UMKC Cell Biology Exam 2

site of protein synthesis in cells 1 pathway (of 2)

Cytosolic ribosomes-->cytosol then to either

-cytosolic proteins

-mitochondrial & chloroplast proteins (in plants)

-nuclear proteins

-peroxisomal proteins

site of protein synthesis in cells 2nd pathway

Cytosolic robosomes--> ER ribosomes--> ER then to either

-ER proteins

-Golgi proteins

-Endosomal & Lysosomal proteins

-plasma membrane & secreted proteins

In pathway 1 of protein synthesis, proteins are _________ into these organelles

imported

in pathway 2 of protein synthesis, proteins are _______ to these organelles in ______

transported, vesicles

cytosol function

contains many metabolic pathways; protein synthesis; the cytoskeleton

Nucleus function

contains main genome; DNA and RNA synthesis

Endoplasmic Reticulum (ER) function

synthesis of most lipids; synthesis of proteins for distribution to many organelles and to plasma membrane

Golgi apparatus function

modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle

Lysosomes function

intracellular degradation

Endosomes function

sorting of endocytosed material

Mitochondria function

ATP synthesis by oxidative phosphorylation

chloroplasts function

ATP synthesis and carbon fixation by photosynthesis

Peroxisomes function

oxidation of toxic molecules

3 steps of proteins synthesized into the cytosol

1. proteins imported into the nucleus

2. proteins imported into peroxisome protein

3. proteins imported into mitochondria

proteins imported into the nucleus is when

nuclear localization sequences (NLS) in cargo proteins bind to importins which direct them through the nuclear pore

structure of nuclear pore

is made of large complex of nucleoporin proteins.

channel is very large so 3 and 4 structure proteins can be exported

proteins imported into peroxisome protein

-functions in metabolism, especially oxidation of fatty acids and removal of toxic molecules

-uses Peroxisomal targeting signal (PTS) to transport directly into peroxisomes in folded state.

PTS1 path

Pex5P cytosolic receptor binds C terminal of cargo

PTS2 path:

Pex7P cytosolic receptor binds N termincal of cargo

proteins imported into mitochondria

cytosolic proteins in mitochondrial matrix have a N-terminal mitochondrial signal sequence (MTS)

Tom is

outer mito membrane

-signal recognized first by receptor on the

Tim is

inner mito membrane

-signal recognized 2nd by receptor on the

mito functions in protein synthesis

1. respiratory metabolism/ generate energy

2. regulate reactive oxygen species levels

3. key roles in programmed cell death

prior to import polypeptides in cytosol are kept _______ by binding ______ Hsp70, a chaperonin

unfolded, cytosolic

Protein synthesized ON endoplasmic reticulum 7 steps

1. ER function

2. Ribosomes derived from cytosolic pool

3. some proteins are INTO ER interior, termed the lument

4. Animation of protein translocation in the ER

5. Translocation of single-pass ER Transmembrane proteins

6. Glycosilation begins as proteins are being synthesized translocated into lumen

7. Folding occurs in lumen as proteins are being translocated

Protein synthesized on ER step 1

- ER function

-site for synthesis of all ER proteins and most membrane associated proteins throughout the cell

- 30 X more membrane than plasma mem

Proteins synthesized on ER step 2

-Ribosomes derived from cytosolic pool

-proteins translocated into ER membrane of lumen

5 Requirements to begin translocation

1. N-terminal ER signal sequence

2. Signal recognition particle called SRP

3. SRP receptor

4. Translocator complex

5. Ribosome (generates the force for translocation)

Proteins synthesized on ER step 3

-some proteins are into ER interior termed the lument

What does signal peptidase do?

Clips off the signal sequence

Proteins synthesized on ER step 4

-animation of protein translocation in the ER

-internal signal sequance = start transfer sequence

proteins synthesized on ER step 5

translocation of single-pass ER Transmembrane proteins

-STOP transfer sequence

proteins synthesized on ER step 6

glyosylation begins as proteins are being synthesized translocated into lumen

protein glycosilation happens at (2 types)

aspraragine (N- linked)

serine or threonine (O- linked)

proteins synthesized on ER step 7

folding occurs in lumen as proteins are being translocated

- includes BiP

what is BiP

a chaperone protein that prevents misfolding by clamping around a hydrophobic patch. It releases it to allow it to fold.

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

endocytosis pathway

cell surface to endocytic vesicle to endosome to lysosome

What is anterograde? How does this apply to protein movement in the ER

away from the cell body, proteins move from ER to Golgi (anterograde) and from golgi to ER

sorting proteins from ER to other cell compartments (2 steps)

1. vesicle formation (recruit GTP binding protein)

2. vesicle scisson (clathrin coat breaks off once cargo molecules are inside)

t snare does what

specialized protein anchored to the presynaptic "target" membrane to bind v-SNAREs to dock vesicles, making them ready for release

Exocytosis and 2 types

Process by which a cell releases large amounts of material

- regulated stores secretory vesicles until there is a signal

- unregulated does not wait for a signal and stores plasma membrane proteins and lipids

cis- golgi

attachment of core O-linked oligosaccgarides

medial-golgi

addition of galactose to oligosaccharide chains

trans-golgi network

removal of terminal monosaccarides

what does AP3 do?

targets trans golgi network proteins with specific sequence to the lysosome

what does Mannose-6 phosphate signal do? (M6P)

targets specific trans golgi network proteins to the AP1 vesicles destined for the early endosome using a M6P receptor.

what is hypercholestremia

cardiovascular disease, build up of cholesterol in the eye

how is the early endosome formed? (Ee)

by fusion of endocytic vesicles from plasma mem and trans-golgi network secretory vesicles

2 forms of endocytosis

phagocytosis (whole bacteria/ defends against pathogens) and pinocytosis (small molecules)

Autophagy

defense against damaged organelles

3 types of cytoskeleton filaments

actin filaments, intermediate filaments, microtubules

IFs are the _______ and most _________ of 3 filaments and example

strongest and most flexible ex: rope

3 domains of intermediate filaments

head, tail, conserved boundary motifs/ central rod domain

in IFs you do not need ______ ________ nucleotide required for assembly

high energy

how many tetromeres make a unit length filament

4 tetromeres or 8 dimers

what is the coil-coil motif

alpha helices wrapped around one another, strengthens IF

what is a tetromer

fundamental IF subunit, symmetric so no polarity

types of IF in cells

muscle, epithelial, connective tissue, nerve cells, animal cells

what is nuclear lamina

mesh of lamin proteins that support nuclear envelope giving shape and strength to nuclei

what is progeria

A disease resulting in rapid aging

What are desmosomes and what do they do?

Skin cells that strengthen and connect cells.

what is epidermolysis bullosa simplex

disease caused by defect in keratin, results in blisters forming between cell sheets

characteristics of microtubules

less flexible, dynamic instability occurs at one end, moves cargo through cell, requires more energy

what is 1 MTOC

the centrosome/ interphase, near the nucleus, radiating out from the centrosome

line our lungs

what is 2 MTOC

spindle poles/ mitotic cell

what happens when alpha and beta bind together?

they form a stable heterodimer

what does dynamic instability mean?

length grows and shrinks

what end of the MT does shrinking and growth occur?

the positive end, right side

2 types of proteins regulate MT (+ end)

1. MAPs (MT associated proteins)

2. TIPs (MT tracking proteins)

MAP example

Tau, stabalizes + end

Two types of MT motors

dyneins (- end directed)

kinesins (largely + end directed)

structure/ mechanism kinesins and dyenins

2 head domains, 2 stalk domains ( coiled- coil), 2 tail domains

How do cilia and flagella move?

moving by MT

what is primary cilia?

single cilium that doesn't move but is a projection from the cell

characteristics of Actin Filaments ( 4 )

most dynamic and highly regulated filament

intermediate in flexibility bw MT and IF

monomers of actin twisted around hold the structure together

has positive and negative end

structural polarity of AF

negative end at the top and shrinks, + end at the bottom

pos end is more ON that OFF and grows more

5 classes of proteins that regulate actin

class 1. monomer-binding proteins

class 2. nucleating proteins

class 3. capping proteins

class 4. severing/depolymerizing proteins

class 5. cross-linking/bundling proteins

what is fimbrin

in class 5

- holds tight bundles

what is actinin

holds loose bundles

actin cytoskeleton function (5 things)

1. cell structure (microvilli)

2. Cell mobility (migration)

3. Cell division

4. muscle contraction

5. trafficking along the periphery

What do microvilli do?

increase surface area

What are filipodia?

finger-like projections

what is the contractile ring made of and what does it do?

Actin filaments that pinch cell during cell division

what does the cell cortex do?

defines the cell shape, size, and mechanical properties

what is filamin?

cross-linked actin filaments that form mesh that support PM

myosin motors 3 functions

1. vesicles move on cell cortex

2. filaments move relative to PM

3. contractile ring-filaments slide past each other and disassemble as the ring shrinks

Myosin 1

Simplest type of myosin, present in all cells; consists of a single actin-binding head and a tail that can attach to other molecules or organelles.

myosin 2

Protein associated with the fiber that makes muscle contractions. Made of 2 sub units of a head and 2 tails that twist together. Pulls the filament across themselves.

cell migration (how do cells move)

cells "crawl" when integrin (attached to ECM) releases myosin the lagging end builds up stress then snaps forward

-uses leading edge and lagging end

skeletal muscle structure

has actin (thin filaments) and thick filaments (myosin)

Many sarcomeres together make up a ?

myofibril

Many myofibrils together make up?

muscle fiber

How do muscles contract?

A muscle contracts when the thin filaments in the muscle fiber slide over the thick filaments.

-thin filaments get shorter

regulation of muscle contraction by calcium (3 steps)

1. signal from neuron release Ca in myocyte

2. Ca binds to troponin, changing conformation of fiber to release tight hold on actin

3. myosin binding site exposed by Ca mediated tropomyosin movement

what does Ca prevent in the muscles? what happens when it is released?

prevents muscle contraction so when it is released it is contracting

First principal of cell cycle regulation

Different cyclin: kinases activate different phases events

Cyclin subunit targets kinase to specific sets of substrates

What are the four basic complexes of cyclin

G1 phase

G1/5-phase cyclin

S phase cyclin

M phase cyclin

What do you need to start the m phase

M cyclin

3 mechanisms in 3rd principle

1. Cyclin degredation (happens in all stages)

2. Cdk phosphorylation (happens in M stage)

3. Cdi binding