BIO 151 Cytoskeleton and Muscle Contraction Unit 1 Week 2

Three types of cell junctions are common in epithelial tissues...

Tight Junctions, Desmosomes, and Gap Junctions.

Animal cells have a(n)...

Extracellular Matrix (ECM).

Desmosomes...

(anchoring junctions) fasten cells together into strong sheets.

Gap junctions...

(communicating junctions) provide cytoplasmic channels between adjacent cells.

Part C - Role of the eukaryotic cytoskeleton The cytoskeleton of a eukaryotic cell plays a major role in organizing the structures and activities of the cell. The cytoskeleton consists of three main types of fibers: microfilaments, intermediate filaments, and microtubules. The three types of fiber differ in size, composition, and the functions they perform in the cell. Diagram showing the structure of the cytoskeleton including microfilaments, intermediate filament, and microtubule Drag the terms on the left to the appropriate blanks in the sentences on the right. Terms can be used once, more than once, or not at all.

1. In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules. 2. Many cell organelles, most notably the nucleus, are anchored by intermediate filaments which are assembled from a diverse class of proteins. 3. Centrosomes are sites where protein dimers assemble into microtubules. 4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfilaments. 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments. 6. During muscle contractions, myosin motor proteins move across tracks of microfilaments.

Microfilaments form a...

3-D network called the cortex just inside the plasma membrane to help support the cell's shape.

Microfilaments

Also called actin filaments, are the thinnest components.

The primary role of _____ is to bind animal cells together.

Desmosomes

How does dynein "walking" moves flagella and cilia?

Dynein arms alternately grab, move, and release the outer microtubules Protein cross-links limit sliding. Forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum

Intermediate filaments

Fibers with diameters in a middle range.

_____ aid in the coordination of the activities of adjacent animal cells.

Gap (communicating) junctions

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through _____.

Gap junctions

Microtubules have...

Hollow tubes, 25 nm with 15-nm lumen, and tubulin, a dimer consisting of alpha-tubulin and beta-tubulin.

Which cell junctions form a barrier to the passage of materials?

Tight Junctions

Three main types of fibers make up the cytoskeleton

Microtubules, Microfilaments, Intermediate filaments

Cilia and flagella move due to the interaction of the cytoskeleton with which of the following?

Motor proteins

Glycolysis and aerobic respiration are involved in...

Muscle contraction.

Which of the following is present in a prokaryotic cell?

Ribosomes

Microtubules

The thickest of the three components of the cytoskeleton.

The sacromere is bordered by...

Z lines where the actin attaches.

In animal cells, microtubules grow out from...

a centrosome near the nucleus.

Cilia and flagella share...

a common structure.

Common structure of cilia and flagella...

a core of microtubules sheathed by the plasma membrane.

At rest, a muscle fiber only contains enough ATP for...

a few contractions.

Calcium is released from the Sarcoplasmic Reticulum (SR) when...

a muscle cell receives the signal to contract...

The sacromere length decreases when...

a muscle contracts.

Part A - Animal cell structures and functions To understand how cells function as the fundamental unit of life, you must first become familiar with the individual roles of the cellular structures and organelles. Drag the labels on the left onto the diagram of the animal cell to correctly identify the function performed by each cellular structure.

a-synthesizes lipids b-assembles ribosomes c-defines cell shape d-produces secretory proteins e-modifies and sorts proteins f-digests proteins g-generates ATP

Muscle cells are made of...

actin and myosin.

Cytoplasmic streaming in plant cells is mediated by...

actin tracks and myosin motors.

The stimulus leading to contraction of a muscle fiber is a(n)...

action potential in a motor neuron that makes a synapse with the muscle fiber.

The structural role of microfilaments is to...

bear tension, resisting pulling forces within the cell.

Cilia and flagella differ in their...

beating patterns.

Motor proteins "walk" vesicles...

along cytoskeletal fibers.

Localized contraction brought about by actin and myosin also drives...

amoeboid movement.

Animal cells lack cell walls but are covered by...

an elaborate extracellular matrix (ECM).

Muscles allow...

animals to move.

The muscle contraction ends when...

calcium is pumped back into the ER.

The action potential causes the ER/SR to release...

calcium which triggers muscle contraction...

In animal cells, the centrosome has a pair of...

centrioles, each with nine triplets of microtubules arranged in a ring.

Animal cells have unique organelles called __________ that are composed of structures called __________.

centrosomes; centrioles

Desmosomes link cells together and...

connect to the cytoskeleton inside the cell.

When myosin binds to the actin...

contraction occurs.

Tropomyosin and troponin prevent muscle contraction by...

covering the myosin binding site on actin.

Motor protein called dynein...

drives the bending movements of a cilium or flagellum.

The cellulose is secreted outside the plant cell membrane via...

exocytosis.

Cells crawl along a surface by...

extending pseudopodia (cellular extensions) and moving toward them.

Plant cell walls are...

extracellular components made of cellulose.

Intermediate filaments are...

fibrous proteins coiled into cables, 8-12 nm, and are one of several different proteins.

Microtubules control the beating of...

flagella and cilia, microtubule-containing extensions that project from some cells.

Tight junctions prevent...

fluid from moving across a layer of cells.

The ECM is made up of...

glycoproteins such as collagen, proteoglycans, and fibronectin.

Microfilaments

help maintain cell shape, muscle contraction, cell motility (phagocytosis).

The network of fibers that organizes structures and activities in a cell __________.

is the cytoskeleton

Cell junctions...

link two adjacent cells.

Intermediate filaments help...

maintain cell shape, anchor the nucleus and form the nuclear lamina (inside perimeter of nucleus).

Microtubules help...

maintain cell shape, chromosome movement during cell division, movement of organelles in the cell and cell motility (cilia and flagella).

At tight junctions...

membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid.

Dynein and kinesin are...

microtubule (MT) motor proteins that carry cargo along the MT cytoskeleton.

The cilia and flagella of eukaryotic cells are composed of _____.

microtubules

Tight junctions prevent...

molecules from moving between cells.

Creatine phosphate and glycogen provide resources to make...

more ATP for further muscle contraction.

The cytoskeleton interacts with...

motor proteins to produce motility.

Dynein and microtubules help...

move a flagellum.

The sliding filament model explains...

muscle contraction.

Microfilaments that function in cellular motility contain the protein...

myosin in addition to actin.

Thicker filaments composed of...

myosin interdigitate with the thinner actin fibers.

In muscle cells, thousands of actin filaments are arranged...

parallel to one another.

Middle lamella is rich in...

pectins and glues adjacent cells together.

Dye injected into a plant cell might be able to enter an adjacent cell through __________.

plasmodesmata

Cell junctions in plant cells are called __________, and communicating junctions in animal cells are called __________.

plasmodesmata; gap junctions

Part B - Comparing eukaryotic and prokaryotic cells Two fundamental types of cells are known to exist in nature: prokaryotic cells and eukaryotic cells (like the one shown in the Tour of an Animal Cell animation). Both prokaryotic and eukaryotic cells carry out all of the processes necessary for life, but they differ in some important ways. In this activity, you will identify which cell structures are found only in prokaryotic cells, only in eukaryotic cells, or in both types of cells. Drag each cell structure to the appropriate bin.

prokaryotic only: nucleoid eukaryotic only: nucleolus, lysosome, mitochondria both: plasma membrane, ribosomes, flagelia

Inside the cell, vesicles can travel along tracks...

provided by the cytoskeleton.

ECM proteins bind to...

receptor proteins in the plasma membrane called integrins.

Ameboid movement is carried out by...

reorganizing the microfilaments.

According to the sliding-filament model, thin and thick filaments...

slide past each other longitudinally, powered by the myosin molecules.

Gap junctions allow...

small molecules to pass between adjacent cells.

Skeletal muscle is called...

striated muscle because of its appearance.

A basal body that anchors...

the cilium or flagellum.

Bundles of microfilaments make up...

the core of microvilli of intestinal cells.

The sarcomere is...

the functional unit of the a muscle.

Acetylcholine depolarizes...

the muscle, causing it to produce an action potential.

Binding of a new ATP molecule releases...

the myosin head from actin.

The synaptic terminal of the motor neuron releases...

the neurotransmitter acetylcholine.

The cytoskeleton helps...

to support the cell and maintain its shape.

Microfilaments are...

two intertwined strands of actin, 7 nm, and actin.

Cell motility, which includes changes both in cell location and in the movement of cell parts, requires interactions of the cytoskeleton __________.

with motor proteins