Ch 7.3 Eukaryotic Cell Structures
Cellular Boundaries
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Plasma Membrane - selectively permeable membrane that acts as a flexible boundary of
a cell
Cell Wall – fairly rigid structure located outside the plasma membrane, protects the cell
and gives it support
The Cell Wall
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Very porous and allows molecules to enter
It does not select which molecules can enter
The Nucleus & Cell Control
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Nucleus contains the blueprints for making proteins
Nucleus controls the activity of the organelles
Directions for making proteins are contained in the chromatin, which are strands of DNA
Nucleolus is within the nucleus and makes ribosomes
Ribosomes are the sites where the cell produces proteins according to the directions of
DNA
Nuclear envelope is a double membrane that separates the nucleus from the cytoplasm
Assembly, Transport, & Storage
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The nucleus contains the instructions for making proteins
A copy of these instructions pass from the nucleus into the cytoplasm
Organelles for assembly & transport of proteins
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Endoplasmic reticulum – the site of cellular chemical reactions
Ribosomes in the cytoplasm are attached to the endoplasmic reticulum (rough
ER)
The ribosomes only job is to make proteins.
Smooth Endoplasmic Reticulum is involved in numerous biochemical activities
like the production and storage of lipids
After proteins are made, they are transferred to the Golgi apparatus
The Golgi apparatus sorts proteins into packages and packs them in membrane
bound structures to be sent to the appropriate destination
Vacuoles & Storage
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Vacuoles are membrane bound compartments, for temporary storage of materials
A vacuole is a sac surrounded by a membrane
o Vacuoles often store food, enzymes, waste products, or other materials needed by
the cell
Lysosomes & Recycling
o Lysosomes are organelles that contain digestive enzymes. They digest worn out
organelles, food particles, and engulfed viruses or bacteria
o A membrane surrounding the lysosomes prevents the enzymes inside from
destroying the cell
o Lysosomes can fuse with vacuoles and empty their enzymes into the vacuole,
digesting its contents
Energy Transformers
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Protein production, modification, transportation and digestion all require energy.
Two organelles, chloroplasts and mitochondria supply that energy
Chloroplasts & Energy
o Chloroplasts are cell organelles that capture light energy and convert it to
chemical energy
o Chloroplasts have a folded membrane system.
o The inner membranes are arranged in stacks of sacs called grana
o The fluid that surrounds the stacks of grana is called stroma
o Chloroplast belong to a group of plant organelles call plastids
Mitochondria & energy
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The chemical energy generated by chloroplasts is stored in sugar molecules until
it is broken down by mitochondria
Mitochondria are membrane bound organelles in plant and animal cells that
transform energy for the cell
This energy is then stored in other molecules that the cell organelles can access
easily and quickly when they need energy
Mitochondria have an outer membrane and a highly folded inner membrane.
Energy storing molecules are produced on the inner folds
Organelles for support and locomotion
The cytoskeleton
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A support structure for the cell
Constantly changing structure
Made up of a network of tiny rods and filaments
Microtubules and Microfilaments act together as a scaffold to maintain cell shape
Centrioles
o Found in animals and most protists
o Play an important role in cell division
Cilia & Flagella
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Organelles made of microtubules that aid the cell in locomotion or feeding
Cilia are short, numerous projections that look like hairs
Flagella are longer projections that move with a whip-like motion
A cell usually has only 1 or 2 flagella.
In unicellular organisms, cilia and flagella are the major means of locomotion.