AP Bio - Unit 2

Prokaryotic cells

Simple, single celled organisms found in Bacteria and Archaea.

Eukaryotic cells

Complex cells found in Eukaryota/Eukarya (animals, plants, fungi, and protists).

Nuclear membrane

Made of two lipid bilayer membranes that enclose genetic material. 

Endoplasmic reticulum (rough)

A network of membranes through which proteins and other molecules move, and proteins are assembled at organelles called ribosomes. Ribosomes are on rough ER.

Endoplasmic reticulum (smooth)

Smooth ER lacks ribosomes and helps synthesize and concentrate various substances needed by the cell (lipids, phospholipids for plasma membranes, and steroids). 

Golgi apparatus

Processes and packages proteins and lipids into vesicles, significantly those going out of the cell.

Lysosomes

Membrane-bound cell organelle that consists digestive enzymes, can break down an array of biological polymers (proteins, nucleic acids, carbohydrates, and lipids).

Vesicles

A structure in/out a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Can be used to move molecules, secrete substances, digest materials, and regulate pressure in the cell.

Endosomes

Intracellular (inside a cell) sorting organelle that carry out endocytosis. 

Plasma (cell) membrane

A phospholipid bilayer forms the plasma membrane’s basic structure, along with embedded proteins. The plasma membrane is a selectively permeable outer barrier for all cells, protecting its cell.

Mitochondria

Vital organelles that convert energy into ATP (power cells) and are involved in cell signaling/death.

Vacuoles

A structure inside a cell that contains cell sap (fluid) that stores water, nutrients, ions, and waste productions.

Surface Area to Volume Ratio of Cells

• SA:V

• SA/V

• Higher SA:V ratio means more surface area for a given amount of internal volume, facilitating efficient exchange.

Endosymbiotic Theory

• Eukaryotic cell organelles (mitochondria and chloroplasts) were engulfed by a larger host cell in a symbiotic relationship that became permanent, which is why they have different DNA.

  PROOF:

  • Mitochondria and chloroplasts are similar in size and shape to prokaryotes.

  • Like prokaryotes, mitochondria and chloroplasts divide by fission.

  • Mitochondria and chloroplasts have a single, circular chromosome for DNA.

  • The ribosomes of mitochondria and chloroplasts have 70S configuration, like prokaryotes. 

Selective membrane permeability

Property of a cell membrane to control the passage of other substances (allowing certain entrance/exit), crucial for homeostasis.

Endocytosis

Process by which a cell takes in material from its surrounding by engulfing them with its cell membrane, forming a vesicle. Active transport.

Exocytosis

Form of active/bulk transport that moves the material of a cell vacuole to the exterior by fusing the vacuole membrane with the cell membrane. 

Passive transport

• Movement of substances across a cell membrane without the expenditure of energy.

• Simple diffusion - Molecules in passive transport move from high to low concentration until equilibrium.

• Osmosis - Movement of water molecules from a semipermeable membrane from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration). 

• Facilitated diffusion - Molecules are aided by proteins (e.g. channel) to cross the membrane.

Active transport

• Requires the cell to use ATP to move substances AGAINST the concentration gradient.

• Ion pumps - Proteins in the membrane use energy to actively transport ions/other molecules from low to high concentrations. Example: Sodium-potassium pump.

• Endocytosis - Engulfing of large molecules to form a vesicle that moves into the cell. 

  • Phagocytosis: Engulfing solid molecules.

  • Pinocytosis: Engulfing liquid molecules.

  • Receptor-Mediated Endocytosis: A specific form where receptor proteins on the cell surface bind to particular molecules before the cell takes them in.