides of membrane
NOT embedded
held in place by cytoskeleton or ECM
provides storage framework
passive transport
no ATP needed
diffuses DOWN the concentration gradient
E.g. hydrocarbons, CO2, O2, H2O
osmosis
lower solute concentration to higher concentration
osmoregulation- control of water balance
Hypertonic- higher concentration of solutes
Hypotonic- higher concentration of solvent
Isotonic- equal concentration of solute/solvent
facilitated diffusion
transport proteins help hydrophilic substances cross
aquaporin: channel proteins for water
active transport
requires energy (ATP)
proteins transport substances against concentration gradient
E.g. Na/K pump, proton pump
cotransport
memrane protein enables “downhill” diffusion of one solute to drive “uphill” diffusion of another
bulk transport
endocytosis: large molecules in
- form new vesicles
exocytosis: large molecules out
- vesicles fuse with cell membrane and expel contents
phagocytosis: cell eating solids
pinocytosis: cellular drinking fluids
receptor mediated endocytosis: ligands bind to specific receptors on cell surface
