3.1 The Cellular Level of Organization
• The cell is the structural and functional unit of an organism, the smallest structure capable of performing all the functions necessary for life.
3.1 The Cellular Level of Organization
• Prokaryotic cells lack membrane enclosed structures.
• Eukaryotic cells possess membrane enclosed structures.
The Cell Theory
• All organisms are composed of one or more cells.
• Cells are the basic living unit of structure and function in organisms.
• All cells come only from other cells.
Sizes of Living Things
Surface Area / Volume Ratio
• The amount of surface area affects the ability to get materials in and out of a cell.
• A cells increase in volume, the proportionate amount of surface area decreases.
Surface Area / Volume Ratio
Plasma Membrane and Cytoplasm
• All cells are surrounded by a plasma membrane.
• The material inside of a cell is the cytoplasm.
• The plasma membrane regulates what enters and exits a cell.
3.2 Prokaryotic Cells
3.2 Prokaryotic Cells
• Cell Wall
• Capsule
• Flagellum
• Nucleoid
• Ribosomes
Prokaryotes are:
• Structurally simple
• Metabolically diverse
• Adapted to most types of environments
3.2 Prokaryotic Cells
3.3 Eukaryotic Cells
• Eukaryotic cells:
– Are structurally complex
– Have a nucleus
– Possess membrane-bound organelles
– May have a cell wall
3.3 Eukaryotic Cells
3.3 Eukaryotic Cells
The Nucleus
• Stores DNA
The Nucleus
• Stores DNA• Nucleolus - rRNA• Nuclear Envelope
– Nuclear pores
Ribosomes
• Site of protein synthesis
• Two subunits (large and small)– Subunits consist of rRNA and protein molecules
• Polyribosomes– Several ribosomes with a single mRNA molecule
Endoplasmic Reticulum
• Consists of membranous channels and saccules
Endoplasmic Reticulum
• Rough ER– Processing and
modification of proteins
• Smooth ER– Synthesizes
phospholipids– Various other
functions
Golgi Apparatus
• The Golgi apparatus collects, sorts, packages, and distributes materials such as proteins and lipids.
Lysosomes
• Lysosomes contain digestive enzymes that break down unwanted, foreign substances or worn- out parts of cells
Vacuoles
• Vacuoles are membranous sacs that store substances.– For example:
Water
Pigments
Toxins
Peroxisomes
• Membrane bound vesicles containing enzymes.
– The enzymes break down molecules and as a result produce hydrogen peroxide.
Energy-Related Organelles
• Chloroplasts
• Mitochondria
Energy-Related Organelles
Photosynthesis Cellular Respiration
Chloroplasts
• Site of photosynthesis
• Structure:– Double-membrane– Stroma– Grana
• Thylakoids
• Chloroplasts contain:– Their own DNA– Ribosomes– Enzymes
Mitochondria
• Found in all eukaryotic cells
• Site or cellular respiration
• Structure:– Double-membrane– Matrix– Crista
The Cytoskeleton
• Maintains cell shape
• Assists in movement of cell and organelles
• Assemble and disassemble as needed
• Three types of macromolecular fibers
– Actin Filaments
– Intermediate Filaments
– Microtubules
Actin Filaments
• Anchored to the plasma membrane• Allows intestinal microvilli to expand and contract• Found in pseudopods allowing amoeboid movement• Play a role in animal cell division
Actin Filaments
• Actin interacts with motor molecules such as myosin.• In the presence of ATP, myosin pulls actin along• Example: muscle cells
Intermediate Filaments
• Intermediate in size between actin filaments and microtubules
• Functions:– Support nuclear envelope
– Cell-cell junctions, such as those holding skin cells tightly together
Microtubules
• Hollow cylinders made of two globular proteins• Assembly:
– Under control of Microtubule Organizing Center (MTOC)– Most important MTOC is centrosome
• Interacts with specific proteins to cause movement of organelles
Microtubule Operation
Centrioles
• Short cylinders with a 9 + 0 pattern of microtubule triplets
Centrioles
• Help organize microtubules during animal cell division• May be involved with microtubule formation and in the
organization of cilia and flagella
Cilia and Flagella
• Hairlike projections that aid in cell movement
• In eukaryotic cells, cilia are much shorter than flagella
• They are membrane-bound cylinders enclosing a matrix area– The matrix consists of microtubules in a 9 + 2 pattern
Cilia and Flagella
3.4 Evolution of the Eukaryotic Cell
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