Ch. 3: Cells Flashcards
Plasma membrane
separates internal metabolic events from external environment
controls movement of materials in and out of cell
phospholipid bilayer
functions: protection, transport, signal transduction, energy storage
Fluid mosaic model
cell membrane has scattered proteins (lateral motion) w/ a flexible matrix of phospholipid molecules
variations in fatty acid makeup influence membrane fluidity –> saturated pack more tightly so more rigid membrane vs. unsaturated which have bends so more flexible
Selectively permeable membrane
only small, uncharged, polar molecules and hydrophobic molecules can pass through freely
large polar molecules and ions are impermeable
Proteins in plasma membrane
channel proteins, ion channels, carrier proteins, transport proteins, recognition proteins, receptor proteins, adhesion proteins
Channel proteins
Provide open passageways through membrane for certain hydrophilic substances like polar and charged molecules
Ex. Aquaporins which increase rate of water passage
Ion channels
allow ion passage across membrane
in nerve and muscle cells, gated ion channels open and close in response to specific chemical/ electrical stimuli (Na+/K+ pass)
Carrier proteins
bind to specific molecules which then are transferred across membrane after carrier protein undergoes change in shape
Ex. glucose
Transport proteins
use ATP to transport materials through active transport
Ex. sodium-potassium pump
Glycoproteins
proteins w/ short polysaccharide chains that extend from membrane surface that act in cell recognition and cell attachment to external molecules/ other cells
Receptor proteins
provide binding sites for hormones and other trigger molecules that if detected will activate specific cell response
Glycoproteins
sugar-protein complexes that attach to peripheral proteins and allow outside molecules to bind to it
Cholesterol
steroid/ ring structure/ amphipathic
moderates fluidity and stabilizes membrane (at higher temp. keeps phospholipids together and at lower temp. keeps phospholipids apart)
Cholesterol
steroid/ ring structure/ amphipathic
moderates fluidity and stabilizes membrane (at higher temp. keeps phospholipids together and at lower temp. keeps phospholipids apart)
Orgnanelles
physically separate various metabolic reactions so can take place w/out interference/ competition w/ other rxns
provide large surface areas to maximize space for chem. rxns to take place
cells are specialized for certain functions depending on the kinds and # of organelles they have
Nucleus
bounded by nuclear envelope consisting of 2 phospholipid bilayers
contains DNA and nucleoli
site of chromosome separation during cell division
nuclear pores on surface of nuclear envelope serve as passageways for proteins and RNA
DNA (nucleus)
DNA in nucleus is chromatin
when cell begins division, chromatin condenses into chromosomes each made up of two long DNA molecules and histones
histones bundle DNA into nucleosomes
Nucleoli
concentrations of DNA in process of manufacturing ribosome components
RIbosome
manufactured in nucleus and consist of RNA molecules and proteins
once exiting through nuclear pores, in cytoplasm they assist in the assembly of amino acids into proteins
Rough endoplasmic reticulum (ER)
stacks of flattened sacs that begin as extension of nuclear envelope, maze like channels with ribosomes closely associated w/ nucleus create glycoproteins (need ribosomes to make proteins)
Smooth ER
no ribosomes, synthesize lipids and steroid hormones, esp. in cells that produce these substances for export from cell
breakdown toxins, drugs, and toxic by-products of chem. rxns (liver)
Golgi apparatus
group of flattened sacs (cisternae) that collect and modify proteins and lipids made in other parts of the cell and package them into vesicles whose contents are released outside of the cell or retained inside
make lysosomes
Lysosomes
vesicles from Golgi that contain hydrolytic enzymes that break down food, cell debris, and foreign invaders (bacteria) and recycle cell nutrients
act best in low pH (acidic) so does not function under pH of cytosol
Peroxisomes
type of lysosome that breaks down H2O2 (by-product of chem. rxns
common in liver and kidney cells where they break down toxins
in plant cells, they modify by-products of photorespiration
Mitochondria
carry out aerobic respiration
2 bilayer membranes, allowing separation of metabolic processes that occur in inner membrane/ intermembrane space