Set 2 Flashcards
1
Q
Why study proteins?
A
They are key to cell function
2
Q
Why do we always work at the RNA level in a laboratory?
A
Because DNA level is exactly the same in all of our cells
3
Q
Who is behind the identification of DNA structure?
A
- Watson & Crick
- Wilson
- Rosalind Franklin
4
Q
What is molecular genetics?
A
Study of how genes are turned on and off and how they affect phenotype
5
Q
How did Watson and Crick come to the conclusion that DNA was double-stranded?
A
- Rosalind Franklin wrote in her lab book that DNA had two chains based on x-ray picture
- They based their model on her x-ray
- They did not give her acknowledgement
6
Q
How does DNA become RNA?
A
- Transcription
- DNA sequence is enzymatically copied by an RNA polymerase to produce mRNA
7
Q
How does RNA become protein?
A
- Translation
1) Protein is unwound by DNA helicase
2) RNA polymerase binds and recognizes the start site
3) RNA nucleotides (U rather than T) base pair with the DNA
4) Forms a chain of mRNA
8
Q
Why do we need RNA?
A
- Because DNA is stuck in the nucleus; cannot pass through the nuclear envelope
- mRNA from transcription can pass through
9
Q
What are transcription factors?
A
Proteins which assist the RNA polymerase in recognizing promoters, thus activating the gene
10
Q
What are the two types of transcription factors?
A
- Gene-specific transcription factors
- General transcription factors
11
Q
What are gene-specific transcription factors? Give an example.
A
- If they can activate a specific gene
- Ex: estrogen receptor
12
Q
What are general transcription factors? How does it work?
A
- Activate all gene
- Bind to DNA regions within promoters and deliver the RNA polymerase to their respective promoter sites
13
Q
What is CREM?
A
- cAMP responsive element modulator
- Transcription factor
- Regulated by the presence of KIF17b in the nucleus
- CREM is important in spermatogenesis (can cause complete arrest); may activate or suppress
14
Q
What is alternative splicing? When does it occur?
A
- Method of processing mRNA
- Occurs when enzymes clip out segment of the middle or off the ends of the mRNA strand
15
Q
Differentiate introns and exons.
A
- Introns: non-coding segments
- Exons: segments that encode proteins (exons = expressed)
- Introns are chopped out; exons are regions that are expressed
16
Q
What are the three types of RNA?
A
- Messenger RNA
- Ribosomal RNA
- Transfer RNA
17
Q
Explain what happens when mRNA is processed in the nucleus after it is made.
A
- Editing of mRNA
- Removal of introns addition of poly A tail and guanine cap
18
Q
What happens after mRNA is processed in the nucleus?
A
It enters the cytosol where it works with rRNA and tRNA to direct translation
19
Q
What is the function of tRNA?
A
Transfer specific amino acids (anticodon) to the mRNA, which is read in triplets at the ribosome
20
Q
What is the function of rRNA?
A
- Interacts with tRNA during translation
- The mRNA can be found between 2 subunits
- The rRNA contains an enzyme that catalyzes the peptide bond between the new amino acids that are being formed
21
Q
What processes proteins to make them functional?
A
- Chaperone molecules (supervision, protein folding)
- Enzymes in the cytosol, ER, and Golgi
22
Q
Define a proteome.
A
All the proteins synthesized by a cell make up the cell’s proteome
23
Q
What post-translational modifications of a protein after translation may occur?
A
- Folding and cross-links
- Cleavage into smaller peptides
- Addition of sugars, lipid, methyl groups, and phosphate groups
- Assembly into polymeric proteins
24
Q
What does constitutively active mean?
A
Only becomes active when it needs to be
25
Differentiate the compositions of ECF and ICF.
- ECF is plasma and interstitial fluid (1/3 of body water)
| - ICF is intracellular fluid (2/3 of body water)
26
Define tonicity.
- How a solution would affect cell volume if the cell were placed in solution
- Describes volume change of a cell
27
Which solutes are mostly found on the outside of the cell?
- Na+
- Cl-
- HCO3-
28
Which solutes are mostly found on the inside of the cell?
- K+
| - Large anions and proteins
29
How are mechanisms of membrane transport classified?
- Energy requirement
| - According to whether transport occurs by diffusion, a membrane protein, or a vesicle
30
What creates a concentration gradient for secondary active transport?
Primary active transport
31
What are the three membrane-bound vesicle transport options?
- Endocytosis
- Exocytosis
- Phagocytosis
32
What is the physical requirement for simple diffusion?
Molecule goes through lipid bilayer
33
Which membrane transport options require a membrane protein?
- Facilitated diffusion
- Secondary active transport
- Primary active transport
34
What are the properties of simple diffusion?
- Passive process: uses kinetic energy inherent in molecule
- High to low concentration gradient
- Net movement until concentration is equal
35
What characteristics allow the rate of simple diffusion to be fastest?
- along higher concentration gradients
- over shorter distances
- at higher temperatures
- for smaller molecules
36
What is the net movement of simple diffusion related to?
- Rapid over short distances
- Directly related to temperature
- Inversely related to molecular size
37
What are the functions of structural membrane proteins?
- Connect membrane to cytoskeleton (integrity)
- Create cell junctions
- Attach cells to ECM
38
What is the function of enzymes in membrane proteins?
Catalyze chemical reactions
39
What is the function of membrane receptor proteins?
- Part of the body's chemical signalling system
| - Receptor-mediated endocytosis
40
Differentiate the two types of membrane protein transporters.
- Channel proteins: direct communication
| - Carrier proteins: carries molecules into the cell
41
What two properties of molecules influence its movement across cell membranes?
- Size
| - Lipid solubility
42
What are the three types of gated channels?
- Mechanically gated
- Voltage-gated
- Chemically gated
43
Differentiate channel proteins and carrier proteins.
- Channel: create a water-filled pore; direct link between ICF and ECF
- Carrier: never form an open channel between the two sides of the membrane; bind with specific substrates and carry them across the membrane by changing conformation
44
Differentiate uniport, symport, and antiport carriers.
- Uniport: one molecule in one direction
- Symport: move 2 ore more substrates in the same direction across the membrane
- Antiport: against concentration gradient (2 molecules), which uses ATP
45
What is the overall function of membrane transporters?
Membrane-spanning proteins that help move lipophobic molecules across membranes
46
What is active transport? What are the two types?
- Moves substances against concentration gradient, which requires energy
- Primary and secondary active transport
47
What is the single most important transport protein in animal cells?
- Na+ K+ ATPase
- 2 K+ in, 3 Na+ out
- Against concentration gradient, requires ATP
48
The Na+ K+ ATPase is an example of what kind of transport?
Primary active transport
49
Describe the Na+ K+ ATPase's mechanism of transport.
1) 3 NA+ from ICF bind
2) ATPase is phosphorylated with P from ATP
3) 3 Na+ is released into ECF
4) 2 K+ from ECF bind
5) 2 K+ is released into ICF
50
What is a pump?
- Membrane transporters that move a substance against its concentration gradient
- Opposite of diffusion
- Ex: calcium pumps, sodium-potassium pumps
51
What does transport by vesicles allow?
Substances to enter or leave the interior of a cell without actually moving through its plasma membrane
52
The SGLT transporter is an example of what kind of transport?
Secondary active transport
53
Describe the SGLT transporter's mechanism of transport.
1) Na+ binds to carrier
2) Na+ binding creates a site for glucose
3) Glucose binding changes carrier conformation
4) Na+ released into cytosol; glucose follows
54
Which substances use vesicular transport?
Macromolecules that are too large to pass through protein channels or carriers
55
What is phagocytosis? How does it create vesicles?
- Cell engulfs bacterium or other particle into a phagosome
| - Creates vesicles using the cytoskeleton
56
What is endocytosis? How does it create vesicles?
- Active process that can be non-selective (pinocytosis) or highly selective
- Membrane surface indents and forms vesicles
57
How are vesicles created in endocytosis? What is their function?
- Caveolae within plasma membrane
| - To help in the transfer of macromolecules and to participate in cell signalling
58
What does receptor-mediated endocytosis use?
Clathrin-coated pits
59
What is the function of exocytosis?
Releases molecules too large for transport proteins
60
What are the four functions of endocytosis and exocytosis?
1) Transfer nutrients
2) Communicate by importing signalling molecules
3) Mediate an immune response
4) Clean up cell debris left by inflammation
61
Explain the mechanism of phagocytosis by a leukocyte.
1) Phagocyte encounters a bacterium, and uses its cytoskeleton to push the cell membrane around it, creating a phagosome
2) The phagosome moves into the cytoplasm.
3) The phagosome fuses with lysosomes containing digestive enzymes.
4) The bacterium is killed and digested.
62
Explain the mechanism of receptor-mediated endocytosis.
1) Ligand binds to membrane receptor
2) Receptor-ligand migrates to clathrin-coated pit
3) Endocytosis
4) Vesicle loses clathrin coat
5) Receptors and ligands separate
6) Ligands go to lysosomes or Golgi for processing
7) Transport vesicle with receptors move to the cell membrane
8) Transport vesicle and cell membrane fuse (membrane recycling)
63
What are the two basic types of endocytosis?
- Phagocytosis
| - Pinocytosis
64
Are endocytosis and exocytosis active or passive transport mechanisms?
Active
65
Define phagocytosis.
- Large particles are engulfed by the plasma membrane and enter the cell in vesicles
- Vesicles fuse with lysosomes, where the particles are digested
- "Cell-eating"
66
Define pinocytosis.
- Fluid and the substances dissolved in it enter the cell
| - "Cell-drinking"
67
Explain the mechanism of exocytosis.
- Enclosed in membranous vesicles
| - Pulled by the cytoskeleton to the plasma membrane, where the contents are released
68
Epithelium is either _____ or ______.
leaky
| tight
69
Transport across an epithelium may take place via two types of transport. What are they?
- Paracellular transport: junctions between adjacent cells (leaky/exchange)
- Transcellular transport: through epithelial cells themselves (tight/transport)
70
What molecules do capillaries allow to pass through?
Dissolved molecules
71
What kind of junction hold kidney cells together? What does that create?
- Tight junction, which creates a barrier
| - Substances must enter cell and pass through it
72
What is the basal lamina?
Acellular matrix layer that is secreted by epithelial cells
73
Differentiate exchange and transport epithelium.
- Exchange: allows movement through gaps between cells (leaky)
- Transport: prevents movement between adjacent cells; must pass through the epithelial cell (ex: tight junctions)
74
Differentiate absorption and secretion.
- Absorption: external to internal
| - Secretion: internal to external
75
What are transporting epithelium characteristics?
- Thicker
- Membrane modifications (ex: villi)
- Cell junctions
- Mitochondria
76
Differentiate exocrine and endocrine glands.
- Exocrine: release into external environment through ducts (skin, airway, digestive)
- Endocrine: release hormones into bloodstream
77
What are goblet cells? What is their function?
- Secrete mucus into the lumen of hollow organs, such as the intestine
- Help with the propulsion of movement
78
What does uracil replace in RNA?
Thymine (T)
79
What is an advantage of alternative splicing?
Allows a single base sequence on DNA to code for more than one protein
80
What is an anticodon?
- One region of tRNA contains a three-base sequence called an anticodon
- An anticodon is complementary to an mRNA codon
- Anticodons carry amino acids
81
The intracellular and extracellular compartments of the body are in osmotic (equilibrium/disequilibrium), but in chemical and electrical (equilibrium/disequilibrium)
equilibrium, disequilibrium
82
What is tonicity?
Description of a solution and how that solution would affect cell volume if the cell were placed in the solution and allowed to come to equilibrium
83
What happens to a cell if a solution is hypotonic?
Cell swells (less concentrated in the solution); water goes in the cell to dilute it
84
What happens to a cell if a solution is hypertonic?
Cell shrinks (more concentrated in the solution); water escapes the cell to dilute the solution
85
What kind of gradient influences ion movement?
- Electrical gradient
| - Thus, ions do NOT move by diffusion
86
What kind of molecules can pass through the phospholipid bilayer?
Lipophilic molecules
87
The rate of diffusion through a membrane is faster if...
- the membrane’s surface area is larger
- the membrane is thinner
- the concentration gradient is larger
- the membrane is more permeable to the molecule
88
Why do cells require both channel and carrier proteins?
- Channel proteins allow more rapid transport across the membrane but generally are limited to moving small ions and water
- Carriers, while slower, can move larger molecules than channels can
89
What are chemically gated channels?
Gating is controlled by intracellular messenger molecules or extracellular ligands
90
What are voltage-gated channels?
Open and close when the electrical state of the cell changes
91
What are mechanically gated channels?
Respond to physical forces, such as increased temperature or pressure that puts tension on the membrane
92
Facilitated diffusion uses _______ proteins, and it has the same properties as _______________.
carrier, simple diffusion
93
Differentiate primary and secondary active transport.
- Primary: energy to push molecules against their concentration gradient comes directly from ATP
- Secondary: uses potential energy stored in the concentration gradient of one molecule to push other molecules against their concentration gradient
94
Name two ways active transport by the Na + -K + -ATPase differs from secondary transport by the SGLT.
- ATPase is an anti porter, but the SGLT is a symporter
- ATPase requires energy from ATP to change conformation, whereas the SGLT uses energy stored in the Na+ concentration gradient
95
What are the three properties of carrier-mediated transport?
1) Specificity
2) Competition
3) Saturation
96
Phagocytosis creates vesicles using the _______. What does it require?
- cytoskeleton
| - Requires ATP
97
What are the three characteristics that differentiates endocytosis from phagocytosis?
- In endocytosis the membrane surface indents rather than pushes out
- The vesicles formed from endocytosis are much smaller.
- Some endocytosis is constitutive; that is, it is an essential function that is always taking place. In contrast, phagocytosis must be triggered by the presence of a substance to be ingested
98
Name the two membrane protein families associated with endocytosis.
Clathrin and caveolin
99
What allows the one-way movement of certain molecules across the epithelium?
Polarized distribution of transporters
100
What does the basolateral membrane face? What does the apical membrane face?
- Apical: lumen
| - Basolateral: extracellular fluid
101
What is transcytosis?
1) Plasma proteins are concentrated in caveolae, which then undergo endocytosis and form vesicles.
2) Vesicles cross the cell with help from the cytoskeleton.
3) Vesicle contents are released into interstitial fluid by exocytosis.
102
If you apply a poison that disassembles microtubules to a capillary endothelial cell, what happens to transcytosis?
Transcytosis will stop because vesicular transport by the cytoskeleton depends on functioning microtubules.
103
The resting membrane potential is due mostly to _______.
potassium
104
The intracellular fluid contains a high concentration of _____ ions and low concentrations of _____, _____, and _____ ions.
- K+
| - Na+, Cl-, Ca2+
105
How does the amount of water between the ECF and ICF differ?
It does not since the body is in osmotic equilibrium
106
If a 58-kg woman has total body water equivalent to 50% of her body weight, what is a) her total body water volume, b) her ECF and ICF volumes?
- a) 29 L
| - b) ECF: 9.7, ICF = 19.3L
107
Which is more likely to cross a cell membrane by simple diffusion: a fatty acid or a glucose molecule?
The fatty acid since it is lipophilic
108
What would you call a carrier that moves two substrates in opposite directions across a membrane?
An antiporter
109
________ epithelia are polarized.
Transporting
110
Match each transporter to its location.
1. GLUT
2. Na+-glucose symporter
3. Na+-K+-ATPase
A) Apical membrane
B) Basolateral membrane
1. b
2. a
3. b
111
Why does Na+ movement from the cytoplasm to the extracellular fluid require energy?
Because it is moving against its concentration gradient
112
What would happen to the resting membrane potential of a cell poisoned with ouabain (an inhibitor of the Na+-K+-ATPase)?
Over time, the Na+ would leak into the cell, and the resting membrane potential would become more positive
113
List the three physical methods by which materials enter cells?
- Simple diffusion
- Protein-mediated transport
- Vesicular transport
114
A cell placed in a solution of unknown composition soon swelled up and burst, so the solution must have been __________ to the cell when it was originally placed in the solution.
hypotonic
