Ch.1 Cell Structure

Wavelength - 400-700 nm

Resolution - 200 nm

Specimen - alive

Image - colored

Light Microscope

Wavelength - 0.1 nm

Resolution - 0.05 nm

Specimen - dead

Image - monochrome

Electron Microscope

Cytoplasm

living material of the cell excluding the nucleus where metabolic reactions take place

Cell Surface Membrane

7 nm with three layers (phospholipid bilayer)

partially permeable and controls exchange between the cell and its environment

Microvilli

finger-like extensions of a cell which increases its surface area for more efficient absorption or secretion

Nucleus

Largest organelle (10 nm) containing genetic material

Chromatin

mass of coiled threads made of DNA, proteins (histones), and RNA

DNA contains the genes which controls cell activity

forms chromosomes during cell division

Nucleolus

made of loops of DNA from several chromosomes and makes ribosomes

densely staining and variable quantity

Nuclear Envelope & Pores

double-membraned with the outer membrane continuous with the RER

perforated by pores which control the exchange of materials between the nucleus and cytoplasm

Rough Endoplasmic Reticulum

covered with ribosomes

network of flattened sacs

molecules (particularly proteins) can be transported instead through the cell

continuous with the outer membrane of the nuclear envelope

Smooth Endoplasmic Reticulum

makes lipids and steroids

storage site of calcium ions

Ribosomes

consists of two subunits

made of rRNA and protein

allow interacting molecules (mRNA, tRNA, amino acids, regulatory proteins) involved in protein synthesis to gather

70S (20 nm) in prokaryotes and mitochondria/chloroplasts and 80S (25 nm) in eukaryotes.

Golgi Apparatus

stack of flattened sacs called cisternae

formed at one end which bud off from the ER and broken down again at the other end to form the golgi vesicle

makes lysosomes, glycoproteins, glycolipids

processed molecules can be transported by the golgi vesicle

Lysosomes

simple sacs surrounded by a single membrane

contains digestive/hydrolytic enzymes(hydrolases) and performs destructive functions

Mitochondria

surrounded by an envelope (two membranes) with the inner membrane folding into cristae which project into the matrix

performs aerobic respiration

energy is transferred to molecules of ATP

energy is released from ATP by breaking down to ADP during hydrolysis

contains circular DNA and 70S ribosomes

Microtubules

long, rigid, hollow tubes that make up the cytoskeleton

α- and β- tubulin combine to form dimers which are joined to make protofilaments. Thirteen protofilaments lines up to form microtubules

forms an intracellular transport system

forms a spindle during nuclear division

part of the structure of centrioles

Centriole

cylindrical structures found outside the nucleus and at the bases of cilia and flagella

formed from a ring of nine triplets of microtubules

centrioles at the bases of cilia and flagella (basal bodies) act as MTOCs

Cilia and Flagella

whip-like, beating extensions

two central microtubules and a ring of nine microtubule doublets (MTD)

MTD has an A microtubule with 13 protofilaments and a B microtubule with 10 protofilaments

has inner and outer arms made of the protein dynein which connect to the B microtubule of the neighboring MTD

used for locomotion

Chloroplasts

carries out photosynthesis

contains flattened sacs called thylakoids with chlorophyll embedded in there membranes

thylakoids are stacked to form grana

the energy converts carbon dioxide into sugars which are stored as starch grains in the stroma (matrix)

lipid droplets, 70S ribosomes, and circular DNA are found in the stroma

Cell Walls

rigid as they are made from polysaccharide cellulose which are inelastic and have high tensile strength

reinforced by lignin

provides mechanical strength, gives the cell a definite shape and prevents bursting by osmosis

Plasmodesmata

pore-like structure found in plant cell walls

forms passage between neighboring cells by fine threads of cytoplasm to allow exchange of materials

Vacuole

holds cells sap which contains pigments, enzymes, sugars, mineral salts, oxygen and carbon dioxide

surrounded by a partially permeable membrane (tonoplasts) which controls the exchange between the vacuole and cytoplasm

helps regulate the osmotic properties of the cell

Bacteria

prokaryotic and unicellular

1-5 µm diameter

circular DNA and plasmids

peptidoglycan cell walls

70S ribosomes

absence of organelles surrounded by double-membranes

Viruses

non-cellular structures with a nucleic acid core (DNA or RNA)

capsid (protein coat) made of the proteins molecules (capsomere)

some viruses have an outer layer made of phospholipids