Term
| What are the four main functions of the cytoskeleton? |
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Definition
1. Provies support
2. Provides mobility
3. Mediates organelle movement
4. Regulates biochemical activities |
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Term
| What are the three main components of the cytoskeleton? |
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Definition
1. Microtubules
2. Microfilaments
3. Intermediate filaments |
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Term
| How are microtubules formed? Where are they made? |
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Definition
Microtubules are formed from alpha and beta subunits of a protein called tubulin. First, one of each subunit attaches together and then they bind to other pairs in a spiral to create the wall of a hollow tube. They resist compression by polymerizing and depolymerizing.
They are created in the centrosome, made up of two centrioles perpendicular to each other. A centriole is a circle of nine sets of three microtubules. |
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Term
| What are cilia and flagella? What are they made of? How do they work? |
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Definition
Cilia and falagella are like feet which give movement to a cell. Cilia are ussually present in large numbers and shorter where as there are ussually only one or two long flagella per cell.
They are ech comprised of nine doublets of microtubules circling around 2 seperate microtubules. This is called a "9+2" structure. Each doublet or microtubules is connected through radial spokes. Dynein, a protein, also connects each doublet to each other and when activated by ATP, causes the doublets to bend and the cilia or flagella to move. A basal bodies (identical to a centriole) anchors the appendage to the rest of the cell.
Video: http://programs.northlandcollege.edu/biology/biology1111/animations/flagellum.html |
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Term
| What are microfilaments? What is their purpose? |
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Definition
| Microfilaments are polymers of the globular protein called actin. They resist tension (pulling). They are a part of muscle contraction, cell division and cytoplasmic streaming. |
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Term
| How does a muscle contract? |
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Definition
| Actin (thin) and myosin (thick) filaments are arranged parallel to each other with actin being to the left and right, above and below, myosin. When a muscle contract, the myosin uses its "arms" to pull the actin filaments closer together. |
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Term
| What is cytoplasmic streaming? What is its purpose? |
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Definition
| Cytoplasmic streaming is when a gel state develops around the perimeter of a plant cell, which causes the cytosol to rush around the central vacuole. It helps large cells to distribute organelles. |
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Term
| How does a cell move through gel-sol interactions? What is one type of cell where this is common? |
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Definition
When a gel state develops due to a build up of microfilaments on one side of a cell, the cytosol strives to get to a sol state on the other side of the cell. This creates a pseudopodium, a buldge, on the sol side of the cell. Surface proteins then attach to the surface on that side of the cell and microfilaments contract on the gel side of the cell to release surface attachment and the cell moves.
This commonly happens in amoeboid (ex. white blood cell) movement. |
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Term
| What are microvilli? What is their purpose? What are they made up of? |
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Definition
| Microvilli are "branches" out of the cell which increases surface area. They are made up of microfilaments. |
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Term
| What are intermediate filaments? What are they between? What purpose do they serve? |
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Definition
Intermediate filaments are composed of fibrous (as opposed to globular) proteins of the keratin family. They are called intermediate because their diameter is inbetween that of microfilaments (smaller) and microtubules (larger). They maintain cell shape, anchor the cell and form the nuclear lamina.
They help connect microfilaments and microtubules. They resist tension and don't disassemble as much as MF and MT. They also form the "cage" (lamina) of the nucleus. |
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Term
| Name three types of intercellular connections in animal cells. What are their functions? |
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Definition
1. Gap junctions are permeable connections. Six connexin proteins form a connexon. A connexon from each cell combines and a gap junction is formed.
2. Tight junctions are non-permeable connections. Proteins "seal" the two cells together so that nothing can go inbetween them.
3. Desmoses are non-permeable connections. They can be thought of more as connecting points between cells, rather than sealing two cell faces together. |
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Term
| What is the intercellular connection in plant cells? |
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Definition
| Plasmodesmata in cell walls connect plant cells to each other. They are capable of changing size to accomodate different loads. The secondary cell wall is attached to the primary cell wall which is attached to the middle lamella. The middle lamella is attached to the primary cell wall of cell 2, which is attached to the secondary cell wall of plant 2, which then leads to the interior of cell 2. |
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Term
| What is a phospholipid? What is the difference between a saturated and unsaturated one? Where are they commonly found? Is it polar or unpolar? |
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Definition
A phospholipid is a glycerol molecule bound through dehydration reactions to two hydrocarbon tails and a polar head.
In saturated phospholipids, all carbons are sp3 hybridized. In unsaturated phospolipids, there is a C=C bond, which causes a kink in the chain. Plants tend to have more unsaturated phospholipids to avoid solidifying when it gets cold, because they can't move.
Phospholipids are the main component of the cell membrane.
Phospholipids are both polar (the head) and nonp0lar (the tails). |
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Term
| What happens when phospolipids micelle? |
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Definition
| When phospolipids micelle, they form a circle by pointing their hydrophobic tails toward each other, away from the polar solvent. |
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Term
| What role does cholesterol play in the plasma membrane? |
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Definition
Cholesterol regulates (buffers) the membrane, increasing fluidity at lower temperatures and decreasing it at higher temperatures. It does this by mediating phospolipid movement.
Phospholipids have a lot of lateral movement (back and forth) and occasional flip-flopping, where the tail and head switch momentarilly. |
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Term
| What is meant by "a mosaic of proteins"? What are different ways that proteins can be in the plasma membrane? |
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Definition
| A mosaic of proteins is when proteins are part of the plasma membrane. They can be peripheral (attached to the membrane), integral (partly inserted into the membrane) or transmembrane (going through the membrane). |
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Term
| Which type of molecules can cross the plasma membrane? |
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Definition
| Because of its non-polar innards, only hydrophopic (non-polar) molecules can cross through the plasma membrane unassisted. However, with the help of things like protein channels, which create a polar environment for polar molecules to pass through, hydrophillic material can enter and exit the cell as well. |
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Term
| What is the ECM? How do integrins relate? |
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Definition
The ECM is the extracellular matrix. Is is composed mainly of the protein callogen.
Fibronectin, a glycoprotein* found in the ECM, can bind to integrins, transmembrane proteins attached to intermediate filaments inside the cell, and communicate with the cell.
*Glycoprotein = protein + carbohydrate |
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