Bio Ch6

Many cytoskeletal functions depend upon motor proteins. What do they do? What energy drives them?

Cytoskeletal elements along with motor proteins work together with plasma membrane molecules to allow whole cells to move along fibers outside the cell. They bring about the bending of the cilia and flagella by gripping microtubules within those organells and sliding them agains each other. A similar mechanism involving microfilaments causes muscle cells to contract.

4.What do ribosomes do in cells?

Carry out protein synthesis. They build protein in two cytoplasmic locales.

What purpose(s) do these structures serve?

Cell wall - prevents cell from excessive water intake, gives support and form to multicellular organisms.

Summarize the structure and function of Golgi Apparatus.

Center of Manufacturing, warehousing, sorting and shipping. Like Post office. Made of flattened membranous sacs-cisternae-looks like stack of pita bread. Membrane of each cisterna in a sack separates its internal space from cytosol. Unlike ER, these sacs not connected.The cis face receives vesicles containing ER products and trans face dispatches vesicles. Found in Eukaryotic cell. Products modified in transit from cis to trans. Also manufactures certain macromolecules on its own. Refines products in stages, golgi enzymes refines products in stages. Before dispatching products, it sorts products and targets them for certain parts of the cell. Molecular identification tags like phosphate groups are added to products act like zip codes.Golgi vesicles go to cell membrane for secretion or to lysosomes.

List all organelles whose membranes are considered part of the endomembrane system.

Endoplasmic Reticulum\nGolgi Apparatus\nlysosomes\nfood vacuoles\nplasma membrane

Describe structural features of chloroplast

Made by free ribosomes in cytosol and by ribosomes contained within these organelles themselves. \nSemiautonomous and reproduce within cell.Contain chlorophyll, along with enzymes and other molecules that function in photosynthetic production of sugar. Contents partitioned from cytosol by envelope consisting of two membranes separated by intermembrane space. Inside are thyllakoids, which are stacked, each stack called granum. Fluid outside of thyllakoids called stroma, which contains chloroplast DNA and ribosomes as well as many enzymes. Membranes of chloroplast divide the chloroplast into 3 compartments, intermembrane space, stroma, and thyllakoid space. Not part of EMS. Have own DNA and ribosomes.

Where do lysosomal hydrolases come from? What prevents the hydrolases from breaking down the organelle they originate in?

Made from Rough ER. They are probably synthesized by ribosomes, which then pass the enzymes through the ER and then Golgi. They are spared from destruction because they have 3d shapes that protect from vulnerable bonds from enzymatic attack.

Where all are proteins made by bound ribosomes found?

Membranes, for packaging within lysosome, or to export for cell secretion.

Which two fiber(s) help in cell division, and what do they do?

Microfilaments and microtubules. Microtubules sperate chromosomes in cell division. Microfilaments aid in the cleavage furrow formation in cell division.

Name the three types of cytoskeletal fibers

Microtubules, microfilaments, and intermediate filaments.

Why does the surface area-to-volume ratio place a limit on the size of cells?

Only a limited amount of a particular substance can cross per second, so ratio is critical. As cell increases in size, its volume increases more than surface area. Thus, smaller object has greater surface area to volume.

How are these organelles believed to have originated? What evidence supports the endosymbiont theory?

Originated from Endosymbiont Theory. Evidence like shape/size, double membrane, semi-atonymous are all examples.

Which types of cells have cell walls?

Plant cells, prokaryotes, fungi and some other protists.

What is cytoskeleton made from?

Proteins actin, keratin and tubulin

Summarize function of contractile vacuole

Pumps excess water out of the cell, thus maintaining a suitable concentration of ions and molecules inside the cell. Offsets osmosis by pumping water out of the cell.

2 types of macromolecules are ribosomes constructed from?

Ribosomal RNA and protein/polypeptides

Describe Nuclear Envelope and Nuclear pores.

The nuclear envelope is a double membrane, each a lipid bilayer with associated proteins.Envelope perforated by pore structures. At lip of each pore, inner and outer envelope are continuous. Protein structure called pore complex lines each pore and regulates entry and exit of most proteins and RNAs. Except at pores, it is lined by nuclear lamina, a netlike array of protein filaments that maintain shape of nucleus by supporting nuclear envelope.

Describe structure and function of microfilaments

Two intertwined strands of actin ( a globular protein ) each a polymer of actin subunits. Main functions are maintenance of cell shape, changes in cell shape, muscle contraction, cytoplasmic streaming, cell motility. cell division ( cleavage furrow formation ). 7nm. Animal cell division - pinches cell in two during animal cell division\nDynamic function! - can break down and reconstruct into a ring shape and has capability of contract. The ring is made up of microfilaments.

Explain the structure and function of the nucleus.

contains most of the genes in eukaryotic cell. Most conspicuous organelle in cell. Enclosed by nuclear envelope which separates its content from cytoplasm. Chromosomes found within Nucleus, they contain DNA. Contains nucleolus, which is a densely stained granule adjoining part of chromatin.Directs protein synthesis by synthesizing mRNA based on instructions of DNA.

Summarize function of food vacuole

formed by phagocytosis. contains food from outside of the cell. Forms by budding in from the cell membrane. Whatever was outside the cell, then comes in.

5.Where in a cell are the proteins made by free ribosomes found

in the cytosol

Summarize the structure and function of the RER

Has ribosomes on the outer part of the membrane. Makes proteins that can stay in ER or leave and travel to other parts of the EMS. It is a membrane factory for the cell. Grows in place by adding membrane proteins and phospholipids to its own membrane. Makes its own membrane phospholipids. Found in Eukaryotic cell. Like highway. Transport vesicles bud off from region of RER called transitional ER and travel to Golgi Apparatus.Within ER you find chaperones ( proteins ) which are made by bound ribosomes.

Explain the functions of lysosomes in the cell. Include in your answer the terms hydrolase and food vacuole (a.k.a. a phagosome).

A membranous sac of hydrolytic enzymes that an animal cell uses to digest macromolecules. These enzymes work best in acidic env. found in lysosomes. If lysosome breaks open its contents aren't very active because cytosol has neutral pH. Excessive leakage from lysosome can destroy cell through autodigestion. They carry out intracellular digestion. Organisms that eat by engulfing smaller organisms through process called phocytosis.This forms food vacuole which fuses with lysosome whos enzyme ( hydrolase) digests the food through hydrolysis which breaks down. Digestion products pass into cytosol and become nutrients for cell. This is done by amoeba and immune cells ( macrophages ). Macrophages are a type of white blood cell that helps defend body by engulfing and destroying bacteria and other invaders. Hydrolytic enzymes also recycles cells own material, a process called authophogy. In this process, a damaged organelle or cytosol becomes surrounded by double membrane and lysosomes fuse with it. Lysosomal enzymes dismantle enclosed material and organic monomers are returned to cytosol for reuse. Lysosomes help the cell constantly renew itself.

Which type has an extracellular matrix?

Animal Cells.

2 places genes are found in animal cells, and 3 places they are found in plant cells.

Animal cells - genes found in mitochondria and nucleus.\nPlant cells - Chloroplast, nucleus, mitochondria.

1. What makes prokaryotic and eukaryotic cells different from one another? What features do ALL cells have?

Eukaryotes - most DNA in nucleus. Have membrane bound organelles. Significanly larger.\nProkaryotes - DNA in Nucleoid\nNo membrane-bound organelles. No nucleus. Have DNA but there is no membrane surrounding it. \n\nAll cells are bound by cell membrane, contain complex aqueous solutions which is cytosol. Contain ribosomes. Contain chromosomes.

Describe structure and function of Intermediate Filaments

Fibrous proteins supercoiled into thicker cables. 8-12 nm. One of several different proteins of keratin family. \nMain functions are maintenance of cell shape, anchorage of nucleus and certain other organelles and formation of nuclear lamina. Gives shape/support to nucleus.Main structural component of hair/nails etc..

Summarize function of central vacuole

Found in plant cells. Develops from coalescence of smaller vacuoles, derived from ER and Golgi. Integral part of plant cells EMS. Holds reserves of important organic compounds, plant cells main repository of inorganic ions, such as potassium and chloride. Used as disposal site for metabolic by products that would endanger the cell. Contain pigment. Protect against predators.Has major role in growth of plant cell, which enlarge as plant cell absorbs water.

What is the difference between free and bound ribosomes?

Free ribosomes are suspended in the cytosol, while bound ribosomes are attached to the outside of the endoplasmic reticulum or nuclear envelope. They are structurally identical. Most proteins made in the free ribosomes function within the cytosol, like enzymes that catalyze the first steps of sugar breakdown. Bound ribosomes make proteins that are destined for insertion into membranes, for packaging within certain organelles such as lysosomes, or to export from cell like secretion.

Describe structure and function of Microtubules

Hollow tubes, walls consist of 13 columns of tubulin molecules. 25 nm. The wall of the tube is made of protein called tubulin. Each protein tubulin is a dimer, a molecule made up of two subunits. A tubulin dimer is made of two different polypeptides, alpha and beta tubulin. Microtubules grow in lenght by adding tubulin dimers. Because of its architecture, the two ends are slightly different. One end can accumulate or release tubulin dimers at higher rate than the other. Thus growing significantly during cellular activities. Shape and support cell and serve as tracks along which organelles equipped with motor proteins can move. Separate chromosomes during cell division.Know that they guide movement of vesicle.\nThe vesicle travels along microtubule \n- they pull apart chromosomes in cell division\n- grow out of a central organelle and prior to cell division will have 2 centrosomes and during cell div. will shoot out microtubles.

Describe 3 functions performed by the SER that were discussed in lecture

Involved in synthesis and transport of lipids. Detoxification of a variety of poisons. stores calcium ions. Stores glycogen.

What functions does the EMS serve for the cell?

Is responsible for biosynthesis, processing, chemical processing or sorting. Metabolism and movement of lipids, detox of poisons

Describe structural features of mitochondria

sites of cellular respiration, the metabolic process that generates ATP by extracting energy from sugars, and other fuels with the help of oxygen. Have two membranes separating their innermost space from the cytosol. Membrane made of phospholipid bilayer with a unique collection of embedded proteins. Outermembrane smooth but innermembrane is crowded, with infoldings called cristae. Inner membrane divides the mitochondrion into two internal compartments. First intermembrane space is narrow region between inner and outer membrane. Second compartment, the mitochondrial matrix, is enclosed by the inner membrane, contains many diff enzymes as well as mitochondrial DNA and ribosomes. Enzymes in matrix catalyze some steps of cellular respiration. Other proteins that function in respiration, including enzymes that make ATP, including enzyme that makes ATP, are built into inner membrane. Cristae give the inner mitochondrial membrane a large surface area, thus enhancing the productivity of cellular respiration.