Biology

• Cell


  Life's basic unit of structure and function
• All living things are composed of cells
• Cell theory


  • The cell is the smallest unit of living material that can carry out all the activities necessary for life
• Compartmentalization is an important part of the organization of unicellular and multicellular organisms
• The surface area to volume ratio must be kept small so that there is lots of space to do exchanges between the inside and outside of things
• Prokaryotic cell


  Relatively simple cell, found in bacteria
• Prokaryotic cell


  • Has a circular DNA molecule free in the cell, a cell wall, ribosomes, and may have flagella
• Eukaryotic cell


  More complex cell, found in fungi, protists, plants, and animals
• Eukaryotic cell


  • Has membrane-bound organelles
• Plasma membrane


  The outer envelope of the cell, a complex double-layered structure made of phospholipids and proteins
• Nucleus


  The control center of the cell, contains DNA organized into chromosomes
• Ribosomes


  The sites of protein synthesis
• Endoplasmic reticulum (ER)


  A continuous channel that extends into the cytoplasm, with rough ER that has ribosomes and smooth ER that makes lipids, hormones, and steroids
• Golgi bodies


  Modify, process, and sort proteins, package final products into vesicles
• Mitochondria


  The "powerhouses" of the cell, convert organic molecules into ATP energy
• Lysosomes


  Membrane-bound structures that contain digestive enzymes to break down unwanted material
• Centrioles


  Small, paired, cylindrical structures that organize microtubules during cell division
• Vacuoles


  Fluid-filled sacs that store water, food, wastes, salts, or pigments
• Cytoskeleton


  Network of fibers that give the cell its shape and enable movement, including microtubules and microfilaments
• Plant cells have a cell wall, chloroplasts for photosynthesis, and a large central vacuole, but lack centrioles
• Membrane transport


  Molecules and fluids can pass through the plasma membrane by diffusion, facilitated transport, and osmosis
• Hydrophobic substances can cross the lipid bilayer membrane without resistance, while hydrophilic substances require facilitated transport
• Passive transport


  Movement of substances down a concentration gradient, without requiring energy
• Osmosis


  The diffusion of water across a membrane
• Aquaporins


  Proteins that allow water to rapidly reverse the membrane whenever it wishes without forming traffic jams
• Without aquaporins, no water would be able to cross the membrane
• Passive Transport


  Movement of substances across a membrane down their concentration gradient, without the input of energy
• Diffusion


  The movement of a substance from an area of high concentration to an area of low concentration
• Simple diffusion


  Diffusion of hydrophobic molecules
• Facilitated diffusion


  Diffusion that requires the help of a channel-type protein
• Osmosis


  The diffusion of water across a membrane from an area of low solute concentration to an area of high solute concentration
• Solution


  A liquid solvent that has dissolved solute particles
• In diffusion


  The membrane is permeable to solute
• In osmosis


  The membrane is not permeable to solute
• Tonicity


  Terms used to describe osmotic gradients (hypertonic, hypotonic, isotonic)
• Hypertonic solution


  Has more total dissolved solutes than the cell
• Hypotonic solution


  Has less total dissolved solutes than the cell
• Isotonic solution


  Has the same solute concentration as the cell
• Active Transport


  Movement of substances across a membrane against their concentration gradient, requiring energy input
• Primary active transport


  When ATP is directly utilized to transport something