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AP Biology > The Cell > Flashcards

The Cell Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Where did all organisms on Earth come from?

A

one common ancestral cell (3.5 billion years ago)

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2
Q

theory of endosymbiosis

A

mitochondria and chloroplasts (free-living prokaryotes) taking up permanent residence inside other larger cells (1.5 billion years ago) creating eukaryotic cells

eukaryotic cells are much more complex cells with internal membrane dividing the cell causing rapid evolution of multicellular organisms

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3
Q

modern cell theory (2)

A
  • all organisms are made of cells
  • all cells come from pre-existing cells
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4
Q

What are the sizes of animal and plant cells?

A

most animal and plant cells have diameters between 10 and 100 μm (many can be smaller, human red blood cells are 8 μm)

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5
Q

cells share 3 characteristics

A
  • enclosed by plasma membrane (protective + selective barrier)
  • contain cytosol (semifluid substance) suspending components
  • contain ribosomes and genetic material in form of DNA
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6
Q

prokaryotes (7)

A
  • no internal membranes (nucleus is replaced with nucleoid region: non-membrane-bound region with chromosome)
  • circular, naked DNA
  • small ribosomes
  • anaerobic or aerobic metabolism
  • no cytoskeleton
  • mainly unicellular
  • 1-10 μm
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7
Q

eukaryotes (7)

A
  • distinct membrane-bound organelles
  • DNA wrapped with histone proteins into chromosomes
  • large ribosomes
  • aerobic metabolism
  • cytoskeleton
  • mainly multicellular with different cell types
  • 10-100 μm
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8
Q

What is notable about the structure of different cells?

(Different cells have different structures)

A

Function dictates form, so different cells have different structures depending on the purpose

Examples:
nerve cells long and spindly to send electrical impulses
cells that store fat are rounded, large, distended
cells that make up a peach pit look like square building blocks

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9
Q

Why are cells small?

A

the surface area of the cell membrane must be able to accomodate the metabolic needs/volume of the cytoplasm

ratio of surface area to volume should be greater (6:1) for more efficiency

as a cell grows and the volume becomes greater, the cell will be divided into 2

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10
Q

nucleolus (5)

A
  • found in the nucleus of a nondividing cell
  • synthesises rRNA (ribosomal RNA) as instructed by DNA
  • subunits of ribosomes also assembled
  • combines the protein from the cytoplasm with the rRNA made
  • not membrane-bound, but a tangle of chromatin + unfinished ribosomal precursors
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11
Q

ribosomes (2)

A
  • protein factories
  • found free in the cytoplasm or bound to the ER

free = protein produced for the cell’s own use
bound = meant for export out of the cell

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12
Q

peroxisomes (3)

A
  • found in both plant and animal cells
  • contain catalase which converts hydrogen peroxide into water with release of oxygen atoms
  • detoxifies alcohol in liver cells

hydrogen peroxide = waste product of respiration

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13
Q

endomembrane system

A
  • regulates protein traffic
  • performs metabolic functions in cells
  • includes: nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, vacuoles, plasma membrane
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14
Q

nucleus (3)

A
  • contains chromosomes wrapped with special proteins into a chromatin network
  • surrounded by selectively permeable nuclear envelope seperating contents of nucleus from cytoplasm
  • nuclear envelope has pores to allow for transport of large molecules that can’t diffuse directly through (e.g. mRNA)
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15
Q

endoplasmic reticulum (ER)

A
  • membranous system of channels and flattened sacs that cross the cytoplasm
  • has two types: rough and smooth

Rough ER: studded with ribosomes + produces proteins
Smooth ER: has 3 functions
1. assist in synthesis of steroid hormones and other lipids
2. stores Ca++ ions in muscle cells to facilitate normal muscle contractions
3. detoxifies drugs and poisons from body

the ER accounts for more than 50% of the total membranes in eukaryotic cells

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16
Q

Golgi apparatus

A
  • near the nucleus
  • flattened membranous sacs stacked next to each other surrounded by vesicles
  • process and package substances produced in the rough ER
  • secrete the substances to other parts of the cell or surface for export
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17
Q

lysosomes

A
  • sacs of hydrolytic (digestive) enzymes surrounded by a single membrane
  • principal site of intracellular digestion
  • helps cell continually renews itself by breaking down + recycling cell parts (autophagy)
  • programmed destruction of cells (apoptosis) by own hydrolytic enzymes is critical part of development of multicelled organisms

not found in plant cells

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18
Q

mitochondria

A
  • site of cellular respiration
  • with outer double membrane and inner series of membranes called cristae
  • contains their own DNA
  • divide and fuse with each other to exchange DNA to fix defects

mitochondria having their own DNA supports endosymbiotic theory

up to 2500 mitochondria found in an active cell

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19
Q

vacuoles

A
  • membrane-bound structures for storage
  • large vesicles from ER and Golgi apparatus
  • mature plant cells have single central vacuole
  • freshwater protists have contractile vacuoles to pump out excess water
  • food vacuoles formed by phagocytosis of foreign material
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20
Q

chloroplast

A
  • contain green pigment chlorophyll that absorbs light energy and synthesizes sugar (along with enzymes)
  • found in plants and algae
  • double outer membrane with inner membrane system called thylakoids

theory of endosymbiosis: once tiny, free-living prokaryotic cells that were engulfed by a larger prokaryotic cell and eventually become one

have their own DNA that resembles bacterial DNA

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21
Q

cytoskeleton (4)

A

complex mesh of protein filaments that extends throughout cytoplasm

Important for:
1. maintaining cell shape
2. controls position of organelles within cell by anchoring them to plasma membrane
3. flow of cytoplasm (cytoplasmic streaming)
4. anchors cell in place by interacting with outside element

Has microtubules + microfilaments

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22
Q

parts of the cytoskeleton

microtubules

A

hollow tubes made of the protein tubulin making up cilia, flagella, and spindle fibers

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23
Q

parts of the cytoskeleton

cilia and flagella

A
  • moves cells from one place to another
  • 9 pairs of microtubules organized around 2 singlet microtubules (9 + 2 formation)
    | flagella are not made of microtubules in prokaryotes
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24
Q

parts of the cytoskeleton

spindle fibers

A
  • helps seperate chromosomes during mitosis and meiosis
  • microtubles organized into 9 triplets with none in the center
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25
Q

parts of the cytoskeleton

microfilaments (3)

A

assembled from actin filaments and support the shape of the cell

Helps:
1. animal cells form cleavage furrow during cell division
2. amoeba to move by sending out pseudopods
3. skeletal muscle to contrast as they slide along myosin filaments

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26
Q

centrioles, centrosomes, MTOCS (microtubule organizing centers)

A
  • nonmembranous structures that lie outside nuclear membranes
  • organize spindle fibers, and give rise to spindle apparatus for cell division
  • 2 centrioles at right angles = one centrosome and consists of 9 triplets of microtubules in a circle

plant cells have no centrosomes, but have MTOCs
centrosome = MTOC in animal cell

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27
Q

cell wall

A
  • made of cellulose in plants and algae
  • made of chitin in fungi
  • consist of polysaccharides + complex polymers in prokaryotes
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28
Q

primary and secondary cell wall

A

primary cell wall is immediately outside plasma membrane

some cells have second cell wall underneath primary

29
Q

middle lamella

A

thin gluey layer between 2 new cells after a plant cell divides

30
Q

plasma membrane

A

selectively permeable membrane that regulates what enters and leaves cell

eukaryotic plasma membrane consists of a phopholipid bilayer with proteins dispersed throughout the layers

around 40% lipid to 60% protein

31
Q

parts of the plasma membrane

integral proteins

A

nonpolar regions that completely span hydrophobic interior of membrane

32
Q

parts of the plasma membrane

peripheral proteins

A

loosely bound to surface of membrane

33
Q

parts of the plasma membrane

cholestrol molecules

A

embedded in interior of bilayer to stabilize membrane

34
Q

parts of the plasma membrane

glycolipids and glycoproteins

A

carbohydrates covalently bounded to proteins or lipids extending form external surface

may serve as signalling molecules that distinguish cell type

35
Q

Function of proteins in the plasma membrane

A
  • Transport: molecules, electrons, ions carried through channels, pumps, carriers, and electron transport chain, which manufactor ATP
  • Enzymatic activity: adenylate cyclase (membrane-bound enzyme) synthesizes cyclic AMP (cAMP) from ATP
  • Signal transduction: binding sites on protein receptors fit chemical messengers (signaling molecule) like hormones, protein changes shape and relays message to the inside of the cell
  • Cell-to-cell recognition: some glycoproteins serve as identificant flags that are recognized by other cells
  • Cell-to-cell attachments: desomosomes, gap junctions, tight junct ions
  • Attachment to the cytoskeleton and extracellular matrix: helps maintain cell shape and stabilizes location of certain membrane proteins
36
Q

transport

A

movement of substances into and out of cell

2 types: active or passive

37
Q

passive transport

A

movement of molecules down a concentration gradient (from high to low) until equilibrium is reached

diffusion and osmosis

does not require energy

38
Q

simple and facilitated diffusion

A

simple does not involve protein channels, but facilitated diffusion does

facilated diffusion requires a hydrophilic protein channel

39
Q

countercurrent exchange

special case of simple diffusion

A

flow of adjacent fluids in opposite directions maximizes rate of simple diffusion

40
Q

osmosis

A

term used for water across a membrane diffusion

41
Q

solvent and solute

A

solvent = substance that does the dissolving
solute = substance that dissolves

42
Q

hypertonic, hypotonic, and isotonic

A

hypertonic: having greater concentration of solute than another solution
hypotonic: having lesser concentration of solute than another solution
isotonic: 2 solutions having equal concentration of solutes

43
Q

osmotic potential

A

tendency of water to move across permeable membrane into a solution

44
Q

water potential

A
  • movement of water
  • pure water has 0 water potential, addition of solutes lower the value to less than 0
  • water moves across a membrane from solution with higher water potential to lower
45
Q

aquaporins

A

special water channel proteins found in certain cells to facilitate diffusion of massive amounts of water across membrane

only affects the rate at which water diffuses down its gradient

46
Q

active transport

A

movement of molecules against a gradient

requires energy (ATP)

47
Q

pumps or carriers

examples of active transport

A

carries particles across membrane by active transport

examples include the sodium potassium pump (pumps Na+ and K+ ions across nerve cell membrane to return the nerve to its resting state) and the electron transport chain (proteins that pump protons across the cristae membrane in mitochondria)

48
Q

contractile vacuole

examples of active transport

A

pumps out excess water that is diffused inward

found in freshwater Protista which lives in a hypotonic environment

49
Q

exocytosis

examples of active transport

A

vesicles release neurotransmitters into a synapse (nerve cells)

50
Q

pinocytosis

examples of active transport

A

cell drinking, uptake of large, dissolved particles

51
Q

phagocytosis

examples of active transport

A

engulfing of large particles/small cells by pseudopods

52
Q

receptor-mediated endocytosis

examples of active transport

A

enables cell to take up large quantities of specific substances

when extracellular substances bind to receptors on the membrane

53
Q

bulk flow

A

overall movement of fluid in one direction in organism

always from source to sink (where it’s used)

54
Q

quorum sensing in bacteria

cell communication

A
  • bateria monitors population density and uses information to control gene expression
  • can allow different bacteria species to communicate
55
Q

direct contact

cell communication

A

signalling substances dissolved in cytosol can pass freely between cells by gap junctions or plasmodesmata (plant cells)

56
Q

local signaling

cell communication

A

release of local signals

For example: growth factors from cell to nearby cells, gives instructions to grow and divide

synaptic signalling (neuron releases neuro-transmitter into synapse) will stimulate adjacent neuron to fire or a muscle to contract

57
Q

long-distance signalling

A

planst use hormones, animals use endocrine glands to release hormones in blood to reach organs/structures

Example: helper T white blood cells can send alarm to entire immune system

58
Q

Three stages of cell signalling:

A
  • Reception: signal molecule (ligand) from outside target cell binds with receptor on or inside target cell
  • **Transduction: **signal converted to form that triggers specific response
  • Response: specific response occurs, by regulation of transcription or cytoplasmic action
59
Q

cell surface receptors

A
  • span entire thickness of membrane, in contact with outside and inside
  • hydrophillic signaling molecules cannot diffuse through membrane
  • receptor changes shape on the cytoplasmic side and is carried by a second messenger (commonly cyclic AMP or cAMP)
  • first messenger (ligand) never enters the cell

cell surface receptors make up 30% of all human protein

60
Q

3 types of cell surface receptors

A
  1. ion-channel
  2. G protein-coupled
  3. protein kinase
61
Q

ion channel receptors

A
  • allosteric receptor that open and shuts gate in membrane, allowing influx of ions (Na+, K+, Ca2+, Cl-)
  • basis of normal nerve function
62
Q

G protein-coupled receptors (GPCR)

A
  • spans cell membrane
  • when a ligand (first messenger) binds to outside domain of receptor, it changes conformation of cytoplasmic side of receptor
  • activates G protein (on/off molecular switch) which bonds to GTP (high energy nucleotide similar to ATP) that activates enzyme adenylyl cyclase
  • enzyme catalyzes conversion of ATP to cyclic-AMP (cAMP) or second messenger
63
Q

protein tyrosine kinases (RTKs)

A
  • has enzymatic activity
  • spans entire membrane
  • part of receptor that extends into cytoplasm functions as tyrosine kinase
  • before ligand binds, receptors are individual units
  • after bind, individual units activate tyrosine kinase region, which bonds to ATP
  • after fully activated, receptor activates relay proteins that lead to cellular response

tyrosine kinase = enzyme that catlyzes transfer of phosphate groups from ATP to amino acid tyrosine)

64
Q

intracellular receptors

A
  • small nonpoplar ligands diffuse through membrane and bind to receptors inside
  • hydrophobic chemical messengers: steroids, thyroid hormones, nitric oxide

some substances in environment (like bisphenol A) mimic hormones like estrogen, believed to be responsible for problems in fetal development

65
Q

transduction

A

activated receptor converts molecular signal into cell response

transduction can sometimes be done in 1 step, but often takes more

66
Q

signal transduction pathway

A

multistep process where little amount of signal molecules produce great response (cascade effect)
good because multistep pathway provides more opportunities to amplify signal

67
Q

5 things about signal transduction pathway

A
  1. characterized by signal, transduction, response
  2. highly specific and regulated
  3. 1 signal molecule can cause cascade effect, releasing thousands of molecules inside
  4. regulate cellular activity, altering gene expression, protein activity, or protein synthesis
  5. pathways evolved millions of years ago in common ancestor
68
Q

apoptosis

A
  • programmed death of infected, damaged, aged cell
  • DNA, organelles, and other components chopped up, packaged in vesicles, and engulgfed by special scavenger cells
  • relies on cell-signallying pathways and outside/inside signals
69
Q

reasons for apoptosis

A
  1. during embryonic development, when cells/tissues are no longer needed and are engulfed by neighboring cells
  2. sustained too much genetic damage and can lead to cancer (esp skin cells)
  3. important for defense against infection by fungus/bacteria in plants
  4. in mammals, several different pathways involving enzymes called caspases carry out apoptosis, signals from inside/outside cell trigger pathways, can be because cell has irreparably damaged DNA in nucleus, or excessive protein misfolding has happened

AP Biology (14 decks)

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