Test 2 Flashcards
0
Q
How do enzymes function?
A
By lowering the activation energy by increasing the rate of the reaction; change rate at which equilibrium is reached
1
Q
What are enzymes?
A
Catalysts for biological reactions
2
Q
How do temperature and pH affect enzymes?
A
Temp- as it increases so does the rate of the reaction and vice versa
pH- changing shape or charge properties or substrate so either substrate cannot bind to active site or undergo catalase
3
Q
What is an enzymes active site?
A
The region where a substrate binds and a catalytic event occurs
4
Q
What is an enzymes prosthetic group?
A
A small organic group of metal ions that frequently function as electron receptors
5
Q
Oxidoreductases causes…
A
Oxidation reduction reactions
6
Q
Transferases
A
Transfer of function groups from one molecule to another
7
Q
Hydrolases
A
Hydrologic cleavage of
One molecule into 2 molecules
8
Q
Lyases is?
A
Addition of a group to a molecule with a rearrangement of electrons
9
Q
Isomerases
A
Movement of a functional group within a molecule
10
Q
Ligases
A
Joining of 2 molecules to form a single molecule
11
Q
How do enzymes bind to substrates to catalyze reactions?
A
Random collision, lock and key model or induced fit model
12
Q
What is the cycle of events that an enzyme goes through?
A
Substrate binding
Substrate activation
Catalytic event
Product release
13
Q
What is Vmax?
A
The upper limit of a reaction rate
14
Q
What is Km?
A
Michaelis constant; a specific concentration of substrate depending on the affinity of the enzyme
15
Q
What is saturation?
A
The relationship between the rate of reaction and concentration of substrate depending on the affinity of the enzyme
16
Q
What are the four methods used in enzyme regulation?
A
Alteration of temp/pH Substrate level regulation Competitive inhibition Allosteric regulation Covalent modification
17
Q
What is competitive inhibition?
A
Molecules bind to the active site so that substrates CANNOT bind
18
Q
What is allosteric regulation?
A
Facilitated by binding of regulatory molecules at the allosteric site
19
Q
What are ribozymes?
A
RNA molecules that act as catalysts; NOT a protein
20
Q
What is covalent modification?
A
Enzyme activity is affected by the addition of removal of chemical groups via covalent bonding
21
Q
What are the functions of membranes?
A
Define boundaries Loci for specific functions Transport proteins Receptors Cell-to-cell communication
22
Q
What is the fluid mosaic model?
A
Mosaic of proteins discontinuously embedded in or attached to a fluid lipid bilayer
23
Q
How was it discovered that the membrane was composed of a lipid bilayer?
A
The lipid bilayer membrane structure in 1925
24
How is cholesterol incorporated into membranes?
By being found in sterols in animal cells
25
What are the 3 classes of membrane lipids?
Phospholipids
Glycolipids
Sterols
26
What are the ways that lipids can move within the membrane?
* Rotation about their long axis
* Lateral diffusion in the plane of the membrane
* transverse diffusion requiring hydrophilic head to pass hydrophobic interior
27
How is lipid mobility measured?
Within membranes by fluorescence recovery after photo bleaching (occurs within seconds)
28
What factors affect membrane fluidity?
Sterols decrease fluidity above Tm(rigid, prevents movement)
Sterols increase fluidity below Tm(prevent phospholipids from fitting together)
29
What are the functions of proteins found in the membrane?
Transport
Receptors
Adhesion
30
What are the classes of membrane proteins?
* Integral- Cyto, exo & transmembrane domain
* Lipid anchored-one or more covalently linked lipids; GPI anchor
* Peripheral- associated with integral & lipid head groups
31
How can scientists visualize the mobility of membrane proteins?
* freeze fracture images
* exposure to electrical field
* mouse & human cell fusion
32
What are glycoproteins?
Conjugated to carbs; almost ALWAYS on exo- face
33
What are the functions of glycoproteins? (4)
Defense
Cellular uptake
Adhesion
Embryonic development
34
What is diffusion?
The movement of solutes
35
What is osmosis?
The movement of water across a selectively permeable membrane
36
What is facilitated diffusion?
The movement of diluted down the gradient mediated by proteins
37
What is active transport?
Moving solutes against concentration gradient
38
What is passive transport?
Simple/facilitated diffusion
39
What is indirect active transport?
One solute moving down gradient while driving the other solute up
40
Why is direct active transport?
Accumulation of molecules is coupled directly to an exergonic chemical reaction
41
What types of molecules can cross the membrane by simple diffusion?
Small, non polar molecules
42
How does water move during osmosis?
From low to high solutes
43
What type of diffusion exhibits saturation?
Facilitated diffusion
44
What is the difference between carrier and channel proteins?
Carrier- bonds solutes on one side of the membrane & changes the conformation which allows solutes to diffuse
Channel- forms hydrophilic channels in member and so diffusion may occur
45
What are three types of carrier transport proteins?
Uniport
Symport
Antiport
46
What is uniport?
1 solute 1 direction
47
What is symport?
2 solute same direction
48
What is antiport?
2 solutes opposite direction
49
How do plant and animal cells respond differently to hyper- iso- and hypotonic solutions?
Hyper- both shrivel
Iso- both are normal
Hypo- animal explodes/plant expands
50
What are the different types of ATPases?
P, V, F, and ABC
51
What is p-type?
Pumps Na, K, Ca ions; reversibly phosphorylated and found in plasma membrane
52
What is v-type?
Pumps hydrogen ions into the vacuole
53
What is f-type?
Pumps H ions using ATP hydrolysis; found in bacteria, mitochondria and chloroplasts; reversible using ATP synthase
54
What is ABC-type?
Pumps a variety of solutes including nutrients, proteins, is also used to pump drugs out of cells
55
Steps of Na/K pump? (6)
1. 3 Na ions bind to a protein in the initial E1 confirmation
2. Binding of the Na ions triggers the phosphorylated enzyme
3. Phosphorylation results in A conformational change from E1 to E2 Na are transported in the membrane to outside the cell
4. K ions outside cell bind to enzyme
5. Binding of K triggers de phosphorylation and rerun to E1
6. K transported through membrane to inside cell
56
Na/glucose pump? (6)
1. 2 external Na ions bind to symporter
2. Glucose is able to bind to symporter
3. Conformational change of protein exposed the molecule to the inside of the cell
4. Na ions released in response to low internal Na concentration
5. Transporters locked in conformation until glucose is released inside cell
6. Empty transporters open to outside of cell again
57
What is depolarization?
A change in membrane potential to a less negative value
58
What is hyperpolarization?
Membrane potential briefly becomes more negative than normal
59
What does a dendrite do?
Receives messages and sends them to other parts of the body
60
What does the axon do?
Conducts impulses away from the body
61
What is the role of the myelin sheath?
To accelerate transmission of nerve impulses
62
What is the nodes of ranvier?
Small segments of axon between segments of myelin sheath
63
What are neurotransmitters?
Chemicals released by neurons that transports impulse across a synapse
64
How do nerve cells respond to depolarization?
They return to resting membrane potential
65
How do voltage gated ion channels function?
As interval membrane proteins that form ion conducting pores who's permeability is regulated by changes in membrane potential
66
What are the 3 types of voltage gated channels?
Open confirmation
Closed confirmation
Channel inactivation
67
What is an action potential and why are they important?
Membrane potential changing from negative to positive back to negative in response to stimulus. It is important bc it transmits signals along cell membranes.
68
How do action potentials travel along nerve cells?
Via Na and K channels
69
How do signals travel different in myelinated vs. non-myelinated nerve cells?
Myelinated travel faster and farther, non-myelinated travel in waves and take longer
70
What is MS?
The moss of myelin sheath due to an autoimmune response. Sodium escapes and damages nerve s which reduced communication and function
71
What are the 2 types of synaptic transmissions?
Electrical and chemical
72
What is electrical transmission?
Neurons connected by gap junctions; spread of depolarization. The signal is immediate and is 3-5 nm
73
What is chemical transmission?
Neurons connected by adhesion proteins; synaptic cleft 20-50 nm. Transmission requires neurotransmitters held in vesicles
74
Name the 4 types of neurotransmitters
Acetylcholine
Amino acids
Monoamines
Neuropeptides
75
What is an example of acetylcholine?
Cholinergic
76
What are 3 examples of amino acid neurotransmitters?
GABA, glycine, glutamine
77
What are 3 examples of monoamine neurotransmitters?
Nonadrenaline, dopamine, serotonin
78
What is an example of the neuropeptide transmitter?
Endorphins
79
How are neurotransmitters sent from one nerve class to another?
Exocytosis
80
What are the types of neurotransmitters receptors that we discussed? And details of both.
```
1. Nicotinic acetylcholine receptor
Binds 2 molecules
Ligand gated Na+ channel
Depolarization
2. GABA receptor
Binds to GABA
ligand gated Cl- channel
Hyper polarization
```
81
How are neurotransmitters inactivated?
1. Reputable
| 2. Degradation
82
What is re uptake?
Neurotransmitters pumped back into presynaptic neurons
83
What is degradation?
Unique to acetylcholine; neurotransmitters broken down by enzymes
84
What are chemical signals?
Molecules that bind to receptors on target cell surface and elicit a response from target cells
85
What are second messengers?
Molecules produced in target cells that relay the signal from one part of the cell to the other
86
What are Ligands?
Small messenger molecules
87
What are high affinity receptors?
Ligand binds easy, low concentrations of ligand can occupy many receptors
88
What are low affinity receptors?
Ligand DOES NOT bind easily, high concentration of ligand required to occupy many receptors
89
What is auto regulation?
Internal adaptive mechanism that works to adjust that systems response to stimuli
90
What is apoptosis?
Clean cell death
91
What properties give receptors affinity and specificity for their Ligands?
Binding site shape, amino acid placement, multiple noncovalent bonds
92
What is the dissociation constant and how does it relate to the receptor affinity?
Kd
| It indicates how much ligand is needed to trigger a response in a target cell
93
How do receptors adapt to prolonged exposure to Ligands?
Receptor- down regulation
94
How are agonists and antagonists similar and different?
Similar by both being artificial Ligands recognized by cellular receptors
Different by agonists activate endorphins and antagonists block Ligands from binding
95
What are the 2 types of plasma membrane receptors that were discussed
G protein linked receptors
| Protein kinase associated receptors
96
What are G protein linked receptors?
Ligand binding causes a change in confirmation that activated a G protein
97
What is a protein kinase associate receptor?
Ligand binding activates causing phosphorylation events
98
What are the structures of the G protein linked and protein kinase associated receptors?
G protein- 3 subunits
| Protein kinase- single polypeptide chain with one transmembrane domain
99
What are the subunits that make up G proteins?
Alpha, beta, gamma (α,β,γ)
100
How are G proteins activated and inactivated?
Activated by lingands bonding to receptor, receptor binding to transcription protein, protein reaches nucleus and is activated
Inactivation- Gα hydrolysis GTP, GTP to GDP, Gα reassociates with Gβγ
101
What is the difference between Gs and Gi proteins?
Gs- stimulatory; activated adenylate Cyclades for ^ in cAMP
| Gi- inhibitory; inhibits adenylate Cyclades for decrease in cAMP
102
What enzyme is responsible for synthesis of cAMP?
Adenine Cyclase
103
How does the cell get rid of cAMP once the stimulatory ligand is no longer bound to the receptor?
Phosphodiesterase to AMP
104
What are 2 diseases that affect signal transduction pathways?
Cancer and diabetes
105
How are calcium ions utilized in signal transduction?
In apoptosis when cytochrome C is activated and released from the mitochondria, it stimulates calcium
106
What types of receptors do growth factors generally bind to? And what specific type does EFG bind to?
EFG; tyrosine kinase
107
How are tyrosine kinases activated?
Ligand binding-> clumped receptors phosphorylated each other -> auto phosphorylation
108
How are hormones different than other Ligands?
Hormones can act from a long distance away, Ligands must touch to react
109
What are the important molecules of apoptosis?
P53
Bcl2
Cytochrome C
110
What is the role of p53 in apoptosis?
Triggers apoptosis in response to DNA damage
111
What is Bcl2 in apoptosis?
Anti-apoptosis proteins found in mitochondrial surface
112
What is the role of cytochrome C in apoptosis?
Release from mitochondria to promote apoptosis
