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MAIN STUDY > CH3 > Flashcards

CH3 Flashcards

1
Q

what are the three parts of a cell?

A

cytoplasm (cytosol and organelles)
cell membrane
nucleus (chromosomes and genes)

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2
Q

what is the plasmalemma?

A

the plasma membrane, a flexible yet sturdy barrier surrounding and containing a cell’s cytoplasm

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3
Q

what does cholesterol do in the plasma membrane?

A

stabilizes membrane by making it more flexible or sturdy depending on the temperature

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4
Q

what are the different types of membrane proteins?

A

Ion channel
Carrier
Receptor
Enzyme
Cell Identity Marker
Linker

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5
Q

what do ion channel proteins do?

A

forms a pore through which a specific ion can flow to get across membrane

most only allow one single type of ion to pass through them

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6
Q

what do receptor proteins do?

A

cellular recognition sites, recognizes specific ligands and alters cell’s function in some way

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7
Q

what is a ligand?

A

a chemical substance that binds to a specific receptor

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8
Q

what do carrier proteins/transporters do?

A

transports a specific substance across membrane by undergoing a change in shape

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9
Q

what do enzyme proteins do?

A

catalyzes reaction inside or outside cell depending on which direction active site faces

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10
Q

what do linker proteins do?

A

anchors filaments inside and outside plasma membrane, providing structural stability and shape for the cell

may also participate in movement of the cells or link two cells together

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11
Q

what do cell identity marker proteins do?

A

also known as glycoproteins, distinguishes cells from foreign ones and recognizes other similar cells during tissue formation

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12
Q

why are plasma membranes fluid structures?

A

most of the membrane lipids and proteins move easily in the bilayer

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13
Q

what is the lipid bilayer always permeable to?

A

small, uncharged, nonpolar molecules that can pass through membrane by simple diffusion without assistance of membrane proteins

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14
Q

how do transmembrane proteins increase the plasma membrane’s permeability?

A

acts as channels or transporters for charged and polar molecules to pass through bilayer

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15
Q

what is a concentration gradient?

A

the difference in concentration of a chemical between one side of the membrane and the other side

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16
Q

what is an electrical gradient?

A

the difference in concentration of ions between one side of the membrane and the other side

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17
Q

what is diffusion influenced by?

A
  1. steepness of conc. gradient
  2. temperature
  3. mass/size of diffusing substance
  4. surface area
  5. diffusion distance
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18
Q

what is facilitated diffusion?

A

solutes that are too polar or too highly charged move through lipid bilayer through transmembrane proteins like carrier or channel proteins without the use of ATP

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19
Q

Why does the body have more than one glucose transporter protein in the plasma membranes?

A

glucose is important and acts as primary source of energy

if one protein fails, the rest can still work

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20
Q

what is osmosis?

A

the net movement of water through a selectively permeable membrane from an area of high conc. to an area of low conc.

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21
Q

what is primary active transport?

A

energy derived from ATP directly changes shape of a transporter protein through phosphorylation which allows a substance to cross membrane against its conc. gradient

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22
Q

where is [Na+] higher?

A

outside of the cell

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23
Q

where is [K+] higher?

A

inside the cell

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24
Q

Describe how Na/K ATPase moves Na+ and K+ against their conc. gradients

A
  1. 3 Na from inside cell bind to inside of pump
  2. Na binding triggers ATP binding, ATP - ADP + P, energy released causes protein to change shape and moves Na to outside
  3. 2 K land on outside surface, P is released
  4. Release of P causes pump to go back to orig. shape, moves K into cell
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25
Q

what is secondary active transport?

A

potential energy stored in the asymmetrical H+ or Na+ conc. gradient is used to drive other substances to cross membranes against their own conc. gradients

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26
Q

what are antiporters?

A

movement of ions in a transmembrane protein goes in opposite directions

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27
Q

what are symporters?

A

movement of ions in a transmembrane protein goes in the same directions

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28
Q

what is autophagy?

A

digestion of worn-out organelles by lysosomal enzymes

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29
Q

what is an autophagosome?

A

when an organelle fuses with a lysosome and digests itself`

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30
Q

what is autolysis?

A

destruction of entire cell by lysosomal enzymes

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31
Q

what are the functions of the plasma membrane?

A
  1. acts as barrier separating inside and outside of cell
  2. controls the flow of substances into and out of cell
  3. helps identify cell to other cells (immune cells)
  4. participates in intercellular signalling
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32
Q

what does the plasma membrane’s selectivity mean for the cell?

A

the selectivity of the membrane helps establish and maintain the appropriate environment for normal cellular activities

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33
Q

what is the cytosol?

A

also called ICF, the semifluid portion of cytoplasm where the organelles and inclusions are suspended in and solutes are dissolved in

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34
Q

how is the plasma membrane a fluid structure?

A

lipids and many of the proteins are free to rotate and move sideways in their own half of the bilayer

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35
Q

is cholesterol amphiphatic?

A

Yes,
POLAR - -OH group can form hydrogen bonds with polar regions of phospholipids and glycolipids
NONPOLAR - rigid steroid rings and hydrocarbon tail can fit among the inner nonpolar region of cell membrane

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36
Q

what are integral proteins?

A

proteins that extend into or through plasma membrane and are embedded in it

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37
Q

what are transmembrane proteins?

A

proteins that span entire plasma membrane and protrude into both cytosol and ECF

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38
Q

what are peripheral proteins?

A

proteins that are not as firmly embedded into plasma membrane, attached to polar heads of membrane lipids or to integral proteins at either surface of membrane

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39
Q

what are glycoproteins?

A

proteins with carbo groups attached to ends that protrude into ECF

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40
Q

what is glycocalyx?

A

the extensive sugary coat formed from the carb portion of glycolipids and glycoproteins

  • pattern of carbs varies from one cell to another
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41
Q

what does the glycocalyx do for the cell?

A
  • acts like a molecular signature that enables cells to recognize one another
  • enables cells to adhere to one another in some tissues
  • protects cells from being digested by enzymes in ECF
  • WBC ability to detect foreign glycocalyx is one basis for immune response
  • hydrophilic properties attract film of fluid to surface of cells, makes them slippery, protects from drying out
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42
Q

what can peripheral proteins do?

A

help support plasma membrane,
anchor integral proteins,
participate in moving materials and organelles within cells,
changing cell shape during cell division, attaching cells to one another

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43
Q

what does membrane fluidity depend on?

A
  • the number of double bonds in the fatty acid tails of the lipids
  • the number of cholesterols present
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44
Q

what do double bonds in the fatty acid tails mean?

A
  • puts a kink on the tail, increases fluidity by preventing tight packing in the membrane
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45
Q

why is maintaining membrane fluidity important?

A

membrane fluidity allows interactions to occur within the plasma membrane and enables movement of membrane components

  • a rigid membrane lacks mobility
  • a completely fluid membrane lacks structural organization and mechanical support required by cell
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46
Q

why do phospholipids rarely flip from one layer of the membrane to another?

A

it is difficult for hydrophilic parts of membrane molecules to pass through hydrophobic core of membrane

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47
Q

what effect does cholesterol have on membrane fluidity at different temperatures?

A

Normal Body temp: cholesterol makes lipid bilayer stronger and more rigid

Lower temp: cholesterol makes lipid bilayer more fluid but less strong

this is because of how it forms H bonds w/ neighbouring molecules and how it fills space between bent fatty acid tails

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48
Q

describe the permeability of different substances through the plasma membrane

A

highly permeable to nonpolar molecules (O2, CO2, steroids)

moderately permeable to small, uncharged polar molecules (H2O, urea)

impermeable to ions and large, uncharged polar molecules (starch, glucose)

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49
Q

Explain why H2O and urea can unexpectedly pass through lipid bilayer given that they are polar molecules?

A

as the fatty acid tails randomly move about, small gaps briefly appear in the hydrophobic interior. because water and urea are small, can move from one gap to another until they cross membrane

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50
Q

what are passive processes?

A

processes where substance moves down its conc. gradient to cross the membrane using only its own kinetic energy

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51
Q

what is the transport maximum?

A

the upper limit on the rate at which facilitated diffusion occurs

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52
Q

when is the transport maximum reached?

A

transport maximum is determined by number of available carriers in the plasma membrane, so maximum is reached once all carriers are occupied

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53
Q

how does glucose enter body cells by carrier-mediated facilitated diffusion?

A
  1. glucose binds to glucose transporter (GluT) on outside surface of membrane
  2. glucose passes through membrane as carrier protein changes shape
  3. carrier protein releases glucose on other side of membrane
54
Q

how does insulin affect glucose’s rate of diffusion into cells?

A

insulin elevates the transport maximum for facilitated diffusion of glucose across membrane because it promotes insertion of many GluT copies into membranes of certain cells, increasing rate of diffusion for glucose

55
Q

what are aquaporins?

A

integral membrane proteins that function as water channels, controlling water content in cells

56
Q

what is a solution’s tonicity?

A

the measure of the solution’s ability to change the volume of cells by altering their water content

57
Q

what is osmotic pressure?

A

force exerted by solution with impermeable solute

58
Q

what happens during exocytosis?

A

membrane-enclosed vesicles called secretory vesicles form inside cell, fusing with plasma membrane and releasing contents into ECF

59
Q

what is the cytoskeleton?

A

network of protein filaments extending throughout cytosol, complex internal structure consisting of microfilaments, microtubules, and intermediate filaments

60
Q

what are microfilaments?

A

thinnest elements of cytoskeleton, composed of actin and myosin and most prevalent at edge of cell

61
Q

what are the functions of microfilaments?

A

help generate movement and provide mechanical support

  • anchor cytoskeleton to integral proteins in plasma membrane
  • involved in muscle contraction, cell division, cell locomotion like in migration of skin cells during wound healing, migration of embryonic cells during development, invasion of tissues by WBCs to fight infection
62
Q

what are microvilli?

A

cell extensions that are supported by microfilaments, greatly increase cell surface area

63
Q

what are intermediate filaments?

A

filaments thicker than microfilaments but thinner than microtubules, composed of several proteins, found in parts of cells subject to mechanical stress, help stabilize the position of organelles like nucleus, and help attach cells to one another

64
Q

what are the functions of the cytoskeleton?

A
  1. serves as scaffold that helps determine cell’s shape and organize cellular contents
  2. aids movement of organelles within cell, of chromosome during cell division, and of whole cells such as phagocytes
65
Q

what are microtubules?

A

largest of cytoskeletal components, long unbranched hollow tubes composed mainly of the protein tubulin

66
Q

what are the functions of microtubules?

A

help determine cell shape, movement of organelles such as secretory vesicles and chromosomes during cell division, and of specialized cell projections like cilia and flagella

67
Q

where do microtubules originate from?

A

centrosomes. microtubules grow outward from centrosome towards periphery of cell

68
Q

what is a centrosome?

A

microtubule organizing center, located near nucleus, consists of a pair of centrioles and the pericentriolar matric

69
Q

what are centrioles?

A

cylindrical structure composed of nine clusters of microtubular triplets arranged in a circular pattern

70
Q

what is the pericentriolar matrix?

A

matrix containing hundreds of ring-shaped complexes composed of tubulin, organizing centers for growth of mitotic spindle and for microtubule formation in nondividing cells

71
Q

what are cilia?

A

short hairlike projections extending from cell surface, each containing a core of 20 microtubules surrounded by the plasma membrane, each is anchored to a basal body just below membrane surface

72
Q

what is a basal body?

A

similar to centriole, cylindrical structure composed of nine clusters of microtubular triplets arranged in a circular pattern, functions in initiating assembly of cilia and flagella

73
Q

what are the functions of cilia?

A

cilia move fluids along a cell’s surface

74
Q

what are the functions of flagella?

A

flagella move entire cell

75
Q

what are flagella?

A

long hairlike projections extending from cell surface, each containing a core of 20 microtubules surrounded by the plasma membrane, each is anchored to a basal body just below membrane surface, generates forward motion by rapidly wiggling in a wavelike pattern

76
Q

what are ribosomes?

A

site of protein synthesis, composed of rRNA, consists of two subunits which are separately made in nucleolus

77
Q

what is the endoplasmic reticulum?

A

network of membranes in the form of flattened saccules, extends from nuclear envelope and projects throughout cytoplasm

78
Q

what do ribosomes associated w rough ER make?

A

proteins destined for insertion in plasma membrane or secretion from cell

79
Q

what do free ribosomes make?

A

proteins to be used in the cytosol

80
Q

what happens to proteins in the rough ER?

A

processing and sorting, formation of glycoproteins, attachment of proteins to phospholipids, secretory proteins, membrane proteins, organellar proteins

81
Q

what is the function of smooth ER?

A

contains unique enzymes allowing it to synthesize fatty acids and steroids (estrogen and testosterone)

inactivates/detoxifies drugs, removes P from glucose-6-phosphate, stores and releases Ca2+ that trigger contraction in muscle fibers

82
Q

what happens in the golgi complex?

A

entry face receives and modifies proteins produced by rough ER, intermediate saccules add carbs and lipids to proteins, exit face modifies molecules further and then sorts and packages them for transport to destinations

83
Q

what are the three general destinations for proteins that leave golgi complex?

A
  1. transport to lysosomes by transport vesicles
  2. secreted to outside by exocytosis by secretory vesicles
  3. integrated into plasma membrane by membrane vesicles
84
Q

why does lysosomal membrane have active transport pumps for H+?

A

because lysosomes work best at low pH

85
Q

what are the functions of lysosomes?

A
  1. digest substances that enter a cell via endocytosis and transport final products of digestion into cytosol
  2. carry out autophagy, digestion of worn out organelles
  3. carry out autolysis, digestion of entire cell
  4. accomplish extracellular digestion
86
Q

what are perixosomes?

A

also called microbodies, similar but smaller than lysosomes and have oxidases that can oxidize substances

abundant in liver, where detoxification of alcohol occurs

byproduct is H2O2

87
Q

what are proteasomes?

A

tiny cellular organelles containing proteases that destroy unneeded, damaged, or faulty proteins in cytosol and nucleus

88
Q

what is apoptosis?

A

the orderly, genetically programmed death of a cell

89
Q

what are the functions of the nucleus?

A
  1. controls cellular structure
  2. directs cellular activities
  3. produces ribosomes in nucleoli
90
Q

what are the functions of mitochondria?

A
  1. Carry out cellular respiration
  2. plays early role in apoptosis
91
Q

what is a nucleosome?

A

double-stranded DNA wrapped twice around a core of eight histone proteins

92
Q

what is a proteome?

A

all of an organism’s proteins

93
Q

what is the promoter region?

A

segment of DNA where transcription begins, located near the beginning of a gene, where RNA polymerase attaches to DNA

94
Q

what is the terminator region?

A

segment of DNA where transcription ends, when RNA poly. reaches terminator, it detaches from the RNA molecule and DNA strand

95
Q

what is pre-mRNA?

A

the primary transcript, introns still present and have not been spliced out by the snRNPS

96
Q

what is alternative splicing?

A

one primary transcript can be spliced differently into various mRNA

one gene can code for more than one proteins

97
Q

describe the role of translation

A
  1. Initiator tRNA attaches to start codon
  2. subunits join, initiator tRNA fits into P site
  3. incoming tRNA fits into A site
  4. AA at A site bonds to AA at P site
  5. the dipeptide attaches to tRNA at A site
  6. Ribosome shifts by one codon. tRNA at P site moves to E site and exits
  7. protein synthesis stops when ribosome reaches stop codon on mRNA
98
Q

what is a polyribosome?

A

multiple ribosomes attaches to one mRNA, permitting translation of one mRNA into several identical proteins at the same time

99
Q

what happens in G1 phase?

A

cell metabolically active, duplicates organelles and cytosolic components, centrosome replication begins, cell prepares for DNA replication (8-10hrs)

100
Q

what happens in S phase?

A

DNA duplication (8 hrs)

101
Q

what happens in G2 phase?

A

cell growth continues, enzymes and proteins used in mitosis synthesized, centrosome replication completed (4-6hrs)

102
Q

why is DNA replication important?

A

so the two identical cells formed in cell division have same genetic material

103
Q

what happens in prophase?

A

chromatin fibers condense and shorten into chromosomes

tubulins in pericentriolar matrix start to form mitotic spindle that attach to kinetochores

as microtubules lengthen, they push centrosomes to opposite poles

nucleolus disappears and nuclear envelope breaks down

104
Q

why is condensation of chromatin into chromosomes important?

A

to prevent detangling of the long DNA strands as they move during mitosis

105
Q

what happens during metaphase?

A

microtubules of mitotic spindle align w centromeres of the chromatid pairs at the exact center of mitotic spindle, aka metaphase plate

106
Q

what happens in anaphase?

A

centromeres are split, separating each chromatid pair and they move towards opposite poles of the cell

107
Q

what happens in telophase?

A

chromosomal movement stops

chromosomes revert and uncoil into chromatin

nuclear envelope and nucleolus reappear in both identical nuclei

108
Q

what happens in cytokinesis?

A

begins in late anaphase with the formation of a cleavage furrow

109
Q

what is the cleavage furrow?

A

actin microfilaments below the membrane surface form a contractile ring that pulls plasma membrane progressively inward, ultimately pinching it into two

110
Q

what are the three possible destinies a cell can have?

A
  1. to remain alive and functioning without dividing
  2. to grow and divide
  3. to die
111
Q

what are cyclin dependent kinases?

A

kinases that transfer a phosphate group from ATP to activate proteins, activated by cyclins

112
Q

what is necrosis?

A

the death of a cell due to tissue injury

113
Q

what are the two events that occur in prophase I but don’t occur in mitotic prophase?

A
  1. synapsis - the two sister chromatids of each homologous pair form a tetrad
  2. crossing over - parts of the chromatids exchange
114
Q

what does crossing over do?

A

the resulting cells are genetically different, genetic recombination

115
Q

what is different between mitotic anaphase and anaphase I?

A

in anaphase I, the sister chromatids remain paired up

116
Q

what is one reason some tissues become stiffer as we age?

A

glucose is haphazardly added to proteins inside and outside cells, forming irreversible crosslinks between adjacent protein molecules

as we age, more crosslinks form, contributing to stiffening and loss of elasticity in aging tissues

117
Q

what is cancer?

A

a group of diseases associated with uncontrolled or abnormal cell division

118
Q

what is a neoplasm?

A

tumor, excess tissue resulting from cells dividing without control

119
Q

what is oncology?

A

the study of tumours

120
Q

what is metastasis?

A

the spread of cancerous cells to other parts of the body, most malignant tumours can metastasize

121
Q

what are carcinomas?

A

cancers from malignant tumours that arise from epithelial cells

122
Q

what are melanomas?

A

cancerous growths of melanocytes

123
Q

what are sarcomas?

A

general term for any cancer arising from muscle fibers or connective tissues

124
Q

what is osteogenic sarcoma?

A

cancer that destroys normal bone tissue

125
Q

what is leukemia?

A

cancer of blood-forming organs characterized by rapid growth of abnormal leukocytes

126
Q

what is lymphoma?

A

cancer of lymphatic tissue, usually lymph nodes

127
Q

what is angiogenesis?

A

the growth of new networks of blood vessels, usually triggered by malignant tumours after invading surrounding tissues

128
Q

what are tumor angiogenesis factors?

A

proteins that stimulate angiogenesis in tumours

129
Q

what are secondary tumours?

A

malignant cells that detach from primary tumor and invade body cavity or blood plasma, then circulate to and invade other body tissues

130
Q

what are some causes of cancers?

A
  1. carcinogens - environmental agents
  2. oncogenes - cancer-causing genes
  3. oncogenic viruses

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