AP Bio Unit 2

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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
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
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
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
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
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
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.
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
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
light-dependent reactions that occur in the grana
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
Membrane-bound organelles evolved from once free-living prokaryotic cells through this; one organism lives inside another
(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
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
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
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
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
internal vesicles fuse with the plasma membrane and secrete large macromolecules out of the cell. (cell throwing up)
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
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
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
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