AP Bio Unit 2

surface area and volume ratios

surface area and volume ratios

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

larger

take in more resources with a __________ SA:V

plasma membrane

The surface area of the ______________________________ must be large enough to adequately exchange materials

smaller ones

These limitations can restrict cell size and shape. What kind of cells typically have a higher surface area-to-volume ratio and more efficient exchange of materials with the environment?

increase; decreases; increases

As cells _______ in volume, the relative surface area _________ and the demand for internal resources _________.

complex cellular structures like membrane folds

necessary to adequately exchange materials with the environment because they create more surface area

decreases

As organisms increase in size, their surface area-to-volume ratio _________ , affecting properties like rate of heat exchange with the environment.

Organisms and cells

have evolved highly efficient strategies to obtain nutrients and eliminate wastes; use specialized exchange surfaces to obtain and release molecules from or into the surrounding environment

ribosomes

comprise ribosomal RNA (rRNA) and protein; synthesize protein according to mRNA sequence; found in all forms of life, reflecting the common ancestry of all known life.

Endoplasmic reticulum (ER)

occurs in two forms—smooth and rough; manufactures membranes and performs many other biosynthetic functions; provides mechanical support, carries out protein synthesis on membrane-bound ribosomes, and plays a role in intracellular transport.

Rough ER

is associated with membrane-bound ribosomes; compartmentalizes the cell; produces proteins for the cell

Smooth ER

functions include detoxification (breaks down drugs) and lipid synthesis; rich in enzymes and plays a role in a variety of metabolic processes, including synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions.

The Golgi Complex

membrane-bound structure that consists of a series of flattened membrane sacs; functions include the correct folding and chemical modification of newly synthesized proteins and packaging for protein trafficking

Mitochondria

have a double membrane. The outer membrane is smooth, but the inner membrane is highly convoluted, forming folds. converts energy to forms the cell can use -- the sites of cellular respiration, using oxygen to generate ATP by extracting energy from sugars, fats, and other fuels. has own DNA and ribosomes, and is the cite of oxidative phosphorylation

Lysosomes

membrane-enclosed sacs that contain hydrolytic enzymes that an animal cell uses to digest macromolecules; contain hydrolytic enzymes, which are important in intracellular digestion, the recycling of a cell’s organic materials, and programmed cell death (apoptosis); janitor of the cell

vacuole

a membrane-bound sac that plays many and differing roles. In plants, a specialized large one serves multiple functions; warehouse of the cell

Food vacuoles

formed by phagocytosis and fuse with lysosomes

Contractile vacuoles

found in freshwater protists and pump excess water out of the cell to maintain the appropriate concentration of ions and molecules inside the cell.

vacuoles in plants and fungi

carry out enzymatic hydrolysis, like animal lysosomes do; aids in retention of water for turgor pressure (plants)

large central vacuole

found in many mature plant cells; the functions: stockpiling proteins or inorganic ions, disposing of metabolic by-products, holding pigments, and storing defensive compounds that protect the plant against herbivores; major role in the growth of plant cells, which enlarge as this absorbs water, enabling the cell to become larger with little investment in new cytoplasm.

chloroplasts

specialized organelles that are found in photosynthetic algae and plants; have a double outer membrane; has own DNA and ribosomes

mitochondrial double membrane

provides compartments for different metabolic reactions (photosynthesis; cell respiration)

hydrolytic enzymes

in lysosomes, they break down molecules like in hydrolysis

nucleus (DNA) --> ribosomes/Rough ER --> RNA --> protein --> Golgi

order of protein production (simple)

folding of inner membrane of mitochondria

increases the surface area, which allows for more ATP to be synthesized

the Krebs Cycle

citric cycle; these reactions occur in the matrix of the mitochondria (fluid-filled space with mitochondrial DNA, ribosomes, and enzymes that is like the cytoplasm)

Electron transport and ATP synthesis

occur on the inner mitochondrial membrane

thylakoids and stroma

located within the chloroplast

thylakoid

organized in stacks called grana; flattened sacs that play a critical role in converting light to chemical energy.

chlorophyll pigments and electron transport proteins

membranes of the chloroplasts contain these that comprise the photosystem

photosynthesis

light-dependent reactions that occur in the grana

stroma

the fluid within the inner chloroplast membrane and outside the thylakoid; like cytoplasm

Calvin-Benson Cycle

the carbon fixation reactions of photosynthesis that occurs in the stroma

pancake analogy of chloroplasts

chloroplast --> plate thylakoid --> pancake grana --> stack of pancakes stroma --> syrup pigments --> chocolate chips

Membranes and membrane-bound organelles in eukaryotic cells

compartmentalize intracellular metabolic processes and specific enzymatic reactions.

Internal membranes

facilitate cellular processes by minimizing competing interactions and by increasing surface areas where reactions can occur

what happens in the nucleus, stays in the nucleus

each organelle has specific reactions; example of how membranes compartmentalize

endosymbiosis

Membrane-bound organelles evolved from once free-living prokaryotic cells through this; one organism lives inside another

prokaryotes

(single celled organisms) generally lack internal membrane-bound organelles but have internal regions with specialized structures and functions

Eukaryotic cells

maintain internal membranes that partition the cell into specialized regions.

mitochondrion of eukaryote

resulted from the engulfing of an oxygen-using non-photosynthetic prokaryotic

chloroplast of eukaryote

resulted from the engulfing of a photosynthetic prokaryote

prokaryotic cells and mitochondria/chloroplasts

have circular DNA, small ribosomes, and divide through binary fission

eukaryotes

have linear DNA, large ribosomes, and divide through mitosis

how the mitochondria and chloroplasts got their double membrane

inner--> their own outer--> membrane from host

Phospholipids

have both hydrophilic and hydrophobic regions

hydrophilic phosphate regions

(of phospholipids) are oriented toward the aqueous external or internal environments; polar heads

hydrophobic fatty acid regions

(of phospholipids) face each other within the interior of the membrane; nonpolar tails

Embedded proteins

can be hydrophilic, with charged and polar side groups, or hydrophobic, with nonpolar side groups.

cell membranes

consist of a structural framework of phospholipid molecules that is embedded with proteins, steroids (such as cholesterol in eukaryotes), glycoproteins, and glycolipids that can flow around the surface of the cell within the membrane; separate the internal and external environments of the cell

unsaturated fatty acids

double bonds, kinks, more flexible/fluid and more space between

saturated fatty acids

single bonds, compact, viscous

plasma membrane

phospholipid bilayer (cell membrane) that functions as a selective barrier that allows the passage of oxygen, nutrients, and wastes for the whole volume of the cell with water inside and outside the cell

selective permeability

results from structure of cell membranes, as described by the fluid mosaic model; allowing some substances to cross the membrane more easily than others.

fluid mosaic model

In this model, the membrane is a fluid structure with a “mosaic” of various proteins embedded in or attached to a double layer (bilayer) of phospholipids.

Small nonpolar molecules,

including N2, O2, and CO2, freely and easily pass across the membrane (nonpolar works well with nonpolar tails)

Hydrophilic substances

such as large polar molecules (glucose and sucrose) and ions (H+), move across the membrane through embedded channel and transport proteins.

Polar uncharged molecules

including H2O, pass through the membrane in small amounts.

cell walls

provide a structural boundary, as well as a permeability barrier for some substances to the internal environments; (of plants, prokaryotes, and fungi) are composed of complex carbohydrates

Passive transport

the net movement of molecules from high concentration to low concentration without the direct input of metabolic energy; diffusion and osmosis and facilitated diffusion -- goes down the concentration gradient

diffusion

the process in which there is movement of a substance from an area of high concentration of that substance to an area of lower concentration until equilibrium is reached

osmosis

diffusion of water

primary role of passive transport

imports materials and exports waste

active transport

requires the direct input of energy to move molecules from regions of low concentration to regions of high concentration (up the concentration gradient)

concentration gradients

The selective permeability of membranes allows for the formation of this of solutes across the membrane; flow of molecules

endocytosis and exocytosis

require energy to move large molecules into and out of cells

exocytosis

internal vesicles fuse with the plasma membrane and secrete large macromolecules out of the cell. (cell throwing up)

endocytosis

the cell takes in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane. (cell eating); phagocytosis, pinocytosis, and receptor-mediated

membrane proteins

required for facilitated diffusion of charged and large polar molecules through a membrane; necessary for active transport

aquaporins

Large quantities of water pass through these channel proteins

channel proteins

Charged ions, including Na+ and K+, require these to move through the membrane; like tunnels

polarized

Membranes may become ________ by movement of ions across the membrane

Metabolic energy (such as from ATP)

required for active transport of molecules and/or ions across the membrane and to establish and maintain concentration gradients

The Na+/K+ ATPase

contributes to the maintenance of the membrane potential; action potentials in nerve cells (sodium potassium pump)

sodium potassium pump

removes Na+ from cell, brings in K+; Na+ in protein + ATP --> Na+ leaves and K+ goes in to protein + ATP --> K+ leaves the cell (high [Na+] and low [K+] outside cell, and low [Na+] and high [K+] inside cell so sodium goes out of the cell and potassium goes in)

hypotonic, hypertonic or isotonic

External environments can be these three things to internal environments of cells

hypertonic solution

more solute (sugar) and lower water potential, and water leaves the cell into the solution; cell shrinks and shrivels

hypotonic solution

less solute than cell and higher water potential, and water enters the cell; cell swells and bursts

isotonic solution

no net difference of water in and out of the solution and the cell; equal concentrations of solutes and water potentials

Water moves by osmosis.....

from areas of high water potential/low osmolarity/low solute concentration to areas of low water potential/high osmolarity/high solute concentration.

Growth and homeostasis

maintained by the constant movement of molecules across membranes

Osmoregulation

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

A variety of processes

allow for the movement of ions and other molecules across membranes, including passive and active transport, endocytosis and exocytosis.

prokaryotic only features

nucleoid region

eukaryotic only features

nucleus, Golgi, mitochondria, ER, cytoskeleton, and central vacuole

features both prokaryotes and eukaryotes have

cell membrane, cytoplasm, ribosomes, and DNA

animal cell only features

lysosomes, centrosomes, and flagella

plant cell only features

central vacuole, chloroplasts, and cell wall

features both animal and plant cells have

nucleus, Golgi, mitochondria, ER, and cytoskeleton,

high Ψw/low [solute] to low Ψw/high [solute]

water moves down the concentration gradient, so from ....

water potential

predicts the direction water moves; = Ψp+ Ψs

pressure potential

zero in animal cells and open containers

solute potential

=-iCRT -- decreases with increasing solute concentration; a decrease in Ψs causes a decrease in the total water potential; moves from less negative to more negative values