Chapter 4
Biology & Chemistry Bi105 with Godrick at Boston University
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cell theory
All organisms are composed of one or more cells.
Cells are the smallest living things.
Cells arise only by division of a previously existing cell.
surface area-to-volume ratio
as a cell's size increases, its volume increases much more rapidly than its surface area
light microscopes
operate with visible light
compound microscopes
magnify in stages using several lenses
electron microscope
employs electron beams
has 1000 times the resolving power of a light microscope
immunihistochemistry
uses antibodies generated in animals
antibodies are purified and chemically bonded to enzymes, to stains, or to fluorescent molecules
transport proteins
help molecules and ions move across the plasma membrane, either from the environment to the interior of the cell or vice versa
receptor proteins
induces changes within the cell when they come in contact with specific molecules in environment, such as hormones, or with molecules on the surface of neighboring cells
markers
molecules that identify the cell as a particular type
cell wall
hold cytoplasm surrounded by a plasma membrane
ribosomes
organelles which carry out protein synthesis
flagella
long, threadlike structures protruding from the surface of a cell that are used as locomotion
protein fibers
endomembrane system
weaves through the cell interior
central vacuole
a large, membrane-bound sac
stores proteins, pigments, and waste materials
vesicles
smaller sacs that store and transport a variety of materials
chromosomes
compact units holding DNA wound tightly around proteins
cytoskeleton
an internal protein scaffold
nucleus
the repository of the genetic information that enables the synthesis of nearly all proteins of a living eukaryotic cell
nucleolus
a region where intensive synthesis of ribosomal RNA is taking place
nuclear envelope
made up of two phospholipid bilayer membranes
endoplasmic reticulum
the cytoplasm's interior membrane system
nuclear pores
form at locations where the two membrane layers of the nuclear envelope pinch together
have a complex structure with a cytoplasmic face, a nuclear face, and a central ring embedded in the membrane
nuclear lamins
intermediate filament fibers that compose the inner surface of the nuclear envelope
chromatin
allows regulatory proteins to attach to specific nucleotide sequences along the DNA and regulate gene expression
ribosomal RNA (rRNA)
RNA within each ribosome
messenger RNA (mRNA)
carries coding information from DNA
directs the synthesis of a protein in ribosomes
transfer RNA (tRNA)
carries amino acids
endoplasmic reticulum (ER)
weaves in sheets through the interior of the cell, creating a series of channels between its folds
cisternal space OR lumen
the inner region of the ER
cytosol
the region exterior to the cisternal space
the fluid component of the cytoplasm containing dissolved organic molecules such as proteins and ions
rough ER (RER)
synthesized proteins on its surface that are destined to be exported from the cell, sent to lysosomes or vacuoles, or embedded in the plasma membrane
glycoproteins
formed by newly synthesized proteins added to short-chain carbohydrates
destined for secretion and separated from other products and later packaged into vesicles
smooth ER (SER)
regions of the ER with relatively few bound ribosomes
contain many embedded enzymes
Golgi body OR Golgi apparatus
a complex formed by flattened stacks of membranes, often interconnected with one another
functions in the collection, packaging, and distribution of molecules synthesized at one location and used at another within the cell or even outside of it
cis face
the front, or receiving end of the Golgi apparatus
cisternae
the newly formed or altered glycoproteins and glycolipids collect at the ends of the Golgi bodies in flattened, stacked membrane folds
lysosomes
membrane-bounded digestive vesicles
contain high levels of degrading enzymes, which catalyze the rapid breakdown of proteins, nucleic acids, lipids, and carbohydrates
phagocytosis
produces a food vesicle that fuses with lysosomes to activate them
trans face
the back, or discharging end of the ER
where ER-synthesized molecules are discharged in secretory vesicles
microbodies
enzyme-bearing, membrane-enclosed vesicles
found in the cells of plants, animals, fungi, and protists
peroxisome
contains enzymes involved in the oxidation of fatty acids
contains the enzyme catalase, which breaks down hydrogen peroxide into its harmless constituents--water and oxygen
vacuoles
specialized membrane-bounded structures
central vacuole: most plant cells
tonoplast
the membrane surrounding the central vacuole
contains channels for water that are used to help the cell maintain its tonicity, or osmotic balance
mitochondria
typically tubular or sausage-shaped organelles about the size of bacteria that are found in all types of eukaryotic cells
cristae
an inner folded membrane with numerous contiguous layers (within mitochondria)
matrix
lies inside the inner membrane of the cristae
intermembrane space
an outer compartment of the cristae
lies between the two mitochondrial membranes
chloroplasts
can manufacture their own food
contain the photosynthetic pigment chlorophyll that gives most plants their green color
grana
closed compartments of stacked membranes
lie inside the inner membrane of chloroplasts
thylakoids
disk-shaped structures within each granum
stroma
a fluid matrix surrounding the thylakoid
contain the enzymes used to synthesize glucose during photosynthesis
leucoplasts
DNA-containing organelles that lack pigment and a complex internal structure
amyloplast
a leucoplast that stores starch (amylose)
plastids
collection of chloroplasts, leucoplasts, and amyloplasts
all are produced by the division of existing plastids
actin filaments
long fibers about 7 nm in diameter
composed of two protein chains loosely twined together like two strands of pearls
actin
each pearl, or subunit, on the chain of each filament
globular protein
microtubule
hollow tubes about 25 nm in diameter, each composed of a ring of 13 protein protofilaments
intermediate filaments
a system of tough, fibrous protein molecules twined together in an overlapping arrangement
8 to 10 nm in diameter
centrioles
barrel-shaped organelles found in the cells of animals and most protists
occur in pairs, usually located at right angles to each other near the nuclear membranes
centrosome
the region surrounding the pair in almost all animal cells
pericentriolar material
surrounds the centrioles in the centrosome
contains ring-shaped structures composed of tubulin
kinesin
a motor protein connected to vesicles by the protein kinectin
uses ATP to power its movement toward the cell periphery, dragging the vesicle with it as it travels along the microtubule toward the plus end
dynein
a motor protein connected to vesicles by the set of vesicle proteins dynactin complex
directs movement in the opposite direction along microtubules toward the minus end, inward toward the cell's center
involved in the movement of eukaryotic flagella
myosin
protein best known for its role in muscle contraction
its motors along the actin filaments contract and pull the contents of the cell toward the newly extended front edge
9 + 2 structure
eukaryotic cells have flagellum, consisting of a circle of nine microtubule pairs surrounding two central microtubules
basal body
antiderivative of the microtubules of the flagellum
situated just below the point where the flagellum protrudes from the surface of the cell
primary walls
in plants
laid down when the cell is still growing
middle lamella
a sticky substance between the walls of adjacent cells
glues the cells together
secondary walls
some plants cells
are deposited inside the primary walls of fully expanded cells
extracellular matrix
formed by an elaborate mixture of glycoproteins into the space around them
in animal cells
fibronectin
glycoprotein that attached the ECM of some cells to the plasma membrane
bind to ECM glycoproteins and to integrins
integrins
proteins that bind to fibronectin
integral part of the plasma membrane, extending into the cytoplasm, where they are attached to the microfilaments and intermediate filaments of the cytoskeletonc
cell junctions
long-lasting or permanent connections with members of organized tissues
tight junctions
connect the plasma membranes of adjacent cells in a sheeta
anchoring junctions
mechanically attach the cytoskeleton of a cell to the cytoskeletons of other cells or to the extracellular matrix
cadherins
single-pass transmembrane glycoproteins
create the ctitical link between adjacent cells
adherin junctions
connect the actin filaments of once cell with those of neighboring cells or with the extracellular matric
plasmodesmata
cytoplasmic connections that form across the touching plasma membranes
are lined with plasma membrane and contain a central tubule that connects the ER of the two cells
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