AP Biology Unit 2---the Cell

Cell

basic functional unit of all living things

Plasma membrane

bounds the cell and encloses the nucleus and cytoplasm. separates internal metabolic events from the external environment and controls the movementof materials into and out of the cell. Double phospholipid membrane. (hydrophilic heads forming the two outer faces and the nonpolar hydrophobic tails pointing toward the inside) Selectively permeable

Cytoplasm

consists of organelles suspended in a fluid matrix (cytosol)

Peripheral proteins

proteins attached to the inner or outer surface of the membrane

Integral proteins

proteins that extend to the inside of the membrane

Channel Proteins

provide open passageways through the membrane for certain substances

Ion channels

allow the passage of ions across the membrane

Carrier Proteins

bind to specific molecules, which are then transferred across the membrane

Transport Proteins

use energy (ATP) to transport materials across the membrane.

Recognition proteins

give each cell type a unique identification.

Receptor proteins

provide binding sites for hormones or other trigger molecules

Cholesterol

distributed throughout the phospholipid bilayer provide some rigidity to membrane of animal cells

Nucleus

Bound by nuclear envelope. contains DNA

Nuclear Envelope

two phospholipid bilayers enclosing the nucleus

DNA

Genetic information of cell. spread out within the nucleus as a threadlike matrix called chromatin

Histones

proteins around which DNA is tightly coiled

Ribosomes

assist in the assembly of amino acids into proteins

Endoplasmic Reticulum

stacks of flattened sacs involved in the production of various materials.

Rough ER

Studded with ribosomes. Creates glycoproteins

Smooth ER

Responsible for synthesis of lipids and hormones, breakdown of wastes and toxins

Golgi Apparatus

modify and package proteins and lipids into vesicles (small, spherically shaped sacs migrate to and merge with the plasma membrane, releasing their contents to the outside of the cell)

Lysosomes

vesicles from a Golgi apparatus that contain digestive enzymes. Break down food, cellular debris, and foreign invaders.(low pH (acidic), favorable to the activity of the enzymes, is maintained inside the lysosome. As a result, any enzyme that might escape from the lysosome remains inactive in the neutral pH of the cytosol)

Peroxisomes

break down various substances, including hydrogen peroxide (H2O2), fatty acids, and amino acids (common in liver and kidney cells)

Mitochondria

carry out aerobic respiration

Chloroplasts

carry out photosynthesis

Microtubules

made of the protein tubulin and provide support and motility for cellular activities

Intermediate Filaments

provide support for maintaining the shape of the cell

Microfilaments

Made of actin. Involved in cell motility

Flagella

long, few, and move in a snakelike motion.

Cilia

short, many, and move with a back-and-forth movement

Food Vacuoles

fluid-filled, membrane-bound bodies. temporary receptacles of nutrients. (often merge with lysosomes)

Transport Vesicles

move materials between organelles or between organelles and the plasma membrane

Storage Vacuoles

plants store starch, pigments, and toxic substances

Central Vacuoles

large bodies occupying most of the interior of certain plant cells. When filled they put pressure, on the cell walls, maintaining rigidity in the cell. Also store nutrients

Contractile vacuoles

Organelles in single-celled organisms that collect and pump excess water out of the cell

Cell Walls

Provide support for the cell. (In plants, made of mainly cellulose. In fungi, made of chitin)

Extracellular matrix

found in animals, in the area between adjacent cells. occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by the cells. provides mechanical support and helps bind adjacent cells together.

Cell junctions

serve to anchor cells to one another or to provide a passageway for cellular exchange

Anchoring junctions

protein attachments between adjacent animal cells. bind adjacent cells together (desmosomes)

Tight Junctions

tightly stitched seams between animal cells. Provide a seal that prevents the passage of materials between the cells

Communicating Junctions

passageways between cells that allow the transfer of chemical or electrical signals

Gap Junctions

narrow tunnels between animal cells that consist of proteins. Neccesary for communication between cells.

Plasmodesmata

narrow channels between plant cells,

Hypertonic

higher concentration of solutes

Hypotonic

lower concentration of solutes

Isotonic

Equal concentration of solutes

Passive transport

movement of substances from regions of higher to lower concentrations. (down concentration gradient). do not require expenditure of energy.

Diffusion

net movement of substances from an area of higher concentration to an area of lower concentration.

Osmosis

diffusion of water molecules across a selectively permeable membrane

Dialysis

diffusion of solutes across a selectively permeable membrane.

Facilitated Diffusion

diffusion of solutes or water through channel proteins in the plasma membrane

Active Transport

movement of solutes against a gradient and requires the expenditure of energy

Exocytosis

process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell (export)

Endocytosis

capture of a substance outside the cell when the plasma membrane merges to engulf it.

Phagocytosis

("cellular eating"). plasma membrane wraps around the solid material and engulfs it

Pinocytosis

(cellular drinking) Plasma membrane folds inward to form a channel allowing the liquid to enter.

Receptor-mediated endocytosis

occurs when specific molecules in the fluid surrounding the cell bind to specialized receptors that concentrate in coated pits in the plasma membrane. membrane pits, the receptors, and their specific molecules fold inward and the formation of a vesicle follows.