Unit 2 Flashcards
1
Q
Describe the general function of biological membranes
A
provide structural basis for metabolic order (without membrane no homeostasis/metabolism)
2
Q
Describe the fluid mosaic model of plasma membrane structure and describe the experiment for this model
A
Mouse and human cells were fused to show that plasma membrane proteins and phospholipids must be able to move around bilayer, since its fluid
3
Q
What is membrane fluidity
A
fluid state of the membrane which depends on lipid components (alter quantity of unsaturated fatty acids in response to temperature changes)
4
Q
What are the 3 main functions of the plasma membrane
A
1-separate the cell from the exterior
2-create a controlled intracellular envrionment
3-Selective permeability: allow some molecules to enter and dispose of waste
5
Q
Describe the relationship between membrane fluidity and membrane permeability
A
Proportional relationship= if fluidity decreases so does permeability (more rigid so harder for molecules to pass through and vice-versa)
6
Q
Describe relationship between membrane fluidity and temperature
A
if temp increase=membrane becomes too fluid/flexible= cant hold its shape
if temp decreases= membrane becomes too rigid and can even break
7
Q
Describe relationship between membrane fluidity and saturation of fatty acids
A
saturated fatty acids reduce fluidity of membrane since they’re solid at room temp
unsaturated fatty acids increase fluidity since liquid at room temp
8
Q
Describe relationship between membrane fluidity and length of fatty acids
A
the longer the chain=more rigid since stronger LDF forces
shorter fatty acid=more fluid since less LDF
9
Q
Describe relationship between membrane fluidity and amount of cholesterol
A
increased cholesterol in the membrane means it will adjust to temp changes more easily (maintain fluidity)
10
Q
What is the role of cholesterol in the membrane
A
acts as fluidity buffer
-if membrane becomes too fluid=it binds to hydrophilic head to stabilize it (restrain phospholipid mouvement)
-if membrane too rigid=inserts itself between fatty acid tails to reduce LDF
11
Q
What is homeoviscous adaptation
A
the ability to change the fatty acid content of membrane lipids to maintain its fluidity
12
Q
What is selective permeabilty and the 2 types of membrane transport
A
ability of membrane to allow some molecules to pass and block others (affected by size/polarity)
Active and passive transport
13
Q
What are the 2 kinds of membrane proteins
A
integral (inside) and peripheral (outside)
14
Q
Describe integral protein
A
assembled by rough ER ribosomes and bounded to the bilayer (in the core)
Amphipathic molecules but mostly non polar (made of nonpolar amino acids)
15
Q
True of false
All integral proteins extend from one end to the other (of plasma membrane)
A
False
16
Q
What are called proteins that extend along the phospholipid bilayer
A
transmembrane protein
17
Q
Why are transmembrane protein amphipatic
A
To be able to bind with the hydrophobic and hydrophillic part of membrane
18
Q
Describe peripheral membrane protein
A
membrane protein on the inner or outer surface (not embedded)
If on the outside surface=made by rough ER
if on inner surface=made by free ribosomes
Can perform enzymatic/receptor functions
19
Q
Give an example of intergral protein
A
aquaporins or glycoproteins
20
Q
Explain the assymetrical distribution of the cytoplasmic and extracellular face of PM
A
asymmetry is produced by the high specific way each protein is inserted
asymmetry gives each side specific characteristics
21
Q
Why is selctive permeability important
A
it allows the cell to control and maintain its internal components (what comes in/out of the cell)
22
Q
How do membrane lipids and membrane proteins contribute to selective permeability
A
membrane protein aid the transport of certain molecules in/out of cell and membrane lipid maintain fluidity constant to allow for the transport of molecules through the bilayer.
23
Q
State the 6 major functions of membrane proteins
A
intercellular joining
cell-to-cell recognition
transport
enzymatic fxn
attachement to the ECM
signal transduction
24
Q
Describe cell-cell recognition
A
provides identity tages for cell
important for immune systems=allows it to regognize and reject foreign bodies
enables cellsto sort themselves into tissue/organs
25
What are autoimmune diseases
immune system fails to distinguish own cells from foreign ones so it attcks healthy cells.
26
Describe intercellular joining
membrane protein of neighbouring cells hook together via different junctions
27
What are the different kinds of junctions in plant cells
plasmodesmata
28
What are the different kinds of junctions in animal cells
desmosomes (for anchoring)
gap junction (for communications)
tight junctions (for leaks)
29
describe briefly the plasmodesmata
channels for rapid communication between plant cells that can dilate
connects PM and cell wall
allows for small molecules/ions/water excahneg and chemical signalling
30
describe briefly the desmodomes
attaches adjacent animal cells without stop passage of sybstances in between
very strong
made of button discs (on cytosplasmic side) and intermediate filaments
31
What is the purpose of intermediate filaments
redistribute mechanical stress on tissue
32
Why cant plant cells have a desmodomes
they have a strong cell wall
33
describe briefly tight junctions
proteins are physical attched= form sheet of tissue
tightly attaches animal cells to prevent any substance leaks
34
Where would tight junctions be found
stomach (prevent acid secretions)
brain capillaries
35
describe briefly gap junctions
brigde space with a channel between animal cells for rapid chemical and electrical communication
connects the cytoplasm of adjacent cells
36
Where would gap junctions be found
heart cells and pancreas
37
Describe the membrane protein that create attachements to ECM
membrane protein that do not move and keep the membran in place
not covenlently bonded to ECM fibers/cytoskeleton
38
How does the ECM work
made of glycoprotein/lipids (like collagen)
has fibronectin that connect to integrin which connect to cytoskeleton
39
What are fibronectins
glycoprotein that organize the matrix and aid cell in attaching to matrix by binding with integrins
40
what are integrins
integral transmembrane proteins that function in cell signalling (ECM receptor), organize cytoskeleton (maintain shape/mouvement) and anchor ECM to microfilaments
41
Describe the process of diffusion
mouvement of solute across a membrane, due to its concentration gradient (high to low) until eq is reached
doesn't need energy input
42
True or false
Diffusion is not spontaneous
false it is
43
What is net diffusion
net mouvement of particles
44
What is dynamic equilibrium in diffusion
concentration gradient no longer exists= no net mouvement BUT particles are still moving across membrane
45
What factors affect the rate of diffusion of a substance
temperature, steepness of concentration gradient, idk
46
Does diffusion reach eq in cells
no since the envrionement is always changing
47
What is the difference between facilitated and simple diffusion in cells
simple: molecules diffuses freely (non polar compound)
facilitated diffusion: transport proteins speed up mouvement of polar/ large molecules across the membrane
48
What are channel proteins
gated membrane protein that open/close to regulate passage of solute
provide hydrophilic corridor for polar molecules to pass
ex: aquporin of ion channels
49
What are carrier proteins
proteins that undergo shape change once they bind with solute cause translocation of binding site across membrane
50
Are carrier proteins faster or slower than channel proteins and why
slower since they change shape
51
What are the 3 types of carrier proteins
uniporter
symporter
antiporter
52
Define osmosis
movement of water across a semi permeable membrane
osmosis is driven by impermeable solute only BUT water is the one that moves across and dissipate the gradient (low to high)
53
Is osmosis spontaneous
yes
54
Define osmotic pressure
hydrostatic pressure needed to stop net flow of water across membrane due to osmosis
55
Define tonicity
the ability of a solution to cause a net gain/loss of water in a cell
56
Define effective osmolarity
the total concentration of impermeable solutes
57
Define hypertonic, hypotonic or isotonic
isotonic= solution has same concentration as the cell= not net mouv. of water
hypertonic=solution has higher concentration than the cell= cause net loss of water= cell becomes shriveled
hypotonic=solution has lower concentration than cell=net gain of water=lysed cell
58
Define osmoregulation
control of water balance
ex: paramecium with contractile vacuole
59
What happens to plant cell when it is place in isotonic solution
becomes flaccid
60
What happens to the plant cell when it is placed in hypertonic solution
becomes plasmolysed aka shriveled
61
What happens to the plant cell when it is placed in hypotonic solution
it becomes turgid so normal
62
Describe active transport
when solutes moves against concentration gradient (needs atp)
63
Is active transport spontaneous
no
64
Whats the difference between primary active transported and facilitated diffusion
active transport goes against concentration gradient
faciliated diffusion follows concentration gradient and is driven by the gradient from active transport
65
Whats an electrogenic pump
Pump that generate a voltage
66
Whats the main electrogenic pupm in animals
Sodium Potassium ATPase
67
Define electrochemical gradient and how they're made
different net charges on each side of the membrane and concentration gradient that's caused by an ion pump (active transport)
68
What is the membrane potential of a cell
voltage difference across the membrane
69
What processes do electrochemical gradients drive
cellular respiration, transmission of nerve impulses and muscle contractions
70
Describe secondary active transport
takes advantage of the concentration gradient created by prijary to drive the diffusion of more useful molecule (against its gradient)
71
Give an example of secondary active transport in plants and animals
animals: Glucose/Na+ symporter (in intestine)
in plants: Sucrose-H+ cotransporter
72
Why are membrane potential important
it favors the passive transport of cations/anions
73
Whats the difference between uniporter, symporter, anti porter
uniporter: carrier protein for one solute
symporter: carrier protein for 2 solutes that goes in 1 direction
antiporter: carrier protein for 2 solutes, go in opposite directions
74
When is bulk transport utilized by the cell
when more than 3-4 molecules are trying to cross at once
75
What are the 2 methods used in bulk transfer and when are they used
exocytosis (to leave the cell)
endocytosis (to enter the cell)
76
What is bulk transport
Crossing membrane via vesicles , energy demanding process
77
Whats the difference between constitutive and regulated bulk transport
regulated: in response to a specific signal
constitutive: vesicles are continuously transporting solutes in/out
78
Whats the difference between exocytocysis and endocytosis
exocytosis:active transport
endo: passive transport
79
Describe endocytosis
endo: uptake of substance via 3 processes
phagocytosis=PM engulfes solute and becomes a vesicle which fuses with a lysosome for digestion
pinocytosis: non specific uptake of extracellular fluid
receptor mediated endocytosis: triggered by ligan binding to receptor
80
True or false
All 3 processes of endocytosis are selective
False on receptor mediated endocytosis
81
Give an example of bulk transport
Pancrease when it delivers insuline
82
Define cell-cell signaling
how cells receive messages from surrounding cells/environment
83
What molecules control cell signalling
proteins
84
Why is cell signaling important in organisms
Cells must communicate, allows them to form tissues/organ and perform other functions
85
Give 2 examples of cell-signalling in multicellular organisms
pheromones= chemicals released in environment for reproduction/marking territory
plants release chemicals when attacked to alert neighbouring plants
86
What is quorum sensing
cell-signaling allows coordination whithin a population of bacteria (they work as one)
87
What is releases in quorum sensing and what responses does it trigger
autoinducers molecules are released and can trigger 4 kinds of response:
Sporulation, exchange od DNA, virulence, biofilm production
88
What are the different kinds of local cell signaling
through cell junctions
Surface receptor
Paracrine signaling
Synaptic signaling
89
What is local signaling
chemical signaling with immediate neighbouring cell.
90
What type of signaling is involved in log distance
endocrine (hormones)
91
Describe cell signaling through cell junctions
adjacent cells communicate directly by tranfering signaling molecules through their junctions (gap junctiopn and plasmodesmata)
92
Describe cell signaling through surface receptors
binding of a surface marker to specific receptor of another alters the activity of a cell
93
Describe cell signaling through paracrine signalling
cell releases local regulator that travel in ECM to nearby cell (short distance between secretory and target cells)
uses exocytosis
94
Describe cell signaling through synaptic signalling
neurons communicate through neurotransmitters: chemical messengers that travel through synapses
95
Describe cell signaling through endocrine signalling
hormones regulate activity of cells, tissue, organs= impacte the whole organism
importnat to have hormone selectivity
96
What is hormone selectivity
Hormone can only affect the activity of a cell if they bind to their specific receptors
97
List all stages of cell signaling
reception
transduction
response
signal deactivation
98
Describe all stages of cell signaling
reception: binding of ligand to receptor of target cell
transduction: Message is transmitted and amplified
Response: Target cell's alters its activity
Signal Deactivation: Signal is turned off
99
Describe stage 1 of cell signaling
the ligan bind to receptor inside or oustide of the cell and triggers a conformational change in protein receptor= this change activates the protein and allows ligand to interact with molecules in cytoplasm
100
What are the 2 types of signaling molecules
water-soluble: amino-acid based and hydrophilic= cant diffuse through membrane= receptor on surface
lipid soluble: steroid/thyroid based and hydrophobi= diffuse throgh membrane abd bind in cytoplasm/nucleus receptor
involved in gene expression
101
What are the 2 types of signaling mechanism
1-Cell surface signaling
2-Intracellular signaling
102
Describe the purpose of signal receptor
undergo shape change when binding with ligand which activates receptor=
can perform many fxns when activated
103
What are the 2 type cell surface receptor
GPCRs and RTKs
104
Compare intracellular and extracellular receptors
extracellular:bind with polar molecules
intracellular: bind with nonpolar molecules
105
What are GPCRs
g-couple receptor proteins, found in every cell and made of specific g-protein
diff structures but all have 7 transmembrane alpha helix connected by hoops
106
Describe briefly the reception pathway of GPCRs
ligan binds to GPCR which causes a shape change in receptor. This change activates the g-protein by replacing GDP into GTP. Activated g protein diffuses through membrane to find specific enzyme, activate it and start transduction
107
How do G-protein deactivate
they're GTPase enzymes so they can hydrolyze GTP to GDP themselves and in consequence deactivate themselves and the enzyme
108
Describe RTK's
receptor tyrosine kinase enzymes that need ATP to function
catalyse the transfer of phosphate grp to another molecule
109
Whats the main difference between GPCR and RTK
gpcr can only trigger one signalling pathway per ligand binding whereas RTKs can start up to 6 transduction cascade per ligand binding
110
Describe briefly the reception pathway of RTK's
RTKs are inserted in PM through alpha helix domain and present as MONOMERS
Ligand binds to one RTK and now has high affinity for other RTK with ligand= dimerize
RTK dimer complex phosphorylates the tyrosine residue to become fully activated
Enzymes recognize the RTK and bind to tyrosine =gets activated and intiates cascade
111
What are second messengers
small water soluble molecules that used to activate other proteins
broadcast the signal quickly
112
Give two examples of second messengers
cyclic AMP
Calcium ion
113
What is a phosphorylation cascade
series of kinase enzymes that phosphorylate the next enzyme
114
What is signal amplification
each step of transduction amplifies the amount molecules which makes the response detected much bigger
1 molecule to 10^8 molecules
115
What are the main molecular mechanisms in signaling response
catalysis by an enzyme(to break molecule)
Rearrange cytoskeleton (in muscle cells)
Activate specific genes
116
What are the 2 categories of sinailing response
nuclear and cytoplasmic
117
Describe signal deactivation
automatic mechanisms that turn off signalling
118
What are the mechanisms that allow for signal deactivation
Stopping the signal (prevent ligand release)
Removal of the ligand(by enzyme or by itself)
Deactivate proteins
119
What is phosphodiesterase and why is important
enzyme that converts cAMP back to ATP to prevent ATP depleation and deactivate the signal
120
What enzyme converts ATP into cAMP
adenylyl cyclase
121
What steps can signal be deactivated
when g-protein leaves the enzymes
during transduction (cAMP becomes ATP)
When ligand leaves after enzyme activation
122
Give an example of abnormal cell signaling
cancer, abnormal cell signalling in apoptosis leads to over/under activity of certain cells, homeostatis leads to diseases
123
Compare aerobic, anaerobic cellular respiration and fermentation in terms of ETC/O2 use
aerobic: uses both ETC and O2
anaerobic: uses ETC and no O2
Fermentation: doesnt use ETC and O2
124
Which of the three main metabolic processes produce the most atp
Aerobic cellular respiration (around 36-38 ATP per glucose)
125
Which of the three main metabolic processes produce the least atp
Fermentation (2 atp from glycolysis only)
126
What are the 2 main types of fermentation and how do they differ from eachother
Alcohol: 3 steps where pyruvate intermediate is converted into ethanol/ used by microorganisms in deep soils or ponds
Fermentation 2 steps where pyruvate becomes lactate/used by yeast and animal muscle cells
BOTH UNDER ANAEROBIC CONDITION
127
true of false
the generation of ATP is restricted to having glucose as the reactant
true
128
What are redox reactions
Reactions that involve a loss/gain of electrons
129
Why are redox rxns always coupled
e- can not exist freely in the cell
130
What does it mean when a molecule is reduced
the species gains electrons
131
What does it mean when a molecule is oxidized
the species loses electrons
132
Whats a reducing/oxidizing agent
reducing: reduces another species while being oxidized (gives electrons)
oxidizing: oxidizes another species while being reduced (removes electrons)
133
Whats the difference between an electron donnor and acceptor
e- donnor= reducing agent
e- acceptor= oxidizing agent
134
identify whats being reduced/oxidized in the overall rxn of cellular respiration
Glucose is oxidized into CO2
O2 is reduced to H2O
135
What are electron carriers
species that carry electrons to transfer their energy in the cell
can easily cycle between their oxidized and reduced form
136
Whats the most versatile e- carrier and is it involved with other molecules
NAD+ its the coenzyme of dehydrogenase enzyme
137
What are dehydrogenase enzymes and how do they function
enzymes that reduce NAD+ into NADH by oxidizing to a substrate which releases 2 H
2H can be separated into 2H+ and 2e- = 2e- and H+ are transferred to NAD+ and one H+ is released in the cell
138
Compare NAD+/FAD to NADH/FADH2
NAD+/FAD: oxidizing agents
NADH/FADH2 : reduced form that carry large amount of energy (temporary)
139
Why are e- carriers in important during cellular respiration
If glucose was broken down in 1 step the energy released with be too intense. Glucose would bind automically with oxygen and provide the E of activation for combustion (woudl burn us alive)
E- carriers transfer part of that energy gradually to the ETC and oxygen
140
List 3 important energy carrier in catabolic pathways of energy metabolism
NADH, FADH2, NADPH
141
What are the main structural components of mitochondria
inner/outer membrane. matrix, intermembrane space and cristae
142
Where does oxidative phosphorylation occur
inner membrane of mitochondria
143
Where do H+ accumulate in oxidative phosphorylation
in the intermembrane space
144
What are the 4 stages of cellular respiration and where to they occur
1-Glycolysis in cytoplasm
2-Pyruvate Oxidation (matrix)
3-Citric acid cycle(matrix)
4-Oxidative Phosphorylation(inner membrane)
145
Describe how energy is harvested by ETC
When e- carriers from 3 previous stages reach the ETC, they are oxidized by their respective multiprotein complex which releases electrons. The electrons then travel down the ETC moving to more lectronegative complexes each time. The transfer of electrons between complexes releases energy which powers the active transport of H+ (no atp used). The electrochemical gradient will be used by ATP synthase for the synthesis of ATP (chemiosmosis)
146
Why is the ETC important (what would happen if e- were transferred to O2 directly)
No H+gradient would be produced to power chemiosmosis and cell would burn
147
Summarize glycolysis
process where glucose in broken in half to make pyruvate. Happens in 2 stages, investement where 2 ATP are used to phosphorylate glucose and an intermediate( with enzymes hexokinase and PFK) and pay off where G3P from investement is oxidized to make NADH (by dehydrogenase) and its intermediate are phosphorylated to make 2 ATP molecules (with enzymes phosphoglycero kinase and pyruvate kinase)
All atp are made by substrate level phosphorylation
In total (per glucose): 2 NADH, 2 net ATP
148
Summarize pyruvate oxidation
Pyruvate enter matrix and its carboxyl group is removed, which releases CO2, what remains is oxidized by dehydrogenase to make NADH. Lastly coenzyme A bind with the remainder to form ACetyl CoA(unstable molecule that immediatly enters Krebs)
In total (per glucose): no ATP, 2 NADH, 2 CO2
149
Why is the Krebs also called citric acid cycle and why is it a cycle
first intermediate made is citrate
the first reactant, oxaloacetate, is regenerated in the last step (last "product")
150
Summarize the citric acid cycle
Acetyl CoA and oxaloacetate form citrate, with enzyme citrate synthase. The second and third intermediates are oxidized by dehydrogenase enzymes to make NADH , CO2 is also released. The fifth step is where 4 carbon compound is phosphorylated to make atp, the remainder is oxidized to produce FADH2. The last step involves the oxidation of 4 carbon compound to make NADH and regenrate oxaloacetate.
151
in total per glucose what is produced after krebs
6 NADH
2 FADH2
2ATP
4 CO2
152
whats the purpose of citric acid cycle
complete the breakdown of glucose
153
what are the 3 characteristic of PFK that makes it a good regulator for glycolysis and cellular respiration
It can be inhibited by citrate, ATP and activated by AMP to maintain levels of ATP within range
154
How can PFK be regulated by ATP
When too much ATP is produced, ATP will become an allosteric inhibitor for PFK. It will inhibit PFK's activity to slow down glycolysis so that more ATP is being used than regenerated. this will allow ATP levels to drop back to their homeostatic range.
155
What are the 2 major phases of oxidative phosphorylation and where do they happen
ETC and chemiosmosis, both in inner membrane of mitochondria
156
Whats the function of chemiosmosis
Use H+ gradient from ETC to power ATP synthase in ATP production
157
Whats the function of the ETC
To transfer the electrons from e- carriers to O2 (oxidize NADH/FADH2), which releases energy to create electrochemical gradient
158
Why is oxidative phosphorylation named as such
ADP get phosphorylated by ATP synthase because of the oxidation of e- carriers that releases E to create an H+ gradient
159
List the major component of the ETC
complex 1, ubiquinone (Q), complex 2, complex 3, Cytochrome C, complex 4 and oxygen
160
What is the ETC made out of
multi-protein complexes embedded in the membrane with cofactors (non protein groups that enhance enzymatic activity)
161
Describe the structure of complex 1
Made up of series of e- acceptor called iron-sulfur complexes/Fe-S centers, that tranfer e- to ubiquinone (last e- acceptor)
Q becomes reduce= QH2 and moves along membrane to find Complex 3
162
Describe the structure of complex 2
Series of Fe-S centers but have a heme group that gets reduced before e- get transferred to Q
163
Describe the structure of complex 3 and 4
Series of cytochromes (proteins with cofactor hememoity) . Last on chain CYt 3 that makes transfer to O2
164
whats reduced and oxidized in complex 1
reduced: Q into QH2
oxidized: NADH into NAD+
165
whats reduced and oxidized in complex 2
reduced: Q
oxidized : FADH2 into FAD
166
True or false
All complexes pump H+ into the intermembrane
False complex 2 does not pump H+
167
How many hydrogens does each complex pump in inter membrane space
1= 4H+
2=0
3=4H+
4=2H+
168
Where is the electrochemical gradient generated by ETC
across inner membrane (intermembrane space is more acidic than matrix)
169
Define terminal electron acceptor
most electronegative oxidizing agent
170
What are the final electron acceptor in aerobic and anaerobic cellular respiration
aerobic: O2
anaerobic: nitrite, nitrate, sulfate, CO2, etc
171
What major components of ATP synthase are joined by stator and rotor
Catalytic sites and internal rod
172
What are the functions of each components of ATP synthase
stationary knob: rotates as H+ ions flow down their concentration gradient
Stator: embedded in membrane and maintains the know stationary
internal rod: connects know with catalytic sites and activates them
catalytic sites: undergo conformational changes as know rotates which activates the 3 active sites= 3 atp produced per rotation.
173
Why is the number of ATP produced per molecules estimated
NADH from glycolysis is reshuffled and some protons might be given back to FADH2 or NADH.
174
When are RTKs inactive
when they exists as monomers
175
What are the 2 types of responses in cell signaling and which one is slower
nuclear and cytoplasmic
muclear is slower since it involve the alteration of a gene expression
176
How does pyruvate enter the mitochondria (specify enzyme used)
outer membrane: facilitated diffusion
inner membrane: use pyruvate/H+ symporter (secondary active transport)
177
How does removing O2 as last e- acceptor affect pyruvate oxidation
without oxygen ETC cant work which means no H+gradient is produced= the secondary active transport of pyruvate in the matrix can not happen
178
What are the 3 purposes of the Kreb cycle
completly break down glucose
store E via oxydation (reduction of NAD+/FAD)
create ATP via substrate level phosphorylation
179
Define photophosphorylation
when light energy from excited electron is used to make a phosphate bond in ATP
180
True of false
in C4 plants only bundle sheath cells have chloroplast
True
