Cellular & Molecular Biology - Chapter 17

The Cytoskeleton

• Gives cell its ______

• Allows cell to _____

• Allows _______ of internal organelles

Shape, move, organization

Thick and tough → meant for a physical beating

Intermediate filaments

• Thick, but hollow (not the strongest thing because they’re hollow)

• Gets things from one place to another

• Made out of proteins

Microtubules

• Most versatile

• Skeletal muscle

• Can become anything depending on cell signaling

Actin filaments

Withstand mechanical stress when cells are stretched

Intermediate filaments

Toughest and most durable cytoskeletal filaments

Intermediate filaments

Surround nucleus and extend to periphery

Intermediate filaments

Anchored to plasma membrane at cell-cell junctions (Desmosomes)

Intermediate filaments

Lots of quaternary structures (taking a lot of proteins and winding them together)

Intermediate filaments

• big

• strong

• thick

• solid

Intermediate filaments

Cells which endure more mechanical stress have more _______ (think muscles, skin, long thin nerve cells)

• Like reinforced concrete (has steel bars running through)

Filaments

Most diverse family of intermediate filaments

Keratin

Important for holding together different layers of skin

Keratin

Make up nails, hair, and skin (i.e., epithelial cells)

Keratin

A disease where cells aren’t glued together well due to ineffective keratin (skin comes off easily and creates blisters)

Epidermolysis bullosa simplex

_____ can break when skin is rubbed too much

• Can lead to blisters

Keratin

Provides structure to nucleus

Nuclear lamina

Intermediate filament class found in nucleus

Nuclear lamina

A disease where the nuclear lamina is ineffective/absent, causing DNA deterioration

Progeria

Defects in nuclear lamina can cause “progeria”, a rare premature ______ disorder

Aging

Protecting nuclear DNA

Nuclear lamina

Found inside of nucleus and gives strength

Nuclear lamina

What is the major microtubule-organizing center of the cell?

Centrosome

• Have polarity (a positive and negative end)

  • Positive end changes more

Microtubules

Microtubules have a ______: plus end and minus end

Direction

Microtubules are ____ and these have directions (two!)

Roads

In microtubules, the area near the centrosome (deep in cell by nucleus) is the?

Minus end (negative end)

In microtubules, the area away from the centrosome is the?

Plus end (positive end)

_________ grow and shrink independent of their neighbors.

Microtubules

Stabilizes microtubules and makes them grow in a nonrandom fashion (ex. during mitosis)

Capping proteins

Capping leads to ________ of the cell.

Polarization

Many chemo drugs target _____ to prevent cell division

Microtubules

Helps organize the cell, allowing transport of cargo

Microtubules

All microtubules in a nerve cell point in the ________, allowing correct movement of materials around the cell.

Same direction

The ____ end of a microtubule is toward the axon terminal, which is OUT!

Plus

The ____ end of a microtubule is deep in the cell near the cell body.

Minus

Proteins that “walk” by binding & unbinding to ATP

Walking proteins

Travel along microtubule in a single direction

Motor proteins

What are the two types of walking proteins?

Kinesins and dyneins

In order for walking proteins to walk, what has to happen?

They bind to ATP and change shape

Walking proteins can walk in ___ direction and can’t turn around.

One

What type of walking protein goes towards the positive/plus end?

Kinesins

What type of walking protein goes towards the negative/minus end?

Dyneins

When it “wakes up”, it hijacks walking proteins to walk to the mouth from nerve cells

Herpes virus

What can be involved in disease processes?

Motor proteins

Allow eukaryotic cells to move fluid over their surface

Cilia

Helps propel sperm/protozoa through fluid

Flagella

Cilium and flagellum beats by performing repetitive rounds of a “________”

Power stroke

In the core of cilium and flagellum you have _____.

Microtubules

Diseases caused by ineffective/absent cilia

Ciliopathies

Cilia don’t properly move fluid which can create cysts in the kidneys

Cystic kidneys

Intermediate filaments, actin filaments, and microtubules are ______ one another and working together.

Physically touching

What allows cells to adopt a variety of shapes?

Actin filaments

Thin flexible protein threads

Actin filaments

What also has polarity - plus end and minus end (Like microtubules)?

Actin filaments

Thinner, shorter & more flexible than microtubules

Actin filaments

How does actin filaments know what to do?

Cell signaling

Depending on _______, that’s how we determine what we make actin into.

Cell signaling

Make up the cell cortex → provides cells their shape!

Actin filaments

Little feet that help the cell move around by pulling it around

Lamellipodium

• Allow the cell to grab onto the Extracellular Matrix

• Can act as signaling proteins

Integrins

Cell crawling relies on _____.

Actin filaments

Transmembrane proteins which binds to the extracellular matrix

Integrins

What helps cells grab onto extracellular matrix?

Integrins

Actin helps make ________, which helps cells crawl around throughout body.

Lamellipodium

How does the cell move around?

Crawls on extracellular matrix

In order to move around, we have the foot, ________, which is made out of actin.

Lamellipodium

Walking proteins used for muscle contraction

Myosin

Multiple come together to form myosin filaments that look like double headed arrows

Myosin

What is the walking protein for actin?

Myosin

What is/are the walking protein(s) for microtubules?

Dyneins and kinesins

_______ takes vesicles and walks on actin.

Myosin

In order for muscles to work, what do you need?

Actin and myosin

______ is the walking protein and in muscle tissues (contractile cells), they can take a lot of myosin and start weaving them together to make a __________.

Myosin, double ended arrow

Explain muscle contraction and how myosin is involved.

Myosins put together walking in different ways which takes either side of the cell and pulls it which causes the shortening of the cell (muscle contraction)

Contraction of a muscle is due to simultaneous _________ of all the sarcomeres.

Shortening

Contractile unit of muscle made of myosin and actin

Sacromeres

What happens when ATP binds?

Myosin lets go of actin

ATP binds and myosin _____ actin.

Releases

If you don’t have any ATP in your cell, what happens?

Myosin and actin remain connected and that causes rigor mortis (rigid muscles)

Body stiffens because there is no ATP and myosin cannot let go of actin

Rigor mortis

Once the ATP does bind, you can then break ATP (hydrolyze ATP) to get energy and that will cause what?

Allow myosin to walk

______ is released in response to electrical stimulation of the neuromuscular junction.

Calcium

What causes muscle contraction?

Calcium release into the cell

_______ tells neurons to release neurotransmitters.

Calcium

Explain what causes calcium release regarding muscle contraction.

An action potential will come down (from different neuron) and when that neuron tells the muscle to contract, that will cause calcium release