Chapter 6 And 7

Learning Objectives For Chapter 6 And 7. Chapter 6 Is The "Tour Of The Cell" And Chapter 7 Is The "Membrane Structure And Function".
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Distinguish between magnification and resolution
Magnification is making an image larger than its original size
Resolution is having a clear picture of 2 structures; Clarity
What are the two types of microscopes?
Light and Electron
What is a Light Microscope?
Visible light is passed through the specimen and then through glass lenses. [Refracted]
What is an Electron microscope?
A beam of electrons through the specimen or onto its surface.
Distinguish between prokaryotic and eukaryotic cells
Prokaryotic: No nucleus, DNA is "Naked", No histones, Doesn't form into chromosomes, Contains only one circular DNA molecule, Contains "smaller circlets of DNA" called plasmids, Ribosomes composed of 3 types of rRNA and about 50 kinds of protein, No membrane bound organelles, Primarily bacteria, Typically unicellular, No cytoskeleton
Eukaryotic: True nucleus - bound by double membrane, DNA is linear, DNA complexed with histones [proteins], ARE organized into chromosomes, Contains a number of chromosomes, Ribosomes are larger and more complex; 5 kinds of rRNA and about 80 kinds of proteins, Cytoplasm filled with large complex collection of organelles - many enclosed in their own membranes, includes animals plants fungi algae and protozoa
Why are there both upper and lower limits to cell size?
A cell has to be large enough to contain the necessary components to live, and it cannot be too big that diffusion would not be able to meet the cell's needs.
Why is compartmentalization important in eukaryotic cells?
A cell's compartments provide different local environments that accommodate specific metabolic processes. This allows for incompatible process to go on simultaneously inside the same cell.
Describe the structure and function of the nucleus.
Involves the nuclear envelope, nucleolus and chromatin.
Regulates all cell activity.
Describe the structure and function of a eukaryotic ribosome.
Made of rRNA and protein. They carry out protein synthesis.
Build proteins in two cytoplasmic locales; free and bound ribosomes.
List the components of the endomembrane system.
Nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, various kinds of vacuoles, plasma membrane.
What functions does the nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles and plasma membrane do?
Nuclear envelope: Encloses the nucleus - separates contents from the cytoplasm
Endoplasmic reticulum: Contains sacs and tubes - active in membrane synthesis and other synthetic and metabolic processes [composed of rough/smooth ER]
Golgi apparatus: Organelle active in synthesis, modification, sorting, and secretion of cell products
Lysosomes: Digestive organelle where macromolecules are hydrolyzed
Vacuoles: Maintains fluid, removes wastes, stores ingested food, provides and maintains cell structure
Plasma membrane: Selective barrier that allows passage of oxygen, nutrients, and wastes to service the entire cell
Describe the types of vacuoles and explain their function differences.
Food, contractile, central
Food vacuoles: Formed by phagocytosis. Responsible for food digestion.
Contractile vacuoles: Pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell.
Central vacuoles: Hold organic compounds and water
Describe three examples of intracellular digestion by lysosomes.
Phagocytosis: When smaller organisms or other food particles are eaten Autophagy: A damaged organelle or small amount of cytosol becomes surrounded by a double membrane, which is of unknown origin, and a lysosome fuses with the outer membrane of the vesicle. Enzymes dismantle the material
Food Vacuoles: Fuses with a lysosome, whose enzymes digest the food
Explain the role of peroxisomes in eukaryotic cells.
Peroxisomes; oxidative organelles [not part of endomembrane system]
ROLE = Contain enzymes that transfer hydrogen from various substrates to oxygen (producing hydrogen peroxide). Some used oxygen to break fatty acids down into smaller molecules that can be transported to mitochondria - where they are used as fuel for cellular respiration. In some organs - they detoxify harmful compounds by transferring hydrogen from the poisons to oxygen.
Describe the structure and functions of a mitochondrian.
STRUCTURE = Outer membrane, Inner membrane, Intermembrane space, Matrix, Cristae
2 MAIN MEMBRANES; Outer membrane: Phospholipid bilayer with proteins. Smooth. Inner membrane: Divides mitochondrian into two internal compartments - intermembrane space = narrow region between the inner and outer membranes. Mitochondrial matrix = enclosed by the inner membrane, contains many different enzymes in the matrix catalyze some steps of cellular respiration. Enzyme that makes ATP is located in inner membrane. Cristae gives inner membrane a large surface area
FUNCTIONS; [generalization]
OUTER = Contains protons [H+ ions] to drive oxidation phosphorylation
INNER = Oxidative respiration and energy production as ATP

Explain the importance of compartmentalization in mitrochondrial function.
Each perform different functions, each has a greater surface area, "specialized"
Define amyloplast.
A colorless plastid that stores starch and occurs in cells of plant storage.
Define chromoplast.
(No chlorophyll, usually yellow or orange) - Chromoplasts are plastids responsible for pigment synthesis and storage.
Define chloroplast.
plastid containing chlorophyll and other pigments; in plants that carry out photosynthesis. (green)
Identify the three functional compartments of a chloroplast.
Stroma, Intermembrane space, Thylakoid lumen
Stroma: Fluid outside the thylakoids; contains the chloroplast DNA and ribosomes as well as many enzymes.
Intermembrane space: Encloses the stroma
Thlyakoid Lumen: Vital role for photophosphorylation during photosynthesis.
Explain the importance of compartmentalization in chloroplast function.
Enables the chloroplast to convert light energy to chemical energy during photosynthesis.
Describe the functions of the cytoskeleton.
Plays a major role in organizing the structures and activities of the cell.
Describe the structure, monomers and functions of microtubules.
Structure: Thick(est) hollow rods. The wall is constructed from tubulin [a globular protein]. Due to its architecture; its two ends are slightly different - one end can accumulate or release tubulin dimers at a much higher rate than the other - thus growing and shrinking significantly during cell activities.
Monomers: Tubulins
Functions: Shape and support the cell and also serve as tracks along which organelles equipped with motor proteins can move. Also separate chromosomes during cell divisions.
Describe the structure, monomers and functions of microfilaments.
Structure: Thin(nest) - built from molecules of a actin (globular protein). Twisted double chain of actin subunits.
Monomers: Actin
Functions: STRUCTURAL ROLE in cytoskeleton is to bear tension (pulling forces). 3-D network formed inside the plasma membrane helps support the cell's shape [Gives the outer cytoplasmic layer of a cell [cortex] the semisolid consistency of a gel). Help in cell motility - mainly muscle cells (actin filaments are arranged parallel to one another along the length of a muscle cell - made of protein called myosin)
*Localized contraction brought about by actin and myosin also plays a role in amoeboid movement; which a cell such as an amoeba crawls along a surface by extending and flowing into cellular extensions called PSEUDOPODIA. (Both actin-myosin interactions and sol-gel transformations may be involved in cytoplasmic streaming)
Describe the structure, monomers and functions of intermediate filaments.
Structure: "In between size" - larger than microfilaments but smaller than microtubules. Diverse class of cytoskeletal elements
Monomers: Keratins
Functions: Bearing tension, may function as the framework of the entire cytoskeleton.
Explain the ultrastructure of cilia and flagella.
Order from "outer to inner": 1. Outer microtubule doublet (both included in microtubules) --> Plasma membrane2. Dynein arms (motor proteins - energy from ATP)3. Cross-linking proteins inside outer doublets4. Radial Spoke: (multi-unit protein structure in axonemes)
*Also; Basal body [control movement]

Motion of flagella and cilia.
Flagella; "Undulates" - direction of swimming [snake like]
Cilia: "Back-and-Fourth Motion" - direction of organism's movement
Describe the structure of plant cell walls.
*Describe FUNCTION, as well.
*extracellular structure - distinguishes them from animal cells
Structure: Made of 3 layer - Primary cell wall (thin and flexible), Middle lamella (between primary walls of adjacent cells - thin layer rich in sticky polysaccharides called pectins; glues adjacent cells together), Secondary cell wall (between the plasma membrane and primary wall, strong and durable matrix that affords the cell protection and support)
Function: Protects the plant cell, maintains its shape, and prevents excessive uptake of water
Describe the structure of intercellular junctions found in plant cells. Also, describe the functions of these structures.
Plasmodesmata - Perforates plant cell walls, creating channels between adjacent plant cells
*Cytosol passes through the plasmodesmata and connects the chemical environments of adjacent cells

Describe the structure of intercellular junctions found in animal cells. Also, describe the function of these structures.
Tight junctions, Desmosomes, Gap junctions (all 3 are especially common in epithelial tissue [lines external/internal surfaces of the body])
Tight junctions = tightly pressed against each other - bound together by specific proteins. Prevent leakage of extracellular fluid across a layer of epithelial cells
Desmosomes = not "too tight or too loose" - fasten cells together into strong sheets, and attach muscle cells to each other in a muscle
Gap junctions = consist of membrane proteins that surround a pore through which ions, sugars, amino acids, and other small molecules may pass. Provide cytoplasmic channels from one cell to an adjacent cell. Necessary for communication between cells in many types of tissues
Describe the functions of the plasma membrane.
What are the 3 ingredients of membranes?
(Also know, a phospholipid is amphipathic - and know what it means)*
(ALL cells have one) Protection, isolation ["physical barrier"], communication, regulated transport ["selectively permeable" = allows some substances to cross it more easily than others], cell recognition ("homeostasis")
(Phospholipids); Lipids and proteins [mainly] and carbohydrates
*Amphipathic = both a hydrophilic and hydrophobic region
Describe the functions of the fluid properties of the cell membrane.
Considered a "fluid mosaic" because the components [phospholipids] can move laterally [sideways] through the membrane; the membrane isn't completely solid
*Though fluidity can be affected by cholesterol, unsaturated/saturated fatty acid tails [reduces movement and disrupts regular packing of phospholipids]
Describe how membrane fluidity is influenced by membrane composition and temperature.
Membrane composition; Membranes must be fluid to work properly. Saturated fats make it "stiff" - because they are solid at room temperature. Unsaturated fats helps it "bend" which helps the cell work better - liquid at room temperature
Temperature; Remains fluid as temperature decreases, membrane remains fluid to a lower temperature if it is rich in phospholipid with unsaturated hydrocarbon tails [cholesterol is a "temperature buffer"]
Explain how hydrophobic interactions determine membrane structure and function.
Holds the membrane in place and what orients them so the phospholipid bilayer forms. Also - affects what can/can't pass through
Distinguish between integral and peripheral proteins. Also know what their functions are.
INTEGRAL; Penetrate the hydrophobic core of the lipid bilayer -permanently attached (many are transmembrane proteins; which span the membrane - others extend only partway) The hydrophobic regions of these proteins consist of one or more stretches of nonpolar amino acids
PERIPHERAL; Not embedded in the lipid bilayer at all. Appendages loosely bound to the surface of the membrane - often to exposed parts of integral proteins.
Functions = cell adhesion, enzymatic activity, transport
Distinguish between channel and carrier proteins.
Channel; (Some are open or gated) - Provide a patheway for small ions to move directly through the cell membrane's hydrophobic core [Allow certain ions]
Carrier; transport a specific substance or group of substances through intracellular compartments or in extracellular fluids
List the major functions of membrane proteins.
Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix [ECM]
Describe factors that affect selective permeability of membranes.
Hormones, temperature, electrical charge of membrane, size
Electrical charge = charged ions can't pass freelyTemperature = increase temperature makes less transmittableSize = smaller means easier to cross

*Depends on the discriminating barrier of the lipid bilayer and the specific transport proteins built into the membrane*
Define diffusion [also include what causes it and why its a spontaneous process]
Diffusion; the movement of molecules of any substance so that they spread out evenly into the available space. From a region where it is more concentrated to a region that is less concentrated. (Net diffusion -> Equilibrium)
WHAT causes it? Result of energy of the system; temperature
WHY is it a spontaneous process? It is an outcome of "random" motion - no energy needed
Explain why a concentration gradient of a substance across a membrane represents potential energy.
POTENTIAL energy is STORED energy; "it drives diffusion" - in general requires no energy
Define hypertonic solution.
Cell LOSES water to its environment - it "shrivels" and more than likely dies
Define hypotonic solution.
Cell GAINS water [too much] - therefore the cell will "burst" like an overfilled water balloon
Define isotonic solution.
NO net movement of water across the plasma membrane. At the same rate, water enters the cell and exits. Therefore it looks "normal"
Define osmosis. [Also predict the direction of water movement based upon differences in solute concentration]
Osmosis; The diffusion of water across a selectively permeable membrane
*Involves tonicity; ability of a solution to cause a cell to gain or lose water
Nonpenetrating solutes = cannot cross the membrane - if this concentration is higher, water will tend to leave the cell and vice versa
Penetrating solutes = can cross the membrane
Explain how bound water affects the osmotic behavior of dilute biological fluids.
(Doesn't affect it a lot) - Tight clustering of water molecules around the hydrophilic solute molecules makes some of the water unavailable to cross the membrane.
"It is the difference in free water concentration that is important" - *Water diffuses across the membrane from the region of lower solute concentration to that of higher solute concentration until the solute concentrations on both sides of the membrane are equal*
Describe how living cells with and without walls regulate water balance.
With walls; "the cell wall will expand only so much before it exerts a back pressure on the cell that opposes further water uptake"
Without walls; can tolerate neither excessive uptake nor excessive loss of water - this is "solved" if a cell lives in isotonic surroundings - (ex: seawater = marine invertebrates) Animals/others living in hypertonic or hypotonic environments must have adaptations for osmoregulation which is the control of water balance. (ex: paramecium lives in pond water which is hypotonic to the cell - doesn't burst because it is equipped with a contractile vacuole - functions to pump water out)
Distinguish among osmosis, facilitated diffusion and active transport.
Osmosis; diffusion of water across a selectively permeable membrane
Facilitated diffusion; NO energy - uses integral channel proteins to transport hydrophilic substances (molecules/ions)
Active transport; movement of a substance across a cell membrane using energy
What is the "Cell Theory"?
Theory that cells form the fundamental structural and functional units of all living organisms
What is exocytosis?
When the cell secretes certain biological molecules by the fusion of vesicles with the plasma membrane
Explain how potential energy generated by transmembrane solute gradients can be harvested by the cell and used to transport substances across the membrane.
This is the electrochemical gradient.
Electrochemical Gradient = Variation of both electrical potential and chemical concentration across a membrane. (due to ion gradients) - and the result can be a type of potential energy available for work in a cell
Explain how large molecules are transported across a cell membrane.
In some instances, [receptor-mediated] Endocytosis ("pockets") and Proteins help by recognizing the molecules to be passed through
Define pinocytosis.
Type of endocytosis - cell ingests extracellular fluid and its dissolve solutes
Define receptor-mediated endocytosis.
Movement of specific molecules into a cell by the inward budding - enables cell to acquire bulk quantities of specific substances even if not concentrated in fluid (proteins are involved)

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