AP BIO UNIT 2 (2020-2025)

Ribosomes

Composed of ribosomal RNA (rRNA) and protein; synthesize protein according to mRNA sequence; found in all forms of life, demonstrating COMMON ANCESTRY OF ALL LIFE

Smooth endoplasmic reticulum (ER)

Performs detoxification and lipid synthesis

Rough endoplasmic reticulum (ER)

Compartmentalizes the cell; PROTEIN SYNTHESIS in MEMBRANE-BOUND RIBOSOMES; intracellular TRANSPORT; mechanical support

Golgi complex

Membrane-bound structure consisting of a series of flattened membrane sacs; fold newly-synthesized proteins correctly and package them for protein trafficking

Mitochondria

Have smooth outer membrane and extremely folded inner membrane (CRISTAE) to increase surface area for cellular respiration/metabolic reactions (energy production)

Lysosomes

Membrane-enclosed sacs that contain hydrolytic enzymes to break down waste and foreign molecules (intracellular digestion) and perform APOPTOSIS; only present in animal cells

Vacuole

Membrane-bound sac playing many differing roles (storage, release of macromolecules and cellular waste); in animals, many small; in plants, one large that retains water that helps maintain shape and TURGOR PRESSURE

Chloroplasts

Specialized organelles found only in photosynthetic organisms (plants, algae) with DOUBLE OUTER MEMBRANE; contain THYLAKOIDS and STROMA

Mitochondria energy features

Folding of inner membrane increases surface area for ATP synthesis; MATRIX (KREBS/CITRIC ACID CYCLE); INNER MITOCHONDRIAL MEMBRANE (ETC, ATP SYNTHESIS)

Chloroplast energy features

THYLAKOIDS organized in stacks called GRANA (LIGHT-DEPENDENT REACTIONS); STROMA (CARBON FIXATION/CALVIN CYCLE) (like cytoplasm); membrane contains CHLOROPHYLL pigments and ETC PROTEINS for PHOTOSYSTEMS

Surface-area-to-volume ratio

Affects ability of biological system to obtain necessary resources, eliminate waste products, acquire/dissipate thermal energy, and otherwise exchange chemicals and energy with the environment

Surface area of plasma membrane

Must be large enough to adequately exchange materials; limitations restrict cell size and shape (small); more complex cellular structures (e.g. membrane folds) necessary to adequately exchange materials with environment

As cells increase in volume

Relative surface area decreases and demand for internal resources increases

As organisms increase in size

Surface-area-to-volume-ratio decrease, affecting properties like rate of heat exchange with environment

Specialized structures and strategies for efficient molecule exchange

Effective exchange surfaces with LARGE SURFACE AREA, SHORT DIFFUSION DISTANCE, MAINTAINED CONCENTRATION GRADIENTS (ex. plant leaves have air spaces in mesophyll layer, thin tissues and stomata, carbon dioxide immediately used by photosynthetic cells)

Vacuole strategies for efficient exchange

Membrane (TONOPLAST) proteins ensure only specific molecule exchanged; can actively pump ions or store solutes to create OSMOTIC GRADIENTS to move water and maintain turgor pressure to ensure efficient exchange; helps to regulate internal environment, interact with other cellular components, maintain homeostasis

Stomata strategies for efficient exchange

Surrounded by two guard cells that expand and contract to control opening and closing of pore to ensure GAS EXCHANGE OCCURS ONLY WHEN NEEDED (photosynthesis), PREVENTING WATER LOSS

Phospholipids

Have hydrophilic phosphate regions oriented toward aqueous external/internal environments and hydrophobic lipid regions oriented toward one another within interior of membrane

Embedded proteins in plasma membrane

Can be hydrophilic (charged and polar side groups) or hydrophobic (nonpolar side groups)

Fluid Mosaic Model

Cell membranes consist of a structural framework of phospholipid molecules that’s embedded with PROTEINS, steroids (cholesterol in eukaryotes) glycoproteins, and glycolipids that can FLOW AROUND THE SURFACE OF THE CELL within the membrane

The structure of cell membranes

directly results in selective permeability, as described by Fluid Mosaic Model

Cell membranes

separate the internal environment from the cell from the external environment; are SELECTIVELY PERMEABLE

Can pass freely through membrane

SMALL, NONPOLAR molecules (e.g. N2, O2, CO2)

Can move across membrane through embedded channel/transport proteins

LARGE, POLAR (hydrophilic) substances

Can move through membrane in small amounts

POLAR UNCHARGED molecules (e.g. H2O)

Cell wall

Found in PLANTS, FUNGI, and PROKARYOTES; provides structural boundary and PERMEABLE barrier for some substances to the internal environments; composed of COMPLEX CARBOHYDRATES (cellulose)

Passive transport

The net movement of molecules from high concentration to low concentration without the direct input of metabolic energy; plays primary role in IMPORT OF MATERIALS and EXPORT OF WASTE

Active transport

Requires the direct input of energy to move molecules from regions of low concentration to regions of high concentration; MEMBRANE PROTEINS and METABOLIC ENERGY (ATP) REQUIRED to move across and ESTABLISH/MAINTAIN CONCENTRATION GRADIENTS

Selective permeability of membrane allows for

the formation of concentration gradients of solutes across the membrane

Endocytosis

Cell takes IN macromolexules and particulate matter by FORMING NEW VESICLES derived from the plasma membrane

Exocytosis

Internal vesicles FUSE WITH the plasma membrane and secrete large macromolecules out of the cell

Membrane proteins required for facilitated diffusion of

CHARGED and LARGE POLAR molecules

Large quantities of water

Pass through aquaporins

Charged ions

Na+, K+, etc. require channel proteins

Membranes may become polarized from

The movement of ions across the membranes

Na+/K+/ATPase

SODIUM-POTASSIUM PUMP; contributes to the maintenance of the membrane potential by EXPORTING 3 NA+ OUT for every 2 K+ IN (AGAINST GRADIENT); ATPase PROVIDES ENERGY

Water moves from (osmolarity)

low osmolarity to high osmolarity

Water moves from (water potential)

high water potential to low water potential

Water moves from (solute concentration)

low colute concentration to high solute concentration

Water potential equation

Water potential = pressure potential + solute potential

Solute potential equation

Solute potential = -iCRT (i=Ionization constant, C=molar Concentration, R=pRessure constant 0.0831 L*bars/mol/K, T=Temperature in Kelvin=Celsius+273)

Hypertonic solution

MORE SOLUTE OUTSIDE of cell; cell will SHRIVEL

Isotonic solution

SAME SOLUTE INSIDE AND OUTSIDE of cell; cell maintains normal function

Hypotonic solution

LESS SOLUTE OUTSIDE of cell; cell will SWELL AND BURST

Osmoregulatory mechanisms contribution to organism health/survival

Growth and homeostasis maintained by constant movement of molecules across membranes

Osmoregulation

Maintains water balance and allows organisms to control their internal solute composition/water potential

How ions and other molecules move across membranes

Passive and active transport, endocytosis, and exocytosis

Membranes and membrane-bound structures in eukaryotes

compartmentalize intracellular metabolic processes and specific enzymatic reactions

Internal membranes facilitate cellular processes by

MINIMIZING COMPETING REACTIONS and INCREASING SURFACE AREAS where reactions can occur

Endosymbiosis/Symbiogenesis

process by which membrane-bound organelles evolved from once free-living prokaryotic cells

Prokaryotes

lack internal membrane-bound organelles but have internal regions with specialized structures and functions

Eukaryotes

Maintain internal membranes that partition the cell into specialized regions

Phagocytosis

Process by which cells take in/”eat” one another (origin of endosymbiosis)

Endosymbiote resemblance

Chloroplasts resemble cyanobacteria and some of BOTH HAVE A PEPTIDOGLYCAN CELL WALL; mitochondria resemble Rickettsial bacteria