What are the Basic Properties of Cells?

• Higly complex and organized
• Maintain and Utilize a genetic program
• Reproduction(generation of daughter cells
• Acquire and Utilize energy 
• Support Enzyme-catalyzed chemical reactions
• Engage in mechanincal activity
• Respond to stimuli
• Sustain Self-Regulation
• Evolve

Cells are Highly Complex and Organized,

How?

-Contain a large number of parts

-Organized with respect to time and space

-Parts interact with little tolerance for error

-fidelity of interactions is maintained by control and regualation of parts

• provides precision in cellular activities

What are the main differences between Prokaryotes and 

Eukaryotes?

1)Prokaryotes                        2) Eukaryotes

 -bacteria                               -protists, fungi, plants, 

-Structurally Simple                   animals

                                             - Structually complex 

Nuclear Pore Complex

Enables the movement of molecules in and out of the the nucleus

What is a viron?

A virus that exists outside the cell as an inanimate particle. 

Virons are able to invade the cell.

Comprised of:

- Small amopunts of DNA and RNA

-Protien Capsule (capsid)

Your roomate seezes on you. You inhale virons. What happens when one of these virons causes a lytic infection in your pper respiratory tract.

Lytic: production of virus particles rupture (and kill) cell.

The viron enters the cell through a specific receptor, inserts genetic materialinto the cell, assembles virus like cell, ruptures and kills the cell. 

What are the functions of the biological membrane? 

• Cell Boundary
• Define/enclose compartments
• Control movement of materialinto/out of cell
• Allow response to external stimuli
• Enable interactions between cells
• Provide scaffold for biochemical activities

Amphipathic 

-Amphipathic: a molecule (protein) that contains hydrophobic and hydrophillic parts

a) The term ....... means water loving, it is also said to be.....

b) The Term ..... means water hating, is is also said to be.......

A) i) Hydrophillic ii) Polar 

B) Hydrophobic ii) Non-polar

Concerning Biological membranes, which statment is true?

a) contain amphipathic lipids

b) contain lipids

c) hydrophobic components (only) 

d) static structures

a) contain amphipathic lipids

What is the Fluid Mosaic Model?

-Contain a hydrated lipid bilayer of amphipathic lipids

-Proteins: Integral

                 Peripheral

                       Lipid-anchored

Components are mobile and can interact

Describe the Structure of Biological Membrane

-Stable (non-static) 

-Flexible

-Capable of self assembly--> driven by hydrophobic interactions.

-different membranes contain different types of lipids and proteins.

-The inner membrane of mitochondria contains a high concentration of protein.

Why does the inner mitochondrial membrane have high concentrations?

Gives opportunity for a variety of structures and functions.

Myelin Sheath

A modified plasma membrane structure providing insulation for the conduction of electrical impulses.

The myelin sheath of a neurin contains very low amounts of protein. This structure consists of layers of plasma membrane wrapped around the nerve axon.

What are the three classes of membrane protein? Describe them. 

1. Integral protein: goes through the lipid bilayer, usually ampipathic.
2. Peripheral protein: doesn't go through a membrane, connects with integral protein, phospholipid bilayer or both. Usually polar since they are hydrophobic.
3. Lipid-anchored: Connected to phospholipid bilayer or anyother lipid in the membrane. 

True or False?

1) All membranes are the same

2) The leaflets that make up the bilayer are symmetrical 

3) The components of a membrane are mobile and interact

1) False, they are all different

2) False, they are assmetrical

3) true

What factors affect fluidity?

The type of lipid membrane:                                            -Unsaturated=increase fluidity

(more fluidity=more mobile)

-Saturated=decrease fluidity

The temperature: 

-Warming=increase fluidity

( Liquid crystal state)

-Cooling=decreases fluidity

(Crystalline gel-rigid)

Why is membrane fluidity crucial to cell function?

• Must be maintained
• In response to change in temperature, lipid composition of membranes can be changed by    

    1) Desaturation of Lipids   2) Exchange of Lipid chains

• Balance between ordered (rigid) structure and disordered structure allows: 

-mechanical and flexibility 

-dynamic iteractions between membrane components

-membrane assembly and modification

True or False:

Cholesterol does not regulate membrane fluidity.

False.

Cholesterol does regulate membrane fluidity.

• Alters packing and flexibility of lipids
• If added to liquid crystalline membrane:             fluidity will decrease
• If added to a crystaline gel membrane fluidity will increase

What are lipid rafts?

areas of the plasma membrane that are enriched with certain types of lipids. (i.e.,cholestrol)

- relatively rigid

- some membrane proteins accumulate in rafts.

-form a 'functional compartment'.

Are biological membranes dynamic? 

yes. 

• Lipids move easily,laterally, within leaflet.
• Lipid movement to other leaflet is slow.
• membrane proteins can diffuse within bilayer

 - protien movemnt is restricted

- some proteins do not move

- rapid movement is spatially limited

-long range diffusion is slow 

-biochemical modification can dramatically changeproteins mobility in a membrane

(part of signal transduction) 

Which of the following compounds will move unassisted across a membrane?

a) Glucose

b) CO₂

c) Na⁺

b) CO₂

Simple Diffusion

- very small molecules

- uncharged

- down a concentration gradient (uphill)

Diffusion through a channel

-small charged molecules (ions)

- Down a concentration gradient

ex/only going to occur when moving from high to low gradient.

True or false:

1) Ion channels are selective, allowing only one type of ion to pass. (semi-permeable)

2) Ions move up a concentration gradient.

3) Channels are often 'gated'(can be open or closed)

4) Ion channels are formed by peripheral membrane protiens that line an aqueous pore.

1) True

2) False, Ions move down a concentration gradient.

3) True.

4) False, Ion channels are formed by integral membrane protiens that line an aqueous pore.

List and Describe the 3 types of gated channels.

1) 1) Voltage-gated channels (ex/K⁺ Channel) 

1) Voltage-gated channels (ex/K⁺ Channel) 

-Channel responds to changes in charge across a membrane, causing channel to open, peptide binds, channel closes.

Ligand-gated channels (CFTR)

-Channels respond to binding of a molecule 

(ligand)

Mechano-gated channels

ex/ cation channels in inner ear

- Channels respond to physical force on membrane

(ex/ stretch)

Facillitated diffusion

• Compund binds specifically to integral membrane protein called facilitative transporter.
• Change in conformation of membrane allows compound to be released on other side of membrane.
• Compound moves down concentration gradient

Active Transport

• Compounds bind to integral membrane protein called active transporter
• 
  Change in conformation of transporter allows compound to be released on other side of membrane
• Compound moves up the concentration gradient.
• Requires input of energy.

List and Describe the process of active transport used by Na⁺/K⁺ ATPase.

-Na⁺/K⁺ ATPase is the transporter responsible for maintaining cytosolic concentrations of Na+ and K+ 

- 3 Na+ and ATP bind to the transporter inside the cell (E1 Conformation) 

-ATP is hydrolyzed and ADP is released; transporter shifts to E2 conformation.

- 3Na+ are releasedout of cell, 2K+ bind outside of the cell. 

-Phosphate group is released

-ATP binds, Protein shifts back to E1 conformation and 2K+ ions are released in cell.  

Which process requires energy?

a)Movement of Na+ through a voltage gatedNa+channel 

b) Movement of O₂ within a cell

c)Proton pump on the inner mitochondrial membrane

d) Glucose transport into/out of our cells

c)Proton pump on the inner mitochondrial membrane

True or False:

1)Diffusion through a channel is a type of mediated transport.

2) Facillitated diffusion is a form of active transport

3) The glucose transport into and out of our cells ivolve a conformational change in the transporter itself. 

4) The Na+ / K+ pump requires ATP for the directional movement of Na+ and K+ 

The Extracellular Space

(outside of ECM)

i)What is the glycolcalyx ?

ii)why is it important to the cell?

i) An assembly of carohydrate groups attached to protiens and lipids on the outside of the plasma membrane.

ii) - it mediates cell-cell and cell-ECM interactions

-provides mechanical protection

-serves as a barrier to some particles

-binds regulatory factors

Define: Extracellular matrix

ECM

 What are the functions of the ECM?

organized network of material produced and secreted by cells.

Functions of ECM:

-site for cell attachment

-physical support for cells

-substrate through which cells can move

-contain regulatory factors (signals)

-Seperate/define tissues

Components of the ECM are produced and assembled into a network including.________,__________ and________.

i) Proteins and glycoproteins(collagen,fibronectin, laminin).

ii) Proteoglycans = proteins with long chains of polysaccharides. 

True or False:

i) The ECM is a static environment.

ii) Cells bind to ECM and this influences cell survival and cellular activity.

iii) Cell-ECM interactions define tissue and the function of proteins within the membrane.

False.

i) False: The ECM is a dynamic environment.

ii) True

iii) False: Cell-ECM interactions define tissue and organ function.

Describe the composition and function of a cellular membrane.

Composed of: cellulose, hemicellulose, pectinand proteins.

Fucntions: 

-Structural support to cell and organism as a whole.

-protect cell from mechanical damage and pathogens

-contains biochemical information for cell.

In the mitochondria, which of the following components is powered by a protein gradient?

a) H+ channel

b) Electron Transport Chain

c) ATP synthase

d) Cytochrome C

c) ATP synthase

Compare the Outer and Inner

Mitochondrial Membrane 

OMM                                            IMM                      -Contains many enzymes with   - high protein:lipidratio3:1

diverse metabolic functions     -forms double layered                                                     sheets (cristae)

ex/porins: -large channels      - rich in phospholipids

               -freely permeable      called cardiolipin

               when open                 (characteristic in 

        (ex/ATP)                          biological membranes).

What is the function of the Cristae?

-increase membrane surface area

-contain machinery for aerobic respiratio and ATP formation.

What compartments seperate the inner and outer mitochondrial space?

Aqeuous Compartments of the mitochondria

1) intermembrane space

2) matrix:

high [protein]- gel like consisitency 

mitochondrial ribosomes 

mitochondrial DNA (mtDNA)

-encodes polypeptides that integrated into the IMM, ribosomes and tRNA. 

Why is the balance of ordered and disordered structure important to the function of biological membranes?

- ordered membrane structure tends to be more rigid

- disordered membrane structure tends to be more flexible

A balance between these allows:

- the membrane to provide mechanical support, and act as a barrier, while still being flexible

- dynamic interactions between components within the membrane

How will the transition temperature of a membrane be affected if the amount of unsaturated lipids is increased?

Unsaturated lipids introduce more disorder. This means the membrane will have an increased tendency to be in a liquid crystal state. The transition temperature will be lower.

What is meant by a membranes transition temperature?

The temperature above which a membrane will be in a liquid crystal state, and below which it will be in a crystalline gel state.

5. (a) Briefly, describe the structure and function of the voltage-gated K+ channel.

The voltage gated K+ channel is made up of integral membrane proteins that forms an aqueous pore that spans the plasma membrane.

- The channel is selective, allowing only K+ ions to be diffused, 

K+ ions move rapidly through the channel, from inside the cell to outside, down their concentration gradient

- the channel is gated, and can be opened and closed by the position of an inactivation peptide in response to changes in voltage across the membrane

5) (b) What would be different about this if the channel was ligand-gated?

the opening and closing of the channel – by the inactivation peptide – would occur in response to binding of a specific molecule (a ligand)

What is Oxidative Phosphorylation?

ATP synthesis n the mitochondria.

Step 1

 electron transport and proton pumping

    -generate electorchemical gradient.

Step 2

 Proton movement down electrochemical gradient powers ATP synthesis. 

Describe what happens in the electron transport chain.

What drives this process?

• high energy electrons pass from coenzymes (NADH and FADH₂) in the matrix to electroncarriers in IMM
•  Series of e- carriers (resiratory enzyme complexes I,II,III,IV) = ETC 
• Energy transfer at each complex used to pump H⁺ from matrix to intermembrane space.
•  low energy e- is transferred to terminal e- acceptor (O₂)--> H₂O produced.

Describe the Process by which ATP is produced by ATP synthase

Oxidative Phosphorylation: ATP Synthesis in Mitochondria

Step 2:

-Movement of H+ down the gradient (across IMM), through ATP synthase, fuels ATP syntheis. 

True or False:

The generation of a proton gradient is an active process

True. Because it will require energy. 

Apoptosis

A normal occurence in which a series of events lead to the death of a cell.

( Self destruction of a cell)

Apoptosis is characterized by: 

-shrinkage of a cell

-blebbing of Plasma Membrane

-Fragmentation of DNA and nucleus

-Loss of attachment to other cells

-Engulfment by phagocytosis

Apoptosis is characterized by all of the following except:

a) Fragmentation

b) Engulfment by phagocytosis

c) Portrusions in Plasma Membrane

d) Expansion of Cell

D) Expansion of a Cell

Vesicular Transport is used in all of the following except:

a) Endocytosis

b)Excocytosis

c) Movement of Materials between cells

d) Movement of Materials between organelles

e) Transport of materials across a membrane

C) Movement of materials between cells

How and for what reasons is Apoptosis initiated?

The Intrinsic Pathway of Apoptosis.

Intinsic stimuli initiate apoptosis. 

-Proapoptotic proteins stimulate mitochondria to leak proteins (ex/cytochrome C) 

- Release of apoptotic mitochondrial proteins commits the cell to apoptsis=destruction of cell

-

What is Excocytosis?

ER-->Golgi-->Plasma membrane

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane

What is Endocytosis?

PM--> organelle 

What is the interior of the ER called?

Lumen

Where does the glycosylation of proteins occur?

Rough ER

What is the ER membrane continuous with?

The nucleus

The function of the smooth ER includes:

-Production of Hormones

ex/ endocrine cells

- Detoxification

ex/Liver cells

- Sequestaration (storage of Ca+2)

(In a Muscle cell, Smooth ER = Sarcoplasmic Reticulum) 

1)Why is Protein Folding Critical?

2)Where does it occur?

1)critical for The Conformation of enzymes (lock and key hypothesis) and receptors (to signal selective transport)

2) Occurs in the Ribosome

What are the functions of the rough ER?

• Protein Synthesis, modification and transport
• Synthesis of membrane phospholipids
• glycosylation of proteins
• Protein folding

Where do ribosomes perform there fuction?

In the Cytoplasm of the Rough ER

Polypeptides are synthesised from mRNA

True or False: Translation of Integral Membrane proteins begins on free ribosomes.

True: 

It will always begin on free ribosomes and end in the ER.

What proteins complete there translation on free ribosomes?

Peripheral membrane proteins because they are targeted to the nucleus,mitochondria, peroxisomes and chloroplasts.

Which of the following proteins are most likely processed in the ER?

a) Cytosilic hexokinase

b) Na+ /K+ ATPase

c) Succinyl Co-A Synthetase 

d)Fibronectin

e) Both C and D

f) Both B and D 

F) Both B and D.

Proteins that are synthesized in the rough ER: 

• Secretory Proteins
• Integral Membrane Proteins
• Soluble Proteins associated with the  inside the endomembrane (lumen)

ex/ Proteins that function in ER golgi, and lysosomes

Amino acids (hydrophobic) in an aqueous environment. 

because the hydrophobic particles are attracted to one another (like-like) 

During translation of a protein, a signal sequence emerges. What happens next to complete translation of the polypeptide?

Cotranslational protein import 

After translation of signal sequence

1.Signal Recognition Particle binds to signal sequence- translation stops.

2. SRP binds to the SRP receptor on ER membrane - translation complex is now at the ER

3. SRP is released; ribosome binds to translocon

4. polypeptide enters the ER, through the translocon, as translation is completed

What are the 2 possible fates after synthesis and processing in the ER. 

1) It is retained in the ER (if that is where the protein functions)

2) ER-->Golgi for further modification and deliery to distal partsof the biosynthetic/secretory pathway. 

Transport from ER to Golgi Complex

Exit Sites: 

- Membrane and ER umen bud off to form transport vessicles.

ER-Golgi Intermediate Compartment(ERGIC) 

-region between ER and Golgi

-Transport vessicles fuse to form larger vessicles+interconnected tubules= vesicular-tubular clusters (VTC's) 

List Areas in sequence from which the proteins travel from ER to golgi

ER---->ERGIC--->cis-golgi network (CGN)---> cisternae ------>Trans-cisternae--->TransGolgi network (TGN)

--->Golgi

What are vesicular-tubular (VTC's)? What do they eventually form? 

VTCs are fused, tubular structures

They form the cis-golgi network. 

Modification of Proteins iGolgi occur in which structure(s)? 

a) Cis cisternae

b) Cis Golgi Network

c) Trans Cisternae

d) a,c,d.

a) Cis cisternae

What are the functions of the vesicular transport protein coat?

-Help form a vessicle.

-Help Select Cargo (material inside/on the vessicle).

What are the two types of vesicular protein coats? How do they differ in their function?

COP1 and COP2 move in different directions.

COP1= retrograde (reverse)

COP2= anterograde (forward)

COP2: ER to Golgi

COP 1: Golgi--> ER

List and Describe the 4 basic steps of vesicular traffiking.

1) Movement of vesicle to the target compartment 

-uses cytoskeleton and motor proteins

2) Tethering vesicle target compartment

-uses RABs

3) Docking of the vessicles to target compartment 

-uses SNAREs

4) Fusion of vessicle and target membrane.

Describe the structure of the lysosome. How does this relate to their function? 

Internal pH of 4.6 (acidic pH can harm/destroy other proteins )

Hydrolytic enzymes

-acid hydolases (only work in acidic environment)

-Lysomal membrane

-contains glycoslated proteins that form a protective lining next to the lumen. 

Endocytosis is:

a) The transpot of materials from an orgaelle to the plasma membrane via vesicles

b) The internalization os materials 

c) The movemtn of materials between an organelle

d) The anterograde movement of COPII coated vessicles from the ER to Golgi

B)  The internalization os materials

A= Excocytosis

D= COP1and COP2

Describe the difference between consitiutive and regualted excocytosis.

Constitutuive- happens all the time 

Regualted- ex/secretion of neurotransmitter,

secretion of insulin

Why is it important for the vesicular membrane to be glycosylated? 

-Come from lysosome (lysosome comes from golgi) 

-protects it from acidic enymes

-When a vessicle comes off, it takes part of the golgi membrane (lysosme)

Why is it important for lysosmes to have a low pH?

to digest, and breakdown other molecules.

Name 2 main functions of Lysosome.

1) Autophagy: organelle turnover. 

2) to breakdown molecules

Define autophay and describe its process 

Destruciton of organelles and their replacement.

-fuses with ER-derived autophagic

vacuole--> autophagolysosome

-Conetents enzymatically digested--> residual body-->2 fates: 

i) released (excocytosis)

ii) retained-->lipofusin granules (storage spot)

too toxic to be released.

Plant Vacuole

fluid filled, membrane bound organelle

What is the tonoplast? Why is it important for the cell to function?

It is a vaculoar membrane

It contains active transport systems that generate a high [ion] concentration (which creates gradient for water to move in). (used in osmotic regulation)

Product of secretory pathway

Why is the storage of toxic componds especially important for a plant cell.

-applies turgor pressure

-supports soft tissues

-stretches cell wall during growth. 

The Function of the Cytoskeleton include:

a)Contractility and motility

b) Spatial Organization

c) Structural Support

d) Intracellular support

e) All of the Above

f) None of the above

e) All of the Above

Which of the following proteins contained a signal sequence when it is being translated?

a) Lysomal hydrolase

b) Lysomal membrane protein

c) impossible to know

d) a and b

a and b

Which components are most commonly associated with motor proteins?

a) actin microfilaments

b)intermediate microfilaments

c) microtubules

d) a + b

e) a +c

a+c

Describe the difference between an axonemal and cytoplasmic microtubule.

Axonemal: Highly organized and stable-

-part of structure involved in cell movement.

Cytoplasmic: lossly organized,dynamic

-located in cytosol

Why is polarity of MT's important?

direction of movement, 

-cell growth/shrinkage

What happens at the microtuble growing centre? 

central site of assembly of Microtubules.

In general, how is a microtubule situated within a cell?

minus end in center extends to plus end on the outside of cell

MT's undergo rapid dynamic assembly and disassembly

Dynamic instability: in vivo leads to rapid turnover of MT's w/in a cell

Catastrophe: shrikage occuring rapidly at plus end.

During vesicle trafficking, which of the following proteins functions closest to the fusion of the vesicle and target membranes? [1 mark]

A) Rabs

B) SNAREs

C) COPI

D) COPII

E) Myosin

B) SNAREs

12. What is a lipofuscin granule? [1 mark]

A) a form of secretory granule

B) the product of lysosomal fusion with the plasma membrane

C) an autophagolysosome

D) a residual body (formed during autophagy) that is retained within a cell

E) a residual body that is secreted by a cell

D) a residual body (formed during autophagy) that is retained within a cell

15. Compare and contrast the structures of microtubules and intermediate filaments.

- both are polymers of protein subunits

- both are non-branched, filamentous structures

- microtubules (MTs) are all made of (globular) tubulin αβ heterodimers; intermediate filaments (IFs) are made from a heterogeneous family of fibrous proteins

- MTs are polar; IFs are not

- IFs are very stable; MTs are dynamically unstable

- MTs have a larger diameter (25 nm) than IFs (10-12 nm)

- MTs support motor-based transport; IFs do not

Describe the difference between the 2 classes of

Motor Associated Proteins (MAPs)

1) Non-motor: In cytosol, organized in microtubles

2) Motor: transports materials 

i) Kinesin

ii)Dynein 

-use ATP to generate force

Toward which end of the microtuble is dyenin directed ?

Minus end directed, facing nucleus.

microtubule involed in movement

Axon walks toward the middle.

A synaptic vesicle is being transported down an axon to a distant synapse. Which type of MAP is most likey powering this transport?

a) Dynenin

b) Tau neurons

c) Myosin via interaction with actin

d) Kinesin

d) Kinesin

Are intermediate filaments polar? Explain.

monomers are aligned; IF dimers are polar with different N-and C- termini 

dimers associate anti-parellel; assembled filaments are not polar. 

Which of following is the most stable cytoskeletal component?

a) microtubules

b) Intermediate Filaments

c) Microfilaments

b)  Intermediate Filaments

What is the primary function of intermediate filaments.

provide structural support and mechanical strength. 

fiburous proteins contain centr alpha helical domain.

5 classes (I-V) 

-keratin:epithelial cells

-neurofilaments:neurons

-Lamins: nucleus of all cells.

Rank thefollowing cytoskeletal elements from largest to smallest: 

intermediate filaments, microtubules, microfilaments.

microtubules>intermediate filaments>microfilaments

Name the individual molecules that make up microfilaments.

Polymer of protein actin(compact)

Polypeptide = 42Kda, binds to ATP

-Individual molecules: G-actin (globular)

Polymerized microfilament: F-actin 

What are the primary functions of microfilaments?

-maintanence of cell shape 

-cell movement

-Cytokinesis

-Muscle contraction

True or False:

During F-actin microfilament assembly, elongation occurs at both ends of the growing filament. 

True:

Elongation is fast, occurs at both ends. 

faster at + end

What is F-actin? 

Monomers that are incorporated into the filament in same orientation

It is polar.

Nuclear Lamina

• Thin meshwork of filamentous proteins

-lamins (intermediate filaments) 

• bound to inner surface of NE 
• Provides structural support for NE 
• attachment sites for chromatin  

Nuclear Envelope

2 parallel phosolipid bilayers

• outer membrane binds ribsomes and is continuous with the membrane of membrane of the rough ER
• inner membrane 

-bears integral proteins, which connect the nuclear lamina

Function of the Nuclear Envolope: 

-seperates nuclear content from cytoplasm 

-seperates trascrciption/translation

-Selective barrier

-allows limited movemtn of molecules between nucleus and cytoplasm.

-suppoted by nuclear lamina

What is the difference between IFs, microtubules and F-actin? 

F-actin networks can be highly branched.

Function of Nucleus:

• Storage, replication and repair of gentic material
• Expression of genetic material
• Transcription of mRNA, tRNA and rRNA

        - splicing

• ribosome biosynthesis

Nucleus Structure:

• Nucrlear Envelope

-nuclear membrane

-nuclear pores

-nuclear lamina

• Nuclear Contents: chromatin, nucleoplasm, nuclear matrix, nucleolus. 

Myosin is an F-actin associated Motor Protein

-large family of proteins, use ATP

-most move toward plus end of microfilament

-divided into 2 broad groups

1) conventional myosins:

-typeII 

-priamry motor for muscle contraction

2) unconventional myosins:

-type I, type III-XVIII

Arp 2/3 complex

The cooridinated activity of actin-binding proteins control microfilaments forming lamellipodium to allow directed movement of cells.

True or false

Microtubule and microfilament based motors are both involved in active transport

False

Microtubule and microfilament based motors are both involved in vesicular transport

Nuclear Pores

• gateways between cytoplasm and nucleoplasm
• 3000-4000 pores/nucleus
• inner and oiter membrane fuse--> pores 
• Pores complain Nuclear Pore complex 

Nuclear Pore Complex 

• composed of nucleoporins
• octagonal symmetry
  
• fits into pore
• projects into cytoplasm & nucleoplasm
• Central channel lined with the filaments of NUPs

Function of NPC

• passive diffusion of molecules smaller than 50kDa or 9nm
• Regulated movemtn of large molecules
• regulated movement of protiens into the nucleus requires a 

nuclear localization signal

NLS= short stretch of positively charged amino acids within the proteins. 

Cellular function is acutely dependent upon nuclear import and export 

- nucleocytoplasmic traffiking 

• Nucleotides 
• Structural - lamins & nuclear matrix proteins
• DNA: packaging proteins
• Proteins for RNA processing and export
• Proteins for ribosome synthesis and export. 

Function of the Nucleolus

• Ribosome biogeneis

-rRNA synthesis

-rRNA processing

-assembly of subunits

-40s and 60s subunits are exported to cytoplasm

• tRNA synthesis