bio chapter 6

Light microscope (LM)

Passes visible light through a specimen and then through glass lenses / the lenses refract (bend) the light so the image is magnified.

Scanning electron microscope (SEM)

Focuses a beam of electrons onto the surface of a specimen - giving images that look 3-D.

Transmission electron microscope (TEM)

Focuses a beam of electrons through a specimen / used mainly to study the internal structure of cells.

Cell fractionation

Takes cells apart and separates the major organelles from one another using centrifuges / lets scientists determine organelle functions.

Differential centrifugation

Series of spins at increasing speed / the supernatant is poured into the next tube. Pellets: 1000 g = nuclei/debris / 20000 g = mitochondria/chloroplasts / 80000 g = microsomes / 150000 g = ribosomes.

Domains with prokaryotic cells

Bacteria and Archaea.

Features common to ALL cells

Plasma membrane - cytosol (semifluid) - chromosomes (carry genes) - and ribosomes (make proteins).

Nucleoid

Region in a prokaryotic cell where the DNA is located / it is not enclosed by a membrane.

Features of eukaryotic cells

DNA in a nucleus bounded by a nuclear envelope / membrane-bound organelles / cytoplasm between the plasma membrane and nucleus / generally much larger than prokaryotic cells.

Cytoplasm (eukaryotes)

The region between the plasma membrane and the nucleus.

Cytosol

The semifluid substance within the cell.

Surface area to volume ratio

As a cell grows - its volume increases proportionately more than its surface area - so metabolic requirements set an upper limit on cell size.

Nuclear envelope

Double membrane (each membrane a lipid bilayer) enclosing the nucleus and separating it from the cytoplasm.

Chromatin

The DNA and proteins of chromosomes together / condenses into discrete chromosomes as a cell prepares to divide.

Chromosome

A discrete unit of DNA organization: a single DNA molecule associated with proteins.

Nucleolus

Structure within the nucleus that is the site of ribosomal RNA (rRNA) synthesis.

Ribosome

Complex of ribosomal RNA and protein that carries out protein synthesis / has a large and a small subunit.

Free vs. bound ribosomes

Free ribosomes are in the cytosol / bound ribosomes are on the outside of the ER or nuclear envelope.

Endomembrane system

Nuclear envelope - ER - Golgi apparatus - lysosomes - vacuoles - and plasma membrane / components are continuous or connected by transfer via vesicles.

Endoplasmic reticulum (ER)

Biosynthetic factory / more than half of the total membrane in many eukaryotic cells / membrane is continuous with the nuclear envelope. Two regions: smooth and rough.

Smooth ER functions

Synthesizes lipids - metabolizes carbohydrates - detoxifies drugs and poisons - stores calcium ions.

Rough ER functions

Bound ribosomes make glycoproteins (proteins covalently bonded to carbohydrates) / distributes transport vesicles / is a membrane factory for the cell.

Glycoprotein

A protein covalently bonded to a carbohydrate.

Transport vesicle

Membrane-enclosed sac carrying secretory proteins / moves materials between parts of the endomembrane system.

Golgi apparatus

Flattened membranous sacs (cisternae). Modifies products of the ER - manufactures certain macromolecules - and sorts and packages materials into transport vesicles.

cis face of the Golgi

The 'receiving' side of the Golgi apparatus.

trans face of the Golgi

The 'shipping' side of the Golgi apparatus.

Cisternae

The flattened membranous sacs of the Golgi apparatus (also used for ER sacs).

Lysosome

Membranous sac of hydrolytic enzymes that digests macromolecules / enzymes work best in the acidic environment inside the lysosome.

Where lysosomal enzymes and membranes are made

Rough ER - then transferred to the Golgi apparatus for further processing.

Phagocytosis

A cell engulfs another cell or particle - forming a food vacuole that fuses with a lysosome to be digested.

Autophagy

Lysosomes use enzymes to recycle the cell's own organelles and macromolecules.

Food vacuole

Vacuole formed by phagocytosis.

Contractile vacuole

Found in many freshwater protists / pumps excess water out of the cell.

Central vacuole

Found in many mature plant cells / holds organic compounds and water.

Mitochondria

Sites of cellular respiration - a metabolic process that uses oxygen to generate ATP.

Cristae

Folds of the inner mitochondrial membrane / provide a large surface area for ATP-synthesizing enzymes.

Mitochondrial matrix

Compartment enclosed by the inner mitochondrial membrane / some metabolic steps of cellular respiration occur here.

Intermembrane space

Compartment between the outer and inner mitochondrial membranes.

Chloroplast

Organelle in plants and algae that is the site of photosynthesis / contains chlorophyll.

Thylakoids / granum

Thylakoids are membranous sacs in the chloroplast / a stack of thylakoids is a granum.

Stroma

The internal fluid of the chloroplast.

Plastid

Group of plant organelles that includes the chloroplast.

Peroxisome

Oxidative organelle.

Endosymbiont theory

Mitochondria and chloroplasts originated from engulfed bacteria. Evidence: double membrane - free ribosomes - circular DNA - grow and reproduce somewhat independently.

Cytoskeleton

Network of fibers extending throughout the cytoplasm / supports the cell - maintains shape - anchors organelles - and interacts with motor proteins to produce motility.

Three types of cytoskeleton fibers

Microtubules - microfilaments (actin filaments) - and intermediate filaments.

Microtubules

Hollow rods about 25 nm in diameter (thickest) / made of tubulin. Shape the cell - guide organelle movement - separate chromosomes in cell division - control beating of cilia and flagella.

Microfilaments (actin filaments)

Solid rods about 7 nm in diameter (thinnest) / twisted double chain of actin. Bear tension / form the cortex / core of microvilli / motility with myosin (muscle contraction - cytoplasmic streaming).

Intermediate filaments

Intermediate diameter fibers / support cell shape and fix organelles in place / the most permanent cytoskeleton fixtures.

Motor proteins

ATP-powered proteins that 'walk' vesicles along cytoskeletal tracks.

Cilia and flagella

Microtubule-containing extensions that project from some cells / they differ in their beating patterns.

Cytoplasmic streaming

Circular flow of cytoplasm within cells that speeds distribution of materials / in plant cells driven by actin-myosin interactions and sol-gel transformations.

Myosin

Protein that works with actin in microfilaments that function in cellular motility (such as muscle contraction).

Extracellular matrix (ECM) of animal cells

Network outside animal cells made of glycoproteins such as collagen - proteoglycans - and fibronectin.

Integrins

Receptor proteins in the plasma membrane that bind ECM proteins (and connect to microfilaments inside the cell).

Plasmodesmata

Channels that perforate plant cell walls / water and small solutes (sometimes proteins and RNA) pass from cell to cell.

Tight junction

Membranes of neighboring animal cells are pressed together - preventing leakage of extracellular fluid.

Desmosome

Anchoring junction that fastens cells together into strong sheets.

Gap junction

Communicating junction / provides cytoplasmic channels between adjacent animal cells