Bio 151 Chapter 7

proteins alter membrane structures and functions

phosphipids provide basic memebrane structure

plasma membranes contzin as much proteins as phospholipids (by weight)

proteins in membranes are amphathic

side chain are polar, charged or polar

secondary and tertiary structures allow proteins to form opening and functional as passagways across lipid bilayers

transmembrane proteins

proteins that span memebrane

have segments faciung with interior and exterior surfaces

peropheral membrane proteins

bind to membrane kipids without passing through it

may be dound in exterior or interior

ion channels

specialized meembrane protiens

form pores, or opening in membranes

allows ions to cross memebranes

electrochemical gradients

occur when ions build up on 1 side of plasma memebrane

establiush both concentration reaction and charge gradient

ions diffuse down their electrochemical gradients

channel proteins

pore-like

selective

residues facing inside pores are hydrophilic

each channel protein permits only particular types of ions or small molecules to pass through it

aquaporins

permits water to cross plasma memebrane

gated channels

open or cles in response to signal

binding of particualr molecules

change in electrical voltage across membranes

ex: aquasporins

flow is carefully controlled

passive transport

does not require energy

ions and small polar molecules diffuse arcoss lipid bilayer

faciliated diffusion

transmeembrane protein assit in passive transport

carrier proteins

mechianis, of transport dioffers from channel proteins

selecting pick upb solute on 1 side of membrane and drop it on the other side

es:glucose transporter

glucose

building block for imporatnt macromolecules

major energy sopurce for cells

GLUT-1

carrier protein

increases membrane permeability to glucose

changes shape when binds to glucose

allows diffusion of glucose arcoss the membrane

active transport

moves substances against their gradient

require input energy

ATP ofter provide energy in cells

phospade group tranferred via active transport protein(pump)

ex:sodium- potassium pump

sodium-potassium pump

uses ATP to pump Na and K ions against their concentration gradient

secondary active transport

by moving material aginst theor concentration gradient, pumps set upo electrochemical gradient

gradients represents potential energy

ATP is not directly used to power transport

elctrochemical gradient power movements of another molecule against its gradient

active then seconday

symport transport protein

transporting 2 things same direction

antiport transport protein

transporting 2 things in opposite dirctions

2 cell types

eukaryotes: memebrane bound nucleaus

prokaryotes: lacks meembrane boud nucleus

prokaryotic cells

at least 1 chromosome

circular, super coiled DNA molecules called plasmids

ribosomes

cell wall

cytoplasm

ribosomes

prokarytoes and eukaryotes

macromolecules machines

have large and small subunits

consist of RNA molecules and proteins

used for protein sythesis

eukayotes

multicellur or unicellur

nucleaus

nuclear evenlope: double membrane and covered in pores

nuclear lamina: protein fibers(very strong)

nucleoloes: DNA and hitones

nucleoplasm

endoplasmic reticulmn

ribsomes

ribosomes

complex molecular machines that make proteins

lack memebranes (not considered organelles)

same are free in cytosal

manufacture proteins that remain in cytosol or imported to other organells

some bound for endoplamsic reticulmn

endoplasmic reticulm

extensive mebrane-bound factory

constist with nuclear envelope

2 regions, distinct in structure and function

rough and smooth ers

rough er

studed with ribosomes

sythesizes protiens that will be

shipped to other organelles

inserted into plasma membrane

secreted to cell exterior

smooth er

lacks ribosomes

contains enzymes that catalyze reaction involuntary lipids that may:

sythesis lipids needed by organism

break down lipids and other molecules that are poisous

reservoir for Ca ions

golgi apparatus

process, sorts, and ships proteins sythesiszed iun rough er

has disinct polarity or sidednes

cis- surface closest to nucleus

trans- surface orineted toward plasma membrane

lysomes

reclycling centers found in animal cells

enzymes specialized for hydrolying different macromolcules

acid hydrolases

digestive enzymes in lysosomes

works best at 5 pH

proton pumps in membranes maintain low internal pH

endomembrane system

lysomes, golgi appartus, nuclear envelope, vesicles, plasma memebrane, er

center for producing, processing, transporting, proteins,carbohydrates, and lipids

vacuole

some digest and recly macromolecules

storgae for water and ions

in seeds, they are filled with proteins

flower petals, contains pigments

may contain csrtain defense compoents

peroxisomes

orginate when empty vesicles from er are loaded with perxime specfic enzymes from cytosol

center of reducyio oxidation reactions(detox)

oxidation produces hydrogen peroxide

mitochondria

supplies ATP

site of celluar respiration

outer and inner membranes

mitochondria matrix

solution encloed within inner membranes

prone to fission and fusion

results in either elongated and branched structures called mitochondrail networks or muiple indivual organells

chlorplasts

most plants

site of photsythesis

2 membranes

outer,inner,thyakoid

endosymbiont theory

proposes mitochondria and chlorplasts were once free living bacteria(prokaryoyes)

latter engolfed by eukayotes

both have circular DNA

mutal benfical relantship evolved

sturcture and fuction in nuclear envelope

seprates nucleaus from rest of the cell

perfomed with openings call nuclear polar complexs

typical nucleaus imports over 500 molecules through 2000-5000 nuclear pores every second

molecules entering nucleous

nuclear proteins contain 170amino acid long nuclear localization siganl(NLS)

serves as a “zip code” (molecular address)

allows them to enter the nucleus

entering endomembrane system

proteins have molrcular zip code

directs growing peptide to RER

zide code is 20 amino acid- long ER signal sequance

3 pathways for lysomes to reclye

autophagy- breaking down damaged organelle

phagocytosis- brings smaller or food cells to digest

receptor- mediated endocytosis - uses reciptoes to biond to macromolecules outside the cell plasma membrane piches in to form a vesicle to lysome

cytoskeleton

Dense and complex network of protein fibers

helps maintain cell shape by providing structural support

3 major cytoskeleton elements

actin filaments

intermediate filaments

macromolecules

actin filaments

smallest cytoskeleton

fibrous structures made of globular proteins subunits (actin)

often most abundant of all proteins in cells

distinct ends of an actin filaments are referred to as plus and minus ends

pull ends grow faster than the minus

actin functions

uses ATP to change motor proteins myosin

cytokines dividing cytoplasm during cell division

cytoplasmic streaming directed flow of cytoplasm

cell crawling

muscle contraction

interminate filaments

strongest filaments

found only in animals

type of protein varies

ex: kiratins

about 20 types of keratins- found in nails and hair

inderminate filament functions

nuclear Lamins are interminate filaments

makes up lamina layer

defines shape of nucleus- stabilizes envelope

form dense mesh under nuclear envelope

anchor chromosomes

microtubules

largest cytoskeletal element

large, hollow tubes made of tubin dimers

a-tublin and B-tublin

microtubules are dynamic, plus ends changes faster than minus

microtubles function

originate from microtubel organizing center (MTCC)

plus, ends grow outward

radiating throughout cell

in animal cells, this center is called centrosome

contains 2 bundles of microtubules called centrioles

aid in cell division (mitosis and meiosis)

sperate sister chromatids during anaphase

vesicles are used to transport to wide array of destinations