Download 3-1 Anatomy of cells - Manasquan Public Schools

CELLS AND TISSUES
Cell Parts
Suzanne D'Anna
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Basic Cell
defined as the structural and functional unit
of all living things
- as small as 1/1000th of an inch (bacteria)
- as large as 4 feet (certain nerve cells)
 Shape:
- disc shaped, thread-like, cube-like, etc.
 Functions:
- protection, hormones, chemical
regulation, gas exchange, cleanse blood

Suzanne D'Anna
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Main Regions of a Cell
plasma (cell) membrane
 cytosol (cytoplasm)
 organelles
- specialized highly
organized structures for
specific cellular activities
 inclusions
- temporary structures

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Plasma (cell) Membrane
outer layer of the cell
 fragile barrier
 separates internal components of the
cell from the external environment
 contains cell contents
 two lipid layers - protein molecules are
suspended between lipid layers

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Plasma (cell) Membrane
(cont.)
unique structure which determines
which substances enter or leave the cell
 Consists of:
- phopholipids
- cholesterol
- proteins

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Functions of Membrane
Proteins
channels
 enzymes
 transportation of substances across
membrane
 receptor sites for hormones,
neurotransmitters, or nutrients
 cytoskeleton anchors
 cell identity markers

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Cytoplasm
outside nucleus
 inside plasma membrane
 site of most cellular activities
 Major elements include:
- cytosol
- inclusions
- organelles

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Cytosol
viscous, transparent, gel-like
 75% H2O + solid components:
- proteins, carbohydrates, lipids, and
inorganic substances
- inorganic substances and smaller
organic substances soluble in H2O
are present as solutes
- larger organic compounds are
found as colloids (semi-solid matrix)

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Organelles
little organs
 specialized structures
 characteristic appearances
 specific roles in growth, maintenance,
repair, and control
 chemically different with one another

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Nucleus

Three distinct components:
- nuclear membrane
- nucleoli
- chromatin
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Nucleus
(cont.)
largest organelle in the cell
 usually oval or spherical - conforms to
shape of the cell
 contains genetic material (DNA)
 controls cellular functions
 directs cellular activities
 surrounded by nuclear membrane

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Nuclear Membrane
double layer
 bound to nucleus
 encloses nucleoplasm in which nucleoli
and chromatin are suspended
 has large pores

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Nucleoli
little nucleus
 dense body
 composed mostly of RNA and protein
 ribosome production (migrate through
pores in nuclear envelope and enter
cytoplasm)
 disappear during cell division and
reappear in daughter cells

Suzanne D'Anna
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Chromatin
loosely coiled fibers of DNA and
associated proteins
 before cell division DNA duplicates,
chromatin fibers coil and shorten to form
chromatids
 one of two spiral filaments joined at the
centromere which make a chromosome

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Ribosomes
tiny, round dark bodies
 sites of protein synthesis
 contain ribosomal RNA (rRNA)

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Endoplasmic Reticulum
system of membrane-enclosed tubules
or channels that coil and twist; called
cisterns
 continuous with nuclear envelope
 serves as minicirculatory system
 provides surface area for chemical
reactions
 Two types:
- granular and agranular

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Endoplasmic Reticulum
Granular
rough
 studded with ribosomes which synthesize
protein
 temporary storage area
 together with Golgi body it synthesizes
and packages molecules that will be
excreted from the cell

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Endoplasmic Reticulum
Agranular (smooth)
site of fatty acid, phospholipid, and
steroid synthesis
 inactivates or detoxifies chemicals such
as alcohol, pesticides, and carcinogens

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Golgi Apparatus
(body or complex)
 stacks of flattened sacs with bulges at
ends
 located close to nucleus
 modifies, packages, and secretes
proteins and lipids
 as proteins accumulate in sacs, the
sacs swell; swollen sac pinches off to
form vesicles that travel to cell
membrane
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Route of Proteins for Export
ribosomes
rough ER
transport
vesicles
Golgi body
vesicles
release to exterior of cell
Suzanne D'Anna
secretory
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Lysosomes
membrane-enclosed vesicles
 formed in Golgi body
 contain powerful digestive enzymes (as
many as 40) responsible for breaking
down molecules
 can also digest worn-out cell structures
(autophagy) and foreign substances

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Peroxisomes
membrane sacs similar to lysosomes
but smaller
 contain enzymes that use molecular
oxygen to oxidize organic substances
 detoxify potentially harmful substances
that may enter the bloodstream
(e.g., free radicals)
 especially important in liver and kidneys

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Mitochondria
(powerhouse of the cell)
sausage-shaped fluid filled sacs
 double membrane wall
 outer wall is smooth
 inner wall - series of folds called cristae
 cristae provide surface area for cellular
respiration (only occurs if O2 is present)
 enzymes on cristae catalyze reactions
that generate ATP

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Cytoskeleton
responsible for cell movement and for
movement of organelles and chemicals
within the cell
 Network of protein structures:
- microfilaments
- microtubules
- intermediate filaments

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Microfilaments
rod-like structures
 formed from the protein actin
 in muscle tissue - actin filaments (thin)
and myosin (thick) slide past one
another to produce contraction
 in non-muscle - actin filaments support
and shape

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Microtubules
larger than microfilaments
 straight, slender cylindrical structures contain the protein tubulin
 support and shape cells
 movement of substances

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Intermediate Filaments
medium size
 strong and tough
 provide structural reinforcement

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Centrosome
cytoplasmic material
 within centrosome is pair a of rodshaped bodies called centrioles
- lie at right angles to each other
- during cell division, centrioles direct
formation of mitotic spindle
- like mitochondria, they contain DNA
and control self replication

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Cilia
minute projection extending from cell
surface
 contain ten pairs of microtubules
 act to move substances along cell surface
 beat rhythmically to move fluids or
particles over cell surface

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Flagella
long whip-like projections extending
from free cell surface
 act to propel a cell
 contain ten pairs of microtubules
 tail of sperm is a flagellum

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