AP Biology: Chapter 6 & 7 Cell Structure and Transport

plasma membrane

separates the living cell from its surroundings. Controls traffic in and out of the cell. Is selectively permeable.

selectively permeable

allows some substances to cross more easily than others.

phospholipids

most abundant lipids

lipids and proteins

main macromolecules in membranes

amphipatic molecules

have hydrophobic and hydrophilic regions

fluid mosaic model

The arrangement of phospholipids and proteins in biological membranes is described by the...

freeze-fracture

preparation technique that splits a membrane along the middle of the phospholipid bilayer

transmembrane proteins

the integral protein completely spans the membrane as...

integral proteins

proteins that penetrate the hydrophobic interior of the lipid bilayer

peripheral proteins

proteins that are not embedded in the lipid bilayer

cell-cell recognition

the ability of a cell to disitnguish one type of neighboring cell from another.

supramolecular structure

many molecules ordered into a higher level of organization with emergent properties than those of the individual molecules.

transport proteins

proteins that span the membrane.

channel proteins

transport proteins that have a hydrophilic channel that certain molecules or ions use as a tunnel though the membrane.

aquaporins

channel proteins that facilitate the passage of water

carrier proteins

transport proteins that bind to molecules and change shape to shuttle them across the membrane.

diffusion

movement of molecules of any substance to spread out in available space

concentration gradient

the region along which the density of a chemical substance increases or decreases.

passive transport

transport that requires no energy from the cell to make it happen

osmosis

the diffusion of water across a selectively permeable membrane

tonicity

the ability of a surrounding solution to cause a cell to gain or lose water.

isotonic (animal cell)

if a cell with no cell wall is immersed in an enviroment where there is no net movement of water across the plasma membrane. Stays the same.

hypertonic (animal cell)

when the cell is immersed in a solution where it loses water to its environment, shrivels and probably dies.

hypotonic (animal cell)

when a cell is immersed in a solution, water enters the cell faster than it leaves, it swells and lyses (explodes) like an overfilled water balloon.

osmoregulation

the control of water balance

Paramecium

is a protist that is hypertonic to the pond water in which it lives.

turgid

when the plant cell is very firm, which is a healthy state for most plant cells.

hypotonic (plant cell)

when a plant cell is immersed in a __________ solution the cell contents swell due to osmosis until the elastic cell wall exerts turgor pressure on the cell that opposes further water outake.

isotonic (plant cell)

when a plant cell is immersed in a _______ solution; there is no net movement. The cell becomes flaccid and the plant may wilt.

flaccid

limp, not firm or strong (If a plant is not watered enough, its leaves become droopy and flaccid.)

hypertonic (plant cells)

the plant cell loses water, its volume shrinks. The plasma membrane pulls away from the wall, this is plasmolysis. It is lethal to the cell.

plasmolysis

This happens when a cell shrinks inside its cell wall while the cell wall remains intact. The plasma membrane pulls away from the wall.

facilitated diffusion

the passive movement of molecules down their concentration gradient with the help of transport proteins.

ion channels (gated channels)

Channels that open or close depending on the presence or abscence of an electrical, chemical, or physical stimulus.

cystinuria

human disease characterized by the absence of a carrier protein that transports cysteine and other amino acids across the membranes of kidney cells.

active transport

transport that requires the cell to expend metabolic energy and enables a cell to maintain internal concentrations of small molecules. Requires energy.

ATP

supplies energy for most active transport

sodium-potassium pump

transport protein that, translocating the bound solute across the membrane. Exchanges sodium ions (Na) for potassium ions (K) across the plasma membrane of animal cells.

membrane potential

voltage across a membrane. Ranges form -50 to -200 millivolts. The inside of the cell is negative to the outside.

electrochemical gradient

2 combined forces drive the diffusion of ions across the membrane.

electrogenic pumps

special transport proteins that generate the voltage gradient across a membrane.

Ex. sodium potassium pump and proton pumps.

sodium-potassium pump

major electrogenic pump in animals. Restores the electrochemical gradient by setting up a concentration gradient. It pumps 2 K ions for every 3 Na ions that it moves out, it generates a voltage.

proton pumps

the major electrogenic pump. Transports protons out of the cell and transfers positive charge form the cytoplasm to the extracellular solution.

cotransport

single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes in a mechanism.

exocytosis

transport vesicle budded from the Golgi apparatus is moved by the cytoskeleton to the plasma membrane. When the 2 membranes come in contact, the bilayers fuse spill the contents.

endocytosis

a cell brings in biological molecules and particulate matter by forming new vesicles from the plasma membrane.

3 types: phagocytosis, pinocytosis and receptor-mediated endocytosis.

phagocytosis

a cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle.

pinocytosis

molecules are taken up when extracellular fluid is "gulped" into tiny vesicles.

receptor-mediated endocytosis

endocytosis that enables a cell to acquire bulk quantities of specific materials that may be in low concentrations in the environment.

lipoproteins

complexes of proteins and lipids. Cholesterol travels in low density _______

ligands

A molecule that binds specifically to a receptor site of another molecule.

dialysis

movement of particles in a solution through permeable membranes. The diffusion of small solutes through a selectively permeable membrane.

organelles

membrane-enclosed structures within a eukaryotic cell

cytosol

a jellylike substance where organelles and other components are found

eukaryotic cell

Cell with a nucleus and membrane bound organelles

prokaryotic cell

Cell with no nucleus nor membrane bound organelles

nucleoid region

a non-membrane-enclosed region of the cell where prokaryotic DNA is found

cytoplasm

the region in a cell between the cell membrane and nucleus; it contains the cell structures and oganelles

plasma membrane

The selective barrier that surrounds a cell; it controls what enters and leaves the cell

nucleus

chromosome-containing part of a eukaryotic cell

nuclear envelope

encloses the nucleus to separate its contents from the cytoplasm

nuclear lamina

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

chromosomes

tightly coiled structures that carry the genetic information (can be seen during nuclear division)

chromatin

loosly coiled genetic material that makes up chromosomes, a complex of proteins and DNA

nucleolus

located in the nucleus, makes, synthesizes, and partially assembles ribosomes

ribosomes

made of ribosomal RNA and protein, synthesize proteins

endomembrane system

membranes that divide the cell into organelles such as the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and the cell membrane.

endoplasmic reticulum (ER)

accounts for more than half of total membrane in many eukaryotic cells, continuous with the nuclear envelope

smooth ER

portion of the endoplasmic reticulum free of ribosomes, synthesize lipids, detoxifies the cell, and regulates calcium levels

rough ER

portion of the endoplasmic reticulum studded with ribosomes, produce and transport membrane and secretory proteins

glycoproteins

proteins with covalently-bonded carbohydrates that play a role in cell to cell interaction

transport vesicles

vesicles in transit from one part of the cell to another

Golgi apparatus

stack of membranes that modifies, sorts, and packages proteins from the endoplasmic reticulum

lysosome

membranous sac of hydrolytic enzymes, which the cell uses to digest unwanted materials

phagocytosis

the process by which a cell engulfs a solid particle

autophagy

lysosomes break down damaged organelles

food vacuoles

formed by phagocytosis, pinches off from plasma membrane and encloses a food particle

contractile vacuoles

pump excess water out of the cell to maintain a suitable concentration of ions and molecules in the cell

central vacuole

the largest organelle in a plant cell. It is surrounded by the tonoplast and functions to hold materials and wastes. It also functions to maintain the proper pressure within plant cells

mitochondria

chemically convert chemical (food) energy into usable ATP energy through cellular respiration

chloroplasts

contain chlorophyll which help absorb solar energy in order to convert carbon dioxide and water into sugars during photosynthesis

cristae

infoldings in the inner membrane of the mitochondria

mitochondrial matrix

compartment of the mitochondrion, enclosed by the inner membrane, contains enzymes and substrates for the citric acid cycle

plastids

manufacture and store important chemical compounds used by the cell such as pigments, oils, and starches

thylakoids

flattened and interconnected sacs found in chloroplasts. The light dependent stage of photosynthesis occurs on the membranes of these sacs

granum

stacks of thylakoids

stroma

fluid outside the thylakoids, contains chloroplast DNA, ribosomes, and enzymes. The light independent stage of photosynthesis occurs in this area

cytoskeleton

a network of fibers bracing the cytoplasm

microtubules

hollow rods of protein, support the cell and moves organelles within the cell

centrosome

a region located near the nucleus where micro-tubules grow from; important in cell division

centrioles

cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division

flagella

a long tail-like structure that aids in cell movement

cilia

a short hair-like structures that enable movement of cells or movement of materials outside a cell, utilizes a back-and-forth motion

microfilaments

the thinnest part of the cytoskeleton, are used to give shape to the cell and support all of its internal parts

actin

a globular protein that makes up microfilaments

pseudopodia

cellular extensions that enable a cell to crawl along a surface

cytoplasmic streaming

the circular flow of cytoplasm within cells

intermediate filaments

diverse class of cytoskeletal elements that bear tension like microfilaments

cell wall

extracellular structure specific to plant cells, protects the cell, maintains its shape, and prevents excessive water uptake

primary cell wall

a relatively thin and flexible layer in plant cells, first secreted by a young cell