cells and genes new content for final

Question 1

Endocrine

Answer 1

signaling cell and target cell are relatively distant (ex=hormones)

Question 2

Paracrine

Answer 2

signaling cell and target cell are relatively close (ex=inflammation)

Question 3

Autocrine

Answer 3

signal released from a cell acts on itself (ex=neurotransmitters)

Question 4

Contact dependent

Answer 4

direct contact between membrane bound signal molecule and receptor protein on neighboring cells (developmental inhibition)

Question 5

• Describe how the response of a cell is dependent of the receptors expressed

Answer 5

Signals bind specific receptors, most signals act on more than one type of receptor, distribution of type of receptors determine what signals a cell can respond to

Question 6

• Generally describe the differences in mechanisms of how fast and slow responses occur in
  Cells

Answer 6

Speed depends on the way a cell responds to a signal.

Fast:responses that involve secretion, cell movement, or metabolism
Slow:responses that require changes to gene expression such as increased cell growth and division

Question 7

• Predict if a signaling molecule will act on extracellular or intracellular receptors based on its
  Properties

Answer 7

1:large or hydrophillic molecules=don’t cross the membrane, extracellular signal molecule binds to cell surface receptors
2:hydrophobic molecules=can cross membrane, bind intracellular receptor

Question 8

• Describe the 4 ways intracellular signals can interact in a signaling pathway

Answer 8

1. Relay – Simple one-to-one transduction from the
   receptor protein once it has bound the signal molecule.
2. Amplify – Each subsequent step increases in response,
   making it stronger
   * Few signal molecules can invoke a large response.
3. Integrate - Receive signals from more than one
   intracellular signaling pathway and integrate them before
   passing along the signal.
4. Distribute – one signal can activate several diverging
   signaling pathways or effector proteins to create a
   complex response.

Question 9

• Describe what is meant by enzymes activated ‘like switches’ and the 2 ways they are
  Regulated

Answer 9

Proteins used in intracellular signaling can be toggled between active and inactive states and remain active until turned off.
1.phosphorylation:covalent modification with addition/removal of phosphate group
2.GTP binding protein:activated with GTP bound, inactive with GDP bound

Question 10

• Compare the 3 types of cell surface receptors

Answer 10

1.Ion channel, receptors themselves are ion channels
2.G protein coupled, membrane bound GTP binding proteins link receptor with changes inside cell (open/close ion channels, alter intracellular enzyme activity
3.enzyme coupled, binding of ligand to receptor changes enzyme activity of receptor or associated enzyme

Question 11

• Describe the speed and general effect when a ligand binds an ion channel receptor

Answer 11

Extremely fast, changes shape, allows flow of ions across the membrane

Question 12

• Describe the components and general mechanism of G protein coupled receptors
  (GPCR)

Answer 12

Receptor bound to heterotrimeric
-ligand binding to receptor causes G protein to dissociate
-3 components can each alter distinct signaling pathways
-change enzyme signaling or can directly open an ion channel
receptors=single protein with 7 transmembrane spanning domains
-largest family of receptors
-slower than ion channels

Question 13

• List the 2 ways a GPCR can alter cell function

Answer 13

Change enzyme signaling or can directly open an ion channel

Question 14

• Define second messengers

Answer 14

Additional intracellular signaling molecules, they rapidly diffuse away from their source to spread signal

Question 15

• Describe how cAMP can alter cell function, including how it is activated and deactivated

Answer 15

Inactivation of cAMP catalyzed by cyclic AMP phosphodiesterase, cyclic AMP activates cyclic AMP dependent protein kinase which catalyzes phosphorylation of proteins altering their activity

Question 16

• Describe the general structure of a typical enzyme coupled receptor

Answer 16

Single transmembrane spanning domain
-single alpha helix
-single extracellular ligand binding domain
-cytoplasmic domain has enzyme activity or interacts with another molecule

Question 17

• Describe how receptor tyrosine kinases may lead to gene transcription using (and
  defining) the following terms:
  Extracellular domain, intracellular domain, dimerization, phosphorylation, Ras, MAP Kinase,
  transcription factors

Answer 17

Ligand binding causes two receptor proteins to come together (dimerization)
-contact between two activates their kinase activity
-each receptor phosphorylates each other
-newly phosphorylated tyrosine serves as binding site for intracellular signaling proteins
Protein complexes on cytosolic tails transmit signal along several routes simultaneously to many places in cell
Ras activates a phosphorylation cascade in which serine/threonine protein kinases phosphorylate and activate one another in sequence
-carries signal from PM to nucleus
-Ras activates MAP kinase kinase kinase
-MAP kinase phosphorylates various effector proteins including transcription regulators, altering gene expression

Question 18

• Describe the two ways receptor tyrosine kinase activity is stopped.

Answer 18

1.tyrosine phosphorylation is reversed by protein tyrosine phosphatase

2.RTKs are inactivated by being endocytosed into the cell and digested by lysosomes

Question 19

• List 4 roles of the cytoskeleton

Answer 19

1.determines shape of cell
2.organizes cell contents
3.provides structure
4.acts as a highway

Question 20

microfilaments

Answer 20

6 nm, actin, thin flexible, cellular movements

Question 21

intermediate fibers

Answer 21

8-10 nm, support, strength, and structure

Question 22

microtubules

Answer 22

25 nm, tubulin, organelle movement

Question 23

• List the 4 classes of intermediate filaments and the type of cell they’d be found

Answer 23

1.Keratin:composed majority of filaments in epithelial cells
2.vimentin and vimentin related filaments:found in connective tissue, muscle cells, and supporting cells of the nervous system
3.neurofilments:found in neurons
4.nuclear lamins:used to strengthen the nuclear membrane

Question 24

• Describe dynamic instability in microtubules and how the GTP cap stabilizes
  Microtubules

Answer 24

Microtubules will grow consistently and then suddenly stop and retreat
Tubulin is GTP binding protein and can hydrolyze GTP to GDP (hydrolysis of GTP to GDP causes instability and microtubule disassembles
When microtubule grows faster then the GTP can be hydrolyzed and another tubulin is added the GTP stays
GTP bound tubulin is more stable than GDP bound
-GTP cap

Question 25

Kinesins

Answer 25

move towards plus end

Question 26

Dyneins

Answer 26

move towards minus end

Question 27

• Describe actin treadmilling and how its different from microtubule dynamic instability

Answer 27

Addition of actin to plus end and simultaneously removing actin from minus end, different from dynamic instability because microtubules grow, stop, and retreat

Question 28

• Generally describe how actin and myosin cause muscle contraction

Answer 28

Sliding contractile proteins generate force in muscle:
actin=thin filaments
Myosin-thick filaments

Question 29

• Not the molecular details, but roughly how they interact

Answer 29

Each myofibril consists of sarcomeres (repeating units of overlapping actin and myosin filaments
Each sarcomere is bounded by z lines which anchor actin, myosin attached at M band
Contraction is z lines moving toward the M band, actin and myosin filaments slide past each other

Question 30

• Describe the 4 phases of the cell cycle (name and main events)

Answer 30

G1 gap:cells grow in sizer and synthesize new proteins needed for DNA replication
S phase(synthesis):DNA replication centrosome duplication
G2 gap:moer cell growth and new proteins
M phase (mitosis and cytokinesis):nuclear division and cell splits

Question 31

• Describe each of the 6 phases of M phase (mitosis + cytokinesis; name and main events)

Answer 31

1.Prophase:chromosomes condense, mitotic spindle forms
2.prometaphase:nuclear envelope breaks down, microtubule connect with chromosomes
3.metaphase:chromosomes align at center
4.anaphase:chromosomes are separated
5.telophase:nuclear envelope reforms, contractile ring forms
6.cytokinesis:cell splits into two by contractile ring

Question 32

Cell cycle control systems

Answer 32

network of regulatory proteins that ensure proper completion of previous step prior to proceeding to next step

1.G1 checkpoint:ensures environmental conditions are favorable before S phase
2.G2 checkpoint:ensures DNA replication is complete and DNA damage is repaired
3.checkpoint in mitosis ensures chromosomes are attached to mitotic spindle properly

Question 33

Cdk

Answer 33

kinase family that activate other proteins which trigger various cell cycle events

Question 34

Cyclin

Answer 34

proteins in cell which bind to and activate cdks

Question 35

• Describe two ways to pause the cell cycle

Answer 35

1.phosphorylation:inhibitory kinases add phosphates to cdks to prevent their activity
2.inhibitor proteins:proteins can bind to cdk or cyclin to prevent their binding or block any activity

Question 36

• Describe the combined role of condensins and cohesions on DNA

Answer 36

Condensins:phosphorylated by M-cdk and begin to form ring-like structures, help to organize and condense chromosomes
Cohesins:hold sister chromatids together, added during S phase and remain until Anaphase

Question 37

• Describe how M-Cdk influences the microtubules in prophase

Answer 37

M-cdk phosphorylates microtubule associated proteins increases dynamic instability

Question 38

• Describe how M-Cdk influences nuclear proteins in prometaphase

Answer 38

M-cdk phosphorylates nuclear envelope, nuclear laminin, and nuclear pore proteins, triggers break up into small proteins

Question 39

Kinetochore

Answer 39

where microtubules connect with chromosomes during mitosis

Question 40

• Define the 3 types of spindle microtubules

Answer 40

1.interpolar microtubules:microtubule which spans from one spindle pole to the other
2.kinetochore microtubule:microtubule attached to one spindle pole and one kinetochore
3.aster microtubule:only connected to one centrosome

Question 41

• Describe how kinetochore microtubules lead to metaphase

Answer 41

In prometaphase, the microtubules pull back and forth on the attached chromosomes to check that chromatids are attached and causes them to align at the center

Question 42

Anaphase A

Answer 42

chromosomes move towards poles, kinetochore microtubules shorten by depolymerization

Question 43

Anaphase B

Answer 43

poles move away from each other, motor proteins on interpolar microtubules push away from the poles

Question 44

• Describe the general process of reassembly of the nuclear envelope in
  Telophase

Answer 44

Nuclear envelope reforms
-phosphorylated nuclear proteins are dephosphorylated
-vesicles of nuclear membrane cluster around individual chromosomes and fuse to reform the envelope

Question 45

• Define the contractile ring and its role in mitosis

Answer 45

Contractile ring:where overlapping actin and myosin filaments form a ring and constricts to separate cell in cytokinesis