2# Debra Flashcards
(232 cards)
1
Q
Why must all cells have a plasma membrane?
A
Phosphate membrane will regulate what moves into and out of the cell
Identity
Responds to signals
2
Q
Why do we say that membranes are semipermeable and why is this important?
A
semi permeable membrane: membrane determines what goes into and out of the cell
Important in regulating the internal contents of a cell
3
Q
Why do phospholipids form bilayers when mixed with water?
A
phospholipids
G 1. Phosphate (hydrophilic/charged)
2. Fatty acid (hydrophobic/not charged) 3. Fatty acid
middle of the membrane is hydrophobic and very fatty
4
Q
Why must membranes be fluid to function?
A
Membranes are fluid in order to be flexible
Proteins in the membrane can change position
5
Q
What are 3 methods cells use to adjust membrane fluidity?
A
- Temperature: alter the melting temperature of fatty acids
* By adding more unsaturated fatty acids- fluidity increase* - Change the properties of the polar head groups
- Add chemicals to the bilayer
* add cholesterol = decrease fluidy*
6
Q
What does amphipathic mean?
A
Interact with hydrophilic molecules and hydrophobic molecules
7
Q
What determines what can move across membrane on its own or not?
A
middle of the membrane is hydrophobic and very fatty
deciding what crosses
8
Q
What sorts of molecules can pass through lipid bilayer membranes?
A
Small non polars (fatty)
Small uncharged polar molecules
Gases - CO2, O2, N2
Ex: steroids (hydrophobic) will go through
9
Q
Why do cells need integral membrane proteins ?
A
Integral membrane protein allows polar molecules to cross the membrane
10
Q
What is the general model for the structure of biological membranes?
A
Carbohydrates: used for cell identity
Eukaryotic Cell
Cholesterol in fatty acids because hydrophobic
diagram
11
Q
What keeps integral membrane proteins from leaving the membrane?
A
Integral proteins remain in place due to hydrophobic interactions in the middle of the membrane and hydrophilic interactions on the outside and inside of the membrane
12
Q
How do we know that proteins can diffuse within membranes?
A
Proteins can change position within a membrane
Experiment by Eddin and Frye
- fused human and mouse cells
- after 40 minutes, proteins were dispersed through hybrid cell
13
Q
How can proteins form holes through membranes?
A
Several different membrane-spanning domains aggregate amino acids line the hole
Hydrophilic amino acids line the pore so polar molecules can be moved across the membrane
14
Q
What is special about the structure of the plasma membrane, and what sorts of proteins do you find in it and name 3 function of those proteins?
A
Lipid bilayer forms fluid, semipermeable barrier
Proteins embedded in the membrane are free to move with the membrane, but they cannot get out
Trans(across)membrane (integral) proteins: proteins in the membrane
Peripheral proteins: inside edge or outside of the membrane
Glycolipid = sugar attached to a phosphate head Glycoprotein = attached to protein
Glycocalyx composed of glycoprotein (carbohydrate attached to protein) and glycolipid (carbohydrate attached to phospholipid) on only CELL SURFACE
USED FOR CELL IDENTIFICATION
Attached to cytoskeleton by supporting fibers
Proteins form transport channels
Some proteins are enzymes
Cell surface receptors
15
Q
What are the functions of the plasma membrane?
A
Passing water Passing bulk materials Selective transport of molecules Receiving and transmitting information Express cell identity Physical connections with other cells
16
Q
What is osmosis and why does it occur?
A
Osmosis-diffusion of water across a semipermeable membrane to equalize water connection on either side
Water will move from a hypoosmotic solution to a hyperosmotic solution
17
Q
What kinds of cells want to be isosmotic, and what kinds want to be hyperosmotic?
A
Cells without cell walls want to be isosmotic with their environment
Ex: RBC
In cell: 0.9% water out: 0.9% water
Cells stay same size because same amount of water goes in and out
Cells without cell walls
Animal cells(ex)
Any cell with cell wall Plant cells(ex) want to be hyperosmotic to their environment Plant cells(ex) want to be in a hypoosmotic environment so water enters cell
18
Q
Terms for comparing 2 solutions:
- definition
- what happens to cell
- what cell want it
A
- isosmotic: two solutions have the same concentration of water and solute; equal amounts of water move into and out of the cell; cell size stays the same; animal cells want this
- hyperosmotic solution: solution with less water and more solute than the solution you are comparing it to
- hypoosmotic solution: solution with more water and less solute than the solution you are comparing it to
19
Q
Solution is made of…
A
Solvent: part of solution in greater amount (water)
Solute: that which is dissolved in the solvent; lesser amount than solvent (lemonade crystals)
20
Q
Why do cells shrink when placed in a hyperosmotic solution?
Example
A
Hyperosmotic solution: more water in cell than outside so water will leave the cell and cell will shrink
Lab: plasmolysis of Elodea
21
Q
Why do red blood cells explode when you place them in distilled water?
A
RBC in Distilled water:
cell is hyperosmotic environment
environment is hypoosmotic to cell
22
Q
What is “turgor pressure” and what is it used for?
A
Turgor pressure will result when plant cells are in hypoosmotic environment
Pressure applied to cell wall of plant cell makes the wall stiff
Plant stands up
23
Q
How is bulk transport accomplished?
A
Bulk transport is the use of membrane vesicles to transport large particles out of cell or into cell
24
Q
What is the difference between endocytosis and exocytosis?
A
Endo = inside/within Exo = outside
Endocytosis: cell brings particles in
Exocytosis: cell gets rid of particles
25
What is the difference between phagocytosis and pinocytosis?
If a cell does phagocytosis, particles (solids) are brought into the cell (with other stuff out there too)
If a cell does pinocytosis, it will take liquids in (with other stuff out there too) from the environment
*pina colada liquid*
26
There are two types of endocytosis:
phagocytosis
| pinocytosis
27
what doe exocytosis mean?
removing something from cell
28
What is “receptor-mediated endocytosis”?
How do they work?
Where are they located?
Bringing something into the cell
Receptor will select what is brought in
More specific
* receptors bind certain molecules, the molecules they want to bring in
* receptors are located in “coated pits”; once enough molecules attach to the receptors, vesicle will form and it will move into the cell
*diagram*
29
What are the differences between bulk transport and selective transport?
Bulk transport:
Requires a lot of energy
Uses membrane vesicles
Non-selective- takes up “whatever’s out there” in the environment”
Selective Transport:
Uses integral membrane protein to transport specific molecules across the membrane
Saves energy
Allows specificity
30
What is "selective transport” and what substances do cells move by selective transport?
This is how ions, glucose, small polar molecules like amino acids and nucleotides pass through
31
How do aquaporins prevent the passage of molecules other than water?
Specialized channels for water enhances the rate of water flow through a membrane, but do not alter the direction of water movement
Very narrow channels with positive charges in the middle that repel + and stop - ions from crossing
32
How can ion channels tell the difference between one type of ion and another?
They can tell the difference between ions based on the size and charge of the ion
33
How are ion channels regulated?
Water-filled pores through which SPECIFIC ions flow
* Driving force will be the concentration gradient
* Regulation is by opening and closing the channels
34
What are the differences [4] between ion channels and facilitated diffusion?
What is the same?
Ion channels:
Pore within integral-membrane protein
Driving force is he concentration gradient
Specific
Non-saturable - if the channel is open, ions are free to move; if the channel is closed, ions cannot move
Facilitated diffusion:
```
Facilitated = helper
Diffusion = no energy / high concentration to low concentration
```
Receptor protein in the membrane which binds the molecule to be transported and carries it through the membrane
Driving force is concentration gradient
Specific (carries across)
Saturable (time limit on how fast it can take the protein and move it on another side)
BOTH CASES THEY MOVE SUBSTANCES DOWN A CONCENTRATION GRADIENT = no energy
35
Why is facilitated diffusion saturable, whereas channels are not?
Facilitated diffusion requires a receptor protein to CARRY the molecule across the membrane = ‘shepard taking sheep across a fence’
Ion channel is either open or closed; if open, ions move through; non saturable = “opening the gate”
36
What are the differences between facilitated diffusion and active transport?
Facilitated diffusion
* Requires protein carrier in the membrane
* Saturable
* Substances are transported down their concentration gradient
* No energy required
Active transport
* Substances are transported up their concentration gradient from an area of lower concentration to an area of higher concentration
* Requires Energy
37
How can you tell if a substance is moved by active transport?
Substance will be accumulated on one side of the membrane
38
How can cells have 35 fold higher concentrations of K+ inside than in the surrounding blood?
Through active transport
39
How do cells remove sodium?
Requires the sodium potassium pump (active transport)
Uses an integral membrane protein
PROCESS...
1. 3 Na+ enter the pump (protein) on the inside of the cell
2. Binds an ATP to the protein; pump is kinased (using phosphate from ATP)
3. Protein will change shape and release Na+ to the outside of the cell
4. Two K+ will enter the pump on the outside of the cell
5. Phosphate is removed
6. Protein changes shape and releases K+ to inside of the cell
40
Why does the toxin from poison arrow frogs kill you slowly and painfully?
Oubain block dephosphorylation (remove phosphate)
Cannot remove phosphate from ATP
Cannot pump ions; cells will swell and burst
41
Why are cardiac glycosides useful for treating heart patients?
Cardiac glycosides have similar effects as oubuain
Ex: digitoxigenin
Cause a slight build up of Na+ in the heart muscle cells by slightly interfering with dephosphorylation of ATP
*heart cells will swell, stimulate heart contraction
42
What is the similarities and difference between active transport and coupled channels?
Both require energy
Both move molecules against their concentration gradient from low to high concentration
------------------------------------
Active transport will use ATP as the energy source
ATP is NOT the source of energy in coupled channels
Coupled channels will use the energy of substances moving down their concentration gradient to move another substance UP its concentration gradient
43
Why are coupled channels often called "secondary active transport?"
Before you can use a coupled channel, the Na/K pump has to pump the Na+ out of cell
Cells use active transport to move Na+ against its concentration gradient and accumulate it outside the cell
Then couple channels use the movement of Na+ down its concentration gradient to “POWER” the movement of something else against its concentration gradient
44
What is the difference between symport and antiport?
Symport: both substances are moving in the same direction
Ex. Na+ moving down its concentration gradient releases enough energy to transport sugar against its concentration gradient
- Both are moving into cell
Antiport:
Use energy from a substance moving down its concentration gradient to another substance up its concentration gradient
‘Revolving Door’
- Substances will bind to opposite integral proteins and are exchanged
45
Why do cells lining the small intestine have two different kinds of glucose transport proteins?
Intestines use symport if glucose and sodium...
Cells use concentration of Na+ to import glucose against its concentration gradient
46
What are ionophores, and why are they so deadly?
Ionophores are antibiotics that transport ions across a membrane
***Picture**
Ionophores dissipate concentration gradients so concentration gradient cannot be built without a concentration gradient, you can't have coupled channels
47
What is metabolism, and what is the difference between anabolism and catabolism?
Chemical reactions that occur in cells
Anabolism: reactions that build molecules
Catabolism: reaction that break down molecules (hydrolysis)
48
Why do cells need energy, and what is the difference between potential energy and kinetic energy?
Cells need energy to do “work” - maintain processes associated with life
Potential energy: stored energy
(living organisms store energy in their chemical bonds)
Kinetic energy: energy of motion
49
What are the first and second laws of thermodynamics?
#1: energy cannot be created or destroyed; energy can be converted from one form to another
#2: entropy (disorder) of the universe is increasing
“S” = entropy
Ex: your bedroom being messy
50
What is free energy?
Energy needed to break and form chemical bonds
“G” = free energy
Have to consider...
Increases enthalpy (H) which is energy in chemical bonds
AND
2 disordering influences: temperature and entropy
Free energy = ordering influences - disordering influences
Chemical reactions usually result in a change in free energy
Δ = change in
ΔG = ΔH - TΔS
Change in free energy = change in enthalpy - temperature x change in entropy
*eq used to determine if reaction is spontaneous or not (not need energy or do)
51
How can you predict in which direction a reaction will proceed?
What is photosynthesis?
- equation
- free energy
Using ΔG
(change in free energy)
-ΔG = exergonic reaction; products have less energy than reactants; energy released
+ΔG = endergonic reaction; products have more energy than reactants; energy absorbed by the reaction (put energy into this reaction)
CO2 + H2O → sugar + O2
(highly endergonic-photosynthesis)
→ = sun (energy)
+ΔG
52
How did you measure how well lactase worked in the enzyme lab?
Lactase was the enzyme that worked on the substrate ONPG
If working, then ONPG was broken down, the solution turned yellow, the absorption (measured with the spectrophotometer) increased
53
What is an exergonic reaction and how does it differ from an exothermic reaction?
Exergonic: reaction that releases energy; products have less free energy or more disorder than reactants
Ex: firecracker going off
Exothermic: reaction that releases heat; spontaneous if ΔS > ΔT
54
Why did the ONPG change color in the enzyme lab?
ONPG changed color when the enzyme, lactase, broke it down
55
Why can one lactase enzyme create thousands of products?
Enzymes can be used over and over
56
Why did the activity of the lactase enzyme vary as you changed the pH?
5.5, 7.5, 9.5
Lactase worked best at 7.5
At 5.5 environment was too acidic, enzyme denatured- no longer functional
At 9.5 environment was too basic, enzyme denatured- no longer functional
57
Why can’t thermodynamics tell you how fast a reaction will go?
ΔG only tells you if the reaction is exergonic or endergonic
Need to know the activation energy to determine the speed of a reaction; first need to break existing bonds; reactions with high activation energy proceed slowly
58
What is activation energy?
| What happens If its lowered?
The minimum amount of energy needed to start a reaction
Need activation energy to break existing bonds; if you lower activation energy, the reaction will proceed faster
59
What is a catalyst?
catalyst lowers activation energy by stressing (putting stress on existing) chemical bonds
Therefore it increases the rate of reaction
60
What is an enzyme?
Biological catalyst
Increases rate of reaction of biological reactions by lowering the activation energy
Controls metabolism
61
Why do cells need enzymes?
Enzymes are required to make reactions associated with life go much faster
e.g. gene disorder
62
How do enzymes work?
Enzyme will convert the substrate to a product
- Substrate binds to a part of the enzyme called the active site
- Enzyme changes shape and stresses existing bonds in the substrate; reduced EA; reaction occurs
- Enzyme releases product
*you can use the enzyme again*
63
What is a substrate?
the molecule on which the enzyme acts
64
Why can some RNA molecules catalyze reactions?
RNA molecules that act as catalysts are called ribozymes
Ribozymes can change shape and put pressure on existing bonds, reducing the energy of activation
65
What is an active site (in an enzyme)?
The part of the enzyme that binds the substrate
66
What is the difference between the “lock and key” and “induced fit” models?
Lock and key: suggest that the enzyme and substrate are exact matches
Induced fit: suggests that when substrate binds to enzyme, the enzyme CHANGES SHAPE and stress existing bonds of the substrate, thus reducing activation energy; reaction occurs quickly
67
Why is the induced fit model favored?
Induced fit explains how the enzyme stresses bonds of the substrate
Explains why enzyme releases product
68
What is the catalytic cycle of an enzyme? IE(how does an enzyme work)
Need enzyme & substrate
Substrate binds to active site of enzyme
Active site changes shape to fit substrate and then stresses existing bonds of substrate to lower activation energy
Reaction occurs
Product released
Enzyme ready to find another substrate & do another reaction
69
Why do we know that binding and catalysis are separate activities?
Binding of substrate and catalysis are separate activities
| Some drugs prevent binding; some drugs prevent catalysi
70
Why can we measure an enzyme’s activity by measuring the rate at which its products accumulate?
Give a lab example
The more active an enzyme is, the more products it will produce
```
Lab…
substrate?...ONPG
enzyme?...lactase
products?... ONP and galactose
??is the reaction occurring??
Solution turned yellow, and then you measured the absorbance
```
71
What factors affect how well enzymes work?
Factors that affect rate of ANY chemical reaction:
- Concentration of product (increase (as you accumulate) product→ rate decrease)
- Concentration of substrate (increase substrate→ rate increase)
- Temperature
- Presence of catalyst (enzyme)
Factors that affect protein folding:
- High temperature will disrupt hydrogen bonding and hydrophobic interactions; all enzymes have an optimum temperature
- pH alters proportion of ionized amino acids; all enzymes have an optimum pH
- Salt competes with protein for hydrogen bonds with water
- Hydrophobic solvents disrupt hydrophobic interactions
- Reducing agents break disulfide bonds
- Covalent addition of a phosphate causes an enzyme to change shape; not always a bad thing; can be used to activate enzyme
72
How does temperature affect enzyme activity?
As temperature increases, enzyme activity increases until optimum temperature is reached; then enzyme becomes denatured
Ex: high fever 104F (will die because enzymes/proteins will denature)
Denature = enzyme loses shape
At cooler temperatures, rate of movement of substrate and enzyme is slower, decreasing the chance that they will get together; but enzymes are not denatured at cooler temperatures
*at pH to high and too low it denatures at both*
73
What is the difference between competitive and non-competitive inhibitors?
Competitive inhibitors:
Will bind to the active site and block the substrate from binding
No reaction / Slow reaction
Noncompetitive inhibitors:
Will bind to allosteric site and the active site will change shape and substrate cant bind
No reaction / Slow reaction
74
How are enzymes regulated?
On enzyme: active site & allosteric site (used by inhibitors or activators)
75
How can we tell whether an inhibitor is competitive or non-competitive?
If we have a competitive inhibitor, can overcome inhibition by adding more substrate; substrate would outcompete inhibitor for getting to active site of the enzyme
76
What is the difference between an active site and an allosteric site?
Active site is where the substrate binds an enzyme
Allosteric site is where an inhibitor or an activator binds and enzyme
77
What is an activator?
Activators bind an enzyme at the allosteric site; keep the enzyme in an ACTIVE CONFIGURATION to increase enzyme activity
e.g. enzyme-linked receptors: when signal binds, shape of enzymes changes and response will occur (increase activity)
78
What is a cofactor?
Cofactor- additional chemical component that aids enzyme activity
Nonprotein
Ex: metallic trace element (Mg)
79
What is a coenzyme?
Coenzyme- non protein organic molecule that functions as a cofactor (organic C-H)
Usually derived from vitamins
80
Why do you get pellagra if you don’t get enough vitamin B3?
Lack of B3 (niacin); B3 is a cofactor involved in redox reactions; it is an active part of NAD
Symptoms: inflammation of nerves, mental disorders
81
Why do cells have an energy currency?
Cells energy currency- intermediates that are used to transfer energy between reactions
```
-Most important:
ATP: adenosine triphosphate
NADH: electron carrier
FADH2: electron carrier
NADPH: electron carrier in photosynthesis
CTP, GTP (krebs cycle), UTP
```
82
What is NAD and what does it do?
NAD: nicotinamide adenine dinucleotide
NADox: (oxidized form): DOES NOT HAVE ELECTRONS
NADH: DOES HAVE ELECTRON
NADH = carries 1H+ and 2 electrons
NAD+ and NADH participate in many metabolic reactions
[Cells Move Energy By Moving Electrons]
83
What is ATP and why is it used in so many different reactions?
ATP: Adenosine triphosphate
ATP = ADP + P-
ATP is the main energy currency for cells
Source of fuel for cells
ATP is used to drive endergonic reactions
ATP → ADP + P + Energy
84
How can cells perform endergonic chemical reactions?
ATP is an energy source to drive the reaction
85
What is a coupled reaction?
Coupled reactions run exergonic reaction and endergonic reaction simultaneously
Break down ATP into ADP + P releases energy; this energy is used for the endergonic reaction which requires energy
The exergonic reaction must release more energy than the endergonic reaction requires
86
What is a biochemical pathway?
Reactions in living cells that occur in sequence; product of the one reaction is the substrate for the next reaction
87
What is feedback inhibition, and why is it useful?
Final product of pathway binds to the allosteric site of the FIRST enzyme in pathway and inhibits
Its reaction STOPS
88
How do cells recover the potential energy stored in reduced organic chemicals?
Where does the energy go?
Oxidation of reduced organic molecule
Recover potential energy by extracting electrons is this
Oxidation
Reduction
Potential energy is stored in chemical bonds, especially C-H
Remove electrons from these molecules
Electrons have energy and we move energy by moving electrons
When electrons are removed through oxidation, the electrons will be picked up molecules like NAD which will become NADH
89
What is electron transport (when talking about respiration)?
Electrons are carried along a series of electron carriers that increase in electronegativity
As electrons are transferred from one carrier to another, energy released is used to pump H+ and ultimately to make ATP
Oxygen has to be at the bottom for the electron transport chain
NADH gets electrons and then goes to top of chain and then NAD+ goes back to get more electrons
As electrons are dropping through the chain energy is released and used to pump H+ and later make ATP
Makes some water at the end
O2 is most electronegative (rlly rlly want e-)
90
What is the role of oxygen in most eukaryotic cells?
Role of oxygen is to accept electrons moving down the ETC; becomes water
Oxygen is the final electron acceptor in oxidative respiration
91
What is the difference between oxidative respiration and fermentation?
Oxidative respiration: requires presence of oxygen to completely oxidize sugar molecules (ripping e- off sugar for NAD or FAD to pick up)
Fermentation will only occur under anaerobic conditions meaning NO O2
Organic molecule will be the electron acceptor in fermentation
92
Why does transporting electrons from H to O release energy?
If electrons are transported from H to O, energy is released
B/c hydrogen electrons have the most potential energy and release energy when transferred
Oxygen valence electrons have least potential energy
Oxygen is VERY electronegative
93
What are the two ways that cells can make ATP?
Substrate level phosphorylation - occurs in glycolysis and the krebs cycle
Oxidative respiration and chemiosmosis - involves the ETS majority of ATP is made this way
94
What is substrate-level phosphorylation?
Direct transfer of Pi from substrate TO ADP
ADP + Pi → ATP
Puts energy in by ripping electrons off sugar and is endergonic (ΔG)
ETS and chemiosis is NOT involved
95
Whats the difference between exergonic and endergonic?
-ΔG is exergonic
Energy released
Products energy < Reactants energy
+ΔG is endergonic
Energy absorbed
Products energy > Reactants energy
96
What are the two distinct parts of oxidative respiration and how are they linked?
1. Oxidize reduced organic molecules (C-H) to CO2 and H2O
2. Make ATP by electron transport and chemiosmosis
***Each provides substrates for the other*** (need both)
97
What are the three stages of glucose oxidation?
```
Glucose- main sugar that is oxidized
(how do I get electrons off glucose??)
1. Glycolysis
2. Pyruvate Oxidation
3. Krebs Cycle
```
98
What are the two stages of ATP generation in oxidative respiration?
NADH pick up electrons and transport the electrons the ETS; electrons transferred to oxygen
Energy from the electrons is used to pump H+ across the membrane into the intermembrane space (against gradient) go back down gradient to make ATP
Chemiosmosis is used to make ATP
99
What is glycolysis?
Reaction converts 1 glucose to 2 pyruvate
100
What are the two stages and four steps of glycolysis?
What steps give the most energy?
2 stages:
1. Energy investment stage (activation energy)
2. Energy yielding stage
4 steps:
1. Glucose priming
2. Cleavage and undergo isomerization
3. Oxidation
4. Production of ATP
**3&4 give most energy**
101
What are the substrates and products of glycolysis?
```
Substrates:
Glucose
2 ATP
4 ADP
2 NAD+
```
```
Products:
2 pyruvate
ADP + P
4 ATP
2 NADH
```
102
Where does glycolysis occur?
cytoplasm
103
Why do we need to consume ATP to start glycolysis?
Prime the glucose; it's our activation energy - energy needed to get the reaction started
104
How is G3P oxidation coupled to ATP synthesis?
As the G3P is oxidized NAD+ picks up electrons and brings them to the electron transport system (as sugar oxidized, NAD+ reduced)
Energy released from the electron transport of the electrons through the ETS is used to pump H+ into mitochondrial intermembrane space
Movement of H+ back into mitochondrial matrix will provide energy for production of ATP through chemiosmosis
105
Why is it necessary to regenerate NAD+ for glycolysis to continue?
Must regenerate NAD+ so NAD+ can continue to pick up electrons when sugars are oxidized; NAD+ is needed for oxidation reactions in the Krebs cycle
106
Why do we accumulate lactic acid at the end of a running race?
Anaerobic respiration - Pyruvate is reduced because it needs to let oof NAD+ (NADH → NAD+)
Without sufficient oxygen, human muscle cells REDUCE PYRUVATE to lactic acid IN ORDER TO REGENERATE NAD+ so glycolysis can keep going
107
Why do yeast make ethanol?
Without sufficient oxygen, yeast cells REDUCE PYRUVATE to ethanol (and CO2) IN ORDER TO REGENERATE NAD+ so glycolysis can keep going
108
Where is pyruvate oxidized?
In the mitochondrial matrix
Glycolysis = cytoplasms
Pyruvate into matrix
109
When is pyruvate reduced and oxidized?
```
Oxidized = oxygen present
Reduced = oxygen NOT present
```
110
What are the substrates and products of pyruvate oxidation?
Need:
Pyruvate
NAD+
CoA ??
Get out:
Acetyl-CoA
NADH
CO2
111
Why is pyruvate oxidation considered a distinct stage of oxidative respiration?
Pyruvate will only be oxidized if oxygen is present
112
Why is acetyl-CoA a central molecule of energy metabolism?
Acetyl-CoA is the link between glycolysis and the Krebs cycle; CoA makes sure acetyl gets to krebs cycle
Many foods are converted to acetyl when they are metabolized
- Some proteins
- Definitely fats
113
Why do people who eat too much carbohydrate or protein get fat?
If you consume too much food, acetyl is not needed to make ATP
Instead it is converted to fat
114
Why do fish acidify the water they swim in?
Fish were giving off carbon dioxide which was converted to carbonic acid (because its in water)
pH is going down
Fish water should have had lower pH than snail water because fish released more CO2
115
Why did the Elodea acidify the water in the dark, but raise the pH in the light?
If in the dark, elodea was undergoing cell respiration and giving off CO2, formations of carbonic acid, pH goes down
If in the light, elodea is doing photosynthesis and taking CO2 from the water; pH goes up
116
Why do yeast produce CO2 when deprived of oxygen but we don’t?
Without O2, yeast will ferment sugars (reduce pyruvate and convert it to ethanol and CO2)
We don't have enzymes that yeast has so we make lactic acid and yeast makes ethanol
117
Why did we give the mitochondria in the electron transport export succinate rather than another sugar?
Succinate is the only sugar that is bound to a membrane; so when we prepare the solution we know that succinate will be present
118
Why did we treat the mitochondria in the electron transport export with azide?
Azide poisons cytochrome oxidase which normally delivers electrons to O2
Wanted electrons to go to DCIP
Electrons present if DCIP changed from blue to colorless
119
What is the Krebs cycle and what are the two stages of the Krebs cycle?
Series of 9 reactions that completely oxidizes acetyl (shredds it to pieces and left with CO2)
Two stages: priming, energy extraction
120
What are the substrates and products of the Krebs cycle?
```
Substrates:
1 Acetyl-CoA
1 GDP
3 NAD+
1 FAD
```
```
Products:
2 CO2
1 GTP
3 NADH
1 FADH2
```
121
How is ATP generated by the Krebs cycle?
GTP is made from a GDP + P by substrate level phosphorylation then GTP is converted to ATP if GTP is not needed for RNA synthesis (not made by chemiosmosis -- made by subr=strate whatever)
Do not make ATP from NADH and FADH2 → they go to ETS
NADH
FADH2
122
How is most of the energy released by the Krebs cycle temporarily stored?
NADH and FADH2
| These are reduced electron carriers that transport the electrons to ETS
123
Why does succinate dehydrogenase reduce FAD rather than NAD+?
Succinate dehydrogenase
“Ase” = enzyme
“De” = remove (hydrogen) from succinate
Will extract electrons from succinate (oxidizes succinate)
BUT the reaction is not energetic enough to reduce NAD+; FAD will be reduced instead to make FADH2
FAD will pick up electrons with less energy than those picked up by NAD+
124
What is electron transport?
Passage of electrons through a series of cytochromes and carrier molecules; these molecules pass electrons from one carrier to the next
ENERGY IS RELEASED FROM THE ELECTRONS is used to drive transmembrane pumps; H+ are pumped into the intermembrane space from the matrix
125
Where does electron transport occur?
ETS is located on the cristae of the mitochondria (inner membrane)
126
What are the substrates and products of electron transport?
Electrons are brought in by NADH and FADH2 which will drop off electrons
So NADH will become NAD+
FADH2 will become FAD
Also requires O2 because O2 will accept electrons and become H2O
And ATP is produced
127
How is electron transport linked to the oxidation reactions of respiration?
Oxidation reactions are glycolysis, pyruvate oxidation, and Krebs Cycle
Electrons from glucose are picked up by NAD+ and FAD; NADH and FADH2 carry the electrons to the ETS
After electrons are released by NADH and FADH2, you regenerate NAD+ and FAD go back to oxidize more sugar
128
How is the energy stored in NADH and FADH2 used to make ATP?
After NADH and FADH2 drop off their electrons to the ETS, energy from the electrons as they pass through the ETS is used to pump H+ from the matrix to the intermembrane space
then , protons go “ripping through” a pore in ATP synthase, releasing enough energy to drive the production of ATP from ADP + P
4 (H+/ ATP) / rotation
129
Why does FADH2 reduce ubiquinone rather than NADH dehydrogenase?
FADH2 carries electrons with less energy than the electrons carried by NAD, so FAD will reduce ubiquinone (the 2nd carrier) instead of the first carrier, NADH dehydrogenase
130
Substrates and products for glycolysis?
```
Substrates/glucose:
1 Glucose
2 ATP
4 ADP
2 NAD+
```
```
Products:
2 pyruvate
2 ADP
4 ATP (net of 2 b/c takes 2 to start)
2 NADH
```
131
Where does glycolysis occur?
cytoplasm
132
Why do we need to consume ATP to start glycolysis?
Prime the glucose; it's our activation energy - energy needed to get the reaction started
133
How is G3P oxidation coupled to ATP synthesis?
As the G3P is oxidized NAD+ picks up electrons and brings them to the electron transport system (as sugar oxidized, NAD+ reduced)
Energy released from the electron transport of the electrons through the ETS is used to pump H+ into mitochondrial inter-membrane space
Movement of H+ back into mitochondrial matrix will provide energy for production of ATP through chemiosmosis
134
Why is it necessary to regenerate NAD+ for glycolysis to continue?
Must regenerate NAD+ so NAD+ can continue to pick up electrons when sugars are oxidized; NAD+ is needed for oxidation reactions in the Krebs cycle
135
Why do we accumulate lactic acid at the end of a running race?
Anaerobic respiration - Pyruvate is reduced because it needs to let oof NAD+ (NADH → NAD+)
Without sufficient oxygen, human muscle cells REDUCE PYRUVATE to lactic acid IN ORDER TO REGENERATE NAD+ so glycolysis can keep going
136
Why do yeast make ethanol?
Without sufficient oxygen, yeast cells REDUCE PYRUVATE to ethanol (and CO2) IN ORDER TO REGENERATE NAD+ so glycolysis can keep going
137
Where is pyruvate oxidized?
Why oxidized?
Where reduced?
In the mitochondrial matrix
```
Oxidized = oxygen present
Reduced = oxygen NOT present
```
138
What are the substrates and products of pyruvate oxidation?
Need:
Pyruvate
NAD+
CoA ??
Get out:
Acetyl-CoA
NADH
CO2
139
Why is pyruvate oxidation considered a distinct stage of oxidative respiration?
Pyruvate will only be oxidized if oxygen is present
140
Why is acetyl-CoA a central molecule of energy metabolism?
Acetyl-CoA is the link between glycolysis and the Krebs cycle; CoA makes sure acetyl gets to krebs cycle
Many foods are converted to acetyl when they are metabolized
Some proteins
Definitely fats
141
Why do people who eat too much carbohydrate or protein get fat?
If you consume too much food, acetyl is not needed to make ATP
Instead it is converted to fat
142
Why do fish acidify the water they swim in?
Fish were giving off carbon dioxide which was converted to carbonic acid (because its in water)
pH is going down
Fish water should have had lower pH than snail water because fish released more CO2
143
Why did the Elodea acidify the water in the dark, but raise the pH in the light?
If in the dark, elodea was undergoing cell respiration and giving off CO2, formations of carbonic acid, pH goes down
If in the light, elodea is doing photosynthesis and taking CO2 from the water; pH goes up
144
Why do yeast produce CO2 when deprived of oxygen but we don’t?
Without O2, yeast will ferment sugars (reduce pyruvate and convert it to ethanol and CO2)
We don't have enzymes that yeast has so we make lactic acid and yeast makes ethanol
145
Why did we give the mitochondria in the electron transport export succinate rather than another sugar?
Succinate is the only sugar that is bound to a membrane; so when we prepare the solution we know that succinate will be present
146
Why did we treat the mitochondria in the electron transport export with azide?
Azide poisons cytochrome oxidase which normally delivers electrons to O2
Wanted electrons to go to DCIP
Electrons present if DCIP changed from blue to colorless
147
What is the Krebs cycle and what are the two stages of the Krebs cycle?
Series of 9 reactions that completely oxidizes acetyl (shredds it to pieces and left with CO2)
Two stages: priming, energy extraction
148
What are the substrates and products of the Krebs cycle?
```
Substrates:
Acetyl
GDP
NAD+
FAD
```
```
Products:
CO2
GTP
NADH
FADH2
```
149
Where does the Krebs cycle occur?
Mitochondrial matrix
150
How is ATP generated by the Krebs cycle?
GTP is made from a GDP + P by substrate level phosphorylation then GTP is converted to ATP if GTP is not needed for RNA synthesis (not made by chemiosmosis -- made by subr=strate whatever)
Do not make ATP from NADH and FADH2 → they go to ETS
NADH
FADH2
151
How is most of the energy released by the Krebs cycle temporarily stored?
NADH and FADH2
These are reduced electron carriers that transport the electrons to ETS
152
Why does succinate dehydrogenase reduce FAD rather than NAD+?
Succinate dehydrogenase
“Ase” = enzyme
“De” = remove (hydrogen) from succinate
Will extract electrons from succinate (oxidizes succinate)
BUT the reaction is not energetic enough to reduce NAD+; FAD will be reduced instead to make FADH2
FAD will pick up electrons with less energy than those picked up by NAD+
153
What is electron transport?
Passage of electrons through a series of cytochromes and carrier molecules; these molecules pass electrons from one carrier to the next
ENERGY IS RELEASED FROM THE ELECTRONS is used to drive transmembrane pumps; H+ are pumped into the intermembrane space from the matrix
154
Where does electron transport occur?
ETS is located on the cristae of the mitochondria (inner membrane)
155
What are the substrates and products of electron transport?
Electrons are brought in by NADH and FADH2 which will drop off electrons
So NADH will become NAD+
FADH2 will become FAD
Also requires O2 because O2 will accept electrons and become H2O
And ATP is produced
156
How is electron transport linked to the oxidation reactions of respiration?
Oxidation reactions are glycolysis, pyruvate oxidation, and Krebs Cycle
Electrons from glucose are picked up by NAD+ and FAD; NADH and FADH2 carry the electrons to the ETS
After electrons are released by NADH and FADH2, you regenerate NAD+ and FAD go back to oxidize more sugar
157
How is the energy stored in NADH and FADH2 used to make ATP?
After NADH and FADH2 drop off their electrons to the ETS, energy from the electrons as they pass through the ETS is used to pump H+ from the matrix to the intermembrane space
then , protons go “ripping through” a pore in ATP synthase, releasing enough energy to drive the production of ATP from ADP + P
4 (H+/ ATP) / rotation
158
Why does FADH2 reduce ubiquinone rather than NADH dehydrogenase?
FADH2 carries electrons with less energy than the electrons carried by NAD, so FAD will reduce ubiquinone (the 2nd carrier) instead of the first carrier, NADH dehydrogenase
159
Why is cyanide so deadly?
```
Prevents the transfer of electrons from cytochrome oxidase to ox to oxygen
Whole e- transport chain shuts down
No H+, no ATP
Will NADH be able to drop off electrons
No more NAD+
No
```
160
What happens to the oxygen that you breathe in?
Oxygen goes to the end of the ETS there it accepts electrons and H+ and becomes water
161
What is chemiosmosis, and where does it occur?
Protons are pumped by carriers in ETS to the intermembrane space
Protons from intermembrane space return to the matrix through special channels in ATP synthase; ATP is made
ATP synthase = using energy from the flow of H+
162
How is chemiosmotic ATP synthesis linked to electron transport?
Energy released from the transport of electrons is used to pump H+ from the matrix to the intermembrane space
Once we have a H+ gradient, H+ flow back to matrix through ATP synthase and ATP is made
163
Why do ionophores which let H+ through membranes prevent ATP synthesis?
Ionophores that allow H+ through a membrane will create “leaks” in the membrane
Protons are pumped into intermembrane space, but they leak back into the matrix
NO H+ GRADIENT
NO ATP BY CHEMIOSMOSIS
164
How does ATP synthase use proton transport to make ATP?
As H+ flow through the channel in ATP synthase, enough energy is released to drive the production of ATP.
Rotational catalyzes: each time H+ go through ATP synthase, swiveling occurs, forcing ADP and P together
165
What evidence supports the theory of chemiosmosis?
1. ATP synthesis stops if you add ionophores that allow H+ back into the matrix
2. Can make artificial systems made of bacteriorhodopsin and ATP synthesis in lipid vesicles; will make ATP if H+ can be pumped
3. Chloroplasts soaked in pH4
- Buffer make ATP when transferred to pH8 buffer
166
What evidence supports the theory of rotational catalysis?
Answer to this question is the same as the answer to #19 plus:
Protein changes shape as H+ goes through; swiveling occurs, forcing ADP and P together
167
What is the basic approach organisms use to extract energy from molecules other than glucose?
Cell will produce intermediates of the krebs cycle or acetyl in as few steps as possible
168
How are fats oxidized?
Fat oxidation
Fat is broken down into fatty acids and glycerol
Glycerol will be oxidized through glycolysis
Fatty acids are oxidized by beta oxidation and are converted to acetyl; acetyl will be further oxidized by the Krebs cycle
169
What is beta-oxidation?
Process by which fats are oxidized occurs in peroxisomes and in mitochondria matrix
170
How are proteins oxidized?
Protein oxidation
1. Convert proteins to amino acids
2. Amino acids will be deaminated
3. The remaining parts of the amino acids will be further oxidized in the krebs cycle or by glycolysis
171
What is transamination and what is deamination?
transamination - interconversion of amino acids
- Convert one amino acid into another
deamination-removal of NH2 (amino) from amino acid
172
Which amino acids can be oxidized directly, and how are the other amino acids oxidized?
Alanine is converted to pyruvate acid is converted to alpha ketoglutarate, an intermediate in the Krebs cycle
Aspartic acid is converted to acetic acid which is part of the krebs cycle
Other amino acids are converted to these amino acids by transamination
173
Why is the Krebs cycle very active in leaf tissues?
Krebs cycle in leaves is also used to MAKE amino acids for protein production
174
How is cellular respiration regulated, and why is it regulated at more than one step?
```
Regulation is by feedback inhibition
As products accumulate, reaction slows down
So
ATP WILL SLOW DOWN cell respiration
ADP will speed up cell respiration
NAD+ will speed
NADH will slow down
```
Molecules with low energy speed up cell respiration
175
Why can’t we calculate the precise number of ATP created by oxidizing a molecule of glucose?
pH gradient is also used for inport/export
| mitochondrial membrane leaks
176
Why do we say that photosynthesis reverses oxidative respiration?
photosynthesis reverses oxidative respiration
CO2+H2O---->C6H12O6 + O2
C6H12O6-chemical energy-energy in chemical bonds
177
What are the two distinct sets of reactions in photosynthesis?
```
two sets of reactions:
light dependent:
-thylakoinds
-light energy used to pump H+ by electron transport uses proton gradient to make ATP by chemiosmosis
-products: ATP and NADPH=reducing power
light independent:
-stroma
-use ATP and reducing power (NADPH) from light reactions to make reduced organic molecules (glucose)
```
178
Where do these two sets of reactions occur, and how are they connected?
light dependent-thylakoids
light independent-stroma
each set of reactions provides substrates for the other
179
What are the three stages of the light reactions?
catching photons (packet of light)
electron transport
ATP synthesis by chemiosmosis
180
Why is UV light more damaging than red light?
shorter wavelength, therefore more energy
| the shorter the wavelength, the greater the amount of energy
181
What is a photosynthetic pigment and how does it absorb a photon?
photosynthestic pigment
- molecules that absorbs light
- excitation energy from light
- -absoption channeled via pigment molecules to reaction center chlorophyll
182
What is an absorption spectrum, and what is an action spectrum?
Absorption spectrum: wavelengths of light a pigment absorbs
Actin spectrum: measures response from a plant based on different wavelengths
183
Why do leaves look green?
chlorophylls absorb all wavelengths but green; green is reflected
184
How do leaves capture light that is not absorbed by chlorophyll a?
accessory pigments
absorbs wavelengths that chlorophyll does NOT absorb
carotenoids reflect orange
xanthophylls reflect yellow
185
Why do leaves change color in the fall?
chlorophyll no longer produced
| accessory pigments can now be seen although they were there all spring and summer
186
What are the 3 possible fates of an electron bumped to the excited state by absorbing a photon?
- return to ground state emitting light and heat (fluorescence)
- transferred to something else
- excitation energy transferred to another molecule by inductive reasoning
187
What is fluorescence?
light released from excited electron as it returns to ground state
188
What is inductive resonance?
transfer of excitation energy from one molecule to another
189
What is a photosystem?
group of chlorophyll molecules in a photosynthetic membrane (thylakoid)
190
What is a reaction center chlorophyll?
energy transferred to it is passed as excited electrons to a primary electron accptor other, chlorophylls transfer energy to the reaction center by inductive resonance
191
How is energy transferred from the pigment which absorbs a photon to the reaction center?
passed as excited electrons to a primary electron acceptor
192
What does the reaction center do with its excited electrons?
other chlorophylls transfer energy to the reaction center by inductive resonance
193
What are the two photosystems, and how can we tell them apart?
pigments are arranged differently to absorb different wavelengths
PSII absorbs 680
PSI absorbs 700
2 photosystems work together in non cyclic photophosphorylation
194
What is cyclic photophosphorylation?
first to evolve; first form of photosynthesis
uses PSI
limitations: only makes ATP, no biosynthesis because electrons aren't used for reducing power
(picture in notes)
photons absorbed; electrons transferred from reaction center to ferredoxin; elections return by electron transport system
permits chemiosmotic production of ATP
195
How do plants convert light energy to ATP?
photons absorbed by chlorophylls
electrons transferred from reaction center chlorophyll to a quinone from plastoquinone
electrons passed down electron transport system to PSI
energy released is used to pump H+
chemiosmosis used to generate ATP
*solar energy has now been converted to chemical energy
(also answer to 54 through cyclic photophosphorylation
196
Why do plants need 2 photosystems?
harness energy of 2 photosystems
provide reducing power for biosynthesis(NADPH) and make ATP
products of light reaction : ATP and NADPH
197
What is the Z-scheme?
noncyclic photophosphoryation
PSI and PSII work together
(picture in notes)
PSII provides energy to pump H+ for chemiosmosis.
As electrons move, the energy is used to pump H+ into the thylakoid.
by chemiosmosis, movement of H+ through ATP synthase provides energy to make ATP
198
What are the roles of the following components of the Z-scheme?: PSI
PSI-light energy absorbed here, generates reducing power=NADPH, Electrons come from PSII
199
What are the roles of the following components of the Z-scheme?: PSII
PSII- light energy absobed here, used to make ATP, electrons move to PSI, electrons come in from splitting H2O
200
What are the roles of the following components of the Z-scheme?: cyt b6/f.
cyt b6/f-protons pump in thaylakoid membrane; pumps H+ into thylakoid space
201
What are the roles of the following components of the Z-scheme?: plastocyanin
plastocyanic-protein that carries electrons to PSI
202
What are the roles of the following components of the Z-scheme?: plastoquinone
plastoquinone- take electrons from PSII; it is a strong electron donor; passes electrons to b6/f complex
203
What are the roles of the following components of the Z-scheme?: oxygen-evolving enzyme
oxygen-evolving enzyme splits H2O into oxygen, protons (H+) and electrons H2O--> O + H+ +e-(PSII)
204
What are the roles of the following components of the Z-scheme?: ferredoxin and NADP reductase
ferredoxin-receives e- from PSI and passes them to NADP reductase, NADP is reduced to NADPH
NADP reductase transfers e- to NADP to form NADPH
205
Why do we call ferredoxin a branch point?
- accepts electrons in cyclic photophasphorylation passes it to ETS that returns electrons to photosystem I, ATP is made
- accepts electron in noncyclic photophasphorylation, passes it to NADP reductase; NADPH forms
- plats switch mechanisms to produce more or less ATP and NADPH
206
Where do the electrons used to reduce NADP+ come from?
PSI
PSI
207
Why do the light reactions of photosynthesis form oxygen?
H2O splits to provide electrons for PSII
H2O splits to provide electrons for PSII
208
How is the pH gradient formed during photosynthesis?
protons are pumped into thylakoid using energy from moving electrons
209
How do chloroplasts make ATP?
chemiosmosis
H+ move from space in thylakoind (pH=5) to stroma (pH=8)
through ATP sythase
(picture in notes(back of yellow paper))
210
What are the differences between chemiosmosis in chloroplasts and mitochondria?
chloroplast-in ETS, protons are pumped into thylakoid space to make ATP, H+ move out into stroma through ATP synthase
mitochondria- in ETS, protons pumped into intermembrane space; make ATP synthase into the matrix
Key differences- ATP synthase is revered in the chloroplast, pump H+ into lumen, pH is smaller than stroma pH.
difference in pH is much larger in chloroplast, lumen pH is less then 5, stroma pH=8, much stronger attraction. ETS, cyclic photophosphorylation, water splitting and NADPH synthesis makes change in pH in chloroplast (picture on back of yellow)
211
What are the 3 stages of the Calvin cycle?
1. fix CO2
2. reverse glycolysase
3. regenerate RuBP
(picture on back of blue)
212
What is carbon fixation?
trapping carbon in an organic molecule
| step #1 of the Calvin cycle
213
What is rubisco and why is it so abundant?
- ribulose 1,5 biphosphate carboxylase/oxygenase
- enzyme that "starts" Calvin cycle
- more important protein on earth
- abundant because it's sluggish so you need more
- attaches CO2 to RuBP (first step in Calvin cycle)
214
What is the usual reaction catalyzed by rubisco, and why is it so important?
ribisco binds CO2 and traps it in organic molecules
| RuBP (sugar) + CO2--->3 phosphoglycerate (ribisco caralyzes reaction)
215
Why do we say that part of the Calvin cycle reverses glycolysis?
forms 2 molecules of 3-phosphoglycerate (PGA) which is convertd to glyceraldehyde-3-phosphate
216
Why do we say that glyceraldehyde-3-phosphate is a branch point?
1. regenerate RuBP
2. make sugars (glucose)
1. regenerate RuBP
| 2. make sugars (glucose)
217
Why do we call glyceraldehyde-3-P the product of the Calvin cycle instead of glucose or starch?
once produced glyceraldyhydre-3-phosphate is exported from the chloroplast to the cytoplasm of the cell. it is converted to glucose and sucrose through the reversal of several reactions of glycolysis
218
What is the fate of 5 out of 6 PGA created by Rubisco after it fixes CO2, and why is this necessary?
used to regenerate RuBP in order to keep the Calvin cycle going
219
Why is the RuBP regeneration phase of the Calvin cycle so fiendishly complex?
complexity is necessary to keep cycle going; need to add 3C subunits to make 5C sugar
-add 5 3-C to make 3 5-C
(only one CO2 added per cycle)
220
What are the inputs and outputs of the RuBP regeneration phase?
input: 5 3-C sugars
output: 3 5-C sugars
this is C3 photosynthesis
221
What is photorespiration?
process that undoes photosynthesis. Rubisco adds O2 to RuBP instead of CO2 (especially at higher temperatures), CO2 is released without production of ATP or NADPH. This is a problem!
222
Why is photorespiration a serious problem for plants?
CO2 is released without production of ATP or NADPH
223
Why are peroxisomes and mitochondria often closely associated with chloroplasts?
```
detoxify glycolate (release 1 CO2 per 2 glycolate)
glycolate is a poison; must be taken to peroxisome for detox. peroxisome converts glycolate to glycine which is sent to mitochondrion for further metabolism
```
224
Why have plants evolved C4 and CAM photosynthesis?
C4 and CAM photosynthesis are used to prevent photorespiration. both processes fix CO2 with a different enzyme
225
What is the difference between C4 and CAM photosynthesis?
C4 pathways: use spatial separation
1. mesophyll cells take CO2 and attach it to a 3C acid-->4C acid
2. 4C acid--> bundle sheath cells (membrane impermeable to CO2)
3. 4C acid-->CO2 + 3C acid
4. use CO2 for Calvin cycle by C3 photosynthesis
-process requires 30 ATPs instead of 18 ATPs therefore only good in high light. bundle sheath cells do C3 photosynthesis
CAM (cacti)
-uses temporal separation
-stroma open at night; let CO2 in
-add CO2 to a 3C compound to make a 4C acid which accumulates overnight-stored in vacuole
-stroma close during day, light reactions make ATP, NADPH
-4C acid--> CO2 +3C acid
CO2 used in Calvin cycle
*in CAM, the same cells do C3 (day) and C4 (night) pathways
-requires lots of energy
226
Why did the solution turn red when Elodea was placed in the light and yellow when left in the dark?
the solution of phenol red was a pH indicator. it turns yellow in an acidic environment and red in a basic environment
227
Why did the DCIP change from blue to colorless when mixed with chloroplasts placed in the light?
oxidized at first and goes through almost all of the z scheme and ends up reduces
the chloroplasts gave the electrons to the oxidized form of DCIP to DCIP 2 (which is colorless)
228
Why did the [oxygen] increase when you placed pond scum in the light and go down in the
dark?
the DCIP went away.
they were performing light reactions and taking electrons away from water, exporting them to NADH.
when the lights were off, they had to perform cell respiration and take in oxygen
229
What pigments were left in the yellow leaves?
xanthophylls and carotenoids
230
Why didn’t the pigment from beets move on the TLC plates?
it was too hydrophilic; it dissolved in water
231
Where were the absorption peaks for the chlorophyll extract?
440 nm
232
Which wavelengths gave the most ATP in the action spectrum?
440 nm to 680 nm
