Bio 2010 Test 2

Front 1

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

Back 1

Eukaryotes - most DNA in nucleus. Have membrane bound organelles. Significanly larger.
Prokaryotes - DNA in Nucleoid
No membrane-bound organelles. No nucleus. Have DNA but there is no membrane surrounding it.

All cells are bound by cell membrane, contain complex aqueous solutions which is cytosol. Contain ribosomes. Contain chromosomes.

Front 2

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

Back 2

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.

Front 3

3.Explain the structure and function of the nucleus.

Back 3

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.

Front 4

Describe Nuclear Envelope and Nuclear pores.

Back 4

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.

Front 5

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

Back 5

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

Front 6

4.What do ribosomes do in cells?

Back 6

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

Front 7

2 types of macromolecules are ribosomes constructed from?

Back 7

Ribosomal RNA and protein/polypeptides

Front 8

What is the difference between free and bound ribosomes?

Back 8

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.

Front 9

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

Back 9

in the cytosol

Front 10

Where all are proteins made by bound ribosomes found?

Back 10

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

Front 11

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

Back 11

Endoplasmic Reticulum
Golgi Apparatus
lysosomes
food vacuoles
plasma membrane

Front 12

What functions does the EMS serve for the cell?

Back 12

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

Front 13

Summarize the structure and function of the RER

Back 13

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.

Front 14

Summarize the structure and function of Golgi Apparatus.

Back 14

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.

Front 15

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

Back 15

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

Front 16

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

Back 16

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.

Front 17

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

Back 17

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.

Front 18

Summarize function of central vacuole

Back 18

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.

Front 19

Summarize function of food vacuole

Back 19

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.

Front 20

Summarize function of contractile vacuole

Back 20

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.

Front 21

Describe structural features of chloroplast

Back 21

Made by free ribosomes in cytosol and by ribosomes contained within these organelles themselves.
Semiautonomous 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.

Front 22

Describe structural features of mitochondria

Back 22

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.

Front 23

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

Back 23

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

Front 24

Name the three types of cytoskeletal fibers

Back 24

Microtubules, microfilaments, and intermediate filaments.

Front 25

Describe structure and function of Microtubules

Back 25

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.
The vesicle travels along microtubule
- they pull apart chromosomes in cell division
- grow out of a central organelle and prior to cell division will have 2 centrosomes and during cell div. will shoot out microtubles.

Front 26

Describe structure and function of microfilaments

Back 26

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
Dynamic function! – can break down and reconstruct into a ring shape and has capability of contract. The ring is made up of microfilaments.

Front 27

Describe structure and function of Intermediate Filaments

Back 27

Fibrous proteins supercoiled into thicker cables. 8-12 nm. One of several different proteins of keratin family.
Main 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..

Front 28

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

Back 28

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

Front 29

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

Back 29

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.

Front 30

Which types of cells have cell walls?

Back 30

Plant cells, prokaryotes, fungi and some other protists.

Front 31

What is cytoskeleton made from?

Back 31

Proteins actin, keratin and tubulin

Front 32

Which type has an extracellular matrix?

Back 32

Animal Cells.

Front 33

What purpose(s) do these structures serve?

Back 33

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

Front 34

How does the chemistry of phospholipids and membrane proteins determine the structure of the cell membrane (i.e. the fluid mosaic model)?

Back 34

Phospholipid has both hydrophilic region and a hydrophobic region. The membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a double layer of phospholipids. Membrane proteins are dispersed, individually inserted into the phospholipid bilayer with their hydrophilic regions protruding. This would maximize contact of hydrophilic regions of proteins and phospholipids with water in cytosol and extracellular fluid while providing their hydrophobic parts with nonaqueous environment.

Front 35

Which chemical interaction holds a membrane together? How thick is the cell membrane?

Back 35

Held together by hydrophobic interactions, which are much weaker than covalent bonds. Cell membrane is 8 nm thick.

Front 36

Explain membrane fluidity. What factors influence fluidity?

Back 36

Membranes must be fluid in order to work. It is needed for proper permeability and for functioning of membrane proteins.Temperature influences fluidity - higher temp more fluid. Variations of fatty acids and cholesterol in animal cells.

Front 37

Why is the plasma membrane referred to as a ‘mosaic’?

Back 37

It is a collage of different proteins embedded in the fluid matrix of the lipid bilayer. There are integral and peripheral proteins that populate membrane.

Front 38

How are integral and peripheral membrane proteins positioned differently in the plasma membrane?

Back 38

Integral proteins - penetrate hydrophobic core of lipid bilayer. Some proteins span the membrane while others only extend only halfway into core. Hydrophobic part of protein consist of one or more stretches of nonpolar amino acids, coiled into alpha helices.Hydrophilic part of the molecule exposed to aqueus solution.
Peripheral proteins - not embedded in the lipid bilayer, they are loosely bound to surface of membrane.

Front 39

Where are proteins of the cell membrane constructed?

Back 39

E R

Front 40

What determines a protein’s position in the membrane? In what way are membrane proteins ‘asymmetrical’?

Back 40

Their primary structure and their orientation. The assymetrical arrangement of proteins, lipids and their associated carbohydrates in the plasma membrane is determined as the membrane is being built by ER and Golgi.

Front 41

List the functions performed by membrane proteins.

Back 41

1. Transport - transport things from one side to another by changing shapes.
2. Enzymatic activity - built into membrane, maybe an enzyme wi/ active site exposed, sometimes org. into teams that carry out steps.
3. Signal Transduction- Protein may have binding site w/ specific shape that fits the shape of chemical messenger, like hormone.
4. Cell cell recognition - serve as id tags that are recognized by membrane proteins of other cells.
5. Intercellular joining - Membrane proteins of other cells may hook together in various kinds of junctions.
5. Attachment to the cytoskeletol and Extracellular matrix.

Front 42

Explain what is meant by a concentration gradient when dealing with a membrane

Back 42

The region along which the density of a chemical substance decreases. no work must be done in order for this to happen. Diffusion is spontaneous and needs no input of energy.

Front 43

How does a substance’s concentration gradient influence its diffusion? How does it influence the diffusion of another substance?

Back 43

Each substance diffuses down its own concentration gradient, unaffected by the concentration differences of other substances. The concentration gradient represents potential energy and drives diffusion.Membranes are selectively permeable and therefore have diff effects on rates of diffusion of various molecules.

Front 44

Explain how water diffuses across membranes (i.e. osmosis)

Back 44

Water diffuses across the membrane from the region of lower solute concentration to that of higher solute concentration until solute concentrations are equal. Diffusion of water across a selectively permeable membrane.

Front 45

Explain the different ways animal cells, plant cells, and protists deal with the problem of osmosis, as discussed in lecture and the lab class.

Back 45

Animal Cells - live in isotonic environments, cells living in hyper/hypo tonic environments must have osmoregulation in order to deal with this. Protists have contractile vacuole to deal with this. Plant cells - cell wall will expand only so much until it exerts back pressure on cell that opposes further water uptake. Cell becomes turgid.