Cell Biology

Dr. Campbell Bisc 315

What is intracellular transport?

Movement in/out of organelles requires crossing membranes.

What is the Nucleus?

Contains main genome site of DNA, RNA synthesis

What is Endoplasmic Reticulum?

Synthesis of most lipid, synthesis of proteins for distribution to many organelles and to the plasma membrane.

What is the Golgi Apparatus?

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

What are a Lysosomes?

Intercellular Degradation

What are an Endosomes?

Sorting of endocytosis material

How do materials move within a cell?

* Simple diffusion across the lipid bilayer
* Carrier or Channel transport proteins
* The transport of proteins across membranes requires different mechanisms

How are cell proteins made?

* Are coded by nuclear DNA
* Are synthesized in cytosol
* Remain in the cytosol, but some are transported from cytosol to organelles thus they must cross membranes

How many proteins are made in the nucleus?

NONE

What are the three types of Intracellular Transport?

* Transport through nuclear pores
* Transport across membrane
* Transport by vesicles

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What is transported through the nuclear pore complex?

\-Proteins containing nuclear localization signals are imported

\-RNA molecules are exported

How is the nuclear pore complex regulated?

the nuclear pore gate expands and shrinks to allow specific molecules in. Nuclear localization signals also only allows specific proteins in.

What is transport through nuclear pores?

molecule transport from the cytosol to the nucleus

What is transportation across the membrane?

molecule transport from the cytosol to the mitochondria/chloroplasts and Endoplasmic reticulum

How do proteins enter the chloroplasts/mitochondria in transportation across the membrane?

Proteins are unfolded and refolded inside the organelle using ATP and Molecular chaperones

How is transport across the membrane regulated?

It is regulated by signal sequences that are short sequences of amino acids and they get cleaved at their destination

What is a major cause of some human diseases?

Dysfunction of the nuclear pore complex.

What is transported in membrane transportation of cytosol to the ER?

mRNA and Ribosomes are transported to the ER surface.

What is endoplasmic reticulum and what are the two types?

Endoplasmic reticulum is a network of membranes.

\-Rough ER - ribosomes attached to the surface of the membrane

\-Smooth ER - absence of ribosomes

How is the signal sequence cleaved inside of the ER?

polypeptide is inserted in the ER Lumen and the signal sequence is cleaved by peptidase.

Where are most cell lipids synthesized?

Most cell lipids are synthesized in the endoplasmic reticulum.

Where do disulfide bonds form?

Disulfide bonds exclusively form in the endoplasmic reticulum (they never form in the cytosol)

What is transportation by vesicles?

Process where molecules from the ER are transported to the Golgi and then to either the plasma membrane or Lysosome.

What are Vesicles?

small membrane enclosed cytoplasmic structures

What is the unfolded protein response?

the cells' way of maintaining the balance of protein folding in the endoplasmic reticulum

What are some of the ways the unfolded protein response use to handle more protein folding?

\-addition ER is produced

\-addition molecular chaperones produced

\-addition protein synthesis inhibited

\-if UPR is unable to keep up it leads to apoptosis

What kind of process is vesicle transport?

Active transport

What is Endocytosis?

Bringing material into the cell via vesicles, uptake of material into the cell

What is exocytosis?

Taking materials out of the cell via vesicles; molecules can be secreted from the cells using vesicles.

What determines the cellular destination of proteins inside the cell?

The signal Sequence

Why don’t cytosolic proteins have signal sequences?

Because they arent being transported to another location

What is an Endosome

Membrane bound compartment that transports between plasma membrane and lysosome.

What is Autophagy?

degrades damaged cellular components, or under starvation conditions

What is the lysosome?

Organelles involved in digestion or degradation of molecule.

What kind of enzymes does the lysosomes carry?

They contain hydrolytic enzymes (acid hydrolases) with acidic pH

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What is the cytoskeleton?

Network of protein filaments extending throughout the cell and only found in eukaryotic cells.

What are the three types of protein filaments forming the cytoskeleton?

* microtubules
* actin filaments
* intermediate filaments

What are intermediate filaments?

Intermediate in size, heterogenous family of proteins that provides mechanical strength.

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made of monomers twisted together to form a rope like structure.

What is Keratin filaments?

class of intermediate filament found in epithelial cells

What is nuclear lamins?

a type of intermediate that strengthens the nuclear envelope

What is the Basil Lamina?

Thin sheet of tissue supporting epithelial cells

What are microtubules?

A type of protein filament that is long, rigid, hollow tubes.

Made of Tubulin protein subunits.

Often rapidly assembled and disassembled.

What’s the difference between the plus end and minus end of microtubules?

\-the plus end is Net growing activity; associated with assembly

\-the minus end is Net shrinking activity; associated with disassembly

What does GTP and GDP have to do with Microtubules?

Tubulin subunits are bound by GTP during assembly and bound by GDP during disassembly.

What are some examples of some stable microtubules?

Cilia- the surface of human respiratory

Flagellum- On sperm cells

What are actin filaments?

Most abundant cytoskeleton proteins

Actin filaments bind with various proteins that give the filaments bind with various protein that gives the filaments a large range of functions.

* microvilli lining of intestine
* ability to move or change shapes
* assist in cell division

What are motor proteins?

Special proteins able to use energy from ATP hydrolysis to generate motion.

What are the three types of motor proteins?

\-Kinesins

\-Dyneins

\-Myosin

What is a Myosin?

A type of motor protein that uses ATP to move along the actin filament in muscle cells.

What happens when myosin lacks ATP?

Myosin will not move (the cause of rigor mortis)

What motor protein composes the contractile ring along with the Actin filament?

Myosin

How do chloroplasts is arranged in Low light and High light environments?

High Light - chloroplasts are arranged to absorb max amount of sunlight.

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Low Light - Chloroplasts are rotated to sides to hide from sunlight

Which direction do kinesins move towards? (+ end or - end)

The plus end

Which direction do dyneins move towards? (+ end or - end)

The minus end

What is the function of Kinesins and Dyneins?

To transport organelles and vesicles along microtubules

What are the important signaling molecules?

\-Proteins/Peptides

\-Nucleotides

\-Lipids

\-Ions

\-Amino Acids

\-Dissolved Gases

What are the two types of cell communication?

Cell

What is transduction?

Information changes from one form to another form. (Mechanical, chemical, electrical, etc.)

What are the steps of Cell signaling?

1- Perception of signal by receptor

2- Transmission of signal into cell

3- Distribution of message within cell

4- Response by Cell

What is Cell to Cell Communication?

Molecule produced/released by one cell (signaling cell and detected/received by another cell

What must the target cell have in order to receive the signal?

The target cells must have the proper receptor protein in order to receive the signals.

Where are the receptors on a cell located?

on the cell surface or inside the cell

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Cells have many different receptors and respond to many different signals.

What are the 5 forms of cell signaling inside animal cells?

\-Autocrine

\-Contact-Dependent

\-Endocrine

\-Paracrine

\-Synaptic

What is the Endocrine system?

Tissues that release hormones (signal molecule)

travels through the bloodstream and exits to enter the cell.

What is the Paracrine system?

Localized cell signaling, cell produces a signal to induce changes in nearby cells.

What is the Synaptic System?

releases chemicals into the synapse and attack to specific receptors on the target cell

\-Nerve cells

What is the Contact-Dependent system?

Signaling cell in direct contact with its target cell.

What is the Autocrine System?

Signal acts on the same cell that releases signal.

\-signaling to itself

What functions does cell signaling provide?

\-must receive certain signals just to survive

\-To indicate to the cell, it is time to grow and divide

\-To inform the cell that differentiation will occur

\-To die (Apoptosis)

What is the difference between the binding mechanism of signal molecules that are unable to cross the cell membrane and those that can cross it, and what types of receptors do they bind to in each case?

Most signal molecules are unable to cross the membrane, so they bind to cell-surface receptors, but some signal molecules are able to diffuse across the membrane and bind to intracellular receptors.

What are the 3 classes of cell surface receptors?

Ion-Channel-Coupled Receptor

Enzyme-Coupled Receptors

G-Protein-Coupled Receptor

What is a G-Protein?

G-proteins are important molecules that help transmit signals from the outside of a cell to the inside of a cell. They act as a kind of messenger, relaying information from hormones or other signaling molecules outside the cell to the cellular machinery inside the cell.

What are the 3 parts of a G-protein-coupled receptor?

\-G-protein

\-Receptor protein

\-target protein

whats the difference between a G-Protein when a signal molecule is present and absent?

* Without a signal molecule, the G protein is inactive and bonded to a GDP
* With a signal molecule, the G protein is activated and bonded to a GTP

What is the most common target for G-proteins?

Adenylyl cyclase

What does Adenylyl cyclase catalyze?

Coversion of ATP → cAMP

What is cAMP?

Major second messenger (the intracellular molecule that regulates HR, glycogen, and fat breakdown)

What are extracellular signals?

first messenger that can alter protein activity thus altering cell behavior that generate intracellular signals (second messengers)

What are signal Cascades?

Amplified and distributed intracellular signals

What is a second messenger?

Small molecule formed/released in cytosol in response to an extracellular signal; relay the signal into the cell interior.

what are the 4 types of Second Messengers?

* cyclic nucleotides
* lipid derived
* Ca2+
* NO (nitric oxide)

What is an example of cyclic nucleotides?

Adenylate cyclase that modifies ATP to form cAMP

What is an example of lipid derived second messenger?

Phospholipase -C

\-membrane bound enzyme

\-hydrolyses certain PM lipids

\-produces IP3 + DAG

What is IP3 and DAG?

IP3: Inositol-Triphosphate

DAG: Diacylglycerol

secondary messengers from phospholipase-c

How can a cell regulate Ca2+ so that it can be recognized as a second messenger and not background noise?

\-moving calcium ions of the cells

\-Sequester (tie up calcium ions) in organelle

\-bind to cytosolic molecule

What is an example of changes in Ca2+ concentration?

In egg cell following fertilization Ca2 initiates development.

What are some examples of NO signaling and what do they do?

\-ex. Nitroglycerin dilates blood vessels, increases blood flow

\-ex. Slidenail (Viagra)l dilates blood vessel, increases blood flow

What is NO and how can it get into the cell?

NO is a gas; a short half-life; acts locally and diffuses across membranes

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important signal mechanism to warn of pathogen attacks

What are often involved in signaling pathways?

Kinases

Signaling pathways are often _____ __and__ ______ integrates.

Complex and integrated

What is an example of slow response in extracellular signals?

Altered gene expressions

What is an example of rapid response in extracellular signals?

Modification of activity of existing proteins

What are the two phases of the cell cycle?

Growth and division

What are the 3 Steps of the cell cycle?

\-Cell growth and replication

\-Chromosome segregation

\-cell division

What occurs when cell reproduce?

DNA replication

protein synthesis

membrane synthesis

distribution of the cell contents

What are the 4 phases of the cell cycle and which ones are associated with growth phase/ interphase and division phase/mitosis?

G1, S, G2, M

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G1/G2/S = Growth Phase

M = Mitosis

What happens in G1 phase?

New daughter cells begin life, cell growth increases cytoplasmic content

What happens in S phase?

DNA replication, occurs only after receipt of the proper signal by the cell

What happens in the G2 Phase?

Cell growth preparation for division spindle fibers synthesized.

What happens in the M Phase?

Nuclear division - mitosis & meiosis

Cytokinesis - cytoplasmic division