Ch. 3: Cells

Question 1

Plasma membrane

Answer 1

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

Question 2

Fluid mosaic model

Answer 2

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

Question 3

Selectively permeable membrane

Answer 3

only small, uncharged, polar molecules and hydrophobic molecules can pass through freely
large polar molecules and ions are impermeable

Question 4

Proteins in plasma membrane

Answer 4

channel proteins, ion channels, carrier proteins, transport proteins, recognition proteins, receptor proteins, adhesion proteins

Question 5

Channel proteins

Answer 5

Provide open passageways through membrane for certain hydrophilic substances like polar and charged molecules
Ex. Aquaporins which increase rate of water passage

Question 6

Ion channels

Answer 6

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)

Question 7

Carrier proteins

Answer 7

bind to specific molecules which then are transferred across membrane after carrier protein undergoes change in shape
Ex. glucose

Question 8

Transport proteins

Answer 8

use ATP to transport materials through active transport

Ex. sodium-potassium pump

Question 9

Glycoproteins

Answer 9

proteins w/ short polysaccharide chains that extend from membrane surface that act in cell recognition and cell attachment to external molecules/ other cells

Question 10

Receptor proteins

Answer 10

provide binding sites for hormones and other trigger molecules that if detected will activate specific cell response

Question 11

Glycoproteins

Answer 11

sugar-protein complexes that attach to peripheral proteins and allow outside molecules to bind to it

Question 12

Cholesterol

Answer 12

steroid/ ring structure/ amphipathic
moderates fluidity and stabilizes membrane (at higher temp. keeps phospholipids together and at lower temp. keeps phospholipids apart)

Question 13

Cholesterol

Answer 13

steroid/ ring structure/ amphipathic
moderates fluidity and stabilizes membrane (at higher temp. keeps phospholipids together and at lower temp. keeps phospholipids apart)

Question 14

Orgnanelles

Answer 14

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

Question 15

Nucleus

Answer 15

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

Question 16

DNA (nucleus)

Answer 16

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

Question 17

Nucleoli

Answer 17

concentrations of DNA in process of manufacturing ribosome components

Question 18

RIbosome

Answer 18

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

Question 19

Rough endoplasmic reticulum (ER)

Answer 19

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)

Question 20

Smooth ER

Answer 20

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)

Question 21

Golgi apparatus

Answer 21

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

Question 22

Lysosomes

Answer 22

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

Question 23

Peroxisomes

Answer 23

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

Question 24

Mitochondria

Answer 24

carry out aerobic respiration

2 bilayer membranes, allowing separation of metabolic processes that occur in inner membrane/ intermembrane space

Question 25

Mitochondria

Answer 25

carry out aerobic respiration (ATP creation) | 2 bilayer membranes, allowing separation of metabolic processes that occur in inner membrane/ intermembrane space

Question 26

Microtubules

Answer 26

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)

Question 27

Intermediate filaments

Answer 27

provide support for maintaining shape of cell

Question 28

Microfilaments (actin filaments)

Answer 28

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)

Question 29

Flagella/ Cilia

Answer 29

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

Question 30

Centrioles/ Basal bodies

Answer 30

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

Question 31

Centrioles/ Basal bodies

Answer 31

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

Question 32

Secretory vesicles

Answer 32

move materials from Golgi to plasma membrane

Question 33

Food vacuoles

Answer 33

temporary receptacles of nutrients | often merge w/ lysosomes for digestion

Question 34

Central vacuole

Answer 34

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

Question 35

Central vacuole

Answer 35

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

Question 36

Cell wall

Answer 36

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)

Question 37

Extracellular matrix

Answer 37

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

Question 38

Cell junctions

Answer 38

serve to anchor cells to one another or to provide a passageway for cellular exchange Ex. anchoring, tight, gap, plasmodesmata

Question 39

Anchoring junctions/ Desmosome

Answer 39

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

Question 40

Tight junctions

Answer 40

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

Question 41

Communicating junctions

Answer 41

passageways between cells that allow transfer of chemical or electrical signals Ex. gap junctions and plasmodesmata

Question 42

Gap junctions

Answer 42

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

Question 43

Plasmodesmata

Answer 43

narrow channels between plant cells | narrow tube of ER, surrounded by cytoplasm and plasma membrane, passes through the channel

Question 44

Plant vs. Animal cell

Answer 44

plants have cell walls, chloroplasts, central vacuoles and animal cells do not animal cells have centrioles and cholesterol while plant cells do not

Question 45

Prokaryotes vs. Eukaryotes

Answer 45

1. prokaryotes do not have a nucleus 2. prokaryotes have single "naked" DNA molecule w/out proteins like in eukaryote 3. prokaryotic ribosomes are smaller 4. cell walls of bacteria made of peptidoglycan; cell wall of archaea may contain proteins, glycoproteins, polysaccharides but not peptidoglycan, cellulose (plants) or chitin (fungi) 5. prokaryotic flagella not made of microtubules and not enclosed by plasma membrane; twist like screw to move

Question 46

Hypertonic

Answer 46

higher concentration of solutes

Question 47

Hypotonic

Answer 47

higher concentration of solvent (lower concentration of solutes)

Question 48

Isotonic

Answer 48

equal concentration of solutes

Question 49

Bulk flow

Answer 49

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

Question 50

Passive transport

Answer 50

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

Question 51

Diffusion

Answer 51

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

Question 52

Osmosis

Answer 52

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

Question 53

Plasmolysis

Answer 53

movement of water out of cell by osmosis that results in collapse of cell (esp. in plants w/ central vacuoles)

Question 54

Facilitated diffusion (channel proteins and carrier proteins)

Answer 54

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

Question 55

Countercurrent exchange

Answer 55

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

Question 56

Active transport

Answer 56

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

Question 57

Vesicular transport

Answer 57

uses vesicles or other bodies in cytoplasm to move macromolecules/ large particles across plasma membrane Ex. exocytosis, endocytosis --> phagocytosis, pinocytosis, receptor-mediated endocytosis

Question 58

Exocytosis

Answer 58

vesicles fuse w/ plasma membrane and release contents to outside of cell, common when cell produces substances for export

Question 59

Endocytosis

Answer 59

captures substance outside the cell when the plasma membrane merges to engulf it in an enclosed vesicle Ex. phagocytosis, pinocytosis, receptor-mediated endocytosis

Question 60

Phagocytosis

Answer 60

``` "cell eating" undissolved material enters cell by phagocytic vesicle phagocytic cells (some white blood cells) engulf bacteria this way ```

Question 61

Pinocytosis

Answer 61

"cell drinking" dissolved substances enter cell | plasma membrane forms a channel, allowing liquid to enter, then channel closes and liquid is enclosed in vesicle

Question 62

Receptor-mediated endocytosis

Answer 62

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