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Life 102 exam 2

Terms in this set (120)

What is a membrane and what is its function?
-boundary layers of cells, & organelles inside cells
-what comes in and out of the cell
What are the parts of a membrane and how do they function?
-phospholipid bilayer
-transmembrane proteins
-interior protein network
-cell-surface markers
What is the fluid mosaic model?
fluid=membrane components are not stationary
Mosaic = phospholipids, proteins & other macromolecules
Evidence: human & mouse specific proteins in merged membranes
Describe the variables that can affect membrane fluidity?
1) temperature
2) Fatty Acid Tail Structure
3) Cholesterol
Explain the example of winter wheat
Change in tails structure compared to the summer weather and winter weather
What types of membrane proteins are there and what are their proteins?
1) integral
2) Peripheral
How do things get through a membrane?
1) phospholipid bilayer: nonpolar molecules, small polar molecules
2) transport proteins: polar molecules
How does active transport compare to passive transport?
passive transport: high concentration to low concentration
active transport: low concentration to high concentration
How does the concentration gradient influence passive vs. active transport?
it is how of solutes change among areas
What is facilitated diffusion, what proteins are associated with it, & how do those work?
-diffusion of molecules/ions across the cell membrane by using transport proteins
-channel proteins: hydrophilic core, allows specific molecules & ions through, selectively transport water
-Carrier Proteins: binds to molecules, changes shape
What moves through the membrane if solutes cannot? What is this process called?
Osmosis: movement of water
-passive transport
-solutes too big
-water moves from low of solute to high of solute
What are the different types of tonicity? Can you recognize what would happen to a cell if it was put into different solutions?
-isotonic solution: equal concentration inside and outside
-hypotonic solution: concentration lower outside of cell (cell size increases)
-hypertonic solution: concentration higher outside of cell (cell size decreases)
What are the repercussions of different concentrations [c] of solute on plant vs. animal cells?
-In an animal cell you want the cell to be isotonic
-in a plant cell you want the cell to be hypotonic
What proteins are required for active transport?
-ATP-Powered Carrier Proteins: allows specific molecules & ions through, requires energy (ATP)
-sodium potassium pump
Explain how the sodium.potassium pump works.
1. pump grabs Na+
2. ATP adds P (phosphorylations)
3. Pump changes shape; dumps Na+
4. Binding site for K+ available
5. Pump grabs K+;drops P
6. Pump folds back; dumps K+
What is membrane potential and how does it arise?
-Differential Charge (voltage) on either side of of the membrane
-unequal transport rate of ions
How does the concentration gradient and membrane potential influence how coupled transport works?
-uses gradients to transport across membranes
What is bulk transport? Why is it used?
endocytosis and exocytosis
What are the different types of bulk transport and what/how do they transport?
-Phagocytosis: bring in particulates
-Pinocytosis: bring in liquid
-Receptor-mediated endocytosis: bring in target molecules once enough are bound to receptors
What is cellular metabolism?
all of the chemical reactions in a cell
What are kinetic and potential energy? What kinds of energy are associated with each?
kinetic energy: energy associated with a moving object (heat, light)

potential energy: energy associated with the location or structure of an object (chemical energy)
Describe in your own words the 1st and 2nd laws of thermodynamics and how they relate to biology?
1st law of thermodynamics: the energy of the universe is constant
2nd law of thermodynamics: entropy (disorder) of the universe is always increasing
What is the main premise of entropy? Can you think of biological examples of increasing and decreasing entropy? What is required to decrease entropy?
-if entropy increases: reaction is spontaneous
-if entropy decreases: reaction is non-spontaneous
-Free energy
What is gibbs free energy? What does a positive value mean? Negative?
-free energy
Can you explain exergonic & endergonic reaction? How can we determine if a reaction will be spontaneous or not?
-exergonic: spontaneous= G<0
-endergonic: G>0 non-spontaneous
-endergonic reactions are fueled by exergonic reactions
What is required to get a spontaneous reaction to proceed? Does spontaneous mean "fast? or "instantaneous"? Why or why not?
-a non-spontaneous reaction is needed to get a spontaneous reaction to proceed
-rates of reactions (same direction)
What is activation energy come from?
-heat
What is catalyst? What changes about activation energy when a reaction is catalyzed?
-catalysts: speed up the process
-stress chemical bonds
-reduce activation energy required
-reduce energy barrier
What are enzymes and how do they function?
-biological catalysts
-proteins
-lower activation energy
-speed up reactions
-not consumed by reaction
How can active sites catalyze a reaction?
1. act as a template
2. stress substrate bonds
3. provide microenvironment
4. bond to substrate briefly
What do enzymes not do?
-DO NOT add energy to a reaction
-DO NOT change the delta G
-DO NOT get changed in the net reaction
Describe different ways enzymes affect the rates of reactions?
1. [c] of substrates
2. [c] of enzymes
3. temperature
4. pH
What can regulate enzyme activity? How?
1. inhibitors: substance that hinder activity
2. activators: substance that induces activity
What are cofactors, activators, inhibitors?
-Cofactors: needed for substrate to fit, coenzyme = organic
-activators: substance that induces activity
-inhibitors: substance that hinder activity
What does it mean for an enzyme to be allosterically regulated?
-non competitive inhibitors because changes shape of active site by bonding to allosteric site
What are metabolic pathways?
-sequence of reactions
-stepwise process
-products of one are reactants of the next
how does feedback inhibition function?
- end product
-inhibits starting enzyme
Explain the difference between catabolic and anabolic reactions, an dhow they regulate to energy
catabolic: energy released
anabolic: energy required
What is ATP's structure? What kind of reaction releases energy from an ATP molecule?
-Adenosine triphosphate
-catabolic
Which bonds in the ATP molecule have the highest stored energy?
phosphate bonds
Is the ATP to ADP reaction endergonic or exergonic? What determines that?
exergonic
-phosphate leaving
What are the reactants and products of the ATP-ADP cycle?
reactants: ATP + H2O
products: ADP + P
What is the main molecular for cellular respiration?
C6H12O6+6O2 -> 6CO2 + 6H2) + energy (ATP, heat)
What is the change in free energy in both directions of the chemical reaction for cellular respiration?
requires -686 kcal/mol -> <- +686 kcal/mol
Explain how electrons can move energy from one atom/ molecule to another.
Transfer of electrons between atoms
What are redox reactions? Identify the processes and "players"
-oxidation-reduction reactions
-Reducing agent atom/molecule is oxidized
-receiving agent atom/molecule is reduced
How does electronegativity affect energy transfer with electrons?
determines if atom will lose or gain e-
What is oxidized and reduced in cellular respiration?
glucose is oxidized and oxygen is reduced
how does the analogy of staircase vs. a cliff help us think about the transfer of energy during cellular respiration?
Using step wise processes allows the cell to extract more energy than if it did it in one step
What are the main steps in cellular respiration? Where do they each occur in the cell? In relative amounts, how much energy is released in each step?
1. glycolysis (occurs outside the mitochondira) 2 ATP is released
2. Krebs Cycle (1 ATP is released) (occurs in the mitochondria)
3. Electron transport chain (occurs in the mitochondria and produces 28 ATP)
What are the different stages of cellular respiration?
1. glycolysis
2. Pyruvate oxidation/ Krebs cycle
3. electron transport chain
Where does cellular respiration take place?
mitochondria
What are the main stages and goals of glycolysis? How can understanding THIS help you understand what happens in glycolysis?
-goal = ATP synthesis
-ADP -> ATP = endergonic
- fueled by exergonic intermediate steps
How does phosphorylation affect the molecules in glycolysis?
it makes the molecule less stable
What is the starting substrate?
glucose
why are isomers made?
to convert the molecules so that it can move forwards as G3P to move on in cellular respiration
When is ATP required? Synthesized?
ATP is required in glycolysis and it is synthesized in there as well to ADP
When are electrons transferred? What are they carrying? Who do they go to?
Electrons are transferred by ATP becoming ADP because its loosing an electron
Cleavage of glucose
by breaking in half it makes it easier for the next stage to slowly extract energy
Converting to G3P (why is this necessary)? What enzyme does this?
This is necessary because it needs to be useable and G3P allows it to move forward
-isomerase does this
How do rearragements of the molecules help it proceed to the next major step (such as ATP synthesis)?
it makes it more reactive
What is the end product?
pyruvate
What else is part of the net yield?
2 NADH
2ATP
What is substrate-level phosphorylation?
The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
What are the main processes occurring during pyruvate oxidation?
transferring e- to NAD+
Getting rid of CO2
Bringing in CoA to make acetyl CoA
What happens to electrons? Who is oxidized/ reduced?
NAD+ gains an electron to make NADH
NADH is reduced
CO2 is oxidized
What are the starting reactants?
pyruvate
What is the end product of pyruvate oxidation?
acetyl CoA
What is yielded by this stage of cellular respiration?
2 NADH
2 CO2
2 Acetyl CoA
Why is the Krebs cycle called a "cycle"
The final product of the process serves as an initial reactant in the process.
What is the starting substrate in the krebs cycle?
acetyl CoA
How many times is NAD+ is oxidized to NADH
3
What is released after each of these redox reactions?
CO2
Why is CO2 released from the molecule?
because it has been fully oxidized
Is ATP made directly or indirectly? What method of ATP synthesis is used?
ATP is made indirectly
oxidative phosphorylation is the ATP synthesis used
What other high0energy electron carrier is made?
FADH2
What is the end product? Does it leave to the next step of cellular respiration? If not, what is it used for
the end product is oxloacetate and this does not leave the krebs cycle it stays in to begin the cycle again
What are the total yields for this step of cellular respiration (the krebs cycle)
10 NADH
2 FADH2
4 ATP
What enters the ETC?
NADH and FADH2
What draws electrons from one protein to next in the chain?
more electronegative proteins
why does FADH2 contribute less energy than NADH?
FADH2 enters at lower energy, so not as much energy is extracted
What is the final electron acceptor? Why?
Oxygen because it doesn't get clogged with electrons.
Once oxygen has the electrons at their lowest energy state, what is the final product of the ETC?
water
How much ATP is made during this stage of cellular respiration?
28 ATP
what ions are released during redox reactions in glycolysis, pyruvate oxidation, and the Krebs cycle?
hydrogen ions
How do these ions generate a gradient? What is it a gradient of?
because of the higher concentration the slow extraction allows pumps to move H+ ions against their concentration gradient
-it is a gradient of proton pumps that generate electrochemical gradient
What is the electrochemical gradient?
the concentration gradient and the membrane potential
How does this gradient power the ETC?
the energy that comes from the hydrogen ions moving against their concentration gradient
What is chemiosmosis and why is it important for oxidative phsophorylation
-chemiosmosis is osmosis floating through it is where majority of ATP is synthesized, protons drawn to low [c] and [-] charge naturally by diffusion
- important for oxidative phosphorylation because chemiosmosis is where the ADP is phosphorylated
What is ATP synthase and how does it work
-it is natures smallest rotary motor
1. channel for H+
2. H+ hit "grooves" and causes rotor to rotate
3. stalk rotates- changed shape of knob
4. knob= enzyme complex. Catalyze ADP -> ATP
What are the total number of ATP molecules synthesized during aerobic cellular respiration from one molecule of glucose?
32 ATP
What is the primary electron acceptor in aerobic respiration versus anaerobic respiration?
-oxygen in aerobic respiration
-something other than O2 in anaerobic respiration
How do aerobic respiration, anaerobic respiration & fermentation differ in their yields of ATP?
aerobic respiration: 32 ATP
fermentation: 2 ATP
What are the 2 kinds of fermentation? How do they generate ATP? How do they differ?
- Ethanol Fermentation: pyruvate is not transported to mitochondria and they recycle NADH-> NAD+ and CO2 is released
- Lactic Acid Fermentation: same process of generating ATP
DIFFERENCE:
ethanol fermentation: by product is ethanol
lactic acid fermentation: by product is lactate
What is the equation for photosynthesis? Is this an endergonic or exergonic reaction?
6CO2 + 6H2O + light energy = C6H12O6 + 6O2.
-endergonic reaction
Where does the energy for photosynthesis come from?
the sun
What are photons? Describe their energy levels & wavelengths
-a quantum of light
-photons move from sun (kinetic energy)
-photons move as a wave
What does it mean for photons to photo-electrify electrons?
-when electrons are absorbing or being emitted
How is light absorbed or reflected using pigments? What is pigment? How do we see color?
-the color we see is reflected
-the color absorbed is from the sunlight
-if a shirt is red, the color red is being reflected and the other colors are being absorbed
Describe the main photosynthetic pigment, where it is located in the organelle, what organelle it is found in, and the main structures of that organelle.
-chlorophyll
-located in the thylakoid disks which are stacked in grana surrounded by stroma
-found in the chloroplasts
How do we go from light energy to chemical energy with photosynthesis?
1. different wavelengths of light have different energy
2. photons excite electrons in pigments, thus transferring that energy
What is ground state vs. excited state?
-electron in its lowest energy state = ground state
-electron in a higher energy shell = excited state
How does the movement of electrons from ground to excited and back again release energy?
-because going from a higher state of energy to a lower state of energy will cause a release of energy and the light reactions will capture that energy
Describe the main goals of the light-dependent and light-independent reacctions of photosynthesis
light-dependent reactions
-capture light
-make & transfer high energy electrons
-make ATP
light-INdependent reactions
-use energy from (1) to assemble CO2 into glucose
What are the parts of the photosystem and how is energy transferred?
-proteins embedded in thylakoid membranes
-filled with chlorophyll
-passes energy from one molecule to next: excited -> grounded -> excited -> grounded
Where do the reaction center chlorophyll molecules (P680 & P700) each get their electrons to replease the ones that were oxidized away?
h2o
What transfers the electrons among photosystems and from the photosystem to the calvin cycle?
chain of proteins
When are ATP and NADPH made in the light reactions and what are they ultimately used for?
-made in photosystem I
-used for the Calvin cycle
What is the electron transport system and non-cyclic phosphorylation?
-creates H+ gradient
-powers chemiosmosis
Where do the different photosynthesis steps take place?
the electron transport chain
What are the main phases of the calvin cycle? what are their goals?
1. carbon fixation: incorporate CO2 into organic molecules
2. reduction: use energy to make sugar
3. regeneration: recycle remaining C to make reactant
what is produced & consumed by the calvin cycle? what is recycled?
-G3P, glucose and other sugars are produced
-Carbon is recycled
What are a plant's options if there is no CO2, or if there is limited gas exchange?
-photorespiration
What is photorespiration, and when does it occur? Why is photorespiration not a good thing for plants?
-If CO2 is low use O2
-occurs when CO2 is low or when gas exchange is low
-no sugar is made as a result
What can lead to CO2 being in low concentration?
-stoma being closed cause gas exchange to decrease and water is lost
What happens when stomata are closed? Open?
-stoma closed: gas exchange is low and water is loss
-stoma open: gas exchange is high and water is loss
Describe how C3, C4, and CAM plants differ
C3 plant: CO2 fixed into 3-C molecule
C4 plant: CO2 fixed into 4-C molecule, spatially separate C-fixation for sugar production
CAM plants: temporally separate C-fixation
How do C4 plants fix carbon? What does cell location have to do with it? What are the starting reactants and important molecules for C4?
-C4 plants mesophyll cells concentrate CO2 and prep it
-starting reactants: PEP + CO2 for mesophyll and RuBP +CO2 for BSC
When do CAM plants fix carbon? Why does time of day matter?
-in the day it grabs protons synthesize sugar from stored C and at night they store C with C4 pathway
Where does the oxygen produced in photosynthesis, and that we breathe, and use for cellular respiration, come from?
-CO2
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