Cell Biology Chapters 1 and 4
What does ATP stand for? What is the function of ATP?
Adenosine Tri-Phosphate High energy compound that is the principal energy storage compound in most cells.
Outline Shleiden and Schwann's Cell Theory
All organisms consist of one or more cells The cell is the basic unit of structure for all organisms All cells arise only from preexisiting cells
Differentiate between the extracellular matrix of an animal cell and the cell wall of a plant cell. What are they made up of and how are their functions different?
Extracellular matrix consists primarily of collagen fibers and proteoglycans. Cell wall consists mostly of cellulose microfibrils embedded in a matrix of other polysaccharides and small amounts of protein. Plants are generally nonmotile and animals are usually motile.
What is the nucleolus? What is its function?
Structures responsible for synthesizing and assembling some of the RNA and protein components needed to form ribosomes. Usually associated with specific regions of particular chromosomes that contain genes encoding ribosomal RNAs
Outline the importance of the surface area/ volume ratio to a cell.
Surface area is critical because it is at the cell surface that the needful exchanges between a cell and its environment take place. The cell's internal volume determines the amount of nutrients that will have to be imported and the quantity of waste products that must be excreted. The surface area effectively represents the amount of cell membrane available for such uptake and excretion. Large cells have a lower ratio of surface area to volume than small cells do. As a cell increases in size, its surface area does not keep pace with its volume, and the necessary exchange of substances between the cell and its surroundings becomes more and more problematic. Cell size, therefore, can increase only as long as the membrane surface area is still adequate for the passage of materials into and out of the cell.
Outline the mitochondrial, peroxisomal, and lysosomal disorders disucssed. What is the basis of each disorder? Are these diseases heritable? How would the patterns of heritability differ?
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Outline the principles of centrifugation. What is the importance of centrifugation in the study of Cell Biology?
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Outline the function of lysosomes. How many membranes surround it? What is the function and importance of the acid hydrolases contained within the lysosome?
An organelle surrounded by a single membrane. Used by the cell as a means of storing hydrolyses, enzymes capable of digesting specific biological molecules such as proteins, carbohydrates, or fats. Like secretory proteins, lysosomal enzymes are synthesized on the rough ER, transported to the golgi complex, and then packaged into vesicles that can become lysosomes. A carbohydrate covering on the inner surface of the lysosomal membrane protects the membrane from hydrolytic activities.
Contrast the function of gap junctions and tight junctions and desmosomes. What type of cell would all of these be found in?
Animal cells communicate with each other through intercellular connections called gap junctions-specialized for the transfer of material between the cytoplasms of adjacent cells. Tight junctions hold cells together so tightly that the transport of substances through the spaces between the cells is effectively blocked.
What is the golgi apparatus? Outline its structure. How many membranes surround it? What specific functions are assigned to it?
Consists of a stack of flattened vesicles (cisternae). Plays an important role in processing and packaging secretory proteins and in synthesizing complex polysaccharides. It is a processing station with vesicles both fusing with it and arising from it. Almost everything that goes into it comes back out-but in a modified packaged form, often ready to export from the cell.
Differentiate between the terms cytoplasm and cytosol.
Cytoplasm consists of that portion of the interior of the cell not occupied by the nucleus.-includes organelles The cytoplasm also include the cytosol, the semifluid substance in which the organelles are suspended.
What are the 2 general cell types? Outline the similarities and differences between these 2 types. Which exhibits more compartmentilization?
Eukaryotes: Large, have nucleus and organelles, has actin and tubulin proteins, performs exocytosis and endocytosis, cell wall of cellulose in plants and none in animals, divides by mitosis and cytokinesis, chromosomal DNA is linear and associated with histone proteins, have extensive RNA processing. Prokaryotic: Small, no organelles or nucleus, has actin like and tubulin like proteins, does not perform exocytosis or endocytosis, has cell walls of peptidoglycan, divides by binary fission, chromosomal DNA is circular with few associated proteins, have minimal or moderate RNA processing Eukaryotes exhibit more compartmentilization Membrane phospholipids: Eukaryotes have glycerol-3-phosphate + linear fatty acids and prokaryotes have either glycerol-3-phosphate + linear fatty acids or glycerol-1-phosphate + branched polyisoprenoids
What is the ER? How many membranes surround it? What makes the Rough ER differ in appearance from the smooth ER? What specific functions are assigned to the Rough ER? The smooth ER?
Extending throughout the cytoplasm of almost every eukaryotic cell is a network of membranes called ER. Consists of tubular membranes and flattened sacs, or cisternae, that are interconnected. 1 membrane. Rough ER appears rough because it is studded with ribosomes on the side of the membrane that faces the cytosol. These ribosomes are actively synthesizing polypeptides that either accumulate within the membrane or are transported across the ER membrane. Not all proteins are synthesized by ribosomes associated with the rough ER. The smooth ER has no role in protein synthesis and hence no ribosomes. Is involved in the synthesis of lipids and steroids. Also responsible for inactivating and detoxifying drugs harmful to the cell.
Transmission electron microscope (TEM):
Forms an image from electrons that are transmitted through the specimen
Outline the function of mitochondria. Sketch and label the structure of a miochondrion. How many membranes surround it? How are these membranes different? What are cristae? What is the matrix? Do mitochondria have their own DNA?
Found in all eukaryotic cells and are the site of aerobic respiration. Large. Comparable in size to a whole bacterial cell. Most eukaryotic cells contain hundreds of mitochondria, and each is surrounded by two membranes, the inner and outer mitochondrial membranes. Also found in mitochondria are small, circular molecules of DNA that encode some of the RNAs and proteins needed in mitochondria, alone with ribosomes involved in protein synthesis. Oxidation of sugars and other cellular fuel molecules to carbon dioxide in mitochondria extracts energy from food molecules and conserves it as ATP. It is within the mitochondrion that the cell localizes most of the enzymes and intermediates involved in such important cellular processes. Cristae are infoldings of the inner membrane. Matrix fills the inside of the mitochondrion. Yes they have their own DNA
Define the terms gene, chromosome, and heredity. How are these terms related?
Hereiditary factor that specifies an inherited trait; consists of a DNA based sequence of one or more polypeptide chains. Or alternatively, for one of several types of RNA that perform functions other than coding for polypeptide chains. In eukaryotes a single DNA molecule complexed with histones and other proteins that becomes condensed into a compact structure at the time of mitosis or meiosis. Passing of traits to the next generation. Genes are units of inheritance usually occurring at specific locations on a chromosome. Genes are responsible for hereditary characteristics.
Outline the functions of vacuoles in animal and plant cells. How many membranes surround a vacuole?
In animal and yeast cells, used for temporary storage or transport. Single bound. Some protozoa take up food particles or other materials from their environment by phagocytosis. A single large vacuole is found in most mature plant cells. Sometimes called the central vacuole, may play a limited role in storage and in intracellular digestion. Its main importance is its role in maintaining the turgor pressure that keeps tissue from wilting.
Outline and explain the Scientific Method
It is the way scientists assess new information. After making observations and consulting prior studies, the scientist formulates a hypothesis, a tentative explanation or model that can be tests experimentally. Next, the investigator designs a controlled experiment to test the hypothesis by varying specific conditions while keeping other variables constant. The scientist then collects the data, interprets the results, and accepts or rejects the hypothesis, which must be consistent not only with the results of this particular experiment but also with prior knowledge.
What specific protein makes up a microtuble? These proteins are arranged into protofilaments that make up a microtubule. How many protofilaments are found in a cross section of a mircotubule? Name 3 structures made of microtubules. Name 4 cell processes that microtubules are involved in.
Largest structural element found in the cytoskeleton. Tubulin is the protein. 13 protofilaments are found in a cross section of a microtubule axoneme of cilia and flagella and the mitotic spindle fibers motility, chromosome movement
What is the main function of intermediate filaments thought to be?
Most stable and least soluble constituents of the cytoskeleton. Have a tension bearing role.
What specific protein makes up a microfilament. Name 3 processes that microfilaments are involved in.
Much thinner than microtubules. Smallest of major cytoskeletal components. Role in contractile fibrils of muscle cells. Actin Locomotion, amoebid movement, cytoplasmic streaming
What are plasmodesmata? What is their function?
Neighboring plant cells, though separated by the wall between them, are actually connected by numerous cytoplasmic bridges called plasmodesmata which pass through the cell wall. The plasma membranes of adjacent cells are continuous through each plasmodesma, such that the channel is membrane lined.
What is the function of ribosomes? How many membranes surround a ribosome? What is a sedimentation coefficient and what units are used to describe it? How many subunits does a ribosome have? How are these subunits different in size?
Not really an organelle because it is not surrounded by a membrane. Protein synthesis Another way to express the size of such a small particle is to refer to its sedimentation coefficient-measure of how rapidly the particle sediments in an ultracentrifuge. The rate of sedimentation is expressed in Svedberg units. Sedimentation coefficients are widely used to indicate relative size, especially for large macromolecules such as proteins and nucleic acids and for small particles such as ribosomes. Ribosomes from eukaryotic cells have sedimentation coefficients of about 80S while those from bacteria and archaea are about 70S. A ribosome consists of two subunits differing in size, shape, and composition. In eukaryotic cells, the large and small ribosomal subunits have sedimentation coefficients of about 60S and 40S. For bacterial and archaeal ribosomes, the values are about 50S and 30S.
The Light Microscope: How does it work, what is it used for, what is its individual resolving powers?
Plays an important role in our elucidation of cellular structure. White light is passed directly through a specimen that is either stained or unstained and the background is illuminated. Maximum magnifications of about 1000-1500X. Subject to the limit of resolution imposed by the wavelength of the light used to view the sample. Limit of about 200-300 nm
Functionally, what is an enzyme?
Protein molecule that acts on one or more specific substrates, converting them to products with different molecular structures. Catalytic functions by lowering the activation energy.
Outline the function of a peroxisome. How many membranes surround a peroxisome? What is the function and importance of the catalase contained within the peroxisome? What is the function of the specialized peroxisomes referred to as glyoxysomes?
Resemble lysosomes in size and general lack of obvious internal structure. Surrounded by a single membrane. Found in plant and animal cells as well as in fungi, protozoa, and algae. Generate and degrade hydrogen peroxide. Hydrogen peroxide can be decomposed into water and oxygen by the enzyme catalase. In animals they are mostly found in the liver and kidney cells. May also be involved in regulating oxygen levels within the cell and may play a role in aging. In plant cells, during the germination of fat-storing seeds, specialized peroxisomes called glyoxysomes play a key role in converting stored fat into carbohydrates.
Scanning electron microscope (SEM):
Scans the surface of the specimen and forms an image by detecting electrons that are deflected from the outer surface of the specimen. Gives a sense of depth to biological structures.
What is the function of the nucleus? How many membranes surround the nucleus?
Serves as the cells information center. Here, separated from the rest of the cell by a membrane boundary, are the DNA-bearing chromosomes of the cell. The boundary around the nucleus consists of two membranes, called the inner and outer nuclear membranes. Together they make up the nuclear envelope.
What is the importance of the plasma membrane? Outline its basic structure. What types of molecules make up membranes? How are they assembled?
Surrounds every cell. Defines the boundaries of the cell, ensuring that its contents are retained. Consists of phosopholipids, other lipids, and proteins and is organized into two layers. Each phospholipid molecule consists of two hydrophobic tails and a hydrophilic head and is therefore an amphipathic molecule. The phosopholipid molecules orient themselves in the two layers of the membrane such that the hydrophobic, hydrocarbon tails of each molecule face inward and the hydrophilic, phosphate containing heads of the molecules face outward. The resulting lipid bilayer is the basic structural unit of virtually all membranes and serves as a permeability barrier to most water soluble substances.
What is the function of chloroplasts? Sketch and label the structure of a chloroplast. How many membranes surround it? What are the thylakoids, grana, and stroma? What other types of plastids exist? What are their functions?
The site of photosynthesis in plants and algae. Large organelles that can be quite numerous in the leaves of green plants. Substantially bigger than mitochondria and all other structures in a plant expect the nucleus. Surrounded by both inner and outer membranes. Inside the chlorplast there is a third membrane system consisting of flattened sacs called thylakoids and the membranes (stroma thylakoids) that interconnect them. Thylakoids are stacked together to from the grana that characterize most chloroplasts. Reactions that depend directly on solar energy are localized in or on the thylakoid membrane system. Reactions involved in the reduction of carbon dioxide to sugar molecules occur within the semifluid stroma that fills the interior of the chloroplast. Found in the stroma are chloroplast ribosomes along with small, circular molescules of DNA that encode some of the RNAs and proteinds needed in the chloroplast. Plastids other than chloroplasts perform a variety of functions in plant cells. Chromoplasts are pigment containing plastids that are responsible for the characteristic coloration of flowers, fruits, and other plant parts. Amyloplasts are plastids that are specialized for the storage of starch.
What is meant by compartmentalization of a cell? How is this important to the function of a cell?
To compartmentalize activities, most eukaryotic cells have a variety of organelles, which are membrane bounded compartments that are specialized for specific functions. Cells can therefore maintain appropriately high concentrations of everything they require without having to maintain corresponding high concentrations of these substances elsewhere in the cell.
Electron Microscope:
Uses a beam of electrons that is deflected and focused by an electromagnetic field. Because the wavelength of electrons is so much shorter than the wavelength of photons of visible light, the limit of resolution for the electron microscope is much better. .01-.02 nm. Magnification up to 100,000X. Used for negative staining, shadowing, freeze fracturing, and freeze etching.
Differentiate between the structure of viruses, viroids, prions. Would you consider a virus living? Would you consider a virus to be cellular in nature? Why is a virus considered to be an intracellular parasite?
Viruses are noncellular, parasitic particles that are incapable of a free-living existence. They can invade and infect cells and redirect the synthetic machinery of the infected host cell toward the production of more virus particles. Cannot perform all of the functions required for independent existence and must therefore depend on the cells they invade for most of their needs. Not considered to be living organisms, nor are they made of cells. No ribosomes, organelles, and few or no enzymes, and only a few different molecules of nucleic acid and protein. Are responsible for many diseases in humans, animals, and plants and are thus important. Viroids are small, circular RNA molecules. They are the smallest known infectious agents.Some have enzymatic properties that aid in their replication. Responsible for dieseases of several crop plants. Not clear how they cause disease. Prions represent another class of noncellular infectious agents. Proteinaceous infective particles that are responsible for neurological diseases such as scrapie in sheep and goats, kuru in humans, and mad cow disease in cattle. Prion proteins are abnormally folded versions of normal cellular proteins. Are not destroyed by cooking or boiling so special precautions are recommened.
How do the units of measurement micrometer, nanometer, and angstrom relate to a meter?
micrometer (aka micron) is one-milionth of a meter (10^-6), also most useful unit for expressing the size of cells and organelles; nanometer is one-billionth of a meter (10^-9), most useful for expressing size of molecules and subcellular structures; angstrom (A) is 0.1 nm, size of a hydrogen atom (pg. 3)
How do millimolar, micromolar, nanomolar, picomolar, and femptomolar relate to molar?
millimole is one-thousandth of a mole, micromole is one-millionth of a mole (10^-6), nanomole is one-billionth of a mole (10^-9), picomolar is one trillionth of a mole (10^-12) and femptomolar is a billionth of a millionth of a mole (10^-15)
Define the term resolution as it relates to microscopy
the ability to see fine details of structure, the smaller the limit of resolution, the greater the resolving power of the microscope; minimum distance that can separate two points that still remain identifiable as separate points when viewed through a microscope/ability of a microscope to distinguish adjacent objects as separate entities
