Chapter 3: Cells: The Living Units (pgs. 54-76)

Question 1

cell theory

Answer 1

cell is basic structural and functional unit of living organisms
activity of organism spends on individual and combined activities of cells
principle of complementary structure and function (biochemical activities of cells are dictated by shapes or forms)
cells arise form other cells

Question 2

generalized or composite cell

Answer 2

contains three main parts

• plasma membrane: outer boundary of the cell that acts as a selectively permeable barrier
• cytoplasm: intracellular fluid containing organelles
• nucleus: organelle that controls cellular activities

Question 3

extracellular materials

Answer 3

substances contributing to body mass found outside the cell

ex: body/extracellular fluids, cellular secretions, extracellular matrix

Question 4

body/extracellular fluids

Answer 4

important transport and dissolving media
ex: interstitial fluid, blood plasma, cerebrospinal fluid
interstitial fluid baths organs in amino acids, sugars, fatty acids, regulatory substances and wastes

Question 5

cellular secretions

Answer 5

substances that aid in digestion and acts as a lubricant

Question 6

extracellular matrix

Answer 6

most abundant extracellular material

molecules secreted by the cell self assemble into an organized mesh where they help hold cells together

Question 7

plasma membrane

Answer 7

separates the intracellular fluid from the extracellular fluid
made up of phospholipids, glycolipids and cholesterol

Question 8

glycolipids

Answer 8

lipids with attached sugar groups
found on outer plasma membrane surface
~5% of membrane lipids
sugar groups make it polar on the outside

Question 9

cholesterol

Answer 9

~20% of membrane lipid
wedges platelike hydrocarbon rings between phospholipid tails which stabilize the membrane and decrease mobility and fluidity of membrane

Question 10

integral proteins

Answer 10

firmly inserted into the lipid bilayer
most are transmembrane proteins that span the entire membrane and protrude on both sides
have hydrophobic and hydrophilic regions
involved in transport

Question 11

channel proteins

Answer 11

transmembrane proteins involved in transport

cluster together to form pores that small, water-soluble molecules or ions can pass through

Question 12

carrier proteins

Answer 12

bind to a substance and move it across the membrane

Question 13

peripheral proteins

Answer 13

not embedded in lipid bilayer, attached loosely to integral proteins and can be easily removed without disrupting the membrane
include a network of filaments that help support the membrane from the cytoplasmic side
some are enzymes, motor proteins or link cells together

Question 14

glycocalyx

Answer 14

glycoproteins and glycolipids that form a sticky carbohydrate rich area on the cell surface
provides highly specific biological markers on different cell types that approaching cells can recognize it by

Question 15

tight junctions

Answer 15

series of integral proteins of adjacent cells fuse together to form an impermeable junction that encircles the cell
prevent molecules from passing through extracellular space between cells (ex: stomach lining keeps acid inside)

Question 16

desmosomes

Answer 16

anchoring junctions
mechanical couplings on the sides of adjacent cells that prevent separation
abundant in tissues subjected to mechanical stress (skin or heart muscle)

Question 17

gap junction

Answer 17

communication junction between adjacent cells
hollow cylinders call connexons composed of transmembrane proteins connect cell membranes
allow ions, simple sugars and small molecules to pass through water filled channels from one cell to the next
present in electrically excitable tissues (heart and smooth muscle) where ion passage from cell to cell to help synchronize electrical activity and contraction

Question 18

connexons

Answer 18

transmembrane proteins that make up gap junctions that form hollow cylinders
different kinds vary selectivity for gap junction channel
allow ions, simple sugars and small molecules to pass through the water filled channels

Question 19

diffusion

Answer 19

tendency of molecules or ions to move from an area where they are in high concentration to an area where they are in low concentration (along concentration gradient)
speed of diffusion is related to molecular size and temperature

Question 20

selectively permeable barrier

Answer 20

allow some substances to pass through while excluding others
plasma membrane is a barrier to free diffusion because of its hydrophobic core
allows lipids, small molecules and molecules assisted by carrier proteins through

Question 21

simple diffusion

Answer 21

non polar and lipid-soluble substances diffuse directly through the lipid bilayer
es: O2, CO2, fat soluble vitamins

Question 22

facilitated diffusion

Answer 22

passive transport process where substances that can’t diffuse through the lipid bilayer
substances could either bind to protein carriers in the membrane and be ferried across or move through water-filled protein channels

Question 23

carrier-mediated facilitated diffusion

Answer 23

transmembrane integral proteins specific for transporting certain polar molecules or classes of molecules (sugars and amino acids) that are too large to pass through membrane channels
alterations in shape of carrier allow it to envelope and release substance so it can pass through the non polar inside of the membrane
moves down its concentration gradient

Question 24

channel-mediated facilitated diffusion

Answer 24

transmembrane proteins that transport substances like ions or water through aqueous channels across the membrane
ex: leakage channels, gated channels

Question 25

leakage channels

Answer 25

channel-mediated facilitated diffusion always open allow water or ions to move across concentration gradient

Question 26

grated channels

Answer 26

channel-mediated facilitated diffusion controlled (opened or closed) by chemical or electrical signals can be inhibited by certain molecules, show saturation and are specific substances move across their concentration gradient

Question 27

osmosis

Answer 27

diffusion of water through plasma membrane water is highly polar, must pass through transmembrane proteins called aquaporins occurs when water concentrations differ across a membrane

Question 28

aquaporins

Answer 28

allow single-file diffusion of water across the plasma membrane abundant in red blood cells and kidney tubule cells

Question 29

osmolarity

Answer 29

total concentration of all solute particles in a solution | based solely on total solute concentration

Question 30

hydrostatic pressure

Answer 30

back pressure exerted by water against the membrane

Question 31

osmotic pressure

Answer 31

tendency of water to move into the cell by osmosis

Question 32

tonicity

Answer 32

ability of a solution to change the shape or tone of cells by altering the cells' internal water volume based on how the solution effects the cell volume which depends on solute concentration and solute permeability

Question 33

isotonic solution

Answer 33

have the same concentration of non penetrating solutes inside and outside of the cell retain normal shape no net loss or gain of water

Question 34

hypertonic solution

Answer 34

have a higher concentration of non penetrating solutes than the inside of the cell cells lose water and shrink

Question 35

hypotonic solution

Answer 35

more dilute than the cells | cells gain water rapidly and will lyse

Question 36

active transport

Answer 36

requires carrier proteins that combine specifically and reversibly with the transported substances move solutes against a concentration gradient using energy

Question 37

primary active transport

Answer 37

energy comes directly from hydrolysis of ATP | ex: calcium and hydrogen pumps, sodium-potassium pump

Question 38

secondary active transport

Answer 38

energy is tired in concentration gradients of ions created by primary active transport pumps coupled systems that move more than one substance at a time ex: in Na+-K+ pump a Na+-glucose symport transporter loads glucose from outside the cell and transports both inside the cell

Question 39

symport

Answer 39

two transported substances move in the same direction

Question 40

antiport

Answer 40

substances are transported across the membrane in opposite directions

Question 41

Na+-K+ ATPase

Answer 41

enzyme that functions in the sodium-potassium pump

Question 42

vesicular transport

Answer 42

fluids containing large particles and macromolecules are transported across the membrane inside membranous sacs called vesicles

Question 43

endocytosis

Answer 43

vesicular transport moves substances into cell

Question 44

exocytosis

Answer 44

vesicular transport moves substances out of the cell typically stimulated by a cell-surface signal like binding of a hormone or change in membrane voltage ex: hormone secretion, neurotransmitter release, mucus secretion and waste secretion

Question 45

transcytosis

Answer 45

combination processes that move substances into, across, and then out of the cell

Question 46

vesicular trafficking

Answer 46

moving substances from one area (membranous organelle) in the cell to another

Question 47

coated pit

Answer 47

vesicles have a coating found on their face | acts to select the cargo in the vesicle and deforming the membrane to produce the vesicle

Question 48

lysosome

Answer 48

specialized cell structure containing digestive enzymes where ingested substances is degraded or released

Question 49

phagocytosis

Answer 49

type of endocytosis cell engulfs relatively large or solid material (ex: clump of bacteria, cell debris etc.) particles bind to receptors on the cells surface and cytoplasmic extensions called pseudopods form and flow around the particle to form a phagosome

Question 50

amoeboid motion

Answer 50

how phagocytes move | cytoplasm flows into temporary extensions

Question 51

pinocytosis

Answer 51

"cell drinking" or fluid-phase endocytosis infolding plasma membrane surrounds a small volume of extracellular fluid containing dissolved molecules and enters the cell and fuses with an endosome routine activity of most cells how cells absorb nutrients membranes are recycled back to the plasma membrane by exocytosis

Question 52

receptor-mediated endocytosis

Answer 52

specific endocytosis and transcytosis cells can take in materials from outside the cell that are in small concentrations receptor and molecule are internalized in a clathrin-coated pit ex: enzymes, insulin, low density lipoproteins and iron

Question 53

v-SNAREs

Answer 53

v = vesicle transmembrane protein on a vesicle that recognizes certain plasma membrane proteins and bind with them to fuse the vesicle and membrane

Question 54

t-SNAREs

Answer 54

t = target | plasma membrane protein that v-SNAREs bind to to fuse vesicle with membrane

Question 55

membrane potential

Answer 55

voltage across a membrane

Question 56

voltage

Answer 56

electrical potential energy resulting from the separation of oppositely charge particles

Question 57

resting membrane potential

Answer 57

-50 to -100 mV for an average cell depending on type cells are polarized because the inside of the cell is negative compared to the outside voltage exists only at the membrane

Question 58

maintaining resting potential

Answer 58

K+ diffuses out of the cell through K+ leakage channels and negatively charged proteins are too large to follow and the membrane interior becomes negative K+ will be attracted back into the cell by the - charge at -90 mV K+ concentration gradient is balanced by the electrical gradient

Question 59

cell adhesion molecules (CAMs)

Answer 59

play a key role in embryonic development, wound repair and immunity sticky glycoproteins that act to - anchor cells to the extracellular space and each other - haul migrating cells past one another - SOS signals to recruit white blood cells to an infected or injured area - mechanical sensors to respond to changes in local tension or fluid movement at cell surface by stimulating synthesis or degradation of tight junctions -transmitters of intracellular signals that direct cell migration, proliferation, and specialization

Question 60

membrane receptors

Answer 60

integral proteins and glycoproteins that serve as binding sites

Question 61

contact signaling

Answer 61

cells come together and touch how cells recognize one another important for normal development and immunity

Question 62

ligands

Answer 62

chemicals that bind specifically to plasma membrane receptors ex: most neurotransmitters, hormones and paracrines

Question 63

G protein-linked receptors

Answer 63

exert effect indirectly through a G protein which generate one or more intracellular chemical signals that connect plasma membrane events to internal metabolic machinery of the cell

Question 64

G protein

Answer 64

regulatory molecule that acts as a middleman or relay to activate or inactivate a membrane-bound enzyme or ion channel

Question 65

second messengers

Answer 65

intracellular chemical signals that connect the plasma membrane to cell machinery ex: cyclic AMP, ionic calcium

Question 66

cyclic AMP

Answer 66

typically activate protein kinase enzymes that transfer Pi from ATP to other proteins, activating a series of enzymes that bring about the desired cellular activity

Question 67

protein kinase enzymes

Answer 67

transfer Pi from ATP to other proteins, activating a series of enzymes that bring about the desired cellular activity