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Cell physiology Flashcards

1
Q

Cell

A

basic unit of life
structural and functional unit
smallest unit that can carry on all of life’s processes independently; ex. obtaining nutrients, converting to ATP, signalling molecules

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2
Q

Cell physiology

A

structure of cells, how they interact with one another and with the larger organism to which they belong

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3
Q

Plasma membrane

A

surrounds cell surface
functions:
1. physical barrier (maintains difference in fluid composition between extra and intracellular fluid [ex. >Na+ outside cell at rest]; maintains homeostasis)
2. Cell-to-cell communication [contains receptors that bind specific signalling molecules like hormones]
3. structural support [specialized connections -proteins- between membranes and extracellular materials]
4. transport [selectively permeable]

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4
Q

cell organelles

A

discrete structures that perform specific functions needed for the cell to survive; compartmentalize
most are membrane bound but some aren’t

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5
Q

cytoplasm

A

region inside the cell, outside of the nucleus
holds organelles
made of cytosol

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6
Q

biological membranes

A

surround cell and most intracellular organelles
double layer of lipid molecules with embedded proteins
have different ratios of lipids and proteins that reflect different functions of cells/organelles

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7
Q

mitochondria membrane

A

higher ratio of proteins (~70%) - crucial for making ATP

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8
Q

lipids

A

made of hydrogens and carbons
some contain oxygen and phosphates
membrane lipids are amphipathic
phospholipids, cholesterol, glycolipids

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9
Q

amphipathic

A

contain both polar (hydrophilic) and non-polar (hydrophobic) regions

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10
Q

phospholipids

A

polar head group - phosphate, nitrogen containing chemical group (R), glycerol backbone
nonpolar tail - 2 fatty acid chains (carbon and hydrogen), both saturated and unsaturated

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11
Q

saturated fatty acid

A

no double bonds in the hydrocarbon chain; all carbons are bonded to the maximum number of hydrogens

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12
Q

unsaturated fatty acid

A

double bonds in the hydrocarbon chain, causes a kink/bend; not all carbons are bonded to the maximum number of hydrogens

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13
Q

phospholipid bilayer

A

amphipathic → forms spontaneously; orients to form an energy favourable structure:
polar heads face aqueous environment; nonpolar tails form hydrophobic core (not in contact with water)

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14
Q

steroids

A

ex. cholesterol
amphipathic - has OH group at end, the only polar region
maintains proper membrane fluidity
organelles do not have cholesterol

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15
Q

glycolipids

A

lipids with CHO chain attached
outside of plasma membrane
amphipathic
form glycocalyx

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16
Q

glycocalyx

A

layer of carbohydrates linked to lipids; role in identification of pathogens and interaction between cells
pericellular matrix - surrounds the cell membranes
made of glycolipids and glycoproteins

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17
Q

membrane proteins

A

integral (intrinsic)
peripheral (extrinsic)
glycoproteins
all membrane proteins have selective permeability and are distributed unequally

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18
Q

integral membrane proteins

A

partially span membrane or transmembrane proteins
amphipathic (part that lies in membrane is non polar, outside of membrane is polar)

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19
Q

peripheral membrane proteins

A

found in the inner or outer surface of membrane
are not amphipathic (polar)

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20
Q

glycoproteins

A

sits outside of membrane on extracellular surface
protein with attached carbohydrates
form glycocalyx

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21
Q

cell junctions

A

stabilize interactions between cells and promote communication
desmosomes - anchor
tight junctions - barrier to movement
gap junctions - communication

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22
Q

desmosomes

A

adhering junctions
anchor cells together in tissues subject to considerable stretching ex. skin, uterus, heart
contain plaques, cadherins, and intermediate filaments

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23
Q

plaques

A

cytoplasmic proteins
attach to cadherins and act as their anchoring point

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24
Q

cadherins

A

span the junction and link the cells together

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25
intermediate filaments
part of cytoskeleton, provide structure and support anchor the cytoplasmic surface of desmosomes to cell components
26
tight junctions
found in epithelial tissue specialized for molecular transport includes occludins
27
epithelial tissue
lines hollow tubes and organs ex. GI tract epithelial cells regulate what crosses from lumen to blood by forming a barrier
28
occludins
form nearly impermeable junctions by linking adjacent cells together attach together like snap buttons limit movement of molecules between cells; pass through cells instead limit movement of integral membrane proteins and lipids
29
example of tight junction
glucose in food has to pass through junction by glucose transporters from lumen/apical side of cell to the basolateral side to reach blood
30
gap junctions
transmembrane channels linking cytoplasms of adjacent cells by connexons electrically (ion movement) and metabolically (bone cells - passage of nutrients) couple cells communicating junctions
31
connexons
transmembrane channels allow movement of molecules if they are small enough
32
nucleus
transmission of genetic material; contains information for protein synthesis (receptors, enzymes, transporters)
33
chromatin
DNA associated with proteins (condenses to form chromosomes during cell division)
34
nuclear envelope
double layered porous membrane (phospholipid)
35
nuclear pores
allow selective movement of molecules in and out of nucleus
36
nucleolus
synthesis of ribosomal RNA
37
structure of nucleus
double phospholipid bilayer makes up the nuclear envelope a protein complex makes up nuclear pores that allow molecules like RNA to pass from cytoplasm to nucleus and back (DNA cannot move through)
38
cells without a nucleus
red blood cells
39
cells with more than one nucleus
(multinucleate) skeletal muscle cells - formed by fusion of precursor cells
40
ribosomes
non membrane bound (no phospholipid bilayer) responsible for protein synthesis have two subunits - each is composed of proteins and ribosomal RNA; subunits join prior to protein synthesis to form functional ribosomes
41
functional ribosomes
free ribosomes - found in cytoplasm ribosomes bound to ER
42
endoplasmic reticulum
fluid-filled membranous system just outside of nucleus
43
rough ER
made of flattened sacs and has a granular appearance - ribosomes bound to its cytosolic surface (the surface facing the cytoplasm) synthesis of proteins with bound functional ribosomes - post-translational modification of proteins
44
smooth ER
branched tubular structure with an agranular appearance - has no ribosomes different functions depending on the cell + its function: - synthesizes lipids (fatty acids, steroids) - stores Ca2+ (muscle cells, sarcoplasmic reticulum) - drug detoxification (liver cells)
45
golgi apparatus
made of 3-8 cisternae incoming and outgoing transport vesicles functions: - post-translational modification of proteins made in RER - sorts and packages proteins
46
cisternae
sets of flattened slightly curved membrane bound sacs stacked in layers
47
path of proteins
protein is made and some modifications occur at RER; then packaged into vesicle and sent to golgi apparatus where further modifications occur; packaged into vesicles and can be: secreted from cell, become integral membrane proteins, or proteins of lysosomes, ER, or golgi
48
lysosomes
~50 per cell contain digestive enzymes - hydrolytic enzymes break down polymers into smaller subunits function at acidic pH degrade extracellular and intracellular debris - recycle cell organelles, destroy endocytosed bacteria and viruses
49
peroxisomes
contain oxidative and antioxidant (catalase) enzymes oxidative use oxygen to remove hydrogen from molecules to break down fatty acids, alcohol, drugs - are abundant in liver and kidneys; produces H2O2 (toxic) catalase breaks down hydrogen peroxide into water and oxygen = no longer toxic
50
mitochondria
has two phospholipid bilayers - inner membrane forms cristae that have lots of enzymes to make ATP cellular respiration have their own DNA (double stranded circular) - symbiotically evolved
51
cells with lots of mitochondria
highly active skeletal muscle, heart muscle, liver, sperm
52
cells with no mitochondria
red blood cells (mitochondria are excreted before maturation)
53
vesicular transport
endocytosis and exocytosis using vesicles (parts of the bilayer) to move materials
54
endocytosis
uptake of material into a cell via vesicles that pinch off from the plasma membrane phagocytosis, pinocytosis, receptor-mediated endocytosis
55
phagocytosis
"cell eating" formation of pseudopodia (extensions of the plasma membrane) to take in something large like bacteria or cell debris ex. white blood cells
56
steps of phagocytosis
1. recognition of bacteria by receptors in membrane 2. attachment of bacteria to phagocyte 3. pseudopodia ingest bacteria into a phagosome (vesicle) 4. phagosome and lysosome fuse to form phagolysosome 5. destruction of bacteria and digestion 6. release of end products into or out of cell (recognition, attachment, ingestion, fusion, digestion, elimination)
57
pinocytosis
"cell drinking" plasma membrane indents to form an endocytic vesicle nonspecific process: extracellular fluid + dissolved substances small molecules
58
receptor mediated endocytosis
receptors in membrane of cell bind specific ligands; clathrin forms a coated pit around inside of membrane and the ligand is concentrated inside the forming vesicle the vesicle may deposit contents into lumen of organelle, travel across cell and fuse with plasma membrane to release contents, or fuse with endosomes which then sort contents to Golgi or lysosomes
59
clathrin
protein that accumulates around membrane in endocytosis to coat vesicle afterwards, it is released to be used again
60
exocytosis
vesicles fuse with plasma membrane and release contents into ECF used to secrete specific substances, release waste products, and replace components to plasma membrane removed by endocytosis
61
driving forces for non-vesicular transport
chemical electrical electrochemical
62
chemical driving force
molecules move passively down the concentration gradient, from an area of high concentration to low as size of gradient increases, the rate of transport of substance increases
63
electrical driving force
ion experiences attractive and repulsive forces due to membrane potential
64
membrane potential
difference in electrical potential or voltage across cell membrane separation of charge
65
electrochemical driving force
sum of electrical and chemical driving forces acting on ion direction depends on the net direction of electrical and chemical driving forces
66
simple diffusion
passive movement of molecules through a biological membrane's lipid bilayer without use of proteins from high to low concentration molecules that are soluble in lipid (non polar/hydrophobic) and smaller in size diffuse more readily ex. fatty acids; ethanol
67
factors influencing the rate of simple diffusion
1. magnitude of driving force 2. membrane surface area ex. villi in intestines 3. membrane permeability
68
membrane permeability
- lipid solubility of diffusing substance is the most important factor in deciding if a molecule can pass by simple diffusion (nonpolar) - size and shape of diffusing substance - smaller and more regularly shaped - temperature = higher temp, higher energy, higher rate - diffusing distance - rate inversely proportional to distance
69
mediated transport
transport of molecule is mediated by proteins facilitated diffusion and active transport
70
facilitated diffusion
passive transport, moving down concentration gradient by carriers or channels specific binding sites for substrate
71
carrier-mediated facilitated diffusion
transported solute binds to the binding site of the transporter protein and causes a conformational change - solute is release inside the cell does not require energy ex. glucose transporters (GLUT family of proteins) move glucose down concentration gradient
72
channel-mediated facilitated diffusion
electrochemical gradient determines ion flux - affected by the potential in the cell channels are selective - for ions or for water (aquaporins)
73
voltage-gated channel
changes in voltage cause the channel to open
74
ligand-gated channel
binding of signaling molecules opens channel
75
mechanically-gated channel
mechanical stimuli such as stretching of the cell causes channel to open
76
active transport
'uphill' transport - against the gradient concentrates substrate requires energy to move from low to high concentration protein has specific binding sites for substrate
77
primary active transport
hydrolysis of ATP releases energy
78
ex. Na+/K+ pump
at rest, the concentration of Na+ is high outside of the cell and the concentration of K+ is high inside the cell the binding of 3Na+ to the pump (intracellular side) causes the hydrolysis of ATP - release of energy and conformational change to pump - releases Na+ outside of cell 2K+ bind to the pump from the outside and cause the release of a phosphate molecule (negatively charged) - re-orient the protein and release K+ inside cell electrogenic creates and maintains Na+ and K+ concentration gradients
79
secondary active transport
couples movement of an ion down its electrochemical gradient with another substance moving against its concentration gradient cotransport and countertransport
80
cotransport
two substances transported in same direction symport
81
ex. Na+/glucose
cotransporter influx of Na+ into the cell provides the energy to drive movement of glucose into the cell the charge on Na+ causes a conformational change to the protein when Na+ binds, moving both Na+ and glucose into the cell electrogenic
82
countertransport
two substances transported in opposite directions antiport
83
ex. Na+/H+ exchanger
countertransport movement of Na+ into the cell drives H+ out of the cell electroneutral (equal charges moving in opposite directions)
84
electrogenic
net movement of charge
85
saturated transport
an increased number of binding sites are occupied as the solute concentration increases - reaches maximum rate when all binding sites are occupied mediated transport
86
non-saturated transport
linear increase in rate according to the concentration; does not reach a maximum simple diffusion (does not involve binding sites)
87
chemical messengers
bind to receptor to produce response can be lipid soluble or water soluble
88
signal transduction
sequence of events between binding of messenger to receptor and the production of a cellular response
89
properties of receptors
specificity for the ligand they bind saturation (amount of ligand they can bind) affinity
90
intracellular receptors
found inside the cell either in the cytoplasm or nucleus, are bound to by lipid-soluble chemical messengers together, the messenger and the receptor bind to response element on DNA
91
transcription factors
alters transcription of mRNA by binding to response element alters rate of protein synthesis
92
response element
specific sequence of DNA near the beginning of a gene
93
membrane-bound receptors
channel, enzyme, or G-protein linked receptors
94
first messenger
hydrophilic extracellular chemical messenger that binds to a specific membrane receptor
95
second messenger
substances that enter or are generated in the cytoplasm in response to the binding of the first messenger to a receptor
96
protein kinase
an enzyme that phosphorylates another proteins and changes the response of something in the cell
97
G-proteins
cytosolic surface of membrane; bind guanosine nucleotides link between GPCR and effector protein 3 types: affect ion channels stimulatory G proteins (Gs) inhibitory G proteins (Gi)
98
G-protein linked receptors
when bound by first messenger, causes conformational change that releases GDP from the G protein (inactive) and causes GTP to bind to the G protein (active)
99
Action of G-proteins on Ion Channels
1. binding of first messenger to receptor causes conformational change in receptor 2. affinity of a-subunit for GTP increases; GDP dissociates, GTP binds 3. GTP-bound a-subunit dissociates from B and y, moves to ion channel 4. ion channel opens or closes to alter flow of ions across membrane
100
Gs proteins
stimulatory; activate enzymes
101
Gi proteins
inhibitory; inhibit enzymes
102
Action of G-proteins on enzymes
1. binding of first messenger to receptor causes conformational change in receptor 2. affinity of a-subunit for GTP increases; GDP dissociates, GTP binds 3. GTP-bound a-subunit dissociates from B and y, moves to enzyme 4. Gs or Gi protein - stimulates or inhibits enzyme 5. alters production of second messenger in cytosol
103
cAMP second messenger system
epinephrine is the first messenger - binds to receptor; a subunit binds to GTP and activates adenylyl cyclase. an enzyme that converts ATP to cAMP - the second messenger cAMP activates cAMP-dependent protein kinase that phosphorylates the protein and causes the cell's response
104
inactivation of cAMP
cAMP is converted to noncyclic AMP by phosphodiesterase
105
calcium as a second messenger
1st messenger binds to receptor (ligand gated ion channel or GPCR) causes increase in cytosolic Ca2+ (influx through calcium channel) → induces Ca2+ release from ER Ca2+ is a second messenger - activates calmodulin → activates calmodulin-dependent protein kinase kinase phosphorylates a protein and causes a cell response
106

Physiology (12 decks)

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