Exam 2 Flashcards
(225 cards)
1
Q
Define selective permeability
A
Allowing some substances to cross it more easily than others
2
Q
What is the fluid mosaic model?
A
Used to demonstrate the membrane is a “mosaic” of various proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water
3
Q
True or False: Phospholipids within the plasma membrane can move within the bilayer
A
True
4
Q
True or False: Proteins can not move within the bilayer
A
False
5
Q
As temperatures cool, membranes switch from a fluid state to a …
A
Solid state
6
Q
True or false: The fluidity of a plasma membrane is affected by the type of hydrocarbon tails in phospholipids
A
True
7
Q
At lower temperatures, the Plasma Membrane is more fluid if…
A
Unsaturated hydrocarbon tails with kinks are present
8
Q
The plasma membrane is less fluid if…
A
Saturated hydrocarbon tails are present
9
Q
Define viscous
A
Less warm temperatures, cholesterol makes the membrane less fluid by restraining the movement of phospholipids
10
Q
How does chloesterol effect membrane fluidity at warm temperatures?
A
cholesterol makes the membrane less fluid by restraining the movement of phospholipids
11
Q
How does cholesterol effect membrane fluidity at low temperatures?
A
At low temperatures, it maintains fluidity by preventing tight packing
12
Q
What are integral proteins?
A
- Penetrate hydrophobic core
- Often transmembrane proteins
- Located all over the membrane
13
Q
What are peripheral proteins?
A
- not embedded in lipid bilayer
- appendages are loosely bound to the surface of the membrane
14
Q
What are the six major functions of membrane proteins?
A
- transport
- enzymatic
- attachment to cytoskeleton and extracellular matrix
- cell-cell recognition
- intercellular joining
- signal transduction
15
Q
What is cell-cell recognition?
A
The cell’s ability to distinguish one type of neighboring cell from another
16
Q
What is the purpose of membrane carbohydrates?
A
To interact with surface molecules of other cells, facilitating cell-cell recognition
17
Q
How are glycolipids formed?
A
Membrane carbs covalently bonded to lipids
18
Q
How are glycoproteins formed?
A
Membrane carbs covalently bonded to proteins
19
Q
Molecules that start on the inside face of the ER…
A
End up on the outside face of the plasma membrane
20
Q
When is symmetrical distribution of proteins, lipids, and assorted carbs in the plasma membrane determined?
A
When the membrane is built by the ER and the Golgi apparatus
21
Q
What causes selective permeability?
A
Membrane structure
22
Q
What is selective permeability?
A
When a cell must exchange materials with its surroundings, a process controlled by the plasma membrane
23
Q
Describe the permeability of hydrophobic molecules?
A
- Nonpolar
- Hydrocarbons, CO2, O2
- Pass through membrane easily
24
Q
Describe the permeability of hydrophilic molecules?
A
- Polar
- Sugars, H20, C6H12O6
- Do not pass through the membrane easily
25
Describe the permeability of ions?
- Na+, K+
- A charged atom and its surrounding shell of water
- Require transport proteins
26
What are the three mechanisms of transport?
Active
Passive
Bulk
27
What is passive transport?
- Substances diffuse DOWN the gradient
- Does not require ATP
- Facilitated diffusion included
28
What is active transport?
- Substances move against gradient
- ATP required
- Includes ion pumps and cotransports
29
What is bulk transport?
-Includes exocytosis and endocytosis
30
Define Osmosis
Mechanism of passive transport
| Diffusion of water across a semipermeable membrane
31
How is the direction of osmosis determined?
By a difference in total solute concentration
32
True or false: Water diffuses from region of higher to lower solute concentration
FALSE
33
Define tonicity
Ability of a solution to cause a cell to gain/lose water
34
True or False: cells without rigid cell walls have osmotic problems in either a hypertonic or hypotonic environment
True
35
How do cells without rigid cell walls maintain internal environment?
Osmoregulation
36
Define osmoregulation
Control of water balance
37
What is special about the protist Paramecium?
It is hypertonic to its pond environment and has a contractile vacuole that acts as a pump
38
Define hypotonic
- When solute concentration is less outside than inside the cell (cell gains water)
- A cell swells until cell wall opposes uptake
39
What is the term for a hypotonic plant cell?
Turgid
40
Define hypertonic
- When solute concentration is greater outside than inside the cell (cell loses water)
- Membrane pulls away from cell wall (defined as plasmolysis)
41
What is the term for a hypertonic plant cell?
Plasmolyzed
42
Define isotonic
When solute concentration is the same inside as outside the cell (no net water movement)
43
What is the term for an isotonic plant cell?
Flaccid
44
What is the optimal environment for an animal cell?
Isotonic
45
What is the optimal environment for a plant cell?
Turgid (hypotonic)
46
True or False: Cell walls do not help maintain water balance
FALSE
47
Define transport proteins
Allow passage of hydrophilic substances across a membrane and are specific for the substance they move
48
What are channel proteins?
Have a hydrophilic channel that certain molecules or ions can use as a tunnel
49
Define aquaporins
Facilitate passage of water
50
Define carrier proteins
Bind to molecules to change shape to shuttle them across the membrane
51
Why is facilitated diffusion passive?
The solute moves down its concentration gradient
52
What are the inputs and outputs of the sodium potassium pump?
3 Na+ out
2 K+in
1 ATP used
53
What kind of transport mechanism is the Sodium Potassium pump?
Active
54
What is membrane potential?
Voltage difference across a membrane
55
True or false: the inside of the cell is negative compared to the outside
TRUE
56
Membrane potential favor the passive transport of ____ into the cell and _____ out of the cell
cations, anions
57
What is the electrochemical gradient?
2 combined forces driving the diffusion of ions across a membrane
58
What are the two forces of the electrochemical gradient?
Chemical and Electrical
59
What is the chemical component of the electrochemical gradient?
The ion's concentration gradient
60
What is the electrical component of the electrochemical gradient?
Effect of the membrane potential on the ion's movement
61
What is the electrogenic pump?
A transport protein that generates the voltage across a membrane
62
What are the typical examples of the electrogenic pump?
```
Sodium potassium pump (In animals)
Proton pump (plants, fungi, bacteria)
```
63
Define cotransport
Occurs when active transport of a solute indirectly drives transport of another solute
64
What is the proton pump
Plants generally use gradient of H+ ions generated by proton pumps to drive active transport of nutrients into the cell
65
What is bulk transport?
- Small molecules and water enter or leave the cell through the lipid bilayer or by transport proteins
- Large molecules such as polysaccharides and proteins cross the membrane via vesicles
66
Define exocytosis
- transport vesicles migrate to membrane, fuse with it, and release their contents
- addition of plasma membranes
67
True or False: Many secretory cells use exocytosis to export their products
TRUE
68
Define endocytosis
- The cell takes in molecules by forming vesicles from the plasma membrane
- loss of plasma membrane
69
True or False: Endocytosis is a reversal of exocytosis involving different proteins
TRUE
70
What are the three types of endocytosis?
Phagocytosis
Pinocytosis
Recepter Mediated
71
What is Phagocytosis?
"Cellular eating"
| Cell engulfs a particle in a vacuole
72
What is Pinocytosis?
"Cellular drinking"
| cell creates vessicle around fluid
73
What is receptor mediated endocytosis?
Binding of ligands to receptors triggers vesicle formation
74
How does phagocytosis occur?
A cell engulfs a particle by wrapping pseudopodia around it, and packaging it within a vacuole. The particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes
75
How does pinocytosis occur?
- The cell gulps tiny droplets of extracellular fluid to tiny vesicles.
- It is not the fluid itself that is needed by the cell, but the mlcs dissolved in the droplets.
- Nonspecific in the protein substances it transports
76
Define Ligand
Any molecule that binds specifically to a receptor site of another molecule
77
How does receptor mediated endocytosis occur?
Enables the cell to acquire bulk quantities of specific substances, even though these substances may not be very concentrated in the extracellular fluid
78
Describe intracellular receptors
- Flourid in the cytosol/nucleus of target cells
| - small hydrophobic chemical messengers can easily cross membrane and activate receptors
79
What are examples of intracellular receptors?
Steroid and thyroid hormones of animals.
80
What is the role of an activated hormone receptor?
It can act as a transcription factor, turning on specific genes
81
Describe Protein Phosphorylation and Dephosphorylation
- Signal is transmitted by a CASCADE of protein phosphorylations
- This phosphorylation and dephosphorylation system act as a molecular switch
82
What is the role of the protein kinase?
Transfer phosphate groups from ATP to a protein
83
What is the role of the protein Phosphatase
To remove the phosphates
84
Describe the response of the phosphorylation and dephosphorylation
- other pathways regulate the activity of enzymes
- At each step, the number of activated products is much greater in the preceding step
- ultimately a signal transduction pathway leads to regulation of one or more cellular activities
85
Define metabolism
- The totality of an orgnaism's chemical reactions
| - an emergent property of life that arises from interactions between molecules within the cell
86
A metabolic pathway
- Begins with a specific molecule and ends with a product
| - Each step is catalyzed by a specific enzyme
87
What is an exergonic reaction?
- releases energy that can perform work
- spontaneous
- negative delta G
- catabolism
- Goes down on a graph
88
What is an endergonic reaction?
- Requires energy to perform work
- nonspontaneous
- positive delta G
- anabolism
- Goes up on a graph
89
What are the three types of work performed by the cell?
Chemical
Mechanical
Transport
90
How do cells perform work?
They manage energy resources by energy coupling
91
Define energy coupling
Use of an exergonic process to drive an endergonic one
92
How are the bonds between phosphate groups of ATP's tail broken?
Hydrolysis
93
True or False: Energy is released from ATP when the terminal phosphate bond is broken
TRUE
94
Why does this release of energy occur?
The chemical change to a state of lower free energy, NOT the phosphate bonds
95
True or false: The energy from the exergonic reaction of ATP hydrolysis can not be used to drive an endergonic reaction
FALSE
96
True or False: ATP drives chemical work
TRUE
97
Chemical work consists of:
- coupled reactions
- overall delta g is negative
- together the reactions are spontaneous
98
During Transport work
ATP phosphorylates transport proteins
99
During Mechanical work
ATP binds noncovalently to motor proteins and then is hydrolyzed
100
How is ATP a renewable resource?
It is regenerated by addition of a phosphate group to ADP
101
Where does the energy used to phosphorylate ADP come from?
Catabolic reactions in the cell
102
Where is chemical potential energy stored?
ATP and drives most cellular work.
103
Define catalyst
A chemical agent that speeds up a reaction without being consumed by the reaction
104
What is an example of a catalytic protein?
An enzyme
105
What is an example of an enzyme catalyzed reaction?
Hydrolysis of sucrose by the enzyme sucrase
106
What is activation energy (Ea)-
-Initial energy needed to start a chemical reaction
107
How is activation energy supplied?
The form of heat from surroundings
108
How do enzymes lower the Ea barrier?
-Enzymes catalyze reactions
109
What are the effects of enzymes on free energy and the rate of reactions?
Enzymes do not effect Ea and hasten reactions that would occur eventually
110
How are enzyme-substrate complexes formed?
When enzymes bind to the substrate
111
What is the active site?
Region on the enzyme where the substrate binds
112
What is the induced fit of a substance
Brings chemical group of the active site into positioins that enhance their ability to catalyze the chemical reaction
113
What can effect an enzyme's activity?
- Temperature
- pH
- Chemicals that specifically influence the enzyme
114
True or false: Each enzyme does not require an optimal temperature and pH in which it can function
FALSE
115
Define cofactors
- Non protein enzyme helpers
- Inorganic
- Tightly bound
116
What are some examples of cofactors?
Iron, zinc, copper
117
What are coenzymes
- Organic cofactors
- Loosely bound
- Released as normal part of the catalytic cycle
118
What are the two types of enzyme inhibitors
Irreversible and reversible inhibitors
119
What are irreversible inhibitors?
Inhibitor usually attaches to the enzyme by covalent bonds
120
What are examples of irreversible inhibitors?
Some toxins and poisons, penicllins
121
What are the two types of reversible inhibitors?
Competitive and noncompetitive
122
What are competitive inhibitors?
- They bind to the active site of an enzyme, competing with the substrate
- can be overcome by increasing the concentration of the substrate
123
What are noncompetitive inhibitors?
-They bind to another part of an enzyme causing it to change shape and making active sites less effective.
124
True or False: Regulation of enzyme activity helps control metabolism
TRUE
125
What would result if a cell's metabolic pathways were not tightly regulated?
Chemical chaos
126
What is allosteric regulation?
- When a protein's function at one site is affected by binding of a regulatory molecule at another site
- May either inhibit or stimulate an enzyme's activity
127
What are most allosterically regulated enzymes made from?
Polypeptide subunits
128
How does binding of an activator enzyme effect the form of the enzyme?
It stabalizes the active form of the enzyme
129
How does the binding of an inhibitor enzyme effect the form of the enzyme?
It stabalizes the inactive form of the enzyme
130
What are the activators and inhibitors of the catabolic enzymes when they regenerate ATP?
Activator: ADP
Inhibitor: ATP
131
Define cooperativity
A form of allosteric regulation that can amplify enzyme activity
132
How does cooperativity work?
Binding of one substrate molecule to active site of one subunit locks all subunits in active conformation
133
Define feedback inhibition
The end product of a metabolic pathway shuts down the pathway
134
How does feedback inhibition work?
It prevents a cell from wasting chemical resources by synthesizing more product than is needed
135
What do catabolic pathways do?
Breakdown organic molecules
136
Define cellular respiration
Breakdown of organic molecules for production of ATP
137
What is aerobic respiration?
Respiration that consumes oxygen
138
What is the chemical formula of cellular respiration?
C6H12O6 + 6O2 ------> 6CO2 + 6H20 + ATP
139
What is anaerobic respiration?
Use inorganic molecules other than the oxygen as the final electron acceptor at the end of the electron transport chain
140
Define fermentation
A partial degradation of sugars that occurs without oxygen
141
What is an oxidation-reduction reaction?
Chemical reactions that transfer electrons by reactants
142
How do you determine what reactant is oxidized/reduced
LEO goes GER
- Loses electrons=oxidized
- Gains electrons=reduced
143
How do you determine what reactant is the oxidzing/reducing agent?
Electron donor=reducing agent
| electron acceptor=oxidizing agent
144
How do you label the reactants in a redox reaction when charges aren't present?
- Oxidized gain O, lose H
| - Reduced gain H, lose O
145
During cellular respiration, what is oxidized and what is reduced?
Glucose is oxidized
| Oxygen is reduced
146
What are the stages of cellular respiration?
Glycolysis
Pyruvate oxidation (acetyl coA formation)
Citric acid cycle
Oxidative phosphorylation
147
Define glycolysis
- Breaks down glucose into two molecules of pyruvate
- Does not require oxygen
- Occurs in cytoplasm
148
What are the two phases of glycolysis
Energy investment
| energy pay off
149
What are the net inputs and net outputs of glycolysis?
Inputs: Glucose, 2 NAD+, 4 ADP +P
Outputs: 2 pyruvates, 2 ATP, 2 NADH, 2 H2O
150
Define pyruvate oxidation (acetyl coA formation)
Completes breakdown of glucose
151
What are the net outputs of pyruvate oxidation?
2CO2, 2 NADH, 2 Acetyl CoA
152
Define citric acid cycle
Completes breakdown of glucose
| Has 8 steps each catalyzed by a specific enzyme
153
What are the net inputs and net outputs per glucose of the Citric acid cycle?
Inputs: 2 FAD, 6 NAD+, 2ADP
Outputs: 4CO2, 2 FADH2, 6 NADH, 2 ATP
154
How do the inputs out and outputs differ if it were asked per pyruvate?
It is just half of each
155
Following glycolysis and the citric acid cycle, what accounts for most of the energy extracted from food?
NADH and FADH2
156
What electron carriers donate electrons to the ETC?
NADH and FADH2
157
What does donation to the ETC do?
Powers ATP synthesis via oxidative phosphorylation
158
What are most of the ETC's components?
Proteins
159
What is the final proton acceptor?
O2
160
Define Oxidative Phosphorylation
Accounts for most of the ATP synthesis, powered by redox reactions
161
Where is the ETC located?
The cristae of the mitochondrion (inner membrane)
162
Where does kreb's cycle occur?
Matrix
163
Does the ETC gnereate ATP directly?
No. It releases energy in manageable amounts
164
What is an example of chemiosmosis?
The use of energy in a H+ gradient to drive cellular work
165
Describe the process of chemiosmosis
- Electron transfer in ETC causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space
- H+ then moves back across the membrane, passing through channels in ATP synthase that uses the exergonic flow of H+ to drive phosphorylation of ATP
166
What are the two components of oxidative phosphorylation?
- ETC
| - Chemiosmosis
167
Describe the energy flow during cellular respiration
Glucose ----> Electron Carriers ----> ETC ----> Proton-motive force ----> ATP
168
How many ATP are made during cellular respiration?
30-32 ATP
169
How many ATP are made during glycolysis?
2 ATP
170
How many ATP are made during citric acid cycle?
2 ATP
171
How many ATP are made during Oxidative Phosphorylation?
26-28 ATP
172
What kind of phosphorylation are glycolysis and citric acid cycle?
Substrate level phosphorylation
173
Can glycolysis produce ATP with/without oxygen?
Yes
174
In the absence of O2, how does glycolysis produce ATP?
Anaerobic respiration, uses an ETC with a different final proton acceptor
175
Define fermentation
Glycolysis plus reactions that regenerate NAD+ which can be reused by glycolysis
176
What are the two types of fermentation?
alcohol and lactic acid
177
Describe alcohol fermentation
- Pyruvate is converted to ethanol in two steps, the first releases CO2
- ex// yeast used in brewing
178
Describe Lactic acid fermentation
- pyruvate reduced to NADH forming lactate as an end product
| - ex// some fungi and bacteria, muscle cells
179
How do muscle cells used lactic acid
To generate ATP when O2 is scarce
180
To sustain high rates of glycolysis under anaerovic conditions, cells require
NAD+
181
Describe facultative anaerobes
- can survive using fermentation or cellular respiration
| - ex// yeast, bacteria
182
Describe obligate anaerobes
-carry out fermentation or anaerobic respiration and cannot survive in presence of O2
183
What is the evolutionary significance of glycolysis
Glycolysis evolved in ancient prokaryotes before there was oxygen in the atmosphere
184
Describe Catabolism
- funnel electrons from many kinds of organic molecules into cellular respiration
- proteins are digested to amino acids
- fats digested to glycerol and fatty acids
185
How do amino groups contribute to glycolysis or the citric acid cycle
they feed the two processes
186
How is glycerol used?
Used in glycolysis
187
How are fatty acids used?
Used to generate acetyl coA
188
When fatty acids are broken down by beta oxidation what do they yield?
Acetyl CoA
189
Describe biosynthesis (Anabolic pathways)
Body uses small molecules to build other substances
190
What is the most common mechanism for control of cellular respiration?
Feedback Inhibition
191
If ATP concentration begins to ____ respiration ____; When there is _____ respiration _____
- drop, speeds up
| - plenty of ATP, slows down
192
What is the equation for photosynthesis?
6 CO2 + 6 H20 ---> C6H12O6 + 6 O2
193
Where do light reactions occur?
The thylakoids
194
What does the process of light reactions do?
- split water
- release O2
- Produce ATP (by phosphorylation)
- Form NADPH
195
Where does the Calvin cycle take place?
The stroma
196
What does the calvin cycle do?
Form sugar from CO2 using ATP and NADPH
197
What is Chlorophylla
-main photosynthetic pigment
198
What does Chlorophyll b do?
Broadens spectrum used for photosynthesis
199
What are carotenoids?
accessory pigments that absorb excessive light that would damage chlorophyll
200
A photosystem consists of...
reaction center surrounded by light harvesting complexes
201
What are light harvesting complexes?
pigment molecules bound to proteins
202
What do light harvesting complexes do?
funnel the energy of photons to the reaction center
203
What accepts an excited electron from chlorophyll a
primary electron acceptor in the reaction center
204
What is the first step of the light reactions?
solar powered transfer of an electron from chloryphyll a molecule to primary electron acceptor
205
What order are the photosystems in?
II first I second
206
What wavelength does PS II absorb?
p680
207
What wavelength does PS I absorb?
p700
208
What do the two photosystems generate?
ATP and NADPH
209
What are the two routes for electron flow during the light reaction?
Linear (noncyclic) or Cyclic
210
What is Linear (noncyclic) pathway
primary pathway
involves both photosystems
produces ATP and NADH
211
What is cyclic pathway
uses only PS I
Produces only ATP
Generates surplus ATP satisfying higher demand in calvin cycle
212
How do chloroplasts and mitochondria generate atp and what sources of energy do they use?
Chemiosmosis
mitochondria: transfer chemical energy from food to ATP
chloroplasts: transform light energy into chemical energy of ATP
213
True or false: Clavin cycle are reffered to as light independent reactions
TRUE
214
What are light independent reactions
Don't require light directly, and occur in daylight
215
During Calvin cycle carbon enters the cycle as CO2 and leaves as a sugar named
Glyceraldehyde 3 Phosphate (G3P)
216
How many times must Calvin cycle take place to generate one G3P? How many CO2 are produced?
Three times, 3 CO2
217
What are the three phases of Calvin Cycle?
Carbon fixation
Reduction
Regeneration of the CO2 acceptor
218
WHat is carbon fixation catalyzed by?
Rubisco
219
What is the CO2 acceptor?
RuBP
220
To generate one G3P mlc, you need
9 ATP
| 6 NADPH
221
What are alternative mechanisms of carbon fixation?
dehydration
222
On hot dry days plants close to ____ which conserves water but also limits photosynthesis
stromata
223
During photorespiration
- Rubisco adds O2 to the calvin cycle instead of CO2
- Neither ATP or sugar are produced
- may be an evolutionary relic because rubisco first evolved when atmosphere had more CO2 than O2
224
Describe C4 Plants
- Minimize cost of photorespiration by incorporating CO2 into 4 carbon compounds
- These compounds are exported to bundle-sheath cells where they release CO2 that is then used in Calvin cycle
225
Describe CAM plants
- Open stromata at night to incorporate CO2 into organic acids
- Stomata close during day and CO2 released from organic acids and used in calvin cycle.
