Cell Biology Exam 4

Front 1

Nuclear protein import steps

Back 1

1) Nuclear localization signal-short amino acid sequence that directs a protein to the nucleus

2) nuclear transport receptors bind nuclear localization signal

3) Receptor interacts with nuclear pore fibrils

4) Receptor and protein pulled into nucleus

5) Receptor returned to cytosol

Front 2

Protein translocation

Back 2

1) Proteins enter mitochondria and cholorplasts

2) Protein is unfolded during transport

3) Signal peptide cleaved after translocation

4) Chaperones refold the protein

Front 3

Purpose of vesicle coating

Back 3

Helps shape vesicle

Front 4

Purpose of protein glycosylation

Back 4

1) Protection from degradation

2) Hold in ER for folding

3) Help guide to appropriate organelle

4) Cell recognition

Front 5

Protein Glycosylation steps

Back 5

1) Polypeptide enters ER

2) Membrane lipid (dolichol) linked to oligosaccharide

3) Oligosaccharide from dolichol transferred to asparagine residue of incoming protein

Front 6

ER-retention signal

Back 6

C-terminal sequence that signals a protein to stay in the ER

Front 7

Protein sorting steps

Back 7

1) Proteins are tagged

2) Proteins are sorted

3) Vesicles bud

4) Proteins interact with receptors

5) Delivery

Front 8

Constitutive secretory pathway

Back 8

1) Continual operation in all cells

2) Bud from golgi

3) Fuse with plasma membrane

4) Deliver protein to membrane or extracellular fluid

Front 9

Regulated secretory pathway

Back 9

1) Only in specialized cells

2) Secretory vesicles accumulate near the plasma membrane

3) Extracellular signal stimulates fusion with membrane

Front 10

Cystic fibrosis

Back 10

1) Production of thick mucus in lungs and digestive tract

2) Autosomal recessive inheritance

3) Caused by protein misfolding

Front 11

Vesicle docking steps

Back 11

1) Rab proteins - on surface vesicle

2) Tethering proteins - on cystolic surface of target membrane

3) v-snares - on vesicle membrane

4) t-snares - on target membrane

Front 12

Types of endocytosis

Back 12

1) Phagocytosis

2) Pinocytosis

3) Receptor-mediated endocytosis

Front 13

Steps of phagocytosis

Back 13

1) Solid particle enters pseudopodium

2) Becomes phagosome in cell

Front 14

Steps of Pinocytosis

Back 14

1) Small particle enters pseudopodium

2) Becomes engulfed by vesicle in cell

Front 15

Steps of receptor-mediated

Back 15

1) Specific particles enter coated pit on receptor

2) Turns into coated vesicle with coat protein in cell

Front 16

How does tuberculosis trick the immune system

Back 16

It is taken up by macrophages but blocks fusion of phagosome and lysosome

Front 17

Cholesterol absorbtion

Back 17

1) LDL binds cell receptors

2) LDL enters cell via receptor-mediated endocytosis

3) LDL fuses with endosome

4) LDL dissociates from receptor

5) LDL delivered to lysosomes

6) Receptor returned to plasma membrane

Front 18

Endosomes

Back 18

- Sorting station for endocytic pathway

- Acidic environment causes receptor and cargo to dissociate

- Digestion of cargo begins

Front 19

Lysosomes

Back 19

- Principle site of intracellular digestion

- Formed by fusion of transport vesicles from the golgi and endosomes

- Contain hydrolytic enzymes

- Acidic environment

Front 20

3 types of cell signaling

Back 20

- Endocrine

- Paracrine

- Neuronal

Front 21

How endocrine cell signaling works

Back 21

The hormone enters the blood stream, finds target cell and binds to the receptor

Front 22

How paracrine cell signaling works

Back 22

Local mediator leaves signaling cell and binds to receptor of target cells

Front 23

How neuronal cell signaling works

Back 23

Neurotransmitter from neuron attaches to target cell at synapses

Front 24

How contact-dependent cell signaling works

Back 24

membrane bound signal molecule binds to target cell directly

Front 25

3 examples of signaling molecules

Back 25

- Hormones: glucagon and insulin

- Local mediators: epidermal growth factor (EGF)

- Neurotransmitters: acetylcholine

Front 26

3 types of receptors

Back 26

- G-protein coupled receptors

- Enzyme-linked receptors

- Intracellular receptors

Front 27

Steroid hormone binding

Back 27

- Bind outside nucleus in cytosol or in nucleus to receptor protein

- Hydrophobic molecules

- Transcription regulators

- Hormone-receptor complex binds to DNA

Front 28

Cell surface receptors

Back 28

- Transmembrane proteins

- Binding to extracellular signal to receptor initiating intracellular response

- Signal relayed from molecule to molecule until desired response is achieved

Front 29

Androgen insensitivity syndrome

Back 29

- Genetic males (XY) unable to respond to angrogen due to defective androgen receptors

- X-linked recessive disorder

- External female genitalia, internal male genitalia

Front 30

Intracellular signaling pathways

Back 30

Relay - pass signal to next moleculeAmplify - make the signal strongerIntegrate - Coordinate signals from multiple pathwaysDistribute - Pass signal to more than one pathway

Front 31

3 Classes of cell surface receptors

Back 31

- Ion-channel-coupled receptors

- G-protein-coupled receptors

- Enzyme-coupled receptors

Front 32

Ion-channel-coupled receptor

Back 32

- Simplest and most direct receptor

- Transduces a chemical signal into an electrical signal

- Results in alteration of membrane potential

- Example: nicotinic actylcholine receptor

Front 33

Structure and function of G-Protein-coupled receptors

Back 33

- Seven pass transmembrane protein receptor

- Hydrolysis of GTP

Front 34

G-protein-couple receptor targets

Back 34

-Ion Channels

- Binds to ion channels to open them

- EG: K+ channel in heart muscle

Membrane bound enzymes

- Adenylyl cyclase - produces cyclic AMP

- Phospholipase C - produces inositol triphosphate and diacylglycerol

Front 35

Cyclic AMP pathway

Back 35

1) Activated g-protein subunit activated adenylyl cyclase

2) Increases production of cAMP

3) cAMP activates cyclis AMP-dependent protein kinase (PKA)

4) Kinase phosphorylates a set of proteins

5) Signal terminated by cyclic AMP phosphodiesterase

Front 36

Inositol phospholipid pathway

Back 36

1) Phospholipase C cleaves inositol phospholipid into 1,4,5-triphosphate (IP3) and diacylglycerol (DAG)

2) IP3 diffuses into cytosol

3) Binds to Ca2+ channel on ER

4) Ca2+ rushes into cytosol and triggers other pathways

5) DAG activated protein kinase C (PKC)

Front 37

Calcium triggered processes

Back 37

- Cytosolic Ca2+ usually low

-Ca2+ stored in cytosol

- Influx of Ca2+ into cell triggers calcium responsive proteins

Front 38

Receptor tyrosine kinase pathway

Back 38

1) Two receptors proteins form a dimer

2) Activation of receptor tyrosine kinase

3) Intracellular signaling proteins bind the active receptor tyrosine kinase (RTK)

4) Signal relayed to numerous cellular locations

5) Protein tyrosine phosphatase terminates the response

Front 39

RAS Protein

Back 39

- membrane bound protein

- active when bound to GTP

- activates a phosphorylation cascade

Front 40

3 types of protein filaments

Back 40

- Intermediate filaments

- Microtubules

- Actin filaments

Front 41

Structure and function of intermediate filament

Back 41

Structure

- Long, twisted strands of protein

- Tetramers twist into a rope

Function - form a network to allow cell to withstand mechanical stress

Front 42

Role of keratins

Back 42

distribute stress throughout cells

Front 43

Lamin

Back 43

Intermediate filaments that make nuclear lamina, must disassemble and reform during mitosis

Front 44

Microtubules

Back 44

- long, stiff hollow tubes of protein

- guide intracellular transport

Front 45

Growth of microtubules

Back 45

- Tubulin subunits added to + end of growing microtubules

- Shows dynamic stabilitiy

- packs efficiently when GTP is bound

- packs loosely when GDP is bound

Front 46

Antimitotic drugs

Back 46

- Colchicine: binds tightly to free tubulin

- Taxol: binds to microtubule to prevent depolymerization

Front 47

Kinesins and Dyneins

Back 47

Kinesins: move towards the + end of microtubules

Dyneins: move towards the - end of microtubules

Front 48

Actin filament

Back 48

Essential for movement

Front 49

Actin filament polymerization

Back 49

- Faster addition of subunits at the + end

- Actin monomer to ATP

- ATP hydrolyzed after incorporation of monomer into the filament

Front 50

Cell cortex

Back 50

Actin rich layer responsible for cell movement

Front 51

Myosin

Back 51

Head and tail region

- Head: interacts with actin, has ATP hydrolyzing motor

- Tail: determines what the motor moves

Front 52

Steps of muscle contraction

Back 52

1) Z lines pulled together

2) A band inceases

3) I band, H zone shorter

4) Contraction increases, overlap increases

5) Thick myofilament stationary (myosin)

6) Thin myofilament moves in/out (actin)

Front 53

Rigor Mortis

Back 53

- Begins 2-6 hours post mortem- ATP no longer available - actin and myosin remain bound to eachother- Muscles stay rigid until autolysis begins- Onset and duration of rigor affected by: - ambient temp - exertion prior to death - body condition - age