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Final Exam Flashcards

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Biology 101 flashcards
1
Q

Secretory pathways

A

proteins moving from ER to Golgi to PM for secretion

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2
Q

Modifications of proteins in the ER

A

Folding and Glycosylation

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3
Q

Folding modification

A

formation of disulfide bonds through oxidation of cysteine residues which stabilized the 3D shape.

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4
Q

glycosylaiton modification

A

addition of carbohydrate groups to the proteins
-an oligosaccharide (14 sugar) is added to asparagine residues by olygosaccahrly transferase. Stars at ER but can be modified in Golgi for diverse sets of glycoproteins

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5
Q

Can proteins leave the ER if misfolded?

A

No, it is monitored, through the direction of chaperon proteins for proper folding

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6
Q

What happens if l there is a large amount of unfolded proteins?

A

the unfolded protein response is triggered
-upregulates the production of chaperon protein s
-slows down generalized protein production
-increase growth of ER

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7
Q

Where are properly folded proteins transported?

A

the Golgi via vesicles

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8
Q

How do proteins travel to the Golgi?

A

merging cis-face of Golgi travel through cisternae towards the trans face
1. budding vesicles
2. maturation of Golgi cisternae migrating through stack cis-> trans

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9
Q

How does protein processing happen in the Golgi

A

enzymatic modification of oligosaccharides on glycoproteins
and specific proteins get sorted into specific vesicles and then buds off the trans face of the Golgi

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10
Q

What are the types of exocytosis and secretion?

A

Constitutive/unregulated exocytosis
regulated exocytosis

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11
Q

Constitutitive/ unregulated exocytosis

A

a constant stream of vesicles from the Golgi fusing with the PM
-refreshing lipid and membrane proteins
-enables PM to expand before cell division in mitotic cell

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12
Q

Regulated exocytosis

A

specialized cells for secretion
eg. glandular cells eg. secretion of hormones, digestive enzyme, mucus
-Products are stored in vesicles until the cell receives the signal for relaxation.

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13
Q

Endocytic Pathways

A

processing of materials brought into the cell in vesicles
1. phagocytosis
2. pinocytosis
3.receptor-mediated endocytosis

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14
Q

Phagocytosis

A

ingestion of larger particles like microorganisms, cellular debris, food
-cells must be specialized
eg. protozoans use phagocytosis to eat

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15
Q

In animals what is the use of phagocytes

A
  1. immunity
  2. clearing debri
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16
Q

How do phagocytes play a role in immunity?

A

white blood cells capable of phagocytosis through neutrophils and macrophages

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17
Q

neutrophils

A

have receptors that can recognize the foreign body or antibodies bound to the foreign body, once the receptor of the neutrophil binds to a foreign body, pseudo extend and engulf the paticle. phagosomes fuse with lysosomes and lysosomal enzymes destroy the foreign body.

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18
Q

Pinocytosis

A

“Cell drinking” nonspecific
-ingestion of small droplets of ECF through the formation of clathrin-coated vesicles( reclaims PM in cell with a lot of exocytosis)
used as a mechanism to balance the size of PM, especially in secretory cells
-when the vesicles come from the PM they fuse with an endosome

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19
Q

Receptor-mediated endocytosis

A

↳ membrane receptors bind specific solutes; solute binding
Initiates the formation of vesicles
-> Selective form of endocytosis
↳ specific for one type of molecule eg. LDL
-> Vesicle fuses with the Endosome: receptor and cargo
often dissociate
↳ receptor returns to PM in a vesicle that
buds from Endosome

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20
Q

endosome

A

sort and process incoming material

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21
Q

what is the general role of endosomes with endocytic pathways

A

-vesicles coming from PM form into an early endosome through the fussion of membranes
-5-15 minutes later the same material is now in a late stage endosomes
-maturation occurs as early endosomes fuse or pre-existing late endosomes
-late endosome fuses with preexisting lysosomes or late endosomes become a lysosome when lysosome enzymes are delivered from Golgi

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22
Q

What are the conditions inside an endosome?

A

-interior of late endosomes is acidic.(H+ pumps pump H+ into endosome)
-An acidic interior can cause some of the dissociation of cargo from reporters

23
Q

Lysosomes

A

contain hydrolytic enzymes capable of digesting unwanted material
-releasing amino acids, nucleotides, monosaccharides, and fatty acids to the cytosol they can be used to build macromolecules
-optimal activity in acidic conditions of the interior of lysosomes

24
Q

Types of lysosomal enzymes

A

-proteases
-glycosidase
-nucleases
-lipase
-phosphatase
-phospholipase

25
Q

Chemical Signaling

A

-> A signaling cell releases a Specific Chemical
Signed (Extracellular Chemical Signal = ECS)
-> ECS is recognized by target cells
that express the Specific Protein
receptor that will bind the ECS
-> The binding of ECS to the receptor initiates
a sequence of Events (signal transduction)
that brings about a cellular response

26
Q

Different forms of chemical signals

A
  1. Endocrine
  2. Paracrine
  3. Neuronal
  4. Contact-Dependent
27
Q

Endocrine Signaling

A

ECS/Hormones are released by Endocrine glandular cells and are
taken up by the bloodstream, delivered through the body by
circulatory system, and brings about the response at a relatively
distant target cells.

28
Q

Paracrine Signaling

A

-ECS is released and diffuses to act on local
target cells
-Autocrine: acts on the cell that secretes it. Or
Other cells close by of the same cell type.

29
Q

Neuronal Signaling

A

-an electrical signal that travels along an upon
extension, and is converted into a chemical signal
released from the axon terminal. ECS = Neurotransmitter
ECS binds to receptors at nearby target cells.

30
Q

Contact dependent signaling

A

-> Chemical Signal is embedded in PM of Signaling cell
-> receptor is embedded in PM of the target cell
-> When the chemical signal binds it creates a
a physical connection between those cells

31
Q

How does the ECS know where to bind?

A

Target cell express the specific receptor protein that will specifically bind the ECS

32
Q

Receptors can be found in?

A

Cell surface
intracellular

33
Q

cell surface receptors

A

PM proteins with ligand binding domain facing ECF, mostly hydrophilic ECS’s

34
Q

intracellular receptors

A

located within the cell
-usually bind small or hydrophobic ECSs

35
Q

Cellular can vary in terms of timing, what are the types of responses?

A

fast response (seconds): usually involves activation/deactivation cascade of existing protein to bring about cellular response
slow response( minutes to hours) Usually involves signal transduction pathways that involve altered protein production

36
Q

Amplification in cell signaling is?

A

A small # of ECSs can trigger a robust cellular response because several intracellular signals are activated in the pathway amplification

37
Q

cell surface receptors

A

-> Span the PM
-> Binding region faces If
-> Bind majority of ECS’s
-> Binding of ECS on the outside of cell is relayed by receptor
to a signal transduction pathway inside the cell

38
Q

signaling transduction

A

usually a cascade of biochemical activations and deactivaitons

39
Q

activation/ deactivation

A

protiens in the signaling cascade is often controlled by altering phosphorylation and dephosphorylation reaction

40
Q

kinase

A

mediate phosphorylation reactions ( addition of phosphate)
eg. serine/threonine: phosphorylate protein at serine or threonine residues
tyrosine kinase

41
Q

phosphatases

A

enzymes that mediate dephospho-rylation( removal of PO4)

42
Q

What are the three types of cell surface receptors

A
  1. Ion- channel coupled receptors
  2. G-protein coupled receptors
  3. Enzyme coupled receptors
43
Q

Ion-channel coupled receptors

A

-> the receptor is Chemically (ligand)gated ion channel
> the ECS binds, which causes a conformation change and
open the Channel
the channel allows specific ion to move passively down
its electrochemical gradient
↳ often leads to an electrical Signals (EPSP’s, IPSP’s)
↳ eg. Na, K, Cl, Ca

44
Q

G-protein coupled receptors: GPCR’s

A

> the GPCRs are conserved evolutionally
all have same basic structure
a single polypeptide that crosses back and forth through
the phospholipid bilayer of PM 7 times
-> GPCR is coupled to a G-protein
G-proteins are Heterotrimeric proteins
↳ composed of 3 different Subunits G alpha, beta , gamma)
-> Stay tethered to the phospholipid bilayer
↳ but subunits are able to move laterally in the membrane

45
Q

What does the activation process of GPCR look like?

A

1)ECS specifically binds to the receptor
2)the binding of ECS to the receptor causes a
conformational change in receptors at cytosolic
Side -> now able to interact with the alpha Subunit of G-protein.
Sidenote: Inactive alpha subunits are associated with GDP
3)When alpha Interacts with the receptor, the alpha will dissociate
from GDP, and a new molecule of GTP is bound
alpha is now activated
4)activated alpha subunits dissociate from beta and gamma, which
now activates them
5)Both active alpha and active beta and gamma can interact with effector molecules
to initiate signal cascades, eventually bringing about cellular response

46
Q

What are the pathways of signal transduction into cellular response for GPCR?

A

activated alpha with GTP bound will interact with effector proteins in PM

beta and gamma also interacts molecules

47
Q

What occurs when alpha is free to move laterally and does it ever get back to its complex?

A

alpha subunits have intrinsic GTPases activity so GTP is hydrolyzed to GDP within seconds -> inactive the alpha will reassocited with beta and gamma

48
Q

G proteins that activated ion channels

A

↳ when activated by G-protein Subunits
the channel opens: ions cross membrane
down electrochemical gradient
eg. Acetlycholine(ACH): a neurotransmitter.
ACH binds to GCPR in heart pacemaker (SA node)
… activated beta and gamma interacts with K + channel
-Channel opens; K+ efflax -> leads to decreased Heart Rate

49
Q

G proteins that activate effector enzymes and intiate second messenger signaling systems

A

-alpha subunits interact with membranes proteins that are enzymes capable
that produce second messenger molecule
(first messenger: GCS that bound to GPCR)
-Small signaling molecules that diffuse and amplify the Signal Within the cell
eg. cAMP
↳ triggers the signaling cascade to bring about response

50
Q

How does the cAMP second messenger system?

A

1)ECS binds to GPCR
2)G protein binds to receptor
3)activates the alpha, which then exchanges GDP for GTP
4)alpha activates beta and gamma: alpha and beta and gamma dissociate
5)alpha is specifically alpha(s) migrates in PM eventually encountering adenyly
cyclax (effector enzyme)
-> ATP-cAMP (second messenger)
6)cAMP activates PKA (protein Kinase A)
7)PKA phosphorylate target proteins in the cell that bring about the
cellular response
↳ dependent on target cells

51
Q

what happens when PKA is activated by cAMP?

A

↳ enzymes or CRE binding Proteins (CREB’s)
↳ once activated by specific Sequences of DNA in the
Promoter regions of target gene.
-> altered rates of transcription
↓
can bring about a cellular response

52
Q

Cholera toxin secreted (vibro cholera)

A

↳ Inhibits the GTPase activity of alpha
-locks the alpha in an active state· leads to continious activation of
adenylyI cyclate· Increased and Sustained levels of cAMP
↳ leads to continuous flow of Cl- out of cells.
water lost to lumen of the gut. => diarrhea disease
massive dehydration
-> can lead to death if untreated

53
Q

pertussis toxin: Bordetella pertusis

A

↳ colonizes the lungs
↳ whooping cough
↳ Inhibits the exchange of GDP to GTP. (at alpha(i) )
↳ alpha(i), when activated inhibits adenylyI cyclase
-> adenylyI cyclase is not inhibited
-> in appropriate activation build up of cAMP
↳ Symptoms. Causing of a Whooping Cough.

Cell Bio (3 decks)

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