Eukaryotic Cell Structure
Organelles
Eukaryotic Cell Structure
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Eukaryotic cells contain many
structures that act as specialized
organs known as organelles
Eukaryotic cells are classified into two
major parts: 1) the nucleus, and 2) the
cytoplasm – the portion of the cell
outside of the nucleus
Nucleus
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is the control center of the cell
contains the genetic material known as
DNA (deoxyribonucleic acid)
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DNA provides the instructions for making
proteins and other important molecules
contains chromatin - consists of DNA
bound to protein → condenses to form
chromosomes
Ribosomes
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Proteins are assembled (synthesized)
on the ribosomes
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produce proteins by following coded
instructions that come from the nucleus
* Cells that synthesize a lot of proteins
are filled with ribosomes
Analogy: a machine in a factory /
construction workers
Endoplasmic Reticulum (ER)
internal membrane system of the cell
 site where lipid components of the cell
membrane are assembled, as well as
proteins and other materials that are
exported from the cell
Analogy: an assembly line
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Endoplasmic Reticulum cont.
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Rough ER – involved in the synthesis
and modification of proteins → lined
with ribosomes

Smooth ER – contain enzymes that
synthesize membrane lipids
Golgi Apparatus
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modifies, sorts, and packages proteins
and other materials from the ER for
storage in the cell or secretion outside
of the cell
Analogy: customization shop / postal
service
Lysosomes
filled with enzymes → proteins
involved in chemical reactions
 digest, or breakdown, lipids,
carbohydrates, proteins, and even
organelles that have outlived their
usefulness (they remove junk)
Analogy: recycling center
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Vacuoles
saclike structures that store materials,
such as: water, salts, proteins, and
carbohydrates
Analogy: Storage Garage
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Vacuoles cont.
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in plants, there is often a large central
vacuole filled with fluid
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Vacuoles are also found in some unicellular
and animal cells
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the pressure of the central vacuole makes it
possible for plant cells to support heavy
structures such as leaves and flowers
a contractile vacuole pumps excess water out
of the cell
important for homeostasis
Mitochondria and Chloroplasts
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All living things require a source of
energy

most cells get energy in one of two ways:
from food molecules or from the sun
* Both organelles contain their own
genetic information
Mitochondria
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convert chemical energy stored in food
into compounds that are more
convenient for the cells to use
enclosed by two membranes
Analogy: Coal-Burning Power Plant
Chloroplasts
contained in plant cells and some
other organisms
 capture energy from the sunlight and
convert it into chemical energy through
a process called photosynthesis
 enclosed by two membranes
Analogy: Solar Powered Cells
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Cytoskeleton
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supporting structure and transportation
system of the cell
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gives cells their shape and internal
organization
microfilaments and microtubules
make up a cells cytoskeleton
centrioles → important in cell division