AP Biology Unit 2: Cell Structure and Function

flaccid

has a water potential of 0 megapascals Water diffuses out of the cell if the solute in the external environment is more concentrated (plasmolysis)- which causes it to shrink

hydrophilic substances

Hydrophilic substances such as large polar molecules and ions cannot move freely across the membrane Hydrophilic substances move with help from transfer proteins

Chloroplast comparmentalization

Same membrane folding Thylakoids are highly folded membrane compartments that increase the efficiency of light dependent reactions

What can go through the cell membrane?

Small molecules can pass freely: N2, O2, CO2

integral proteins

Spans the membrane Hydrophilic with charged and polar side groups Hydrophobic with nonpolar side groups penetrate hydrophobic interior of bilayer

symplast

entire mass of cytosol of all the living cells in a plant, and has the plasmodesmata (cytoplasmic channels that connects them)

isotonic

equal concentration of solvent and solute an equilibrium exists and there is is an equal ratio between water moving in and out of the cell

solute potential

-iCRT -i= ionization- depends on how many components the chemical dissociates into(ie. sucrose is 1 because its one unit, but NaCl is 2 because it dissociates into Na and Cl), always 1 in an open container C= molarity R=constant- 0.0831 T= temp in Kelvin directly proportional to molarity

sodium-potassium pump process

1. Cytoplasmic sodium binds to the sodium-potassium pump. The affinity for sodium is high when the protein has this shape 2. sodium binding stimulates phosphorylation by ATP 3. Phosphorylation leads to a change in protein shape, reducing its affinity for NA which is released outside 4. the new shape has a high affinity for potassium which binds on the extracellular side and triggers release of the phosphate group 5. loss of the phosphate group restores the protein's original shape, which has a lower affinity for potassium 6. potassium is released, affinity for sodium is high again and the cycle repeats

fluid mosaic model

A mosaic of protein molecules in a fluid bilayer of phospholipids Not static and held together by hydrophobic interactions (weaker than covalent bonds) Most lipids and some proteins can shift and flow along the surface of the membrane or across the bilayer

Chemiosmosis

A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.

Phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells

cell compartmentalization in prokaryotic vs eukaryotic cells

Both have plasma membranes that separate the internal from the external environments Prokaryotic cells have an internal region, nucleoid region, that contains genetic material Eukaryotic cells have additional internal membranes and membrane-bound organelles that compartmentalize the cell Genetic material is contained within the nucleus which is membrane bound

What does the folding of the mitochondrial inner membrane, shown here, provide?

Folding of the inner membrane increases surface area→ more ATP can be made

peripheral proteins

Loosely bound to the surface of the membrane Hydrophilic with charged and polar side groups

Mitochondria comparmentalization

Membrane folding maximizes surface area for metabolic reactions to occur Electron transport and ATP synthesis occur in the inner mitochondrial membrane Folding of the inner membrane increases the surface area which allows for ATP to be made

factors that increase surface area of cell

Membrane folding, Root hairs on the surface of plant roots (increased absorption), The villi has microscopic projections called microvilli that aid absorption

Lysosome compartmentalization

Membrane minimizes competing interactions Hydrolytic enzymes of the lysosome function at an acidic environment Inside of the lysosme can remain acidic and allow for hydrolysis to occur, while the rest of the cytoplasm can have a more neutral environment

hydrogen ions in transport in plant cells

Membrane potential is established by pumping hydrogen ions via proton pumps rather than sodium ions in sodium potassium pumps H is cotransported in plants- absorbs neutral solutes by phloem cells by moving it against the concentration gradient Also helps with uptake of nitrate by root cells Semipermeable channel- only lets certain ions pass through

osmosis

Osmosis: the diffusion of free water across a selectively permeable membrane Moves via aquaporins

phospholipids

Polar head and nonpolar tail Forms a bilayer in aqueous environments Tails are in the bilayer and heads are exposed to the outside environment

Mitochondria

Powerhouse of the cell, organelle that is the site of ATP (energy) production. Captures its energy from macromolecules.

cell wall

Structural boundary: Protects and maintains the shape of the cell, Prevents cellular rupture when internal water pressure is high, Helps plant stand up against gravity Comprised of complex carbohydrates: Cellulose- polysaccharide Fungi- chitin, polysaccharide Prokaryotes: peptidoglycan

cell size

The larger the cell, the harder it is to transport things in and out of the cell

surface area to volume ratio

The larger the ratio, the more efficient the cell will be

nuclear lamina

a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope

membrane protein functions

Transport, Cell-cell recognition, Enzymatic activity, Signal transduction, Intercellular joining, Attachment for cellular matrix or cytoskeleton

how does water move

Water diffuses out of a hypotonic solution into a hypertonic solution via osmosis (inversely related) Solutions diffuse along their concentration gradient from hyper to hypotonic

nuclear matrix

a framework of protein fibers extending throughout the nuclear interior.

Pinocytosis

cell takes in extracellular fluid containing dissolved substances

endocytosis

cell uses energy to take in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane

ligand-gated channels

channel that opens when a neurotransmitter attaches

chromatin

consists of DNA and proteins. The chromatin fibers condense when a cell prepares to divide so that it becomes thick enough to be distinguished as separate structures.

apopplast

consists of everything external to the plasma membrane- cell wall, ECM, interior of dead cells

Electronegativity

decreases from left to right on a gradient

maintaining membrane potential

diffusion of ions across the membrane helps maintain resting potential, microenvironment of membrane determines channels opening/closing, channels are passive, ion pumps actively use energy to transport ions across the cell membrane

Smooth ER

doesn't have ribosomes attached, carries out detoxification and lipid synthesis

aquaporins

facilitates the transport of water molecules across the plasma membrane Mediated by aquaporin channels

stroma

fluid between the inner chloroplast membrane and outside thylakoids; carbon fixation reactions occur here

Chloroplast

found in eukaryotic cells (algae/plants) and has a double outer membrane Function: capturing energy from the sun and producing sugar for the organism

stoma (plant)

found on leaf surface; used for gas exchange; opening controlled by guard cells

Rough ER

has ribosomes attached to its membrane, compartmentalizes the cell, associated with packaging the newly synthesized proteins made by attached ribosomes for possible export from the cell; carries out protein synthesis on ribsomes bound to its membrane

thylakoid

highly folded membrane compartments that are organized into stacks (grana) Membranes contain chlorophyll pigments that comprise the photosystems and electron transport proteins can be found between the photosystems embedded in the thylakoid membrane Light-dependent reactions occur there Folding of these internal membranes increases the efficiency of these reactions

channel proteins

hydrophilic tunnel spanning the membrane that allow specific target molecules to pass through

exocytosis

internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules out of the cell Signaling proteins, hormones, and waste

glycolipids

lipid with one or more carbohydrate attached

osmoregulation in plant cells

maintains water balance and controls solute composition/water potential Environmental hypertonicity: less solute and more cellular water, Plasmolysis Isotonic Solutions: equal solute and water, flaccid Environmental hypotonicity: more solute less water, turgid Cell wall helps maintain homeostasis for the plant to maintain environmental hypotonicity Osmotic pressure is high outside the plant cell due to environmental hypotonicity Water flows into the plant vacuoles via osmosis causing the vacuoles to expand and press against the cell wall Cell wall expands until it exerts pressure back on the cell (turgor pressure) Turgidity: optimum state for plant cells

vacuoles

membrane-bound sacs found in eukaryotic cells Function: Storage, release of macromolecules, water, and cellular waste products

lysosomes

membrane-enclosed sacs found in some eukaryotic cells that contain hydrolytic enzymes used in: Intracellular digestion, Recycling of organic materials, Programmed cell death

turgid

more concentration than its surroundings, very firm

hypertonic

more solute, less solvent, more concentrated

hypotonic

more solvent less solute, outside environment

glycoproteins

one or more carbohydrates attached to a membrane protein

Golgi complex

organelle found in eukaryotic cells that modifies, packages, and transports material out of the cell.

pressure potential

physical pressure on a solution Can be positive or negative Water in living cells is under positive pressure because the protoplast presses against the cell wall (turgor pressure)- helps maintain stiffness

Eukaryotic cell compartmentalization

plasma membrane: allow the cell to establish and maintain internal environments that are different from their external environment, has additional internal membranes and membrane bound organelles that compartmentalize the cell The compartments allow for various metabolic processes and specific enzymatic reactions to occur simultaneously, increasing the efficiency of the cell

Cholesterol in fluid mosaic model

randomly distributed and wedged between phospholipids in the cell membrane of eukaryotic cells Regulates bilayer fluidity under different environmental conditions Diversity and location of the carbohydrates and lipids enable them to function as markers

receptor-mediated endocytosis

receptor proteins on the cell membrane are used to capture specific target molecules

osmoregulation in animal cells

regulates water balance and allows control of inner solute composition/water potential Environmental hypertonicity: less solute more water , shriveled Isotonic solution: cell is normal Environmental hypotonicity: cell is lysed (burst)

active transport

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

free ribosomes

ribosomes suspended in the cytosol

cotransport

secondary active transport that uses the energy from an electrochemical gradient to transport two different ions across the membrane through a protein

Plasmodesmata

small holes between plant cells that allow the transfer of nutrients, waste, and ions, helps with permeability

water potential

solute potential + pressure potential Water moves from a high to low potential Values of water potential can be positive, negative, or zero The more negative, the more likely it will move into the area Pure water has a value of zero because it has no solute in it Increasing solute: increases solute potential, decreases water potential (and vice versa) Increasing water potential: increase in pressure potential Decreasing pressure potential: decrease in water potential

carrier proteins

spans the membrane and change shape to move a target molecule from one side of the membrane to another

Ribosomes

synthesize proteins, composed of RRNA and proteins, and is composed of 2 subunits that are NOT membrane enclosed

what processes occur in the mitochondria?

the Krebs cycle occurs in the matrix of the mitochondria and electron transport/ATP synthesis occur in the inner mitochondria membrane

tonicity

the measurements of the relative concentrations of solute between 2 solutions (inside and outside the cell)

bulk flow

the movement of liquid in response to a pressure gradient, which occurs from high to low pressure Independent of solute concentration Conducted through the xylem and phloem

facilitated diffusion

the movement of molecules from a higher concentration to a lower concentration through transport proteins Allows for hydrophilic molecules and ions to pass through the cell membrane

diffusion

the movement of molecules from a higher concentration to a lower concentration- small non-polar molecules, requires energy

passive transport

the net movement of molecules from a high concentration to a low concentration Plays an important role in the import of materials and export of wastes

cytoplasm

the region between the nucleus and the cell membrane organized in small compartments

osmolarity

the total solute concentration in a solution Water has high solvency abilities Solute is being dissolved Solvent dissolves a solute A solution is a solute mixed with a solvent

phloem

transports photosynthetic products from sources to sinks

xylem

transports water and minerals from roots to shoots

antiport

two different ions are transported in opposite directions

symport

two different ions are transported in the same direction

symplastic transport

water/solutes move along the cytosol by crossing the plasma membrane and then moving via the plasmodesmata

transmembrane transport

water/solutes moves out of one cell and into a neighboring cell, which is repeated

Apoplastic transport (in an organ/tissue)

waters/solutes move along the continuum of the cell wall and extracellular spaces

concentration gradient

when a solute is more concentrated in one area than another A membrane separates two different concentrations of molecules

flagella

whiplike tails found in one-celled organisms to aid in movement