Slide sets

Cell components and functions

Cell membrane structure and function

Cell transport and osmosis

1. 1. 1. 1. Cell structure: subcellular components

            1. Describe the structure and/or function of subcellular components and organelles.

               1. Ribosomes comprise ribosomal RNA (rRNA) and protein. Ribosomes synthesize protein according to the mRNA sequence.

               2. Ribosomes are found in all forms of life- reflecting the common ancestry of all known life.

               3. Endoplasmic reticulum (ER) occurs in two forms- smooth and rough. Rough ER is associated with membrane-bound ribosomes

                  1. Rough ER compartmentalizes the cell.

                  2. Smooth ER functions include detoxification and lipid synthesis.

                  3. Do not need to know specific functions of Smooth ER in specialized cells.

               4. The Golgi complex is a membrane-bound structure that consists of a series of flattened membrane sacs:

                  1. Function of Golgi include the correct folding and chemical modification of newly synthesized proteins and packaging for protein trafficking.

                  2. Do not need to know the role of the Golgi in the synthesis of the specific phospholipids and the packaging of specific enzymes for lysosomes, peroxisomes, and secretory vesicles.

               5. Mitochondria have double membrane. The outer is smooth, while the inner membrane is highly convoluted forming folds.

               6. Lysosomes are membrane enclosed sacs that contain hydrolytic enzymes.

               7. A vacuole is a membrane-bound sac that plays many and differing roles. In plants, a specialized large vacuole serves multiple functions

               8. Chloroplast are special organelles that are found in photosynthetic algae and plants. They have a double outer membrane.

         2. Cell structure and function

            1. Explain how subcellular components and organelles contribute to the function of a cell.

               1. Organelles and subcellular structures and the interactions among them, support cellular function:

                  1. ER provides mechanical support, carries out protein synthesis on membrane-bound ribosomes, and plays a role in intracellular transport.

                  2. Mitochondrial double membrane provides compartments for different metabolic reactions.

                  3. Lysosomes contain hydrolytic enzymes, which are important in intracellular digestion, the recycling of a cell’s organic materials, and programmed cell death (apoptosis).

                  4. Vacuoles have many roles, including storage and release of macromolecules and cellular waste products. In plants, it aids in retention of water for turgor pressure.

            2. Describe the structural features of a cell that allow organisms to capture, store and use energy.

               1. The folding of the inner mitochondrial membrane increases the surface area, which allows for more ATP to be synthesized.

                  1. The Krebs cycle (citric acid cycle) reactions occur in the mitochondrial matrix

                  2. Electron transport and ATP synthesis occur on the inner mitochondrial membrane.

               2. Within the chloroplast are thylakoids and the stroma.

                  1. Thylakoids are organized into stacks called grana.

                  2. Membranes contain chlorophyll pigments and electron transport proteins that comprise the photosystems.

                  3. The light-dependent reactions of photosynthesis occur in the grana.

                  4. The stroma is the fluid within the inner chloroplast membrane and outside the thylakoid.

                  5. The carbon fixation (Calvin cycle) reactions occur in the stroma.

         3. Cell size

            1. Explain the effect of surface area-to-volume ratios on the exchange of materials between cells or organisms and the environment.

               1. Surface area-to-volume ratios affect the ability of a biological system to obtain necessary resources, eliminate waste products, acquire or dissipate thermal energy, and otherwise exchange chemicals and energy with the environment.

            2. The surface area of the plasma membrane must be large enough to adequately exchange materials-

               1. These limitations can restrict cell size and shape. Smaller cells can typically have a higher surface area-to-volume retain and more efficient exchange of materials with the environment.

               2. As cells increase in volume, the relative surface area decreases and the demand for internal resources increases.

               3. More complex cellular structures (membrane folds) are necessary to adequately exchange materials with the environment.

               4. As organisms increase in size, their surface area-to-volume ratio decreases, affecting properties like rate of heat exchange with the environment.

            3. Explain how specialized structures and strategies are used for the efficient exchange of molecules to the environment.

               1. Organisms have evolved highly efficient strategies to obtain nutrients and eliminate wastes. Cells and organisms use specialized exchange surfaces to obtain and release molecules from or into the surrounding environment.

         4. Plasma membranes

            1. Describe the roles of each of the compartments of the cell membrane in maintaining the internal environment of the cell.

               1. Phospholipids have both hydrophobic and hydrophilic regions. The hydrophilic phosphatase regions are oriented toward the aqueous external or internal environments while the hydrophobic fatty acid regions face each other within the interior of the membrane.

               2. Embedded proteins can be hydrophilic, with charged and polar sides groups or hydrophobic with non-polar side groups.

            2. Describe the Fluid mosaic model of cell membranes.

               1. Cell membranes consist of a structural framework of phospholipid molecules that is embedded with proteins, steroids (such as cholesterol in eukaryotes), glycoproteins, and glycolipids that can flow around the surface of the cell within the membrane.

         5. Membrane permeability

            1. Explain how the structure of biological membranes influences selective permeability.

               1. The structure of the cell membrane results in selective permeability.

               2. Cell membranes separate the internal environment of the cell from the external environment.

               3. Selective permeability is a direct consequence of membrane structure, as described by the Fluid mosaic model.

               4. Small non-polar molecules, including N2, O2, and CO2 can pass freely across the membrane. Hydrophilic substances such as large polar molecules and ions, move across the membrane through embedded channel and transport proteins.

               5. Polar uncharged molecules, such as water, pass through the membrane in small amounts.

            2. Describe the role of the cell wall in maintaining cell structure and function.

               1. Cell walls provide a structural boundary, as well as a permeability barrier for some substances to the internal environments.

               2. Cell walls of plants, prokaryotes, and fungi are composed of complex carbohydrates

         6. Membrane Transport

            2. 1. Describe the mechanisms that organisms use to maintain solute and water balance.

                  1. Passive transport is the net movement of molecules from a high concentration to a low concentration without the direct input of metabolic energy.

                  2. Passive transport plays a primary role in the import of materials and export of wastes

                  3. Active transport requires the direct input of energy to move molecules from regions of low to high concentrations.

               2. Describe the mechanisms that organisms use to transport large molecules across the plasma membrane.

                  1. The selective permeability of membranes allows for the formation of concentration gradients of solutes across the membrane.

                  2. The processes of endocytosis and exocytosis require energy to move large molecule into and out of cells-

                     1. In exocytosis, internal vesicles fuse with the plasma membrane and secrete large macromolecules out of the cell.

                     2. In endocytosis, the cell takes in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane.

         7. Facilitated Diffusion

            2. 1. Explain how the structure of a molecule affects its ability to pass through the plasma membrane.

                  1. Membrane proteins are required for facilitated diffusion or charged and large polar molecules through membrane-

                     1. Large quantities of water pass through aquaporins

                     2. Charged ions including Na+ and K+ require channel proteins to move through the membrane

                     3. Membranes may become polarized by movement of ions across the membrane.

               2. Membrane proteins are required for active transport

               3. Metabolic energy (ATP) is required for active transport of molecules and/or ions across the membrane to establish and maintain concentration gradients.

               4. The Na+/K+ ATPase contributes to the maintenance of the membrane potential.

         8. Tonicity and Osmoregulation

            1. Explain how concentration gradients affect the movement of molecules across membranes.

               1. External environments can be hypotonic, hypertonic, or isotonic to internal environments of cells-

                  1. Water moves by osmosis from areas of high water potential/low osmolarity/low solute concentration to areas of low water potential/high osmolarity/high solute concentration

               2. Explain how osmoregulatory mechanism contribute to the health and survival of organisms

                  1. Growth and homeostasis are maintained by the constant movement of molecules across membranes.

                  2. Osmoregulation maintains water balance and allows organisms to control their internal solute composition/water potential.

         9. Mechanisms of transport

            1. Describe the processes that allow ions and other molecules to move across membranes

               1. A variety of processes allow for the movement of ions and other molecules across membrane, including passive and active transport, endocytosis and exocytosis.

         10. Compartmentalization

             1. Describe the membrane-bound structures of the eukaryotic cell

                1. Membranes and membrane-bound organelles in eukaryotic cells compartmentalize intracellular metabolic processes and specific enzymatic reactions.

             2. Explain how internal membranes and membrane bound organelles contribute to compartmentalization of eukaryotic cell functions.

                1. Internal membranes facilitate cellular processes by minimizing competing interactions and by increasing surface areas where reactions can occur.

         11. Origins of cell compartmentalization

             1. Describe similarities and/or difference in compartmentalization between prokaryotic and eukaryotic cells

                1. Membrane-bound organelles evolved from once free-living prokaryotic cells via endosymbiosis.

                2. Prokaryotes generally lack internal membrane-bound organelles by having internal regions with specialized structure and functions.

                3. Eukaryotic cells maintain internal membranes that partition the cell into specialized regions.

             2. Describe the relationship between the functions of endosymbiotic organelles and their free-living ancestral counterparts

                1. Membrane-bound organelles evolved from once free-living prokaryotic cells via endosymbiosis.