CH3 Flashcards
1
Q
what are the three parts of a cell?
A
cytoplasm (cytosol and organelles)
cell membrane
nucleus (chromosomes and genes)
2
Q
what is the plasmalemma?
A
the plasma membrane, a flexible yet sturdy barrier surrounding and containing a cell’s cytoplasm
3
Q
what does cholesterol do in the plasma membrane?
A
stabilizes membrane by making it more flexible or sturdy depending on the temperature
4
Q
what are the different types of membrane proteins?
A
Ion channel
Carrier
Receptor
Enzyme
Cell Identity Marker
Linker
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
6
Q
what do receptor proteins do?
A
cellular recognition sites, recognizes specific ligands and alters cell’s function in some way
7
Q
what is a ligand?
A
a chemical substance that binds to a specific receptor
8
Q
what do carrier proteins/transporters do?
A
transports a specific substance across membrane by undergoing a change in shape
9
Q
what do enzyme proteins do?
A
catalyzes reaction inside or outside cell depending on which direction active site faces
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
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
12
Q
why are plasma membranes fluid structures?
A
most of the membrane lipids and proteins move easily in the bilayer
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
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
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
16
Q
what is an electrical gradient?
A
the difference in concentration of ions between one side of the membrane and the other side
17
Q
what is diffusion influenced by?
A
- steepness of conc. gradient
- temperature
- mass/size of diffusing substance
- surface area
- diffusion distance
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
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
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.
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
22
Q
where is [Na+] higher?
A
outside of the cell
23
Q
where is [K+] higher?
A
inside the cell
24
Q
Describe how Na/K ATPase moves Na+ and K+ against their conc. gradients
A
- 3 Na from inside cell bind to inside of pump
- Na binding triggers ATP binding, ATP - ADP + P, energy released causes protein to change shape and moves Na to outside
- 2 K land on outside surface, P is released
- Release of P causes pump to go back to orig. shape, moves K into cell
25
what is secondary active transport?
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
26
what are antiporters?
movement of ions in a transmembrane protein goes in opposite directions
27
what are symporters?
movement of ions in a transmembrane protein goes in the same directions
28
what is autophagy?
digestion of worn-out organelles by lysosomal enzymes
29
what is an autophagosome?
when an organelle fuses with a lysosome and digests itself`
30
what is autolysis?
destruction of entire cell by lysosomal enzymes
31
what are the functions of the plasma membrane?
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
32
what does the plasma membrane's selectivity mean for the cell?
the selectivity of the membrane helps establish and maintain the appropriate environment for normal cellular activities
33
what is the cytosol?
also called ICF, the semifluid portion of cytoplasm where the organelles and inclusions are suspended in and solutes are dissolved in
34
how is the plasma membrane a fluid structure?
lipids and many of the proteins are free to rotate and move sideways in their own half of the bilayer
35
is cholesterol amphiphatic?
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
36
what are integral proteins?
proteins that extend into or through plasma membrane and are embedded in it
37
what are transmembrane proteins?
proteins that span entire plasma membrane and protrude into both cytosol and ECF
38
what are peripheral proteins?
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
39
what are glycoproteins?
proteins with carbo groups attached to ends that protrude into ECF
40
what is glycocalyx?
the extensive sugary coat formed from the carb portion of glycolipids and glycoproteins
- pattern of carbs varies from one cell to another
41
what does the glycocalyx do for the cell?
- 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
42
what can peripheral proteins do?
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
43
what does membrane fluidity depend on?
- the number of double bonds in the fatty acid tails of the lipids
- the number of cholesterols present
44
what do double bonds in the fatty acid tails mean?
- puts a kink on the tail, increases fluidity by preventing tight packing in the membrane
45
why is maintaining membrane fluidity important?
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
46
why do phospholipids rarely flip from one layer of the membrane to another?
it is difficult for hydrophilic parts of membrane molecules to pass through hydrophobic core of membrane
47
what effect does cholesterol have on membrane fluidity at different temperatures?
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
48
describe the permeability of different substances through the plasma membrane
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)
49
Explain why H2O and urea can unexpectedly pass through lipid bilayer given that they are polar molecules?
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
50
what are passive processes?
processes where substance moves down its conc. gradient to cross the membrane using only its own kinetic energy
51
what is the transport maximum?
the upper limit on the rate at which facilitated diffusion occurs
52
when is the transport maximum reached?
transport maximum is determined by number of available carriers in the plasma membrane, so maximum is reached once all carriers are occupied
53
how does glucose enter body cells by carrier-mediated facilitated diffusion?
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
how does insulin affect glucose's rate of diffusion into cells?
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
what are aquaporins?
integral membrane proteins that function as water channels, controlling water content in cells
56
what is a solution's tonicity?
the measure of the solution's ability to change the volume of cells by altering their water content
57
what is osmotic pressure?
force exerted by solution with impermeable solute
58
what happens during exocytosis?
membrane-enclosed vesicles called secretory vesicles form inside cell, fusing with plasma membrane and releasing contents into ECF
59
what is the cytoskeleton?
network of protein filaments extending throughout cytosol, complex internal structure consisting of microfilaments, microtubules, and intermediate filaments
60
what are microfilaments?
thinnest elements of cytoskeleton, composed of actin and myosin and most prevalent at edge of cell
61
what are the functions of microfilaments?
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
what are microvilli?
cell extensions that are supported by microfilaments, greatly increase cell surface area
63
what are intermediate filaments?
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
what are the functions of the cytoskeleton?
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
what are microtubules?
largest of cytoskeletal components, long unbranched hollow tubes composed mainly of the protein tubulin
66
what are the functions of microtubules?
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
where do microtubules originate from?
centrosomes. microtubules grow outward from centrosome towards periphery of cell
68
what is a centrosome?
microtubule organizing center, located near nucleus, consists of a pair of centrioles and the pericentriolar matric
69
what are centrioles?
cylindrical structure composed of nine clusters of microtubular triplets arranged in a circular pattern
70
what is the pericentriolar matrix?
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
what are cilia?
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
what is a basal body?
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
what are the functions of cilia?
cilia move fluids along a cell's surface
74
what are the functions of flagella?
flagella move entire cell
75
what are flagella?
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
what are ribosomes?
site of protein synthesis, composed of rRNA, consists of two subunits which are separately made in nucleolus
77
what is the endoplasmic reticulum?
network of membranes in the form of flattened saccules, extends from nuclear envelope and projects throughout cytoplasm
78
what do ribosomes associated w rough ER make?
proteins destined for insertion in plasma membrane or secretion from cell
79
what do free ribosomes make?
proteins to be used in the cytosol
80
what happens to proteins in the rough ER?
processing and sorting, formation of glycoproteins, attachment of proteins to phospholipids, secretory proteins, membrane proteins, organellar proteins
81
what is the function of smooth ER?
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
what happens in the golgi complex?
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
what are the three general destinations for proteins that leave golgi complex?
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
why does lysosomal membrane have active transport pumps for H+?
because lysosomes work best at low pH
85
what are the functions of lysosomes?
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
what are perixosomes?
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
what are proteasomes?
tiny cellular organelles containing proteases that destroy unneeded, damaged, or faulty proteins in cytosol and nucleus
88
what is apoptosis?
the orderly, genetically programmed death of a cell
89
what are the functions of the nucleus?
1. controls cellular structure
2. directs cellular activities
3. produces ribosomes in nucleoli
90
what are the functions of mitochondria?
1. Carry out cellular respiration
2. plays early role in apoptosis
91
what is a nucleosome?
double-stranded DNA wrapped twice around a core of eight histone proteins
92
what is a proteome?
all of an organism's proteins
93
what is the promoter region?
segment of DNA where transcription begins, located near the beginning of a gene, where RNA polymerase attaches to DNA
94
what is the terminator region?
segment of DNA where transcription ends, when RNA poly. reaches terminator, it detaches from the RNA molecule and DNA strand
95
what is pre-mRNA?
the primary transcript, introns still present and have not been spliced out by the snRNPS
96
what is alternative splicing?
one primary transcript can be spliced differently into various mRNA
one gene can code for more than one proteins
97
describe the role of translation
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
what is a polyribosome?
multiple ribosomes attaches to one mRNA, permitting translation of one mRNA into several identical proteins at the same time
99
what happens in G1 phase?
cell metabolically active, duplicates organelles and cytosolic components, centrosome replication begins, cell prepares for DNA replication (8-10hrs)
100
what happens in S phase?
DNA duplication (8 hrs)
101
what happens in G2 phase?
cell growth continues, enzymes and proteins used in mitosis synthesized, centrosome replication completed (4-6hrs)
102
why is DNA replication important?
so the two identical cells formed in cell division have same genetic material
103
what happens in prophase?
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
why is condensation of chromatin into chromosomes important?
to prevent detangling of the long DNA strands as they move during mitosis
105
what happens during metaphase?
microtubules of mitotic spindle align w centromeres of the chromatid pairs at the exact center of mitotic spindle, aka metaphase plate
106
what happens in anaphase?
centromeres are split, separating each chromatid pair and they move towards opposite poles of the cell
107
what happens in telophase?
chromosomal movement stops
chromosomes revert and uncoil into chromatin
nuclear envelope and nucleolus reappear in both identical nuclei
108
what happens in cytokinesis?
begins in late anaphase with the formation of a cleavage furrow
109
what is the cleavage furrow?
actin microfilaments below the membrane surface form a contractile ring that pulls plasma membrane progressively inward, ultimately pinching it into two
110
what are the three possible destinies a cell can have?
1. to remain alive and functioning without dividing
2. to grow and divide
3. to die
111
what are cyclin dependent kinases?
kinases that transfer a phosphate group from ATP to activate proteins, activated by cyclins
112
what is necrosis?
the death of a cell due to tissue injury
113
what are the two events that occur in prophase I but don't occur in mitotic prophase?
1. synapsis - the two sister chromatids of each homologous pair form a tetrad
2. crossing over - parts of the chromatids exchange
114
what does crossing over do?
the resulting cells are genetically different, genetic recombination
115
what is different between mitotic anaphase and anaphase I?
in anaphase I, the sister chromatids remain paired up
116
what is one reason some tissues become stiffer as we age?
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
what is cancer?
a group of diseases associated with uncontrolled or abnormal cell division
118
what is a neoplasm?
tumor, excess tissue resulting from cells dividing without control
119
what is oncology?
the study of tumours
120
what is metastasis?
the spread of cancerous cells to other parts of the body, most malignant tumours can metastasize
121
what are carcinomas?
cancers from malignant tumours that arise from epithelial cells
122
what are melanomas?
cancerous growths of melanocytes
123
what are sarcomas?
general term for any cancer arising from muscle fibers or connective tissues
124
what is osteogenic sarcoma?
cancer that destroys normal bone tissue
125
what is leukemia?
cancer of blood-forming organs characterized by rapid growth of abnormal leukocytes
126
what is lymphoma?
cancer of lymphatic tissue, usually lymph nodes
127
what is angiogenesis?
the growth of new networks of blood vessels, usually triggered by malignant tumours after invading surrounding tissues
128
what are tumor angiogenesis factors?
proteins that stimulate angiogenesis in tumours
129
what are secondary tumours?
malignant cells that detach from primary tumor and invade body cavity or blood plasma, then circulate to and invade other body tissues
130
what are some causes of cancers?
1. carcinogens - environmental agents
2. oncogenes - cancer-causing genes
3. oncogenic viruses
