Chr. 3 - Organization of Cellular Level Flashcards
List the three parts of a cell.
Plasma membrane, cytoplasm, and nucleus.
Describe the fluid mosaic model.
The molecular arrangement of plasma membrane resembling a moving landscape of lipids with different attached proteins.
Describe the lipid bilayer.
Two layers of made of phospholipids, glycolipids, and cholesterol. Structured with hydrophilic phosphate facing outwards, and hydrophobic lipids in between forming the center.
What is an integral protein?
Proteins extending into or through lipid bilayer, firmly embedded.
What is a transmembrane protein?
Protrude from plasma membrane into extracellular fluid, found across the membrane.
What is a peripheral protein?
Proteins attached to polar heads of membrane lipids or integral proteins.
What are glycoproteins?
Integral proteins with carbohydrate groups extending into extracellular fluid.
What is the glycocalyx?
Sugary coating comprised of the carbohydrate groups of glycoproteins.
Describe ion channels.
Pores/holes formed by integral proteins allowing ions to flow in or out of a cell. Usually selective.
Describe a transporter in regards to integral proteins.
Integral proteins that selectively move a polar substance. AKA a carrier.
Describe a receptor in regards to integral proteins.
Integral proteins that recognize and bind a ligand.
Describe an enzyme in regards to integral proteins.
Integral proteins that catalyze chemical reactions inside or outside the cell.
Describe linkers in regards to integral proteins.
Integral proteins that anchor other proteins in the plasma membranes of neighbouring cells via protein filaments inside and outside the cell.
What are cell-identity markers and what are their functions?
Glycoproteins and glycolipids that signal information about that specific cell.
- They recognize other cells during tissue formation.
- Recognize and respond to potentially dangerous foreign cells.
Describe selective permeability.
The ability of the plasma membrane to be permeable to nonpolar molecules, moderately permeable to small uncharged molecules, and impermeable to large uncharged polar molecules.
What is a concentration gradient?
A difference in the concentration of chemicals across a distance.
What is an electrical gradient?
A difference in electrical charge between two regions, usually with a barrier separating charges.
What is a membrane potential?
A difference in electrical charge between the interior and exterior of a cell with the plasma membrane as a barrier.
Describe an electrochemical gradient.
The combined influence of concentration gradient and electrical gradient on the movement of a particular ion/molecule.
What are passive and active transport processes?
Passive processes are when a substance moves only using its own kinetic energy, usually derived from the electrochemical gradient.
Active processes are when a cell uses energy to drive substances against the electrochemical gradient.
What is diffusion, and what are the five factors affecting it?
Passive process in which a solute in solvent moves across concentration gradient.
- Steepness of concentration gradient.
- Temperature.
- Mass of diffusing substance.
- Surface area.
- Diffusion distance.
What is facilitated diffusion?
When an integral protein assists substances across the membrane without expending cellular energy.
Describe channel-mediated diffusion.
Diffusion where solutes unable to pass through the plasma membrane enter the cell via integral proteins acting as channels.
Describe carrier-mediated diffusion.
Diffusion where solutes bind to a protein, causing it to change shape where it releases the solute on the opposite side.
What is osmosis?
A type of diffusion where a solvent moves through a selectively permeable membrane, inversely across a concentration gradient of solute.
How does osmosis occur across the plasma membrane?
In two ways:
- Moving between neighboring phospholipid molecules via diffusion.
- Moving through integral proteins that function as water channels, called aquaporins.
Describe hydrostatic pressure.
Pressure exerted by a fluid at equilibrium at any point due to gravity.
Define osmotic pressure.
Pressure exerted by a difference in amounts of solutes between solutions that are separated by a semipermeable membrane.
What is tonicity?
The measure of a solution’s ability to change volume of cells.
What is an isotonic solution.
A solution in which a cell will maintain it’s normal shape and volume.
What is a hypotonic solution.
A solution with lower concentration of solutes than a cell, causing water molecules to enter the cell by osmosis.
What is a hypertonic Solution.
A solution with higher concentration of solutes, dehydrating a cell by osmosis.
What is primary active transport?
Transport of molecules using protein pumps driven by cellular energy derived from ATP.
Describe how a protein pump functions.
Sodium ions bind to a protein pump inside the cell, initiating hydrolysis of ATP into ADP + Phosphate. The phosphate ion attaches to the protein pump, changing its shape and expelling the sodium into extracellular fluid. After sodium is released, it binds potassium. This causes a release of the phosphate, reverting the protein to its original shape and bringing the potassium inside the cell.
What is secondary active transport?
When a carrier protein binds two substances and changes its shape to move both across the membrane, one with concentration gradient and one against. Usually harnesses sodium.
What is endocytosis and exocytosis?
Endocytosis is when materials move into a cell within a vesicle formed by the plasma membrane.
Exocytosis is when materials move out of a cell within a vesicle that fuses with the plasma membrane, releasing its contents.
List the three types of endocytosis, and give a short explanation of each.
- Receptor-mediated endocytosis - highly-selective endocytosis where specific ligands bind to plasma membrane in extracellular space and initiate formation of a vesicles towards inside of the cell.
- Phagocytosis - process where particles bind to proteins in the extracellular plasma membrane, causing the membrane to extend and engulfing the particle.
- Bulk-phase endocytosis - Inward folding of the plasma membrane to uptake extracellular fluid. This process does not require ligands.
What is transcytosis?
When a transport vesicle forms during intake of contents into a cell, transports it across the same cell, and releases it at another location.
List the components of the cytoplasm.
- Cytosol.
- Organelles.