Biology 2.1 Exam 2

sarcoplasmic reticulum

Organelle of the muscle fiber that stores calcium.

Phospholipids

1. A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail ( amphipathic) 2. Essential for the cell because they are major constituents of cell membranes. 3. their structure proves a perfect example of how form fits function at the molecular level. 4. has two fatty acids attached to glycerol. The third hydroxyl group of glycerol is joined to a phosphate group, which has a negative electrical charge in the cell.

Cytoskeleton's Role in Eukaryotic

Plays a major role in organizing the structure and activities of the cell.

Plant cells (microfilaments)

1. Actin protein interactions contribute to cytoplasmic streaming, a circular flow of cytoplasm within cells. 2. this movement which is especially common in larger plant cells, speeds the movement of organelles and distribution of materials within the cell.

intermediate filaments function

1. Are very sturdy and they play an important role in reinforcing the shape of the cell and fixing the position of certain organelles. 2. the nucleus sits within a cage of intermediate filaments, fixed in the location by branches of filaments, fixed in location by branch of filaments that extend into the cytoplasm. 3. other intermediate filaments make up the lining of the interior of the nuclear envelope. 4. by supporting the cells shape it allows the cell to carry out its specific functions.

Cilia and Flagella

1. In eukaryotes, a specialized arrangement of microtubules is responsible for the beating of flagella and cilia. 2. Flagella and cilia are microtubule containing extensions that project from some cells. 3. Many unicellular eukaryotes are propelled through water by cilia or flagella. 4. when cilia or flagella extend from cells that are held in place as part of a tissue layer, they can move fluid over the surface of tissue 5. Motile cilia usually occur In large numbers on the cell surface. Cilia have alternating power and recovery strokes. 6. Flagella are usually limited to just one or few per cell, and they are longer than cilia. It has an undulating motion like the tail of a fish. 3. Flagella and cilia differ in beating patterns, length, number per cell, but they share a common structure, a group of microtubules sheathed in an extension of the plasma membrane.

Cytoskeleton function

1. Main function is to give mechanical support to the cell and to maintain the cells shape. 2. This is especially important in animal cells, that lack a cell wall.

Three types of molecular structures of the Cytoskeleton (Eukaryotic)

1. Microtubules 2. Microfilaments 3. Intermediate Filaments

Comparing microfilaments, microtubules, and intermediate filaments

1. Microtubules and microfilaments are consistent in diameter and composition in all eukaryotic cells. Intermediate filaments are only found in cells of some animals, and vertebrates. 2. Intermediate filaments are more permanent fixtures of cells than microfilaments and microtubules, which are often disassembled and reassembled in various parts of the cell. 3. Chemical treatments that remove microfilaments and microtubules from the cytoplasm of living cells leave a web of intermediate filaments that retain its original shape.

microtubule function

1. They shape and support the cell, and also serve as track along which organelles equipped with motor proteins can move. 2. They help guide vesicles from the ER to the Golgi apparatus and from the Golgi apparatus to the plasma membrane. 3. They're involved in the separation of chromosomes during cell division. 4. Microtubules function as tracks in the intracellular transport of membrane-bound vesicles and organelles, and this process is propelled by motor proteins such as dynein. Microtubules are cytoskeletal fibers that have an important role in the mitotic spindle during mitosis.

microfilament structural role

1. comparing to the compression- resisting role of microtubules, the structural role of microfilaments in the cytoskeleton to bear tension (pulling forces). 2. A 3D network formed by microfilaments just inside the plasma membrane helps support the cells shape.

Intermediate filament structure

1. each type is constructed from a particular molecular subunit belonging to a family of proteins whose members include keratins. 2. even when the cell dies the intermediate filaments will persist, for example the outer layer of our skin consists of dead skin cells full of keratin. 3. various intermediate filaments may function together as the permanent framework of the entire cell.

Bacterial Cells

They also have fibers that form a type of cytoskeleton, constructed of proteins similar to Eukaryotic ones.

Steroids

1. lipids characterized by a carbon skeleton consisting of four fused rings 2. cholesterol is a type of steroid, helps with stability in a membrane, a temperature buffer for both increase and decrease in temperature.

Microtubules in Animals

1. microtubules grow out of the centrosome, a region located near the nucleus. 2. They function as compression- resisting girders of the cytoskeleton. 3. Within the centrosome are centrioles, each are composed of nine sets of triplet microtubules arranged in a ring. 3. The centrosomes and centrioles help organize microtubule assembly in animal cells. Many eukaryotic cells lack these two structures.

microtubules

1. present in all eukaryotic cells 2. Hollow rods constructed from globular proteins called, tubulins. 3.Each tubulin protein is a dimer, which is a molecule made up off components. 4. The two components are two slightly different polypeptides, a-tubulin and b-tubulin. 5.microtubules grow in length by adding dimers, they can also disassemble and their tubules are used to build microtubules somewhere else in the cell. 6. The orientation of the tubulin dimers, two ends of a microtubule are slightly different, causes one end to accumulate or release tubulin dimers at a much higher rate than the other. This results in growing and shrinking during cellular activities.

Muscle Contraction: calcium

1. the concentration of calcium is low in cells 2. rare that calcium is exposed to the cytoplasm 3. calcium is stored in the smooth ER of a muscle cell, sarcoplasmic reticulum

Tropomyosin

1.A protein of muscle that forms a complex with troponin regulating the interaction of actin and myosin in muscular contraction. 2. blocks myosin binding site (reason behind why muscles aren't always in a contracted state) 3.

Troponin

1.A protein of muscle that together with tropomyosin forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction 2. Controls tropomyosin 3. Calcium binds with troponin which then allows the active site to be exposed leading to muscle contraction

Lipids

1.Compounds grouped together because of their hydrophobic behaviors due to its molecular structure. Although they have some polar bonds associated with oxygen lipids mostly consist of hydrocarbon regions. 2. fats, phospholipids, steroids

Dyneins

1.In cilia and flagella, a large motor protein extending from one microtubule doublet to the adjacent doublet. 2.ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and flagella. 3. a typical dynein has two feet that walk along the microtubule of the adjacent doublet using ATP for energy.

Muscle Contraction

1.Interactions between actin and myosin filaments of the sarcomere are responsible for. 2. When muscles contract they shorten and the cell then shortens when myosin interacts with actin. 3. The binding of ATP to the myosin head, the head releases from the thin filament. 4. Hydrolysis Reaction (exergonic) is used to recoil the myosin head ( high energy state) ATP is no longer attached because of the movement of the filaments

Muscle Cell

1.Muscle cell has fibers, fasciles= bundle of muscle cells. 2. Each muscle cell has multiple nuclei and filled with myofibrils. 3. the muscle fiber has nucleus pushed to the edge because of the myofibrils 4, myofibrils have thin filaments (actin) and thick filaments (myosin)

fluid mosaic model

1.The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids. 2. proteins are not randomly distributed in the membrane. 3. groups of proteins are associated in long lasting specialized patches, lipid rafts.

Cortex

1.The network formed by microfilaments just inside the plasma membrane gives the outer cytoplasmic layer of a cell. 2. semisolid consistency of a gel, in contrast to more fluid state of the interior cytoplasm

Cytoskeleton's Structure

1.The structure of the cytoskeleton is remarkable for its strength and resilience. Like a dome shaped tent, the cytoskeleton is stabilized by a balance between opposing forces exerted by its elements. 2. The cytoskeleton provides anchorage for many organelles and even cytosolic enzyme molecules. 3. It can be quickly dismantled in one part of the cell , and reassemble in a new location, changing the shape of the cell.

Fats

1.constructed of smaller molecules, glycerol and fatty acids. Glycerol is an alcohol each of its three carbons bears a hydroxyl group. A fatty acid is a long carbon skeleton. The carbon of one end is part of a carboxyl group, and the rest of the skeleton consists of a hydrocarbon chain ( non polar C-H bond reason for hydrophobic behaviors). 2. when constructing a fat, three fatty acid molecules are each joined to glycerol by an ester linkage, a bond formed by dehydration reaction between a hydroxyl group and carboxyl group. 3. also known as a triacylglycerol 4. saturated fatty acid= saturated with hydrogen. unsaturated fatty acid= has one or more double bond with fewer hydrogens.

amoeba (unicellular eukaryote) and white blood cells

1.localized contractions brought about n=by actin and myosin are in the ameboid crawling movement of the cells. 2. the cells crawl along a surface by extending cellular extensions called pseudopodia(foot) and moving toward them.

Intermediate filaments

1.their diameter is larger than the diameter of microfilaments but smaller than microtubules. 2. Only found in some animals, including vertebrates.

Microfilaments

1.thin solid rods. They are also called actin filaments because they are built from molecules of actin, a globular protein. 2. a microfilament is a twisted double chain of actin subunits. 3. besides occurring as linear filaments, microfilaments can form structural network when certain proteins bind along the side of such a filament and allow a new filament to extend as a branch. 4. present in all eukaryotic cells. 5. Responsible for cytokinesis (division)

Basal Body

A eukaryotic cell organelle consisting of a 9 + 0 arrangement of microtubule triplets; anchors the microtubule assembly of a cilium or flagellum; structurally identical to a centriole.

Cytoskeleton

A network of fibers extending throughout the cytoplasm

Cell Motility

Changes in the cell location, and movement of cell parts. Generally requires the interaction f the cytoskeleton with motor proteins.

microfilaments role in cell motility

Thousands of actin filaments and thicker filaments made of the protein, Myosin, interact to cause contraction of muscle cells.

Microfilaments in animal cells

Such as the nutrient absorbing intestinal cells, bundles of microfilaments make up the core of microvilli, delicate projections that increase the cells surface area.

Plus End

The term used to describe the end of the microtubule that can accumulate or release tubulin dimers at a higher rate.

Motor Proteins

There are many examples: 1. cytoskeletal elements and motor proteins work together with the plasma membrane molecules allow whole cells to move along fibers outside the cell. 2. inside the cell, vesicles and other organelles often use motor protein "feet" to walk to their destinations along a track provided by the cytoskeleton. 3. the driving force behind muscle contraction and are responsible for the active transport of most proteins and vesicles in the cytoplasm. They are a class of molecular motors that are able to move along the surface of a suitable substrate, powered by the hydrolysis of ATP. There are three superfamilies of cytoskeletal motor proteins. Myosin motors act upon actin filaments to generate cell surface contractions and other morphological changes, as well as vesicle motility, cytoplasmic streaming and muscle cell contraction. The kinesin and dynein microtubule based motor superfamilies move vesicles and organelles within cells, cause the beating of flagella and cilia, and act within the mitotic and meiotic spindles to segregate replicated chromosomes.

Myosin filaments

thick filaments

Actin Filaments

thin filaments