bio ch 2: cells and organelles

Question 1

cell membranes

Answer 1

hold cellular contents and are mainly composed of (1) phospholipids and (2) proteins with (3) small amounts of cholesterol

Question 2

phospholipids

Answer 2

glycerol backbone, one phosphate group (hydrophilic), and two fatty acid tails (hydrophobic)
- amphipathic: the molecules have both polar and nonpolar parts, allowing them to form a lipid bilayer in an aqueous environment

Question 3

cholesterol

Answer 3

has four fused hydrocarbon rings
- precursor to steroid hormones
- amphipathic and helps regulate membrane fluidity

Question 4

membrane proteins

Answer 4

are either integral or peripheral membrane proteins

Question 5

integral (transmembrane) proteins

Answer 5

traverse the entire bilayer, must be amphipathic
- their nonpolar parts lie int he middle of the bilayer
- their polar ends extend out into the aqueous environment on the inside and outside of the cell
- usually assist in cell signaling or transport

Question 6

peripheral membrane proteins

Answer 6

are found on the outside of the bilayer, and they are generally hydrophilic

Question 7

receptor proteins

Answer 7

trigger secondary responses within the cell for signaling
- if a receptor protein transmits a signal all the way through the lipid bilayer, it is considered an integral protein

Question 8

drugs that bind to receptors

Answer 8

can either be agonists or antagonists

Question 9

agonists

Answer 9

are molecules that bind to receptors and functionally activate a target

Question 10

antagonists

Answer 10

bind and prevent other molecules from binding, inhibiting production of a response

Question 11

adhesion

Answer 11

attaches cells to other things (e.g. other cells) and act as anchors for the cytoskeleton

Question 12

cellular recognition

Answer 12

proteins which have carbohydrate chains (glycoproteins)
- used by cells to recognize other cells.

Question 13

fluid mosaic model

Answer 13

describes how the components that make up the cell membrane can move freely within the membrane (“fluid”)
- the cell membrane contains many different kinds of structures (“mosaic”)

Question 14

the fluidity of the cell membrane can be affected by

Answer 14

● Temperature - ↑ temperatures increase fluidity while ↓ temperatures decrease it.

● Cholesterol - holds membrane together at high temperatures and keeps membrane fluid at low temperatures.

● Degrees of unsaturation - saturated fatty acids pack more tightly than unsaturated fatty acids, which have double bonds that may introduce kinks .
- Trans-unsaturated fatty acids pack more tightly than cis-unsaturated fatty acids (which have a more severe kink).

Question 15

three types of transport across the cell membrane

Answer 15

1. simple diffusion
2. facilitated transport
3. active transport

Question 16

simple diffusion

Answer 16

flow of small, uncharged, nonpolar substances (e.g. O2 and CO2) across the cell membrane down their concentration gradient (high to low) without using energy

Question 17

osmosis

Answer 17

is a type of simple diffusion that involves water molecules
- water is polar, but is small enough to cross the membrane

Question 18

facilitated transport

Answer 18

integral proteins allow larger, hydrophilic molecules to cross the cell membrane
- proteins can be uniporters, symporters, or antiporters
- proteins can also be classified as channel proteins or carrier proteins

Question 19

uniporters

Answer 19

single substance, single direction

Question 20

symporters

Answer 20

two substances, same direction

Question 21

antiporters

Answer 21

two substances, opposite directions

Question 22

channel proteins

Answer 22

open tunnels that face both sides of bilayer

Question 23

carrier proteins

Answer 23

bind to a molecule on one side and change shape to bring it to the other side

Question 24

passive diffusion

Answer 24

is a type of facilitated transport that is performed by channel proteins
- bring molecules down their concentration gradient without energy use
- similar to simple diffusion, but a protein channel is used
- e.g. porins for hydrophilic molecules and ion channels for ions

Question 25

active transport

Answer 25

substances travel against their concentration gradient and require the consumption of energy by carrier proteins

Question 26

primary active transport

Answer 26

uses ATP hydrolysis to pump molecules against their concentration gradient - e.g. the sodium-potassium (Na+/K+) pump establishes membrane potential

Question 27

secondary active transport

Answer 27

uses free energy released when other molecules flow down their concentration gradient to pump the molecule of interest across the membrane - the gradient is established by primary active transport

Question 28

cytosis

Answer 28

refers to the bulk transport of large, hydrophilic molecules across the cell membrane and requires energy - active transport mechanism

Question 29

endocytosis

Answer 29

involves the cell membrane wrapping around an extracellular substance, internalizing it into the cell via a vesicle or vacuole

Question 30

different forms of endocytosis

Answer 30

phagocytosis, pinocytosis, receptor-mediated endocytosis

Question 31

phagocytosis

Answer 31

cellular eating around solid objects

Question 32

pinocytosis

Answer 32

cellular drinking around dissolved materials (liquids)

Question 33

receptor-mediated endocytosis

Answer 33

requires the binding of dissolved molecules to peripheral membrane receptor proteins

Question 34

peripheral membrane receptor proteins

Answer 34

initiates endocytosis

Question 35

clathrin

Answer 35

is a protein that aids in receptor mediated endocytosis by forming a pit in the membrane that pinches off as a coated vesicle - this is known as **clathrin mediated endocytosis**

Question 36

exocytosis

Answer 36

is the opposite of endocytosis, in which material is released to the extracellular environment through vesicle secretion

Question 37

organelles

Answer 37

are cellular compartments enclosed by phospholipid bilayers (membrane bound) - they are located within the cytosol and help make up the cytoplasm - only eukaryotic cells contain membrane-bound organelles - prokaryotes do not contain membrane-bound organelles but they have other adaptations, such as keeping their genetic material in a region called the nucleoid - ribosomes not considered to be organelles

Question 38

cytosol

Answer 38

aqueous intracellular fluid

Question 39

cytoplasm

Answer 39

cytosol & organelles

Question 40

nucleus

Answer 40

primarily functions to protect and house DNA - DNA replication and transcription (DNA → mRNA) occurs here

Question 41

nucleoplasm

Answer 41

the cytoplasm of the nucleus

Question 42

nuclear envelope

Answer 42

the membrane of the nucleus - contains two phospholipid bilayers (one inner, one outer) with a perinuclear space in the middle

Question 43

nuclear pores

Answer 43

holes in the nuclear envelope that allow molecules to travel in and out of the nucleus

Question 44

nuclear lamina

Answer 44

provides structural support to the nucleus, as well as regulating DNA and cell division

Question 45

nucleolus

Answer 45

a dense area that is responsible for making rRNA and producing ribosomal subunits (rRNA+proteins)

Question 46

ribosomes

Answer 46

work as small factories that carry out translation (mRNA → protein) - composed of ribosomal subunits - not considered to be organelles

Question 47

eukaryotic ribosomal subunits

Answer 47

60S and 40S - assemble in the nucleoplasm and then are exported rom the nucleus to form the complete ribosome in the cytosol - S refers to sedimentation characteristics - eukaryotic complete ribosome (in cytosol): 80S

Question 48

prokaryotic ribosomal subunits

Answer 48

50S and 30S - assemble in the nucleoid and form the complete ribosome in the cytosol - prokaryotic complete ribosome (in cytosol): 70S

Question 49

free-floating ribosomes

Answer 49

makes proteins that function in the cytosol

Question 50

ER ribosomes

Answer 50

ribosomes that are embedded in the rough endoplasmic reticulum (rough ER) - makes proteins that are sent out of the cell or to the cell membrane

Question 51

rough ER

Answer 51

continuous with the outer membrane of the nuclear envelope - "rough" because it has ribosomes embedded in it - proteins synthesized by the embedded ribosomes are sent into the lumen for modification - afterwards they are either sent out of the cell or become part of the cell membrane

Question 52

lumen

Answer 52

inside of the rough ER

Question 53

smooth ER

Answer 53

smooth endoplasmic reticulum, not continuous with other membranes - main function is to synthesize lipids, produce steroid hormones, and detoxify cells

Question 54

Golgi apparatus

Answer 54

stores, modifies, and exports substances that will be secreted from the cell - made up of cisternae (flattened sacs) that modify and package substances - vesicles come from the ER and reach the cis face of the Golgi apparatus - vesicles leave the Golgi apparatus form the trans face

Question 55

cis face of Golgi apparatus

Answer 55

the side closest to the ER

Question 56

trans face of Golgi apparatus

Answer 56

the side closest to the cell membrane

Question 57

lysosomes

Answer 57

membrane-bound organelles that break down substances that are taken in through endocytosis (break down by hydrolysis) - contains acidic digestive enzymes that function at a low pH - carries out autophagy and apoptosis

Question 58

autophagy

Answer 58

the breakdown of the cell's own machinery for recycling

Question 59

apoptosis

Answer 59

programmed cell death

Question 60

proteasomes

Answer 60

protein complexes that degrade unneeded or damaged proteins by proteolysis - such proteins have a ubiquitin molecule attached, tagging these proteins for degradation

Question 61

types of vacuoles

Answer 61

transport, food, central, storage, contractile

Question 62

transport vacuole

Answer 62

transport materials between organelles

Question 63

food vacuoles

Answer 63

temporarily hold endocytosed food, and later fuse with lysosomes

Question 64

central vacuoles

Answer 64

very large in plants and have a specialized membrane called the tonoplast - functions in storage and material breakdown

Question 65

tonoplast

Answer 65

in central vacuoles - helps maintain cell rigidity by exerting turgor

Question 66

storage vacuole

Answer 66

store starches, pigments, and toxic substances

Question 67

contractile vacuoles

Answer 67

found in single-celled organisms and works to actively pump excess water

Question 68

endomembrane system

Answer 68

composed of the different membranes that are suspended in the cytoplasm within a eukaryotic cell - it is a group of organelles and membranes that work together to modify, package, and transport proteins and lipids that are entering or exiting a cell - the components includes: the nucleus, rough and smooth ERs, Golgi apparatus, lysosomes, vacuoles, and cell membrane

Question 69

peroxisomes

Answer 69

perform hydrolysis, break down stored fatty acids, and help with detoxification - these processes generate hydrogen peroxide - hydrogen peroxide = toxic, it can produce reactive oxygen species (ROS) - peroxisomes contain an enzyme called catalase → quickly breaks down hydrogen peroxide into water and oxygen

Question 70

mitochondria

Answer 70

powerhouse of the cell, produces ATP for energy use through cellular respiration - mitochondrial inheritance is maternal, meaning that all mitochrondrial DNA in humans originates from the mother

Question 71

chloroplasts

Answer 71

found in plants and some protists - carries out photosynthesis - type of plastid

Question 72

plastid

Answer 72

double-membraned organelles found exclusively within plant cells and algae - functions in photosynthesis and storage of metabolites

Question 73

centrosomes

Answer 73

organelles found in animal cells containing a pair of centrioles - they act as microtubule organizing centers (MTOCs) during cell division

Question 74

cytoskeleton

Answer 74

provides structure and function within the cytoplasm