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dat exam study > bio ch 2: cells and organelles > Flashcards

bio ch 2: cells and organelles Flashcards

1
Q

cell membranes

A

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

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2
Q

phospholipids

A

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

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3
Q

cholesterol

A

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

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4
Q

membrane proteins

A

are either integral or peripheral membrane proteins

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5
Q

integral (transmembrane) proteins

A

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

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6
Q

peripheral membrane proteins

A

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

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7
Q

receptor proteins

A

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

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8
Q

drugs that bind to receptors

A

can either be agonists or antagonists

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9
Q

agonists

A

are molecules that bind to receptors and functionally activate a target

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10
Q

antagonists

A

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

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11
Q

adhesion

A

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

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12
Q

cellular recognition

A

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

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13
Q

fluid mosaic model

A

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”)

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14
Q

the fluidity of the cell membrane can be affected by

A

● 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).

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15
Q

three types of transport across the cell membrane

A
  1. simple diffusion
  2. facilitated transport
  3. active transport
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16
Q

simple diffusion

A

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

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17
Q

osmosis

A

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

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18
Q

facilitated transport

A

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

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19
Q

uniporters

A

single substance, single direction

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20
Q

symporters

A

two substances, same direction

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21
Q

antiporters

A

two substances, opposite directions

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22
Q

channel proteins

A

open tunnels that face both sides of bilayer

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23
Q

carrier proteins

A

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

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24
Q

passive diffusion

A

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

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25
Q

active transport

A

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

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26
Q

primary active transport

A

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

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27
Q

secondary active transport

A

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

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28
Q

cytosis

A

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

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29
Q

endocytosis

A

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

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30
Q

different forms of endocytosis

A

phagocytosis, pinocytosis, receptor-mediated endocytosis

31
Q

phagocytosis

A

cellular eating around solid objects

32
Q

pinocytosis

A

cellular drinking around dissolved materials (liquids)

33
Q

receptor-mediated endocytosis

A

requires the binding of dissolved molecules to peripheral membrane receptor proteins

34
Q

peripheral membrane receptor proteins

A

initiates endocytosis

35
Q

clathrin

A

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

36
Q

exocytosis

A

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

37
Q

organelles

A

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

38
Q

cytosol

A

aqueous intracellular fluid

39
Q

cytoplasm

A

cytosol & organelles

40
Q

nucleus

A

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

41
Q

nucleoplasm

A

the cytoplasm of the nucleus

42
Q

nuclear envelope

A

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

43
Q

nuclear pores

A

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

44
Q

nuclear lamina

A

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

45
Q

nucleolus

A

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

46
Q

ribosomes

A

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

47
Q

eukaryotic ribosomal subunits

A

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

48
Q

prokaryotic ribosomal subunits

A

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

49
Q

free-floating ribosomes

A

makes proteins that function in the cytosol

50
Q

ER ribosomes

A

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

51
Q

rough ER

A

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

52
Q

lumen

A

inside of the rough ER

53
Q

smooth ER

A

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

54
Q

Golgi apparatus

A

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

55
Q

cis face of Golgi apparatus

A

the side closest to the ER

56
Q

trans face of Golgi apparatus

A

the side closest to the cell membrane

57
Q

lysosomes

A

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

58
Q

autophagy

A

the breakdown of the cell’s own machinery for recycling

59
Q

apoptosis

A

programmed cell death

60
Q

proteasomes

A

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

61
Q

types of vacuoles

A

transport, food, central, storage, contractile

62
Q

transport vacuole

A

transport materials between organelles

63
Q

food vacuoles

A

temporarily hold endocytosed food, and later fuse with lysosomes

64
Q

central vacuoles

A

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

65
Q

tonoplast

A

in central vacuoles
- helps maintain cell rigidity by exerting turgor

66
Q

storage vacuole

A

store starches, pigments, and toxic substances

67
Q

contractile vacuoles

A

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

68
Q

endomembrane system

A

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

69
Q

peroxisomes

A

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

70
Q

mitochondria

A

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

71
Q

chloroplasts

A

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

72
Q

plastid

A

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

73
Q

centrosomes

A

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

74
Q

cytoskeleton

A

provides structure and function within the cytoplasm

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