1
Q
What is the study of molecular genetics?
A
how genes turn on and off and how they affect phenotype
2
Q
Who is the person who discovered DNA as a double helix?
A
Rosalind Franklin
3
Q
What is the process of transcription?
A
- DNA is unwound by DNA helicase
- RNA polymerase binds and recognizes start site
- RNA nucleotides (Uracil NOT thymine) base pair with DNA
- form a chain of mRNA
4
Q
What are transcription factors?
A
proteins that assist RNA polymerase to regnozie promoters (which activates the gene)
5
Q
What are the two divisions of transcription factors?
A
- gene specific transcription factors: activate specific genes like estrogen receptor = estrogen target gene specific
- general transcription factors: can activate all genes, bind to DNA regions within promoters and deliver RNA polymerase to their respective promoter sites.
eg. CREM is a general transcription?
6
Q
What is alternative splicing?
A
- mRNA processing
- enzymes clip out segments of middle or ends from the mRNA strand
- exons are expressed (segment that contains the encoding proteins)
- also contain noncoding segments called introns
7
Q
What are the three types of RNA?
A
mRNA (messenger), rRNA(ribosomal), tRNA (transfer)
8
Q
Where is mRNA processed and what does it do in the modifications?
A
in the nucleus (after it’s been made)
- edits mRNA
- removes introns
- adds poly A tail
- adds guanine cap
9
Q
After processing, where does the mRNA go?
A
enters he cytosol where it works with rRNA (ribosome) and tRNA to direct translation
10
Q
What do tRNA molecules do?
A
- transfer specific amino acids (via the process of anti codons) to the mRNA which is read in triplets at the ribosome
- as amino acids are brought into place, peptide bonds join the growing chain of polypeptide
11
Q
What is the structure of rRNA and where mRNA fits within the structure?
A
- made of a large and small rRNA subunit
- interacts with tRNA during translation
- mRNA can be found between the 2 subunits
- rRNA has enzymes that makes a peptide bond between new amino acids being added
12
Q
What happens during the processing of the protein?
A
- chaperone molecules supervise protein folding
- other enzymes in cytosol, ER and Golgi helpt polypeptide fold and combine into larger protein molecules or hybrids (like hormones)
13
Q
What is a proteome?
A
- all the protein synthesized by the cell
- all proteins synthesized in the whole body are collectively called human proteome
14
Q
What are some chemical post-translational modifications?
A
Mainly the addition of:
- sugars
- lipids
- methyl group (CH3)
- phosphate
15
Q
Describe the process of synthesis: DNA to protein.
A
- activate gene (constitutively active or regulated activity-either induction or repression)
- transcription (to mRNA)
- mRNA processing (alternative splicing or siRNA - interference - mRNA is “silenced”)
- translation (in rRNA with tRNA bringing in amino acids to make an aa chain -polypeptide)
- post translational modification (includes folding + cross-links, cleavage into smaller peptides, addition of groups and assembly into polymeric proteins)
16
Q
What is tonicity?
A
how a solution affects cell volume if the cell were placed in the solution (volume change of a cell)
17
Q
Describe the distribution of solutes at homeostasis?
A
Na+: out K+: in cell Cl-: out HCO3-: out Large anions + protein: in cell
18
Q
What are the three ways of membrane bound vesicle transport?
A
endocytosis
exocytosis
phagocytosis
19
Q
Describe how primary active transport leads to secondary transport?
A
primary transport: uses ATP like a Na/K pump
secondary transport: uses the concentration gradient setup (by primary transport) to transport other molecules against their concentration gradient
20
Q
How does passive process of diffusion work? (changes in size, temperature and distance)
A
- uses kinetic energy already in molecule
- net movement until concentration is equal
- high to low
- rapid over short distances
- directly related to temperature
- inversely related to molecular size
21
Q
How is the rate of diffusion faster through a membrane?
A
- larger surface area of membrane
- thinner membrane
- larger concentration gradient
- molecule’s permeability through membrane
22
Q
What does the membrane permeability to a molecule depend on?
A
- lipid solubility
- molecule size
- lipid composition of membrane {size, lipid solubility}
23
Q
What are the 4 functions of membrane proteins?
A
- structural: connect membrane to cytoskeleton, cell junction, attach cells to ECM
- enzymes: catalysis
- membrane receptor protein: chemical signalling
- transporters: channel/carrier
24
Q
How do channel proteins work? How are they classified?
A
- direct link between intra and extracellular compartments
- gated: have a ball that opens or closes the gate
- open channels
25
How do carrier proteins work? What are the 3 types?
- never form an open channel between the two sides
- either opened at the ICF side or the ECF (never both) like a clamp
- uniport, symport, antiport
26
What are membrane transporters for? (distinguished from membrane proteins-more general)
- they are membrane spanning proteins
- move lipophobic molecules across membrane
- channel (narrow doorway, can be gated or open)/carrier (specific substrates and carry across by changing of conformation) proteins
27
What is the difference between gated and open channels?
gated: open and close in response to signal
open: usually opened (like leaks)
28
What is the mechanism of Na+/K+ ATPase?
- 3Na+ bind (from ICF) with ATP
- ATPase is phosphorylated causing conformational change
- 3 Na+ is released into ECF while 2K+ from ECF bind to carrier changing the conformation
- 2K+ released into ICF
29
How is active transport different from diffusion?
diffusion: no ATP required because it moves along its concentration gradient
active transport:
pumps: ATP required because it moves substances against its gradient (opposite)
vesicles: allow substances to enter or leave interior of cell without moving through plasma membrane = exocytosis so like fuses with membrane...
30
Describe the mechanism of SGLT transport.
1. Na+ binds to carrier (SGLT protein)
2. Na+ binding creates site for glucose in the protein as well
3. glucose binding changes the carrier conformations
4. Na+ released into cytosol and glucose follows.
31
How do macromolecules (too large for channels or carrier) enter cell?
move in and out with the aid of vesicles (made of the cell membrane)
phagocytosis: engulfs particles/bacterium = called phagosome once it has something inside
- creates vesicle using cytoskeleton
Endocytosis: membrane surface indents and forms vesicles
- active process that can be nonselective (pinocytosis=drinks everything in) or highly selective
- uses caveolae = like a un creux indent in the plasma membrane where it concentrates small molecules to help transfer macromol
- receptor-mediates uses clathrin-coated pits
exocytosis: releases molecules too large for transport protein
- opposite of endocytosis
32
What do endocytosis and exocytosis do?
-transfer nutrients
communication via importing signaling molecules
-mediate immune response
-clean up debris left by inflammation
33
Describe an example of phagocytosis of a leukocyte (WBC)
1. phagocytic WBC meets bacterium and binds to cell membrane
2. phagacotyse uses cytoskeleton to push ell membrane around bacterium creating a vesicle/phagosome
3. phagosome contains bacterium separating from the cell memebrane and moves into cytoplasm
4. phagosome fuses with lysosome with digestive enzymes
5. bacterium is killed and digested inside vescile
34
Describe the steps of receptor-mediated endocytosis.
Receptors recognize subtances to be brought in.
- ligand binds to membrane receptor an migrate to clathrin coated pit
- endocytosis (enters cell) and forms a vesicle within cell and gets rid of clathrin coat
- receptors and ligand separate where receptors are returned to the surface of membrane by fusing =exocytosis
- ligand go to lysosome or Golgi for processing
35
What are the two basic types of endocytosis?
phagocytosis: large particles engulfed by plasma membrane and enter in vesile and fuse with lysosome and digested
pinocytosis: cell drinking (fluid and substances dissolved)
36
Is endocytosis and exocytosis a form of active transport?
yes
37
What is exocytosis?
- large molecules leave cell even though too large to move out via plasma membrane
- enclosed in a membranous vesicle pulled by cytoskeleton to plasma membrane where contents are released
38
Describe the physiological structure of molecules entering and leaving the body. (what types of tissues must it pass by?)
a layer of epithelial cells that is either leaky or tight
39
Where does transport take place?
1. paracellular transport (junction between two cell next to each other: leaky/exchange)
2. transcellular transport (through epithelial cells themselves: tight/transport)
Capillaries allows dissolved molecules to pass
Kidneys: since they have tight junctions that glues cells together not allowing substances to pass between the two cells, substance must enter cell and pass through the cell to get across.
40
Where and how are epithelial cells attached to?
To the basal lamina via adhesion molecules
41
What is the basal lamina?
acellular matrix layer secreted by epithelial cells (epithelial cells always rest on a basal lamina)
then there is the underlying tissue.
42
What is the organisation of tissues in EXCHANGE epithelium? (name the order of layers from top to bottom)
epithelial cells
basal lamina
underlying tissue
43
How is transporting epithelia different from exchange epithelia?
transporting epithelia:
- selective permeability
- thicker
- membrane modifications
- cell junctions: tight junctions so substances must pass through he epithelial cell (crossing 2 PL membranes)
- mitochondria
44
What are two functions transport epithelium do?
absorption (external to internal)
secretion (internal to external)
45
What are the types of epithelia based on function?
1. exchange: think, flat cells allow movement through and between cells (from blood to ECF)
2. transporting: selectively moves substances between lumen and ECF
3. cilitated: beating cilia create fluid currents that sweep across epithelial surface (usually in airways)
4. protective: many stacked layers constantly being replaced (eg. skin)
5. secretory: make and release products (exocrine secretion are secreted outside the body, endocrine secretions are released into blood)
46
What are the two types of secretory epithelium?
1. exocrine glands: release into external environment skin, airways, digestive, DUCTS
2. endocrine: release hormones into bloodstream
47
What are goblet cells?
They secrete mucus into the lumen of hollow organs
48
Where can we find secretory epithelium?
- respiratory system
- digestive system
- urinary system
- musculoskeletal system
- reproductive system
- circulatory system
49
What is transcytosis?
type of cellular transport
50
Describe transcytosis across capillary and endothelium.
1. plasma protein from capillary concentrate in the caveolae and undergo endocytosis and form vesicles
2. vesicles cross the epithelial cell with the help from the cytoskeleton
3. vesicle contents are released into interstitial fluid by exocytosis
51
Cystic fibrosis: why would someone have salty skin?
There are high levels of chloride and salt inside the cell (pulls water in making thick mucus), homeostasis is altered:
high Cl- and Na+ inside cell
since they are trapped inside.
Sweat rises to the skin surface, usually ions are reabsorbed but it is not reabsorbed, 5x saltier sweat + lead to abnormal heart rhythms
52
What is the cause of CF?
- faulty gene on chromosome 7
- malfunction of the CFTR (transmembrane conductance regulator)
- leads to defective cAMP activated CL and Na present on surface types
- NaCl becomes trapped n the cell, pulling water in = dehydrated mucus (thick viscous mucus)
- CFTR mediated regulation of sodium channel may fail so increased sodium absorption from airways
53
What are the treatments for CF?
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airway clearance therapy
antibiotics
bronchial dilators (make them bigger... why?)
vitamin supplements
enzymes to aid digestion
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Mammalian Physiology
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