AP Biology Unit 2

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

middle lamella

a thin layer between primary walls of adjacent cells that glues them together with pectin

secondary cell wall

a strong and durable matrix in plant cells, often deposited in several laminated layers for cell protection and support

extracellular matrix

where animal tissue cells are embedded, consists of protein and polysaccharides

collagen

most common glycoprotein in the ECM, forms strong fibers outside the cells

plasmodesmata

channels that perforate cell walls, allow for connections between cells in plants

tight junctions

intercellular junction in animal tissues where plasma membranes of neighboring cells are very tightly pressed against each other, bound by specific proteins

desmosomes

intercellular junction in animal tissues that function like rivets, fastening cells together into strong sheets

gap junctions

intercellular junction in animal tissues that provide cytoplasmic channels from one cell to an adjacent cell, similar to plasmodesmata in plants

Plasma membrane

The boundary that separates the living cell from its surroundings

Selective permeability

_________ ____________ is a characteristic of cell membranes that means what passes in and out is regulated. It allows some substances to cross the membrane more easily than others.

Amphipathic

Having characteristics of being hydrophobic and hydrophilic, such as a phospholipid.

Phospholipid

The basic structural component and most abundant lipid of cell membranes is ____________.

Fluid Mosaic Model

Describes a membrane as a fluid structure with a "mosaic" of various proteins embedded in it.

Osmosis

The diffusion of water across a selectively permeable membrane.

Diffusion

A passive process that involves the movement of substances or molecules from high solute concentration to low. It is also the tendency for molecules to spread out evenly into the available space.

Active transport

Uses energy (usually in the form of ATP) to move solutes against their concentration gradients and to maintain concentration gradients that differ from their surroundings, i.e. sodium-potassium pump.

Electrogenic pump

An ion transport protein that generates voltage across a membrane.

Endocytosis

The cell takes in macromolecules by forming vesicles from the plasma membrane.

Phagocytosis

Also known as cellular eating. A cell engulfs a particle in a vacuole.

Pinocytosis

Also known as cellular drinking. Molecules dissolved in droplets are taken up when extracellular fluid is "gulped" into tiny vesicles.

Receptor-mediated endocytosis

Special receptor proteins catch molecules and bring them into the cell against a concentration gradient

Exocytosis

Transport vesicles migrate to the
membrane, fuse with it, and release their contents outside the cell

Cotransport

Occurs when active transport of a solute indirectly drives transport of other substances.

Peripheral proteins

Proteins bounded to the surface of the membrane.

Integral proteins

Proteins that penetrate the hydrophobic core.

Transmembrane proteins

Proteins that span the membrane.

What are the 6 major functions of membrane proteins?

Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix (ECM)

Hydrophobic (nonpolar) molecules

Can dissolve in the lipid bilayer and pass through the membrane rapidly, such as hydrocarbons.

Hydrophilic molecules

Do not cross the membrane easily, such as ions and polar molecules.

Transport proteins

Allow passage of hydrophilic substances across the membrane.

Channel protein

A type of transport protein that has a hydrophilic channel that certain molecules or ions can use as a tunnel.

Aquaporins

Channel proteins that facilitate the passage of water.

Carrier protein

A type of transport protein that binds to molecules and changes shape to shuttle them across the membrane.

Passive transport

The diffusion of a substance across a membrane with no energy investment.

Concentration gradient

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

Tonicity

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

Isotonic solution

Solute concentration is the
same as that inside the cell; no net water
movement across the plasma membrane.

Hypertonic solution

Solute concentration is
greater than that inside the cell; cell loses water.

Hypotonic solution

Solute concentration is less
than that inside the cell; cell gains water.

Osmoregulation

The control of solute concentrations and water balance that is a necessary adaptation for life in such environments.

Turgid

A plant cell in a hypotonic solution swells until the
wall opposes uptake; the cell is now turgid (firm).

Flaccid

If a plant cell and its surroundings are isotonic,
there is no net movement of water into the cell;
the cell becomes flaccid (limp).

Plasmolysis

A process in which plant cells lose water in a hypertonic environment, making the membrane pull away from the cell wall and causing the plant to wilt.

Facilitated diffusion

Transport proteins speed the passive movement of molecules across the plasma membrane. I describe the passive assistance of a transport protein to move substances from high solute concentration to low. I require no energy expenditure, instead using transport proteins to pass through membranes. What am I?

Ion channels

Channel proteins that facilitate the diffusion of ions.

Gated channel

A type of ion channel that opens or closes in response to a stimulus.

Electrochemical gradient

Two combined forces that drive the diffusion of ions across a membrane: A chemical force (the ion's concentration gradient) and an electrical force (the effect of the membrane potential on the ion's movement).

Sodium-potassium pump

The major electrogenic pump of animal cells

Proton pump

The main electrogenic pump of plants, fungi, and bacteria

What is the purpose of electrogenic pumps?

To help store energy that can be used for cellular work

Bulk transport

Occurs by exocytosis and endocytosis and requires energy

How do small molecules and water enter or leave the cell?

Through the lipid bilayer or via transport proteins