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
Mitochondria
carry out aerobic respiration (ATP creation)
2 bilayer membranes, allowing separation of metabolic processes that occur in inner membrane/ intermembrane space
Microtubules
made of tubulin and provide support and motility for cell activities
found in spindle (move chromosomes during cell division) and in flegella and cilia (motility)
Intermediate filaments
provide support for maintaining shape of cell
Microfilaments (actin filaments)
made of protein actin and involved in cell motility
found in muscle cells and in cells that move by changing shape (phagocytes: white blood cells that wander through body attacking bacteria and other invaders)
Flagella/ Cilia
structures made of microtubules that protrude from cell membrane for cell movement
Flagella: long and few, snake like movements
Cilia: short and many with back and forth movement
Centrioles/ Basal bodies
act as microtubule organizing centers (MTOCs)
pair of centrioles is enclosed in centrosome and gives rise to microtubules that make up spindle apparatus used in cell division
Basal bodies org. development of flagella and cilia and anchor them to cell surface
Plants do not have
Centrioles/ Basal bodies
act as microtubule organizing centers (MTOCs)
pair of centrioles is enclosed in centrosome and gives rise to microtubules that make up spindle apparatus used in cell division
Basal bodies org. development of flagella and cilia and anchor them to cell surface
Plants do not have–not necessary for mitosis
Secretory vesicles
move materials from Golgi to plasma membrane
Food vacuoles
temporary receptacles of nutrients
often merge w/ lysosomes for digestion
Central vacuole
large bodies occupying most of plant cell interior
when fully filled, exert turgor pressure on cell wall to maintain rigidity
functions: store starch, nutrients, pigments; carry out digestive functions; provide cell “growth” by absorbing water to expand cell (plant advantage); large surface areas to volume ratio
Central vacuole
large bodies occupying most of plant cell interior
when fully filled, exert turgor pressure on cell wall to maintain rigidity
functions: store starch, nutrients, pigments; carry out digestive functions; provide cell “growth” by absorbing water to expand cell (plant advantage); large surface areas to volume ratio
Cell wall
found in plants, fungi and protists
develop outside the plasma membrane (do not replace it!) to provide support for the cell
plants: cellulose (polysaccharide of B-glucose
fungi: chitin (differs from cellulose in that one -OH group replaced by N containing group)
Extracellular matrix
found in animals –> area between adjacent cells
occupied by fibrous structural proteins, adhesion proteins and glycoproteins secreted by cells
provides mechanical support and helps bind adjacent cells
protein collagen is most common
Cell junctions
serve to anchor cells to one another or to provide a passageway for cellular exchange
Ex. anchoring, tight, gap, plasmodesmata
Anchoring junctions/ Desmosome
protein attachments between adjacent animal cells
Ex. desmosome: bind adjacent cells together, providing mechanical stability to tissues. associated w/ intermediate filaments that extend into interior of cell and hold cell structures together. found in cells that undergo constant stretching like skin cells
Tight junctions
tightly sticked seams between animal cells
junction completely encircles each cell, producing a seal that prevents the passage of materials between cells
characteristic of cells lining digestive tract where materials have to pass through cells (rather than intercellular spaces) to enter bloodstream
Communicating junctions
passageways between cells that allow transfer of chemical or electrical signals
Ex. gap junctions and plasmodesmata
Gap junctions
narrow tunnels between animal cells
allow passage of ions and small molecules so that cells can communicate by molecular/ electrical signals
essentially channel proteins of two adjacent cells closely aligned
Plasmodesmata
narrow channels between plant cells
narrow tube of ER, surrounded by cytoplasm and plasma membrane, passes through the channel
Plant vs. Animal cell
plants have cell walls, chloroplasts, central vacuoles and animal cells do not
animal cells have centrioles and cholesterol while plant cells do not
Prokaryotes vs. Eukaryotes
- prokaryotes do not have a nucleus
- prokaryotes have single “naked” DNA molecule w/out proteins like in eukaryote
- prokaryotic ribosomes are smaller
- cell walls of bacteria made of peptidoglycan; cell wall of archaea may contain proteins, glycoproteins, polysaccharides but not peptidoglycan, cellulose (plants) or chitin (fungi)
- prokaryotic flagella not made of microtubules and not enclosed by plasma membrane; twist like screw to move
Hypertonic
higher concentration of solutes
Hypotonic
higher concentration of solvent (lower concentration of solutes)
Isotonic
equal concentration of solutes
Bulk flow
collective movement of substances (solutes and solvents) in the same direction in response to a force or pressure
Ex. blood moving through a blood vessel
Passive transport
movement of substances from high to low concentration (down concentration gradient)
does not require energy
rates of passive transport increase w/ higher concentration gradients, higher temps., and smaller particle size
Ex. diffusion, osmosis, plasmolysis, facilitated diffusion, countercurrent exchange
Diffusion
net movement of substances from high to low concentration with the ultimate goal of equilibrium (still motion but net is 0)
occurs as result of random and constant motion characteristic of all molecules
Osmosis
diffusion of water across selectively permeable membrane
when water moves into a body by osmosis, osmotic pressure increases (turgor pressure in plants)
cell lysis occurs when too much water enters cell and it bursts (lysis), esp. in animal cells w/out cell wall
Plasmolysis
movement of water out of cell by osmosis that results in collapse of cell (esp. in plants w/ central vacuoles)
Facilitated diffusion (channel proteins and carrier proteins)
diffusion of solutes or water through channel proteins/ carrier proteins in plasma membrane
channel proteins: move ions like Na+, K+, Ca2+, Cl-; aquaporins move water
carrier proteins: move ions and larger organic molecules like amino acids and glucose
Countercurrent exchange
diffusion of substances between two regions in which substances are moving by bulk flow in opposite directions
Ex. direction of water flow through gills of fish is opposite to blood flow. diffusion of oxygen from water to blood is maximized bc relative motion of the molecules is increased, and bc concentration gradients between two regions remain constant
Active transport
movement of solutes against concentration gradient, needs energy
does not result from random movement of molecules like diffusion, rather moves specific solutes from low to high
Vesicular transport
uses vesicles or other bodies in cytoplasm to move macromolecules/ large particles across plasma membrane
Ex. exocytosis, endocytosis –> phagocytosis, pinocytosis, receptor-mediated endocytosis
Exocytosis
vesicles fuse w/ plasma membrane and release contents to outside of cell, common when cell produces substances for export
Endocytosis
captures substance outside the cell when the plasma membrane merges to engulf it in an enclosed vesicle
Ex. phagocytosis, pinocytosis, receptor-mediated endocytosis
Phagocytosis
"cell eating" undissolved material enters cell by phagocytic vesicle phagocytic cells (some white blood cells) engulf bacteria this way
Pinocytosis
“cell drinking” dissolved substances enter cell
plasma membrane forms a channel, allowing liquid to enter, then channel closes and liquid is enclosed in vesicle
Receptor-mediated endocytosis
form of pinocytosis
occurs when specific molecules (ligands) in the fluid surrounding the cell bind to specialized receptors that concentrate in coated pits in plasma membrane. this all folds inward and a vesicle is formed
Ex. proteins that transport cholesterol in blood (LDLs) and certain hormones target specific cells this way
