BIOL 1406 FLASHCARDS: Exam #2

Cell

The smallest unit of life that can function independently

Early Cell Theory

> All organisms are made up of one or more cells

> The cell is the fundamental unit of life

> All cells come from preexisting cells

Additional Ideas in Modern Cell Theory

> All cells have the same basic chemical composition

> All cells use energy

> All cells contain DNA that is duplicated and passed on as each cell divides

Common Characteristics of All Cells

> Contain genetic material

> Contain ribosomes

> Contain cytoplasm

> Have a cell membrane

> Carry out chemical reactions needed to sustain life, such as cellular respiration and protein synthesis

Characteristics of Prokaryotic Cells

> Nuclear membrane is absent so they do not have a distinct nucleus

> They do not have many of the membrane-bound structures

> DNA is free in its naked form

> Examples include bacteria, cyanobacteria, and archaebacteria

Characteristics of Eukaryotic Cells

> A double nuclear membrane is present, so they have distinct nuclei

> They have membrane bound structures

> DNA is packaged in chromosomes

> Examples include algae, fungi, animals, and plants

Magnification

The ratio of the size of an image to the size of the object

Resolution

The clarity of a magnified object; the minimum distance two objects can be apart and still be seen as two distinct objects

Light Microscopes

Used to view the entire cell

Electron Microscopes

Used to view the parts of cells, and viruses, which are smaller and require higher magnification

Bright-Field Microscopy

Light passes directly through the cell

Phase-Contrast Microscopy

Contrast in the image is increased by emphasizing differences in the refractive index, thereby enhancing the light and dark regions of the cell

Differential Inference-Contrast Microscopy

Uses two beams of polarized light - the combined images look as if the cell is casting a shadow on one side

Stained Bright-Field Microscopy

A stain enhances contrast and reveals details of the cell that would otherwise not be visible; the stains differ greatly in their chemistry and in their capacity to bind to cell materials, so many choices are available

Fluorescence Microscopy

A natural substance in the cell or a fluorescent dye that binds to a specific cell material is stimulated by a beam of light, and the longer-wavelength fluorescent light is observed coming directly from the dye

Transmission Electron Microscopy

A beam of electrons is focused on the cell by magnets; objects appear darker if they absorb the electrons; if the electrons pass through, they are detected on a fluorescent screen

Scanning Electron Microscopy

Directs electrons to the surface of the cell sample, where they cause other electrons to be emitted; these electrons are then viewed on a screen where the three-dimensional surface of the sample can be visualized

Flagella

A slender threadlike structure, especially a microscopic appendage that enables many protozoa, bacteria, spermatozoa, etc. to swim

Pili (Fimbriae)

Short, hair-like structures on the cell surface of prokaryotic cells

Cilia

A short microscopic hairlike vibrating structure found in large numbers on the surface of certain cells; either causes currents in the surrounding fluid, or, in some protozoans and other small organisms, provides propulsion

Sex Pili

An appendage of a male bacterium by which it attaches to a female bacterium, preparatory to the transfer of DNA from male to female

Plasmids

A small, circular, double-stranded DNA molecule that is distinct from a cell's chromosomal DNA

Nucleoid

A chromatin-dense area within the cytoplasm of prokaryotic cells; contains bacterial DNA, associated proteins, and RNA responsible for controlling bacterial activity and reproduction

Nucleus

Protective container for the cell’s DNA; DNA never leaves this structure, but messages (mRNA) can be sent to other parts of the cell

Nucleolus

An area inside the nucleus of a cell that is made up of RNA and proteins and is where ribosomes are made

Nuclear Envelope

A highly regulated double membranous barrier that separates the nucleus from the cytoplasm in eukaryotic cells

Nuclear Pores

Allow for the movement of specific molecules between the nucleus and cytoplasm

Ribosomes

Builds proteins by piecing together long chains of amino acids according to mRNA messages (copies of pieces of DNA)

Chloroplast

Plastid containing chlorophyll and other pigments; in plants that carry out photosynthesis

Chlorophyll

A pigment that gives plants their green color; helps plants create their own food through photosynthesis

Thylakoid

The site of photochemical or light-dependent reactions of photosynthesis in chloroplasts

Granum

One of the lamellar stacks of chlorophyll-containing thylakoids found in plant chloroplasts

Stroma

The fluid-filled internal space of the chloroplasts which encircle the grana and the thylakoids

Mitochondria

Found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur; it has a double membrane, the inner layer being folded inward to form layers

Cristae

Each of the partial partitions in a mitochondrion formed by infolding of the inner membrane

Mitochondrial Matrix

The mitochondrion internal spaces enclosed by the inner membrane

Endosymbiont Theory

States that some of the organelles (such as mitochondria and chloroplasts) in eukaryotic cells were once prokaryotic microbes

Plasma Membrane

A thin membrane enclosing the cytoplasm of a cell; proteins in the membrane control passage of ions in and out of the cell

Cell Wall

A rigid layer of polysaccharides enclosing the membrane of plant and prokaryotic cells; contain peptidoglycan in bacteria

Cytoplasm

The protoplasm of a cell excluding the nucleus; is full of proteins that control cell metabolism

Golgi Body

Receives products from the ER and adds final modifications; it also sorts these products and sends them to their final destinations; in plants, polysaccharides used in the production of cell walls are synthesized here

Lysosomes

A membrane-enclosed bag of digestive juices; breaks down large molecules and old cell parts into their components which can be recycled to build new cell parts

Primary Lysosomes

Originate from the Golgi body

Secondary Lysosomes

A product of phagocytosis - during phagocytosis, a phagosome is formed, which fuses with a primary lysosome in order to form this

Peroxisomes

Collect and break down toxic byproducts of metabolic reactions, such as hydrogen peroxide, using specialized enzymes

Glyoxysomes

Convert lipids into carbohydrates which are used for cellular growth

Rough Endoplasmic Reticulum

Large folded membrane system studded with ribosomes; ribosomes build proteins and this structure helps to fold or modify them; products made here are sent to the Golgi body

Smooth Endoplasmic Reticulum

Large folded membrane system; pieces together lipids and plays an important role in the production of new membranes

Cytoskeleton

System of protein filaments that maintain cell shape and play roles in cell movement and cell division

Microtubules

Filament of tubulin monomers, 25 nm in diameter; play an important role in cell structure, organization, mitosis, and movement

Intermediate Filaments

Cytoskeletal filament, 8-12 nm in diameter; structural protein in eukaryotic cell

Microfilaments

Polymer of actin monomers, 7 nm in diameter, globular protein arranged in a helix; major contractile component of muscle cells

Plasmodesmata

Intercellular pores connecting adjacent plant cells allowing membrane and cytoplasmic continuity; essential routes for intercellular trafficking, communication, and signaling in plant development and defense

Vacuoles

Large vesicles derived from the ER and Golgi body; diverse maintenance compartments

Central Vacuoles

Large, membrane-bound organelles found in plant cells that act as a storage space for water and other molecules in the cell

Food Vacuoles

A vacuole with a digestive function in the protoplasm of a protozoan

Contractile Vacuoles

A vacuole in some protozoans which expels excess liquid on contraction

Leucoplasts

A colorless organelle found in plant cells, used for the storage of starch or oil

Chromosomes

A threadlike structure of nucleic acids and proteins found in the nucleus of most living cells; carries genetic information in the form of genes; composed of long, thin strands of chromatin

Chromatin

The material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed; consists of protein, RNA, and DNA

Phagocytosis

Process in which phagocytes engulf and digest microorganisms and cellular debris; "cellular eating"

Pinocytosis

Process by which certain cells can engulf and incorporate droplets of fluid; "cellular drinking"

Exocytosis

The process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell

Endocytosis

The process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell

Receptor-Mediated Endocytosis

A process by which cells absorb metabolites, hormones, proteins – and in some cases viruses – by the inward budding of the plasma membrane (invagination)

Extracelular Matrix

Composed of fibrous proteins such as collagen, gel-like proteoglycans, and other proteins; holds cells together in tissues, contributes to properties of bone, cartilage, skin, etc., filters materials passing between different tissues, orients cell movements in development and tissue repair, and plays an important role in chemical signaling

Selective Permeability

Refers to the cell membrane's ability to differentiate between different types of molecules, only allowing some molecules through while blocking others

Fluid Mosaic Model

Describes the cell membrane as a tapestry of several types of molecules (phospholipids, cholesterols, and proteins) that are constantly moving

Phospholipids

The most abundant lipids in the plasma membrane; amphipathic molecules, containing hydrophobic and hydrophilic regions and varying in fatty acid chain length, degree of saturation, and phosphate groups

Peripheral Proteins

A class of membrane proteins that attach to the lipid bilayer, acting on the lipid-water interface

Integral Proteins

A class of membrane proteins that are permanently embedded within the plasma membrane; they serve a range of important functions, including transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix

Aquaporins

Integral membrane proteins that serve as channels in the transfer of water, and in some cases, small solutes across the membrane

Transmembrane Proteins

A type of integral membrane protein that spans the entirety of the cell membrane

Glycolipids

A carbohydrate that is covalently linked to a lipid

Glycoproteins

A carbohydrate that is covalently linked to a protein

Cell Junctions

Intercellular connections between the plasma membranes of adjacent cells

Tight Junctions

Help ensure directional movement of materials; the proteins of these cell junctions form a “quilted seal”, barring the movement of dissolved materials through the space between epithelial cells

Desmosomes

Mimic “spot welds”; link adjacent cells together tightly, but permit materials to move around them in the intercellular space

Gap Junctions

Allow for communication between adjacent cells

Passive Transport

A type of cellular transport in which substances such as ions and molecules move down their respective concentration gradients; does not require energy

Diffusion

The net passive movement of molecules or particles from regions of higher to regions of lower concentration

Simple Diffusion

A form of diffusion that does not require the assistance of membrane proteins

Osmosis

The diffusion of water across a selectively permeable membrane

Osmoregulation

The maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations

Transport Proteins

Allow for the passage of hydrophilic substances across a cell membrane

Facilitated Diffusion

The diffusion of solutes through transport proteins in the plasma membrane

Concentration Gradient

Occurs when the concentration of particles is higher in one area than another

Active Transport

A type of cellular transport in which substances such as ions and molecules move against their respective concentration gradients; requires energy

Primary Active Transport

The transport of molecules against a concentration gradient by the use of energy from ATP

Secondary Active Transport

The transport of two different molecules across a transport membrane using energy in other forms than ATP

Tonicity

The capability of a solution to modify the volume of cells by altering their water content

Isotonic Solution

Any external solution that has the same solute concentration and water concentration compared to body fluids; no net movement of water will take place

Hypotonic Solution

Any external solution that has a low solute concentration and high water concentration compared to body fluids; the net movement of water will be into the body and out of the solution

Hypertonic Solution

Any external solution that has a high solute concentration and low water concentration compared to body fluids; the net movement of water will be out of the body and into the solution

Turgidity

Refers to the state of being turgid or swollen due to high fluid content inside the cell

Flaccidity

Refers to the state between turgidity and plasmolysis in which the plasma membrane is not pushed against the cell wall

Plasmolysis

The process of contraction or shrinkage of the protoplasm of a plant cell and is caused due to the loss of water in the cell

Sodium-Potassium Pump

A protein pump found in the cell membrane of neurons (and other animal cells); acts to transport sodium and potassium ions across the cell membrane in a ratio of 3 sodium ions out for every 2 potassium ions brought in

Uniporter

A membrane transport protein that transports a single species of substrate (charged or uncharged) across a cell membrane

Symporter

An integral membrane protein that is involved in the transport of two different molecules across the cell membrane in the same direction