Unit 2 Flashcards
Cell Communication and Homeostasis (Ch 40,41,7,11) (344 cards)
1
Q
What are peripheral proteins
A
peripheral proteins = outer side of the plasma membrane (phospholipids head)
they need to be able to interact with ions (charges)
2
Q
How can flip-flopping across the membrane increase?
A
if you destroy / poke a hole through the phospholipids bilayer itself.
3
Q
What is permeability of the cell?
A
moving in or out of the cell
the permeability of the cell (how good it lets stuff cross through) is based on the polarity and size of the substance.
4
Q
What can cross through the membrane with high permeability?
A
gases (CO2, N2, O2)
Lipids/fats (ie: hormones)
small uncharged molecules (ethanol)
5
Q
What can cross through the membrane with moderate permeability?
A
water
urea
6
Q
What can cross the membrane with low permeability?
A
polar organic molecules (sugars)
very very low permeability:
ions
charged polar molecules (amino acids, ATP, proteins, DNA/RNA)
7
Q
What cannot cross through the membrane?
A
-> large amount of substances (ie: lots of water won’t be able to cross on its own)
8
Q
what is the relationship between solute concentration and osmotic pressure? (proportional or inversely proportional)
A
proportional correlation
high solute concentration = high osmotic pressure
small solute concentration = low osmotic pressure
9
Q
What are the 3 types of passive transport?
A
- diffusion
-> happens in-out and out-in, as long as their one side with less concentration
ex: glucose will go through facilitated protein - osmosis
- facilitated diffusion (need the help of an integral membrane)
10
Q
Explain passive transport : diffusion
A
does not need energy to happen (spontaneous)
substance move from high concentration to low concentration area
11
Q
what is the direction of the net movement of molecules ?
A
in direction of the concentration gradient (high to low concentration)
12
Q
what is the net movement of molecules at equilibrium?
A
zero
but exchanges still occur
13
Q
Explain passive transport: osmosis
A
= diffusion of water across a membrane
from area of low solute concentration (lot of water) to an area of high solute concentration (few water)
14
Q
what does free water mean in osmosis?
A
molecules that are free to use (bc they aren’t interacting with solute)
15
Q
Passive transport
A
diffusion
- does not require energy
- will continue to diffuse until equilibirum
- in a biological pov, our body are never actually in equilibrium. bc your fat cells want as much fat inside the cell, not outside, it will diffuse in the direction that it needs for your body to work.
- movement from high to low concentration
16
Q
Why is the flow of concentration not really in a biological equilibrium
A
in a biological pov, our body are never actually in equilibrium. bc your fat cells want as much fat inside the cell, not outside, it will diffuse in the direction that it needs for your body to work.
17
Q
osmosis is limited to what substance?
A
water
18
Q
osmotic pressure
A
ability that a molecule has to pull water towards it.
or
the amount of pressure you need to apply to stop water flow across a membrane
a side has more solute = a higher capacity to pull water towards it = higher osmotic pressure
minimum amount of force that you can apply
19
Q
Tonicity
A
tonicity = ability of a solution to gain/lose water = measure of the osmotic pressure gradient
20
Q
what is an isotonic solution ?
A
you want the concentration in and out of the cell to be the same, so that there is no net movement of water across the plasma membrane
= isotonic solution
21
Q
what does an isotonic solution in plants look like?
A
plants are looking good, but no pressure from the vacuole to help them stay upright
22
Q
what is an hypertonic solution?
A
hypertonic solution
more solute in solutions that in the cell, so osmotic pressure will be larger outside and pull the water outside = shrivelled cells
23
Q
what does an hypertonic solution in plants look like?
A
plants are dying/dried out
24
Q
what does an hypotonic solution in plants look like?
A
plants have a water vacuole = no bursting, the extra water just goes inside the vacuole
filled water vacuole = vacuole helps the plant stay rigid = cell is “turgid”
25
what is an hypotonic solution?
hypotonic solution
more solute in the cell than in the solution, so osmotic pressure is larger inside the cell and pull the water inside = lysed/burst
26
What is osmolarity
= what is the concentration of your solution?
=the total concentration of all solutes
27
iso-osmotic
of solutes outside = # of solutes inside the membrane
28
hyper-osmotic
of solutes outside is higher than # of solutes inside the membrane
29
hypo-osmotic
of solutes outside is lower # of solutes inside the membrane
30
Is ethanol hypotonic or isotonic?
hypotonic
regardless of the concentration of ethanol, it will end up being hypotonic and lead (log-term) to bursting of cells
31
what does plasmolyze mean in plants?
hypertonic solutions with shrivelled cells in plants
32
what does flaccid mean?
isotonic solutions with normal cells in plants
33
what does turgid mean?
hypotonic solution with lysed cells in plants
34
What does glycerol do
alcohol will enter the cell and cause hypertonicity and eventually cause the cell to burst
35
what is osmoregulation?
the control of water balance
36
Give 3 biological examples of osmoregulation.
1. paramecium
it is hypertonic to the water in which it lives (water rushes inside the paramecium)
to avoid bursting, the paramecium's cells have a contractile vacuole that pumps water out of the cell
= Paramecium's cells never burst
2. ethyl alcohol has the same osmolarity as the cytoplasm of mammals, yet it is hypotonic to mammals (it enters the cell)
3. cell walls of plant cells help maintain water balance
37
Explain passive transport: facilitated diffusion
use of transport proteins to speed up the movement of molecules across the plasma membrane
- no energy required
-high to low concentration ("down its concentration gradient")
can occur with channel proteins or carrier proteins
1. channel proteins
no change to the channel ever
2. carrier protein
change the channel depending on what it is transporting
some channels stay open, some open/close and act as regulators
38
Explain facilitated diffusion: channel proteins
- channel proteins act as hydrophilic corridors
- allows specific molecules to cross.
- usually gated, which gives the cell a regulation of what comes in/out
2 types of channel proteins:
1. Aquaporins (facilitate the diffusion of water)
2. Ion channels (open/close in response of stimulus)
39
Give 2 examples of a gated channel protein.
1. voltage-gated channels in neurons
= ion channels that only let ions pass through the membrane
2. aquaporins
40
what does GLUT4 mean?
glucose transporter (a type of carrier protein)
41
Explain facilitated diffusion: carrier proteins
- change their shape when binding to a solute
- they can be:
uniporter (ONE solute moves in one direction)
symporter (2 solutes move in one direction)
antiporter (2 solute move in opposite direction)
42
which protein is faster between channel and carrier? why
carrier is slower than channel because they change shape first
43
what does the speed of carrier proteins depend on?
the rate of carrier proteins depends on the number of carriers in the membrane
44
What are the 2 types of active transport?
1. transporter pumps
- requires energy
- see ATP = active transport
- moves from low to high concentration
- requires protein channel
2. bulk transport:
- you package what youre transporting in molecules to release them outside of the cell
-requires energy
-endocytosis and exocytosis
45
What are the 2 types of transporter pumps?
Primary active transport
Secondary active transport
46
What is active transport?
moving of substances against their concentration gradient
with the help of specific integral proteins and an input of energy (ATP)
47
What are the 2 characteristics of primary active transport?
1. carrier-mediated
2. transport with energy from ATP
48
What are the 3 characteristics of secondary active transport?
1. transport with co-transport
2. transport with ATP
3. ion gradient as a mean of transport
49
Explain primary active transport
requires ATP
1st: ATP gives a phosphate group to a carrier protein
2nd: the carrier protein changes conformation
3rd: the substance passes through the membrane against the gradient
50
How does NA+/K+ ATPase work?
1. Downward shape of a pump = high affinity for Na+ from the cytoplasm
2. phosphorylation of ATP occurs (ATP gives a phosphate group to the pump) & the pump changes conformation (flips upward)
4. new conformation =
low affinity for Na+ -> Na+ is released
high affinity for 2 K+ from the extracellular matrix side
6. the binding of 2 K+ triggers the release of the phosphate group, which restores the conformation of the pump (low affinity for K+)
7. K+ is released into the cytoplasm
cycle repeats
51
What is an example of a primary active transport ion pump?
NA+/K+ ATPase
52
What are ion pump's role in primary active transport?
generate a membrane potential
53
What is another name for ion pump?
electrogenic pump
54
What is the specific type of gradient that active transportation creates?
electrochemical gradient
electrical gradient (net charge inside vs outside)
concentration gradient (net concentration of Na+ higher outside the cell)
55
What processes do the electrochemical gradient drive?
cellular respiration
transmission of nerve impulse
muscle contraction
56
What is a membrane potential?
a voltage difference across a membrane
ex: cytoplasmic membrane = negative charge
extracellular matrix side = positive charge
57
What is the membrane potential generated by Na+/K+ ATPase?
pumps sends 3 Na+ out and brings 2 K+ in
= positive exterior
= negative interior
58
What are the differences between passive and active transport?
passive is in the direction of the gradient, so no energy input
active is always against the gradient, so energy input is needed. also, active needs a carrier/transporter protein
59
what happens first, primary active or secondary active transport?
Primary active transport must first happen to create concentration gradient
then secondary active transport can happen with the use of concentration gradient
60
Explain secondary active transport
using an existing gradient (which stored energy) to drive the active transport of a solute
61
What is an example of a secondary active transport in plants?
plants
First step:
they use ATP to pump H+ against the gradient (out of the cell) through a proton pump
= high [H+] outside the cell
Second step:
Now, as the H+ naturally diffuse back inside the cell into its gradient , the sucrose will "sneak in" and go inside the cell
62
What type of pump is the sucrose-H+ transporter pump? (active/passive transport protein, uniporter/symporter/antiporter protein)
active transporter protein
(as soon as you hear "pump" you know its active transport)
and symporter bc it transports H+ and sucrose inside the cell (one direction)
63
What is an example of secondary active transport that happens with the help of the Na+/K+ ATPase pump
Na+/K+ ATPase created a sodium gradient (low [Na+] inside the cell)
Na+ outside the cell will thus naturally diffuse through its gradient (inside the cell)
a 2 Na+/glucose symporter will take the opportunity and provide a pathway for Na+ to diffuse into the cell.
glucose will sneak in and diffuse into the cell using the same pump
64
Why does glucose need a sodium gradient to happen (in the human intestine)?
we want glucose to go inside the intestine, which is a net movement against its gradient
against gradient = need a transport protein, can't happen spontaneously
65
What happens if a drug inhibits sodium deposit in the intestine?
no sodium = no sodium gradient = no 2Na+/glucose symporter = glucose will deposit elsewhere = death
66
Explain active transport: bulk transport
primary/secondary active transport & passive transport are not efficient enough to let large molecules, viruses and bacteria cross the membrane.
= Bulk transport comes in handy
-> large molecules enter the cell by endocytosis
-> exit by exocytosis
-> both processes requires ATP
67
Explain endocytosis
1. large molecule = trapped on the surface of the outside membrane
2. membrane folds in on itself and forms a vesicle around the large molecules
3. the vesicle buds off the membrane and enters the cell
68
explain exocytosis
1. materials too large to diffuse out the cell accumulate on the surface of the inside membrane
2. a vesicle forms around them and buds to the membrane
3. the vesicle opens and empties itself into the extracellular environment
69
What is exocytosis useful for?
membrane proteins and phospholipids are incorporated into the membrane by exocytosis
70
What are the 2 types of exocytosis?
1. regulated
only occurs in response to a signal
ie: insulin release by pancreatic cells & neurotransmitter release by neurons
2. constitutive
71
What are the 3 types of endocytosis?
1. phagocytosis
LARGE molecules/bacteria
use of a lysosome
2. pinocytosis
"cell-drinking"
FLUID gets surrounded by a vesicle
3. receptor-mediated endocytosis
specific mechanism
specific molecules bind to their respective receptors on the outside surface of the membrane -> vesicle forms -> endocytosis
72
What is an example of receptor-mediated endocytosis?
lipoproteins that transport cholesterol
73
Can you name examples of each of the two classes of membrane proteins?
74
Can you explain the assymetrical distribution of the cytoplasmic and extracellular faces (leaflets)
of the plasma membrane?
75
Can you explain the six major functional classes of membrane proteins?
76
Describe how the plasma membrane (phospholipid bilayer, proteins, ect.) is made within a
eukaryotic cell. If a glycoprotein or glycolipid is being made for the plasma membrane, where would you expect to see the carbohydrate part of a glycoprotein or glycolipid in a transport vesicle (inside? outside?) and where does this end up once the vesicle fuses with the plasma membrane?
77
Does diffusion typically reach equilibrium in cells? Explain.
78
Can you list factors that can affect the rate of diffusion of a substance? What effect do they have on the rate? Why do they have this effect?
79
Compare the kinetics of simple and facilitated diffusion using a graph that illustrates the
diffusion rate vs. the concentration of diffusing substance (on one side of the membrane) for
each mechanism. Explain why this relationship is observed for each.
80
Does osmosis typically reach equilibrium in cells? Explain.
81
Does the mechanism of a pump more closely
resembles a channel or a carrier?
carriers
bc they undergo conformational changes, like pumps
carriers can transport molecules against their gradient (active transport, using ATP) or into its gradient (passive). pumps are always against
82
What is the main function of membranes?
give structure, which allows metabolic order
ex: enzymes are kept in a specific metabolic pathway by the membrane
83
what are the 2 functions of the plasma membrane?
separate living cells from their surroundings
selective permeability (passive transport and active transport)
84
what is the plasma membrane composed of?
phospholipid bilayer
protein
stereoid lipids
85
what is the structure of the phospholipid bilayer?
amphipathic
hydrophilic head = phosphate group
hydrophobic tails = fatty acid chains
86
is a membrane fluid? what experiment proved whether it was fluid or not fluid?
fluid
1 mouse cell and a human cell were fused
each membrane was labelled
after fusion, we observed that the labelled plasma membrane moved = fluid membranes
conclusion : plasma membrane proteins must be able to move around the phospholipid bilayer
87
what does the membrane fluidity depend on?
on the lipid components
hot temperature
-> membrane is too fluid and doesn't hold shape
cold temperature
-> membrane is rigid, not flexible
-> it might break
88
what happens to the membrane when it reaches a critical point?
critical point = very low temperature
the membrane becomes solid gel
transport across the membrane stops
89
how do organisms maintain optimal fluidity?
they change the fatty acid content of their membrane lipids (change # of unsaturated fatty acids)
90
what is homeoviscous adaptation?
temperature goes down (cold)
increase the proportion of unsaturated fatty acids
membrane stays fluid
91
how can fatty acid chain length affect membrane fluidity?
the longer the chain, the less fluid the membrane
bc longer chain = more van der Waals forces between chains = strong attraction = less fluid
92
what happens to the membrane fluidity if the # of double bonds in fatty acids is increased?
more double bonds = more unsaturated = more fluid
93
What is a fluidity buffer? give an example
cholesterol
at high temperature
it stabilizes the membrane
OH- group of cholesterol binds to a nonpolar head
this adds stability = less fluid
at low temperature
cholesterol gets in between fatty acid chains
this reduces van der Waals interaction = less attraction between chains = more fluid
94
what are the 2 types of membrane proteins?
integral (inside)
peripheral (outside)
95
what are the characteristics of integral proteins?
bound to the membrane (in the middle of the lipid bilayer)
amphiphatic:
- hydrophilic region qui depasse le lipid bilayer et touche le cytoplasm/l'extérieur of the cell
- hydrophobic region in the middle of the bilayer that interacts with fatty tails
96
what is the difference between transmembrane integral proteins and integral proteins?
transmembrane = extend all the way through the membrane = dépasse à l'extérieur de la cellule et dans le cytoplasm
normal integral = embedded inside the bilayer, mais ne dépasse pas
97
what is the most common transmembrane structure?
alpha helix
98
in the alpha-helix structure of a transmembrane protein, where is the C-terminus and the N-terminus oriented towards?
C-terminus on the cytoplasmic side (inside the cell)
N-terminus on the extracellular side (outside the cell)
99
what are 2 examples of integral proteins?
aquaporins
transport water in/out the cell by osmosis
glycoproteins
its sugar is oriented towards the extracellular matrix
100
what are the characteristics of peripheral proteins?
located on the surface of the membrane (outer/inner surface)
101
what is th asymmetry of the bilayer due to?
proteins are inserted into different sides (p-face / e-face) of the membrane in an asymmetric orientation
102
What differs from one side of the bilayer to another?
one side has more proteins embedded to it
different proteins on it = membrane with different characteristics
103
What is the P-face vs E-face of a bilayer?
e-face = towards extracellular matrix
p-face = towards cytoplasm
104
which organelle makes the peripheral proteins on the inner surface of the membrane?
free ribosomes in the cytoplasm
105
which organelle makes the peripheral proteins on the outer surface of the membrane?
ribosomes in the rough ER
106
which organelle makes integral proteins?
ribosomes in the rough er
107
why are cell-cell recognition proteins important ?
1- give identification tags to cells for them to be recognized by other cells
2- the immune system can recognize and reject foreign
3- cells can sort themselves into tissues and organs
108
how do cell-cell recognition work?
outer portion of plasma membrane contains glycoproteins and glycolipids that vary from:
species to species
individual to individual of the same species
from cell to cell of the same individual
109
how do autoimmune disease occur?
immune system have antibodies.
the antibodies thinks its own healthy tissue is a foreign cell and attacks it.
110
gives an example of autoimmune disease
rheumatoid arthritis
antibodies attack the synovial membrane of joints
111
what is intercellular joining?
membrane proteins of 2 different cells hook together via different junctions
long-lasting binding
112
how is plant cell junctions in intercellular joining called?
plasmodesmata
113
what are plasmodesmata?
channels where 2 plant cells can communicate rapidly
water and small molecules can pass through plasmodesmata
114
how are the animal cell junctions in intercellular joining called? (name 3)
1. demosomes
2. tight junctions
3. gap junctions
115
what are desmosomes?
junction that allows intercellular joining
1. attach animal cell to another animal or
attach animal cell to the extra cellular matrix
2. very strong junctions
3. explain more structure***
116
what are tight junctions?
junction that allows intercellular joining
so tight that substances cannot leak between them
hold the cell together in physical contact, forming a sheet of tissue
117
what are biological examples of tight junctions?
stomach uses tight junctions to prevent its very acidic secretions to leak on organs/tissues near it
brain uses tight junctions to prevent substances in the blood to enter the brain
118
what are gap junctions?
form a sort of bridge between animal cells where substances can pass through rapidly
similar to desmosomes, but they cover a narrower space
allows rapid chemical/electrical communication
119
what are examples of gap junctions?
cells in pancreas are linked by gap junctions
one cell receives a signal to secrete insulin = signal is passed to other pancreatic cells
gap junctions of heart muscle cells allow flow of ions & help synchronize contractions of the heart
120
what are proteins that do not move freely within the plasma membrane good for?
they help keep the membrane in place
121
what are proteins that do not move freely within the plasma membrane linked to?
they are covalently liked to the cyto-skeleteon and to fibers of the extracellular matrix
122
what is the structure of the extracellular matrix?
ECM is made of :
carbohydrates (fibronectins, a type of glycoprotein)
fibrous proteins (collagen)
123
What do fibronectins in the ECM bind to?
they bind to proteins called integrins
124
What are integrins?
integral transmembrane proteins
125
what are the 4 functions of integrins?
1. membrane receptors for the ECM
- activate pathways that allows information to travel from the ECM to the cell
2. help cell movement
3. organize the cytoskeleton
4. anchor the ECM to the microfilaments of the internal cysto-skeleton
126
what is an example of a dysfunctional ECM?
cancer cells that cannot anchor properly to the ECM spread through the body
127
Describe the activity of signal receptors. Compare intracellular and extracellular receptors. What
physical characteristics (polar/non-polar amino acids/-helices or not) would you expect for
signaling molecules for each type? Why?
List and describe the activity of the two main types of membrane receptors discussed in class.
How do GPCRs and TKRs differ from each other? What do G-proteins do? What do they
hydrolyze? What does dimerization mean?
Can you define a second messenger and discuss how these are involved in cell signaling? List the
2 second messengers discussed in class and describe how their concentrations in the cytosol can
build up during cell signaling.
What is a phosphorylation cascade and how are these are involved in cell signaling? What is the
term used for enzymes that can phosphorylate other proteins?
What is signal amplification and why it is possible during signal transduction?
List the main molecular mechanisms for how a cell changes its activity in response to a signal.
Which of these would be considered a nuclear response? Cytoplasmic response? Which one
takes longer?
Describe signal deactivation and its importance in cell signaling. Describe how a signaling
pathway can be deactivated at its various steps.
Describe how signaling pathways form signaling webs. Describe pathway branching and
pathway crosstalk.
Explain how one signaling molecule can have different effects on different cell types and lead to
different effects in different organs.
Can you name specific examples of when cell-signaling is abnormal?
128
What is the purpose of cell-cell signalling in unicellular organisms?
to make sure cells can coordinate with one another and work as a team to accomplish a task
129
Explain how cell-cell signalling in unicellular organism work.
when the concentration of autoinducer made by a bacteria reaches a high level, the population coordinate a response
130
What are the different types of responses in a cell-cell signalling (unicellular)?
- sporulation
- exchange of plasmid DNA
- bioluminescence
- virulence
- production of biofilms
131
What are 2 examples of molecules used in cell signalling in multicellular organisms?
1. pheromones
- chemicals released by organisms
- used for sexual reproduction/mark territory
- ie: male luna moth detects pheromone released by a female
2. plants
- release volatile compounds when attacked by herbivores
- = a way to ask their "friends" for help
132
What are different types of local cell-signalling?
1. though cell junctions
2. cell surface molecules
3. paracrine signalling
4. synaptic signalling (neurotransmitters)
133
Explain local cell-signalling: cell junction
adjacent cells communicate by transferring signalling molecules through cell junctions
= using gap junctions (animals) or plasmodesmata (plants)
134
Explain local cell-signalling: cell-to-cell recognition
the surface marker of one cell binds to the receptor of another
= alters cell activity
135
what is cell-to-cell recognition important for?
embryonic development
immune response
136
Explain local cell-signalling: paracrine signalling
a cell secretes local regulator molecules that travel through the ECM and reaches another cell
= the local regulator molecule affects the second cell
137
what is an example of paracrine signalling?
the release of growth factor by a secretory cell
138
Explain local cell-signalling: synaptic signalling
1. neurotransmitters are released
2. they act as chemical messenger:
3. the neurotransmitter is released into the synapse
4. the neurotransmitter binds to the receptors of the target cell
= allows neurons to communicate with other cells.
139
What is the type of signalling involved in long-distance cell-signalling?
endocrine signalling (hormones)
140
Explain long distance cell-signalling: endocrine signalling
hormones are specific
= they only affect cell with specific receptors for them to bind to (called target cells)
= lock&key principle
different cells = different target cells, but 1 hormone can bind to receptors in different target cell
= 1 hormone will = different response depending on the kind of cell
141
name a hormone with a wide range of targets? what does that mean
sex hormones
many different cells in the body have receptors that are compatible with testosterone
but each cell's receptor will respond differently to the binding of testosterone
142
name a hormone with a narrow range of targets? what does that mean
gastrin in the stomach
pretty much only one type of cell that has the receptors that are compatible to gastrin
= only one response possible
143
Can you list the four main stages in cell-signalling?
1. Reception
signalling molecule binds to receptor of target cell
2. Transduction
message is transmitted & amplified into the cell
involves multistep pathway
3. Response
target cell alters its activity
4. Signal deactivation
signalling is turned off
144
Explain the first stage of cell-signalling (Reception)
- a signalling molecule (ie: hormone) approches its target cell
- it binds to the receptor protein the target's cell surface or its inside
- binding leads to a change in the shape of the receptor protein = active shape
- = can interact with the inside of the cell
145
Explain the second stage of cell-signalling (transduction)
146
Explain the third stage of cell-signalling (Response)
147
Explain the fourth stage of cell-signalling (Signal deactivation)
148
What types of signalling molecules would have
their receptors on the surface and those within?
surface
= hydrophilic signalling molecule (ie: GASTRIN, neurotransmitters, insulin/glucagon)
= bc they can't cross the membrane (polar)
within
= hydrophobic (ie: STEROIDS\THYROID, TESTOSTERON, ESTROGEN)
= can cross the membrane (bc non polar)
149
What type of signalling molecules is directly involved in gene expression? How?
intracellular signalling
they activate transcription factors:
up-regulation of genes = more proteins made
down-regulation of genes = less proteins made
150
how is signalling molecule with receptors on the surface called?
cell surface signalling
151
how is signalling molecule with receptors on the inside called?
intracellular signalling
152
what are the 2 major types of cell-surface signalling?
G protein-coupled receptors (GPCRs)
receptor tyrosine kinase (RTKs)
153
how does a G protein gets activated?
a signalling molecule binds to the receptor of a GPCRS, which turns it into its activated shape on the extracellular side.
this change allows the GPCRs to interact with a G protein from the cytoplasmic side
the G protein is previously bound to a GDP. once it binds to the GPCRs, the GPCRs replace the GDP for a GTP (GTP = abundant molecule in the cytoplasm).
154
Once the G protein has been activated, what is the next step in transduction signalling
the activated G protein detaches from
the GPCRs
->diffuse along the membrane
-> attach to an enzyme
-> the enzyme becomes activated and can trigger the next step in signal transduction
155
What happens to the G protein after a cellular response has been emitted?
the G protein hydrolyzes their GTP back into GDP
= inactivates itself
156
what is a way to regulate the activity of enzymes?
G proteins are GTPase enzymes
= they hydrolyze their GTP to GDP
= inactivate theirselves
157
what are the characteristics of G protein-coupled receptors (GPCRs) ?
- present in every type of cell in our body
- composed of 7 transmembrane alpha-helices joined by intracellular and extracellular loops
- each type of GPCRs
= specific active site conformation & specific cytoplasm conformation
= bind to a different ligand
158
what are functions of GPCRs in the body?
embryonic development
sensory reception
autonomic nervous system transmission
mood regulation
159
are GPCRs peripheral proteins or integral proteins?
peripheral
160
if a G protein is bound to a GDP, is it active or inactive?
inactive
161
if a G protein is bound to a GTP, is it active or inactive?
active
162
Receptor tyrosine kinases are kinase enzymes. But what are kinase enzymes?
enzyme that catalyze the transfer of a phosphate group
163
what is the key difference between GCPRs and RTKs?
RTKs have the ability to initiate multiple signalling cascades from a single ligand-binding event
164
What is the structure or RTKs?
- the tyrosine amino acid end is in the cytoplasmic region
- the alpha helix domain is in the plasma membrane
- the ligand-binding site is in the extracellular end
165
what is the difference in configuration of the active RTKs vs inactive RTKs?
inactive = monomer
active = dimer
166
how to dimerization of RTKs occur?
a signalling molecule bind to the receptors of the RTKs
one monomer RTKs now has high affinity for the other monomer RTKs = they dimerize
167
how are dimerized RTKs able to trigger a cellular response?
1. dimerization activates the tyrosine end of the RTKs
2. each tyrosine bind to a phosphate group (from an ATP)
3. specific proteins bind to the phosphorylated tyrosine end, which turns the proteins in its active form
4. each protein is now able to emit a cellular response
168
How are the molecules in a transduction pathway called?
relay (effector) molecules
169
Why is transduction said to amplify the response? How many molecules in each step of the signalling process?
reception = 1 molecule
transduction = cascade of reactions where more molecules are activated in each step
(1 step = 10^2 molecules
last step = 10^6 molecules)
response = 10^8 molecules
total = 1 molecule -> 10^8 molecules
170
What is the first step of transduction?
activation of a G protein
= 1 molecule (from reception) into 10^2 molecules
171
What is the second step of transduction?
activation of adenylyl cyclase
= 10^2 molecules
172
What is the third step of transduction?
ATP into cyclic AMP
= 10^4 molecules
173
What is the fourth step of transduction?
activation of protein kinase A
= 10^4 molecules
174
What is the fifth step of transduction?
activation of phosphorylase kinase
= 10^5 molecules
175
What is the sixth step of transduction?
activation of glycogen phosphorylase
= 10^6 molecules
176
What is the step of reception?
epinephrine binds to GPCRs
= 1 molecule
177
What is the step of response?
Glycogen -> glucose-1-phosphate
178
how is cAMP made in transduction pathways?
removing 2 phosphate groups from ATP
179
how does cAMP differ from the other steps of a transduction pathway?
it is not a protein; it is a water-soluble molecule
180
how can cAMP be deactivated? why is this important?
an enzyme called phosphodiesterase converts cAMP to AMP = it deactivates cAMP once enough enzymes have been made
bc otherwise way too much enzymes will be produced
181
apart from cAMP, what is another type of second messenger? where is it found?
CA2+
higher [Ca2+] in the smooth ER & mitochondria than in the cytosol
182
explain the link between phosphorylation and how it creates this cascade event in transduction
the transduction cascade is a series of phosphorylation: the signalling molecule attaches to the receptor, and an activated relay molecule activates the first kinase protein. then the activated kinase 1 transfers an phosphate group from ATP to a inactivate kinase protein and ainsi de suite.
183
how do Ca2+ build up in the cytosol?
neurotransmitter lead to the release of Ca2+ into the cytosol, which creates a cell response
184
What types of response can a cell produce?
catalysis by an enzyme
rearrangement of cytoskeleton
activation of specific genes in nucleus
185
what are the 2 categories of response in a cell?
1. nuclear
change in which genes are expressed = slow
2. cytoplasmic
activation/deactivation of target protein that are in the cytoplasm = fast
ie: glycogen into glucose-1-phosphate
186
how can the same signalling molecule create different response? what does the response depend on? give an example
depend on the type of receptor and type of molecule involved
epinephrine = different effects throughout the body:
liver = increase blood glucose level
muscle cell = increase/decrease flow of blood to different part of the body
187
what is the 4th step in cell signalling ?
signalling deactivation
= turn cell signals off
188
What is apoptosis?
programmed cell suicide
protects the animal from abnormal/infected cells
189
what are the 2 possible pathways in abnormal cell signalling in cell division?
positive regulators (kinase) are over-activated and become oncogenic
negative regulators called tumor suppressors are inactivated
190
Can you name specific examples of when cell-signaling is abnormal?
cancer
191
What are 3 ways cells generate atp (energy)?
glycolysis with fermentation
aerobic cellular respiration
anaerobic cellular respiration
192
what are 2 types of fermentation?
alcohol fermentation
= produce ethanol + organic acids
= happens in bacteria (anaerobic conditions)
lactic acid fermentation
= produce lactacte
= happens in fungi, bacteria and animals (anaerobic)
193
define glycolysis with fermentation
organic compounds (ie: monosaccharide) are incompletely broken down to produce few ATP
194
is glycolysis with fermentation aerobic or anaerobic?
anaerobic
195
what does aerobic & anaerobic mean
aerobic = requires of oxygen
anaerobic = no use of oxygen
196
define aerobic cellular respiration
breakdown of glucose to produce many ATP
- in eukaryotes
- some prokaryotes
197
how many ATP per glucose in aerobic cellular respiration?
32
198
how many ATP per glucose in anaerobic cellular respiration?
199
what is the most efficient catabolic pathway?
aerobic cellular respiration
200
define anaerobic cellular respiration?
- breakdown of glucose to produce many ATP by using nitrate or sulfate instead of oxygen
- some prokaryotes
201
what is the formula of aerobic cellular respiration?
C6H12O6 + 6 O2 + ADP + Pi -> 6 CO2 + 6 H2O + Energy
*glucose here can be replaced by any carbohydrates, fats and protein
202
why doesn't aerobic cellular respiration (breakdown of glucose) happen in one simple step?
- the body temperature is not high enough to start the instantaneous process (of combining H with O)
- if energy is released at once, it cannot be used efficiently for constructive work
203
what powers the cellular work in cellular respiration? where is the energy coming from?
phosphorylation
transfers of electrons
204
what are the 3 electron carrier molecules ? What are they used for?
NAD+
FAD
dehydrogenases
electrons are removed from glucose. each electron travel with a H+. the electron & H+ combo does not directly transfer to oxygen -> it needs an electron carrier
205
what is the most versatile electron acceptor?
NAD+
206
NAD+ is a coenzyme to enzymes called ____________
dehydrogenases
207
What are the 2 forms in which NAD+ can cycle between? the oxidized and reduced forms
NAD+ = oxidized form
NADH = reduced form
208
What are the 2 forms in which FAD can cycle between? the oxidized and reduced forms
FAD = oxidized form
FADH2 = reduced form
209
FAD & NAD+ can temporarily store free energy in their oxidized or reduced form?
reduced
FADH2 and NADH
210
how do the electron carriers dehydrogenases work?
by oxidizing the glucose molecule
in other words:
by removing a pair of hydrogen (H2, which = 2 electrons and 2 protons) from the glucose molecule
the enzyme dehydrogenase then delivers the 2 electrons and 1 proton to its coenzyme NAD+.
NAD+ + 2H -> NADH + H+
the extra proton is released into the surroundings
211
as NADH transfers electrons to molecules, what else gets transferred?
energy
212
what happens when you bring H2 and O2 together?
cellular respiration: goal = bring H2 and O2 together
in nature:
electrons from hydrogen are pulled to the electronegative oxygen = creates "explosive" energy
213
why is electron transport chain crucial in cellular respiration?
if NADH brought the electrons directly to oxygen, the cell would not be able to harness the explosive energy
= too much for the cell = uncontrolled
ETC "breaks" the explosiveness of the bringing of electrons to oxygen into several steps
= controlled
214
define the structure of ETC
proteins built in the inner membrane of the mitochondria (animals) or the plasma membrane (prokaryotes)
215
how does the ETC work?
dehydrogenase enzyme transport electrons removed from glucose to NADH at the top (high energy) end of the chain.
O2 captures the electrons & the H+ from NADH + H+ at the bottom (lower energy end)
every electron transfer = electrons energy level decreases = release of energy = make ATP
216
how can electron travel downhill, from one carrier protein to the other in ETC?
each carrier protein is more electronegative than the previous
= pulls the electrons towards it
217
a carrier protein is said to ______ its previous "uphill" neighbour
a carrier protein is said to oxidize its previous "uphill" neighbour by pulling its electrons
218
what are the different components of the mitochondria? start from the outside and work your way to the inside
porin (on the outer membrane)
outer membrane
inter-membrane space
cristae
inner membrane
atp synthase (on inner membrane)
ETC (on inner membrane)
matrix (liquid inside the inner membrane)
ribosome
circular DNA
219
what are the components surrounding the ETC?
ETC = in the inner membrane
inter-membrane space = outside of the inner membrane
matrix = inside of the inner membrane
220
in which step of the cellular respiration multiple cycle is ETC found?
oxidative phosphorylation
221
what is substrate-level phosphorylation?
when a small amount of atp is formed directly in the process of glycolysis and in the citric acid cycle
222
what is the difference between oxidative phosphorylation and susbtrate-level phosphorylation?
in oxidative phosphorylation:
an enzyme transfers an inorganic phosphate group to ADP
but in susbtrate-level phosphorylation:
an enzyme transfers a phosphate group from a substrate molecule to ADP
= ATP
223
how much of atp is generated by substrate-level phosphorylation?
10%
the remaining 90% comes from oxidative phosphorylation
224
how does oxidative phosphorylation occur?
ETC oxidizes NADH & FADH2
= H+ gradient (a lot of H+ in the inter membrane space)
= lots of free energy
= lower activation energy needed to for ATP synthase
= 32 ATP molecules!!
225
what are the 4 stages of the aerobic cellular respiration?
1. glycolysis
2. pyruvate oxidation
3. citric acid cycle
4. oxidative phosphorylation
226
what is the only stage that happen outside the mitochondria? where is it located exactly?
glycolysis
in the cytoplasm
227
define the process of glycolysis
the cutting of the big glucose molecule (6 carbons) into 2 smaller molecules (3 carbons)
glucose -> 2 pyruvate + 2 atp + 2 NADH
228
glycolysis if O2 vs if no O2 , what happens?
O2
glycolysis produces pyruvate and nadh, 2 molecules with chemical energy stored.
that energy is taken into the mitochondria and aerobic cellular respiration takes place
= 32 atp
no O2
pyruvate and nadh stay in the cytoplasm to make fermentation
= 2 atp
229
what are the 2 phases of glycolysis?
energy investment phase
energy payoff phase
230
explain the energy investment phase of glycolysis
6-carbon glucose is broken down into 2 3-carbon sugars ("G3P")
you need energy to breakdown glucose, so you need to invest atp molecules in the rxn
231
what does the energy payoff phase yield?
substrate level phosphorylation successfully made 4 molecules of atp
2 molecules of NADH are formed
2 molecules of pyruvate are formed
232
what does the energy investment phase of glycolysis yield?
1 molecule of glucose
+
2 molecules of atp
= 2 ADP + 2 G3P
233
what are 2 important regulatory enzymes in glycolysis?
hexokinase
PFK (phosphofructokinase)
234
how does glucose enter the cell?
through a carrier protein called GLUT4
235
what is the first step in glycolysis in which atp is CONSUMED?
Glucose + ATP -> G6P+ ADP
as soon as glucose enters the cell, hexokinase takes a phosphate group from an atp and adds it to glucose
= glucose is now very charged = can't escape, it must proceed forwards
= this also maintains the glucose concentration gradient
236
what are the intermediate step in the energy investment phase, from a glucose until right before the energy pay-off phase?
glucose
atp + hexokinase
G6P (glucose-6-phosphate)
F6P (fructose-6-phosphate)
atp + PFK
G3P (glucose-3-phosphate)
237
explain the energy pay-off phase of glycolysis
before it starts, we have 2 G3P
each G3P rearrange & form a pyruvate
all whilst reducing 1 NAD+ into 1 NADH
all whilst producing 2 ATP from 2 ADP
238
what is the net yield of the energy pay off phase?
2 G3P become:
2 NADH
4 ATP
239
what are the intermediate step in the energy pay-off phase, from a G3P until right before the pyruvate oxidation cycle?
G3P
2 NADH
2 ATP
pyruvate kinase forms pyruvate (and releases 2 ATP)
240
in the energy pay-off phase, the $ of each molecule is ______?
doubled
241
how does PFK regulation work?
AMP is a molecule that activates PFK
citrate inhibits PFK
when [citrate] or [atp] are too high, PFK is allosterically inhibited = stops the process of cellular respiration
when [citrate] or [atp] drop, [amp] increases, which activates PFK, which starts cellular respiration again
242
in which organisms is glycolysis enough source of energy?
yeast
bacteria
(glycolysis by fermentation)
243
What is the next step after glycolysis and right before pyruvate oxidation?
each pyruvate formed must enter the mitochondrion's inner membrane
244
Where does each of the 4 steps of cellular respiration occur?
glycolysis = cytoplasm
pyruvate oxidation = matrix
citric cycle = matrix
oxidative phosphorylation = inner membrane of mitochondrion
245
How does the pyruvate pass through the outer membrane of the mitochondrion?
by facilitated diffusion
246
How does the pyruvate pass through the inner membrane of the mitochondrion?
via pyruvate/H+ symporter carrier protein (secondary active transport)
high [H+] in the inter-membrane space and low [H+] in the matrix
= concentration gradient
= pyruvate "sneaks in" and profits from the natural movement of H+ down its gradient
247
what happens if there is no O2 to accept electrons at the end of the ETC?
no H+ gradient, so pyruvate won't be able to cross the inner membrane and get to the matrix;
it will stay in the inter membrane space
248
what is the 1st stage of pyruvate oxidation?
the pyruvate enters the mitochondrion
- carboxyl group of pyruvate has very few chemical energy and is thus easily removed
- carboxyl group then diffuses out of the cell into blood
249
what is the 2nd stage of pyruvate oxidation?
- what's left of pyruvate molecule is oxidized into acetate
- an enzyme transfers 2 e- & 1 H+ to NAD+ -> NADH
250
what is the 3rd stage of pyruvate oxidation?
co-enzyme A (coA) attaches to acetate and turns it into acetyl coA
acetyl coA = now very high potential energy
251
What is the total yield of pyruvate oxidation ?
2 pyruvate (3C) -> 2 acetyl-coA (2C)
Pyruvate + coA + NAD+ -> acetyl-coA + CO2 + NADH + H+
yield for 1 glucose:
2 CO2
2 NADH
252
what are the inputs vs outputs of the Krebs cycle?
inputs
2 acetyl-coA (from 2 pyruvate)
outputs
2 atp & 6 NADH
4 CO2 & 2 FADH2
253
what happens to acetyl-coA once the pyruvate oxidation stage is done?
2 options:
1. enter the Krebs cycle
2. enter different metabolic pathways to make fatty acids and cholesterol (when acetyl-coA is in excess)
254
in each step of the Krebs cycle, which carbon is the one that leaves (to form CO2)?
the COO- that is attached to a tertiary carbon
= carbon from the oxaloacetate end
NOT the COO- that is at the top of the molecule (this one is attached to a secondary carbon)
= carbon from the acetyl coA end
255
the Krebs cycle is the regeneration of which molecule?
oxaloacetate
256
what are the 3 goals of the Krebs cycle?
1. complete the breakdown of glucose
2. store electron energy (by oxidizing NAD+ and FAD into NADH and FADH2)
3. create atp by substrate-level phosphorylation
257
what is the first step of the Krebs cycle?
acetyl-coA (2C) binds its acetyl end to oxaloacetate (4C)
= forms citrate (6C)
258
what enzyme is used in the first step of the Krebs cycle?
citrate synthase
259
What is the relationship between citrate and citric acid?
citrate is the ionized form of citric acid
260
Describe the 6 steps of the Krebs cycle
1. formation of citrate using the enzyme citrate synthase
= 6 Carbons
2. 1 CO2 is released & 1 NADH is formed
= 5 Carbons
3. 1 CO2 is released & 1 NADH is formed
= 4 Carbons
4. ADP is made by substrate-level phosphorylation
5. FADH2 is formed
6. NADH is formed
oxaloacetate is left
261
what is the net yield of the Krebs cycle?
for 1 glucose molecule:
2 atp
6 NADH
2 FADH2
4 CO2
262
how many CO2 molecules are produced in each stage of the glucose catabolism? for 1 glucose molecule
for 1 glucose molecule :
glycolysis = 0
pyruvate oxidation = 2
Krebs cycle = 4
263
how many atp are produced from glycolysis and Krebs cycle together?
4 atp only (per glucose molecule)
264
what are the 2 processes involved in oxidative phosphorylation
electron transport chain
oxidizes NADH and FADH2
creates a H+ gradient across the inner membrane
chemiosmosis
phosphorylation of ADP by ATP synthase
265
what molecule(s) link the Krebs cycle to oxidative phosphyrlaton?
NADH and FADH2
266
what is the [H+] across the mitochondrion? where is the concentration gradient ?
outer membrane
inter-membrane space = high [H+]
inner mitochondrial membrane (concentration gradient)
mitochondrial matrix = low [H+]
267
what is the first step of the ETC?
NADH (from the Krebs cycle) comes near the inner membrane.
NADH is oxidized into NAD+
268
what is the second step of the ETC?
1 e- and 1 H+ from NADH oxidation goes inside the first protein complex of electron carriers
269
what is the third step of the ETC?
the electron travels to the Q complex
270
is electron transfer endergonic or exergonic ?
exergonic; each complex is more electronegative than the previous one
271
what accounts for the very high number of ETC in a single mitochondrion? how many chains/ mitochondrion?
the folding of the inner membrane into cristae
= increases surface area
= very "long" inner membrane
= 1000 ETC
272
what component does the ETC need for its electrons to move from 1 complex to another?
the prosthetic group
273
when is a component of the ETC said to be reduced vs oxidized ?
reduced
= accepts electrons
= becomes more negative
= when a component accepts e- from its "uphill" neighbour
oxidized
= donates electrons
= becomes more positive
= when a component donates e- to its "downhill" neighbour
274
in the ETC, are NADH and FADH2 reduced or oxidized?
oxidized (donates electrons = more positive charge)
275
what is the order of the 6 complexes in the ETC?
complex I
CoQ
complex II
complex III
CoCyt C
complex IV
276
what happens in the complex I of the ETC
- NADH from the Krebs cycle & glycolysis enters the Complex I
- NADH is oxidized into NAD+ and H+
- FMN accepts the electron from the previous oxidation
- 4 H+ are pumped into the inner membrane
- FMN transfers the electrons to coQ, which leaves the complex I and reaches the complex III
277
what happens in the complex II of the ETC
- FADH2 from the Krebs cycle & glycolysis enters the Complex II
- FADH2 is oxidized into FAD and 2H
- FE-S centers accepts the electrons from the previous oxidation
- no H+ are pumped here
- Fe-S centers transfers the electrons to coQ, which leaves the complex I and reaches the complex III
278
the coQ transfers e- from where to where ?
takes e- from the complex I and from the complex II
transfers it all to the complex III
279
the enzyme Cyt c transfers e- from where to where?
from the complex III to the complex IV
280
how many H+ are pumped into the inner mitochondrial membrane in each complex of the ETC?
complex I = 4H+
complex II = none
complex III = 4 H+
complex IV = 2 H+
total: 1 NADH ends up pumping 10 H+ in total
281
why is oxygen important in the ETC stage in terms of the inter-membrane space content?
O2 is the final acceptor in the ETC
if no O2:
ETC is blocked
= H+ can't be pumped into the inner membrane
282
why is oxygen important in the ETC stage in terms of the mitochondrial matrix content?
O2 takes H+ from the matrix to form H2O and then create an electronegative O that can accept the e- from the ETC
if no O2:
matrix will not have a low [H+]
= no concentration gradient
283
why does FADH2 pump 1/3 less H+ than NADH
bc FADH doesn't go through the complex I, which pumps 4 H+
FADH = 6 H+
NADH = 10 H+
284
what is a poison that inhibits ETC? how does it work and what is the consequence?
cyanide
it binds to Cyt a3 of the complex IV
= prevents the release of e- to oxygen
= stops the whole ETC process
= no H+ gradient
= no chemiosmosis
= no atp
= cell dies
285
how does chemiosmosis start?
by using the H+ gradient formed by the ETC to power the synthesis of ATP by atp synthase
286
atp synthase can work one way or both ways?
both ways
it can hydrolyze atp or synthesize it
depends on the delta G of the rxn (exergonic or endergonic)
287
describe the 4 main parts of the ATP synthase's structure.
rotor
on the plasma membrane
spins when H+ transfers through it
stator
on the plasma membrane (anchored=fix)
holds the knob in stationary position
keeps the enzyme in the plasma membrane
rod
spins, which activates the knob's active sites
top end = linked to rotor
bottom end = knob
knob
stationary
has 3 active sites that allows ADP -> ATP
288
how much atp do NADH give
1 NADH = 3 ATP
289
how much atp do FADH2 give
1 FADH2 = 2 ATP
290
what are the 2 mechanisms that provide ATP to cells without oxygen O2?
anaerobic respiration
fermentation
291
which organisms form atp without oxygen?
obligate anaerobes
organisms that can only live in anaerobic conditions
fermentation or anaerobic respiration
facultative anaerobes
organisms that can live in both conditions
if O2: aerobic cellular respiration
if no O2: fermentation
292
are yeasts (fungi) obligate anaerobes or facultative anaerobes?
facultative anaerobes
293
what is the difference between aerobic and anaerobic respiration?
less atp made in anaerobic
bc the final electron acceptor of the ETC is not as electronegative as oxygen = less efficient
294
what can be used in anaerobic respiration instead of O2?
the final electron acceptor can be:
NO2, NO3, CO2, metal ions, SO4
295
what is the difference between fermentation and anaerobic respiration?
anaerobic = you go through all the cycles of respiration, just replace the O2 in the ETC by another electronegative molecule
fermentation only uses glycolysis
296
how is NAD+ recycled in fermentation? why is it crucial?
NAD+ is recycled by substrate-level phosphorylation
= important to amorce the next glycolysis cycle, otherwise glycolysis will stop
297
what are the 2 types of fermentation? explain them
alcohol fermentation
1. glucose -> pyruvate
2. pyruvate -> acetaldehyde
3. this release 1 CO2
4. acetaldehyde is reduced into ethanol by NADH
acetaldehyde + NADH -> ethanol + NAD+
lactic acid fermentation
1. glucose -> pyruvate
2. pyruvate -> lactate (no CO2 release)
3. NAD+ is regenerated
298
what are applications in our life of fermentation? (lactic and alcohol)
lactic acid fermentation
- the making of cheese & yogourt by fungi & bacteria
- our muscle cells in anaerobic conditions
alcohol fermentation
- yeast in bread
299
how does lactic acid build up in muscle occur?
during a hard/long gym sesh
= when our body need to make atp faster than the blood can supply oxygen
= when our body's glucose metabolism is higher than the rate of oxygen intake from the blood
300
compare lactic acid fermentation and aerobic, which is faster?
lactic acid fermentation is 2.5x faster
but makes much less ATP
301
what is a consequence of lactic acid build up in muscle?
cause muscle fatigue and pain
302
what happens to lactate in muscle cell after fermentation happened?
lactate is transported to the liver via the blood
lactate is converted into pyruvate
it then enters mitochondria in liver cells and complete cellular respiration
303
compare the where the electrons of NADH goes in
aerobic, anaerobic and fermentation
aerobic / anaerobic
to the ETC complex I
fermentation
to an organic molecule (pyruvate or acetaldehyde)
304
what other groups apart from carbohydrates can be broken down to feed cellular respiration? rank them in order of usage
1. carbohydrates
2. fats (lipids)
3. proteins
305
what is the breakdown of glycogen called? what is the product?
glycogenolysis
glycogen -> Glucose-6-phosphate
306
what is glycogen synthesis called ? what is the reactant?
glycogenesis
glucose-6-phosphate - glycogen
307
excess amino acids from protein we eat are converted to what? before doing so, what is one important step?
to intermediates of cellular respiration
before entering cellular respiration, amino acid deamination must occur
= amino groups are removed by deamination
308
how do organisms get rid of the amino groups from amino acid deamination?
amino acid deamination:
amino acid -> amino group + carboxyl group
amino group -> ammonia -> ammonium -> urea
urea is then excreted in urine
309
when do proteins come into play in the cellular respiration?
at the end of glycolysis, or after glycolysis
after deamination, the carboxyl groups of an amino acids enters different pathways:
carboxyl end -> pyruvate & enters Krebs cycle
carboxyl end -> acetyl coA & enters Krebs cycle
310
when do lipids come into play in the cellular respiration?
lipids -> glycerol + fatty acids
glycerol -> G3P -> glycolysis
fatty acids -> beta oxidation -> acetyl coA
311
how does beta oxidation work
fats are broken down into 1 glycerol + fatty acids
beta oxidation breaks down each fatty acid chain into smaller chains of 2-carbon length called acetyl-coA
312
why does lipid metabolism creates more ATP
bc apart from yielding acetate units , beta oxidation also generates NADH and FADH2 thus increasing the efficiency of the ETC.
each "cut" into an acetate unit releases 1 FADH2 and 1 NADH
313
what is the difference in atp yield with lipids vs carbohydrate cellular respiration?
lipids = more than twice the amount of ATP
314
a fatty acid is a 16-carbon chain, how many rounds of beta-oxidation does it have to go through?
how many acetate units will be yielded?
how many FADH2/NADH will be yielded?
7 cuts necessary
= 7 rounds of beta-oxidation
= 8 units of acetate
= 8 FADH2 and 8 NADH
315
why is bruning fats by exercising very hard?
bc fats yields so much atp, so fats holds so much energy, it is difficult to release that energy
316
is the atp yield obtained from glycerol high?
no, what you get from 1 glycerol is half of what you get from 1 glucose
but fatty acids compensate for that
317
how is the synthesis (building) of glucose named?
gluconeogenesis
318
how is the synthesis (building) of fats named?
lipogenesis
319
show that the pathways of cellular respiration are reversible
the compounds formed in the Krebs cycle can be modified into amino acids
pyruvate can form glucose
acetyl coA can form fatty acids
DHP -> G3P
= all endergonic rxn = require ATP
320
what is the difference between autotrophs and heterotrophs?
autotrophs
=producers
= "self"-feeders; produce their own food
heterotrophs
= consumers
= consume food made by other organisms
321
what are photoautotrophs?
organisms that use:
- light as source of energy to make the organic substances they need
- CO2 from atmosphere as their source of carbon
convert light energy into chemical energy through photosynthesis
322
give 4 examples of photoautotrophs
plants
algae (protist)
cyanobacteria
purple and green sulfur bacteria
323
what trophic levels are the primary producers? what is their role
chemoautotrophs
photoautotrophs
= they are the base of all food chain & provide energy to all other organisms
324
in photosynthesis, where does O2 in the product comes from?
from water
CO2 gets reduced to sugar, and water gets reduced to oxygen
325
what is the equation for oxygenic vs anoxygenic photosynthesis
oxygenic
light + 6 CO2 + 6 H2O = C6H12O6 + 6 O2
= uses water and produces 6 O2
anoxygenic
light + 6 CO2 + 6 H2S = C6H12O6 + 6 S
= uses H2S and produces 6 S
326
which of the 4 organisms that are photoautotrophs undergo oxygenic photosynthesis?
plants
algae
cyanobacteria
327
which of the 4 organisms that are photoautotrophs undergo anoxygenic photosynthesis?
green and purple sulfur bacteria
328
between plants and animals, what is the main difference regarding the cellular respiration process?
plants make their own glucose through photosynthesis
and then go through the same stages of respiration
329
what is the structure of a leaf? 4 components of its structure
cuticle
palisade mesophyll
vascular bundle
spongy mesophyll
stoma
330
how does the stomata help in photosynthesis?
gas exchanges, which are crucial in photosynthesis happen through the stomata
= pores in the lower epidermis
331
the stomata has 2 components, which are they?
the hole where gas goes through
and guar cell that controls it (close1open)
332
how does the vascular tissue help in photosynthesis?
by distributing substances throughout the plant
= crucial for survival of all plant cells
333
how does the mesophyll help in photosynthesis?
mesophyll cells contain an extremely large amount of chloroplasts for photosynthesis
334
what is the structure of a chloroplast? start from the outer membrane and work your way to the middle
outer membrane
inter membrane space
inner membrane
stroma (liquid inside the inner membrane; equivalent of matrix)
thylakoid (disk shape)
stroma lamellae (bar that connects 2 thylakoid)
lumen (inside of a thylakoid)
335
where are pigments that capture light found in a chloroplast
on the membrane of a thylakoid
336
what are the 3 pigments of chloroplast?
chlorophyll a
chlorophyll b
carotenoids
337
what is the difference between chlorophyll a and b?
one different functional group
a = CH3
b = CHO
so b is more polar than a
338
what is the job of caratenoids?
photo protection
= absorb and dissipate excess light
(to prevent damage to the chlorophyll pigments)
339
what is the absorption spectrum of each pigment of chloroplasts?
Chlorophyll a:
absorbs
blue-violet = 430-450 nm
red 660-680 nm
It reflects blue-green light
Chlorophyll b:
absorbs
blue 450-500 nm
orange-red 640-660 nm
It reflects yellow-green
Carotenoids:
absorbs
blue 400-500 nm
reflect yellow, orange, and red
340
why do see orange leaves only in autumn?
We see carotenoid pigments only in autumn because chlorophyll breaks down as temperatures drop and daylight decreases.
In summer: orange pigments are masked by strong green pigments.
341
what accounts for the specificity of certain pigment molecules for certain wavelengths?
many photons can be emitted, but
only the photons that are exactly equal in energy to the energy difference between the ground and the excited states are absorbed
342
what happens when one photons hits one pigment molecule?
electrons are excited, which creates vibration
the vibration is transferred from one pigment to the next by inductive resonance until it reaches the reaction center.
343
in photosynthesis, what is reduced and what is oxidized?
Energy + 6CO2 + 6 H2O -> C6H12O6 + 6O2
the LION says GRR
loss of e- = oxidized / gain of e- = reduced
H2O loses electrons
= becomes more negative
= H2O is oxidized into 6 O2
= oxidation
CO2 gains electrons
= becomes more negative
= 6CO2 is reduced into C6H12O6
= reduction
344
in cellular respiration, what is reduced and what is oxidized?
C6H12O6 + 6O2 -> Energy + 6CO2 + 6 H2O
the LION says GRR
loss of e- = oxidized / gain of e- = reduced
O2
= reduced into H2O
= reduction
C6H12O6
= oxidized into 6CO2
= oxidation
