AP Bio Unit 2 Review

Plasma Membrane

Plasma Membrane

A bilayer composed of phospholipids that acts as a barrier to most water-soluble substances.

Phospholipid

A molecule with a hydrophilic head and two hydrophobic tails that forms the plasma membrane.

Integral Protein

A protein embedded in the phospholipid bilayer that functions in transport, communication, and enzymatic activity.

Peripheral Protein

A protein attached to the membrane's surface involved in signaling and maintaining cell shape.

Cholesterol

A molecule interspersed within the phospholipid bilayer that stabilizes membrane fluidity; stops membrane from freezing in cold temps, and melting in high temps

Cytoplasm

The gel-like substance within the plasma membrane that contains organelles and is the site of many cellular processes.

Cell Wall

A rigid structure that provides support and protection; composed of cellulose in plants and peptidoglycan in bacteria.

Organelle

Membrane-bound structures within a cell that perform specific functions, such as energy production and protein synthesis.

Nucleus

The membrane-bound organelle that contains genetic material in the form of chromatin and chromosomes.

chromatin

complex of DNA and proteins; condenses to form chromosomes during cell division

chromosome

structures containing genetic material

Nucleolus

A dense region within the nucleus where ribosomal RNA synthesis and ribosome assembly occur.

Nuclear Envelope

The double membrane surrounding the nucleus.

Nuclear Pores

Openings in the nuclear envelope that allow the exchange of materials between the nucleus and cytoplasm.

Endoplasmic Reticulum (ER)

A network of membranes involved in the synthesis and processing of proteins and lipids.

Smooth ER

The portion of the ER that synthesizes lipids, metabolizes carbohydrates, and detoxifies toxins.

Rough ER

The portion of the ER studded with ribosomes that synthesizes and processes proteins.

Lysosome

An organelle containing digestive enzymes that break down macromolecules, old cell parts, and pathogens.

Chloroplast

The organelle in plant cells where photosynthesis occurs, containing chlorophyll.

Microtubule

A component of the cytoskeleton that provides structural support and facilitates intracellular transport.

Centriole

A cylindrical structure involved in organizing microtubules during cell division.

Centrosome

The region of the cell where microtubules are organized.

Cilia

Short, hair-like structures that move substances along the cell surface; main function is transport

Flagella

Long, whip-like structures that propel cells, both having a 9+2 arrangement of microtubules.

Central Vacuole

A large organelle in plant cells that stores nutrients and waste products and helps maintain turgor pressure.

Vacuole

A storage organelle in plant and fungal cells.

Vesicle

A small, membrane-bound sac that transports materials within the cell.

Ribosomes

The sites of protein synthesis, which can be free in the cytoplasm or attached to the rough ER.

Golgi Apparatus

An organelle that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Mitochondria

The powerhouse of the cell that converts nutrients into ATP through cellular respiration.

Peroxisome

An organelle containing enzymes that break down fatty acids and detoxify harmful substances by producing and breaking down hydrogen peroxide

Endomembrane System

A system that includes the ER, Golgi apparatus, lysosomes, and vesicles; proteins and lipids synthesized in the ER are modified and packaged in the Golgi Apparatus; lysosomes receive enzymes from the Golgi Apparatus and are involved in the digestion of materials.

Prokaryotic Cells

Cells that lack a nucleus and membrane-bound organelles, with circular, free-floating DNA.

Eukaryotic Cells

Cells that have a nucleus and membrane-bound organelles, with linear DNA stored in the nucleus.

evidence for common ancestry

all cells have ribosomes indicating the shared mechanism for protein synthesis; all cells also have a plasma membrane, showing a common structural feature

Endosymbiont Theory

The theory that mitochondria and chloroplasts originated from free-living prokaryotes that entered into a symbiotic relationship with early eukaryotic cells.; evidence includes both organelles having a double membrane, both having their own circular DNA similar to bacteria, and both reproduce independently from the host cell

Compartmentalization in Eukaryotic Cells

The presence of membrane-bound organelles in eukaryotic cells that allows for specialization and efficiency in biochemical reactions.

Surface Area to Volume Ratio

A calculation that indicates the efficiency of nutrient uptake and waste removal in cells; higher rates are advantageous for nutrient uptake and waste removal

Membrane Folding

The process that increases surface area for reactions or processes, such as ATP production in mitochondria and photosynthesis in chloroplasts

polar molecules

generally cannot pass through cell membrane without transport proteins (ex: water)

nonpolar molecules

can pass through relatively easily through the cell membrane (ex: O2, CO2)

ionic molecules

cannot pass through easily through the cell membrane without transport proteins (ex: sodium ions)

size and molecule passage through cell membrane

larger molecules or those with charges may require transport proteins to pass through the cell membrane

functions of membrane proteins

signal transduction - receive and transmit signals (ex: hormone receptors)

transport- facilitate movement of substances (ex: channels, carriers)

cell-to-cell recognition - (identify cell; ex: glycoproteins [carbohydrate attached to a peripheral protein on cell membrane])

attachment - anchor to the extracellular matrix or cytoskeleton (ex: integrins)

intercellular joining - link cells together (ex: tight junctions)

enzymatic activity - catalyze reactions (ex: digestive enzymes)

hypertonic

solution has higher solute concentration; water moves out of cell causing it to shrink; plants cells become flaccid or plasmolyzed

hypotonic

solution has a lower solute concentration; water moves into the cell causing it to swell or burst; plant cells will become turgid (central vacuole is swelled)

isotonic

solution has same solute concentration and solute; no net movement of water; plant cells become flaccid

water potential

a measurement of how freely water molecules can move within a system; water moves from high water potential (less negative areas) to low water potential (more negative areas); the higher the solute concentration the lower the water potential

Passive Transport

The movement of molecules across a membrane without energy input, including diffusion and osmosis.

Aquaporins

Membrane proteins that facilitate the rapid transport of water molecules through cell membranes.

passive transport

movement of substances across the cell membrane that does not require energy input

diffusion

type of passive transport; movement of molecules from high to low concentration

facilitated diffusion

type of passive transport that uses transport proteins to move molecules down their concentration gradient across the cell membrane

osmosis

diffusion of water through a selectively permeable membrane; moves from areas of low solute concentration to areas with high solute concentration (ex: move from areas with high water potential to low water potential)

Cohesion

The property of water molecules sticking to each other, aiding in transport through plant tissues.

Adhesion

The property of water molecules sticking to the walls of plant vessels.

Transpiration

The process of water movement through plants, driven by water potential and environmental factors; effected by temperature, humidity, wind, etc.

active transport

transport that requires ATP to move substances AGAINST their concentration gradient (from low concentration to high concentration)

cotransport

simultaneous active transport of two different substances

countertransport

active transport of one substance in one direction while another moves in the opposite direction

Endocytosis

The process of engulfing materials into the cell, including phagocytosis and pinocytosis.

Phagocytosis

type of endocytosis; engulfing of large particles or cells via vesicles

Pinocytosis

type of endocytosis; engulfing of fluids or small particles via vesicles

receptor-mediated endocytosis

certain molecules has to bind to receptor to trigger a vesicles to perform endocytosis

Exocytosis

The process of expelling materials from the cell by vesicle fusion with the cell membrane