Test 2 objectives Flashcards
Compare and contrast the general characteristics of prokaryotic and eukaryotic cells, and contrast plant and animal cells.
- Prokaryotic cells are enclosed by a plasma membrane but have little or no internal membrane organization. They have a nuclear area rather than a membrane-enclosed nucleus. Prokaryotic cells typically have a cell wall and ribosomes, and may have propeller-like flagella.
- Eukaryotic cells have a membrane-enclosed nucleus, and their cytoplasm contains a variety of organelles; the fluid component of the cytoplasm is the cytosol.
- Plant cells differ from animal cells in that plant cells have rigid cell walls, plastids, and large vacuoles, which are important in plant growth and development.
Describe the structure and functions of cell membranes.
- Amphipathic Structure: Phospholipid Bilayer, Hydrophilic and hydrophobic=amphipathic, Also contains proteins, cholesterol, glycoproteins and glycolipids
- Function: Selectively permeable (regulates movement into & out of the cell); Physical barrier; Communication; Structural support
Describe the structure and functions of the nucleus.
- Structure: three regions: Nuclear envelope (double membrane)-barrier of the nucleus and contains nuclear pores that allow for exchange of material; Nucleolus-Nucleus contains one or more nucleoli and Sites of ribosome assembly and rRNA synthesis; Chromatin- Composed of DNA and protein, Present when the cell is not dividing, Scattered throughout the nucleus, Condenses to form chromosomes when the cell divides
- Function: Control center of the cell (contains genetic material DNA), gives/recieves info regarding all cellular processes, site of DNA and RNA synthesis
Distinguish between smooth and rough endoplasmic reticulum in terms of both structure and function.
Structure: fluid-filled tubles for carrying substances, part of the endomembrane system; Function: manufactures, packages and distributes in transport vesicles
Trace the path of proteins synthesized in the rough endoplasmic reticulum as they are subsquently.
- The Golgi complex consists of stacks of flattened membranous sacs called cisternae that process, sort, and modify proteins synthesized on the rough ER. The Golgi complex also manufactures lysosomes.
- Glycoproteins are transported from the ER to the cis face of the Golgi complex by transport vesicles, which are formed by membrane budding. The Golgi complex modifies carbohydrates and lipids that were added to proteins by the ER and packages them in vesicles.
- Glycoproteins exit the Golgi through vesicles that are formed at its trans face. The Golgi routes some proteins to the plasma membrane for export from the cell. Others are transported to lysosomes or other organelles within the cytoplasm.
Describe the functions of lysomes and peroxisomes.
- Lysosomes contain enzymes that break down worn-out cell structures, bacteria, and debris taken into cells.
- Peroxisomes are important in lipid metabolism and detoxify harmful compounds such as ethanol. They produce hydrogen peroxide, but contain the enzyme catalase, which degrades this toxic compound.
compare the functions of mitochondria and cholorplasts.
- Mitochondria, organelles enclosed by a double membrane, are the sites of aerobic respiration. The inner membrane is folded, forming cristae that increase its surface area.
- The cristae and the compartment enclosed by the inner membrane, the matrix, contain enzymes for the reactions of aerobic respiration. During aerobic respiration, nutrients are broken down in the presence of oxygen. Energy captured from nutrients is packaged in ATP, and carbon dioxide and water are produced as byproducts.
- Plastids are organelles that produce and store food in the cells of plants and algae.
- Chloroplasts are plastids that carry out photosynthesis.
- The inner membrane of the chloroplast encloses a fluid-filled space, the stroma.
- Grana, stacks of interconnected disclike membranous sacs called thylakoids, are suspended in the stroma.
- During photosynthesis, chlorophyll, the green pigment found in the thylakoid membranes, traps light energy. This energy is converted to chemical energy in ATP and used to synthesize carbohydrates from carbon dioxide and water.
Describe the structure and functions of the cytoskeleton.
- The cytoskeleton is a dynamic internal protein fiber framework that includes microtubules, microfilaments, and intermediate filaments. The cytoskeleton provides structural support and functions in various types of cell movement, including transport of materials in the cell.
- Microtubules are hollow cylinders assembled from subunits of the protein tubulin. In cells that are not dividing, the minus ends of microtubules are anchored in microtubule-organizing centers (MTOCs). The main MTOC of animal cells is the centrosome, which usually contains two centrioles. Each centriole has a 9 × 3 arrangement of microtubules.
- Microfilaments, or actin filaments, formed from subunits of the protein actin, are important in cell movement.
- Intermediate filaments strengthen the cytoskeleton and stabilize cell shape.
Compare clilia and flagella, and describe their functions.
- Cilia and flagella are thin, movable structures that project from the cell surface and function in movement.
- Cilia: numerous, short hair-like projections made of microtubules; move materials across the cell suface thus commonly associated with goblet cells; located in the respiratory bronchi and uterine tubes, on the protist paramecium
- Flagella: long, whip-like structure made of microtubules; propels the cell; found on sperm
Describe the function of the cell wall.
•Cells of most bacteria, archaea, fungi, and plant cells are surrounded by a cell wall made mainly of carbohydrates. Plant cells secrete cellulose and other polysaccharides that form rigid cell walls.
Compare the structures and functions of tight junctions, desmosomes, gap junctions, and plasmodesmata.
- Tight junctions seal membranes of adjacent animal cells together, preventing substances from moving through the spaces between the cells.
- Gap junctions, composed of the protein connexin, form channels that allow communication between the cytoplasm of adjacent animal cells.
- Plasmodesmata are channels connecting adjacent plant cells. Openings in the cell walls allow the plasma membranes and cytosol to be continuous; certain molecules and ions can pass from cell to cell.
Evaluate the importance of membranes to the homeostasis of the cell, emphasizing their various functions.
- The plasma membrane physically separates the interior of the cell from the extracellular environment, receives information about changes in the environment, regulates the passage of materials into and out of the cell, and communicates with other cells.
- Biological membranes form compartments within eukaryotic cells that allow a variety of separate functions. Membranes participate in and serve as surfaces for biochemical reactions.
Explain how the properties of the lipid bilayer govern many properties of the cell membrane (ie understand the chemical lipid bilayer structure.)
•The lipid bilayer is a fluid mosaic model, meaning the cell membrane consists of a fluid bilayer of pospholipid molecules in which the proteins are embedded or otherwise associated. they move like icebergs in a sea. Mostly consists phospholipids but cholesterol, glycolipids., and different type of proteins.
Describe how membrane proteins associate within the lipid bilayer, and discuss the types, functions and importance of membrane proteins.
- Proteins determine most of the membrane’s specific functions
- types are peripheral and integral. Peripheral proteins is bound to the surface, NOT embedded in the lipid bilayer. Integral proteins penetrate the hydrophobic core. The majority of integral proteins are transmembrane proteins tat span the membrane
- 6 major functions: Transport, enzymatic activity, signal transductions, cell-cell recognition, intercellular joining, and attachment to cytoskeleton and extracellular matrix.
Describe the components of a solution.
A solution is a homogeneous mixture of two or more components. Components are a solvent, dissolving medium, and a solute, what is being dissolved.
Contrast the processes of passive and active transport, including simple diffusion, osmosis, facilitated diffusion, carrier-mediated active transport and bulk transport. How might temperature play a role in these processes?
- Passive transport is when substances are moved down their concentration gradient across the membrane without any energy input from the cell.
- Active transport is when a cell is required to input energy (ATP) to transport substances across the membrane.
- Passive transport: Simple diffusion (unassisted movement of solutes across the cell membrane from high to low concentration), facilitated diffusion (passive transport aided by proteins, carrier or channel proteins), and osmosis (the diffusion of WATER across a selectively permeable membrane.
- Active transport: solute pumping (a protein carrier is powered by ATP to move a substance against its concentration or electrical gradient, that is from low to high) and vesicular or “bulk” transport ( moves substances into or out of cells without their actually crossing the plasma membrane, packages in vesicles and requires ATP).
Which molecules will move across the membrane freely? Which utilize facilitated diffusion? Active transport?
- Simple diffusion through cells membrane would be nonpolar molecules like oxygen and carbon dioxide.
- Facilitated diffusion are used for specific ion or polar molecules.
- Active transport like a sodium-potassium pump (exchanges sodium inside the cell for potassium outside) or proton pump (pumps an hydrogen ion outside the membrane).
Be able to solve problems involving osmosis and diffusion: for example, predict whether cells will swell or shrink under various tonic conditions (iso- vs. hyper- vs hypotonic). Reference your lab experiments for practical application.
- Isotonic is the same solute. Hypertonic is more solute. And hypotonic is less solute.
- If the solution is hypertonic compared to the cell, the cell would shrink. If the solution is hypotonic compared to the cell the animal cell would burst or provide turgor pressure in plant cells.
Use key terminology to describe transport processes (ie the tonicity of the solution versus that of the cell; concentration gradient and pressure gradient (osmotic pressure))
- Tonicity of a solution is the ability of a sourrounding solution to cause a cell to gain or lose weight.
- Net movement of water from hypotonic environment to hyertonic enviroment.
- Osmoic pressure (the tendency of a solution to pull water into it) is directly related the concentration of solutes in the solution. The higher the solute concentration the greater the osmotic pressure and the greater the tendency of water to move into the solution.
Describe the sodium-potassium pump, proton pumps, and cotransport.
- Sodium-potassium pump actively carries sodium oins out of and potassium oin into the cell for transmission of nerve cell impulses.
- Proton pump is an active pump that uses ATP to transport protons (hydrogen ions) across membranes causing an electrochemical gradient that can be used in other processes.
- Cotransport is the transport of two solutes occurs when a membrane protein enables the “downhill” diffusion of one solute to drive the “uphill” transport of the other.
Compare endocytosis and exocytosis transprot mechanisms.
- Exycytosis “out of the cell”: moves substances out of the cells by fusing a vesicle full of product with the plasma membrane
- Endocytosis “into the cell”: engulfing extracellular substances by enclosing them in a vesicle. Types: phagocytosis (cellular eating), pinocytosis (cellular drinking”), and receptor mediated endocytosis (receptor proteins bind with a ligands whcih are then internalized in a vesicle)
