Download • Cells and Tissues o Introduction to cell organelles and tissue types

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Cells and Tissues
o Introduction to cell organelles and tissue types
Cells and Tissues
o Carry out all chemical activities needed to sustain life
o Cells are the building blocks of all living things
o Tissues are groups of cells that are similar in structure and function
Anatomy of the Cell
o Cells are not all the same
o All cells share general structures
o All cells have three main regions
 Nucleus
 Cytoplasm
 Plasma membrane
o The Nucleus
 Control center of the cell
 Contains genetic material (DNA)
 Three regions
 Nuclear envelope (membrane)
 Nucleolus
 Chromatin
o Nuclear envelope (membrane)
 Barrier of the nucleus
 Consists of a double membrane
 Contains nuclear pores that allow for exchange of material with the rest
of the cell
o The Nucleus
 Nucleoli
 Nucleus contains one or more nucleoli
 Sites of ribosome assembly
 Ribosomes migrate into the cytoplasm through nuclear pores
 Chromatin
 Composed of DNA and protein
 Present when the cell is not dividing
 Scattered throughout the nucleus
 Condenses to form chromosomes when the cell divides
o Plasma Membrane
 Barrier for cell contents
 Double phospholipid layer
 Hydrophilic heads
 Hydrophobic tails
 Also contains:
 Proteins; structure, attachment, transport
 Cholesterol; Stiffens the cell membrane
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 Glycoproteins; help identify the cell as ours
Plasma Membrane
o Plasma Membrane Specializations
 Microvilli
 Finger-like projections that increase surface area for absorption
 Cilia
 Longer projections that waver rhythmically to move substances.
 Membrane junctions
 Tight junctions
o Impermeable junctions
o Bind cells together into leakproof sheets
 Desmosomes
o Anchoring junctions that prevent cells from being pulled
apart
 Hemidesmosome
o Anchoring junctions which attach cells to a basement
membrane
 Gap junctions
o Allow communication between cells
 Plasma Membrane Specializations
 Cytoplasm
Cytoplasm is the material outside the nucleus and inside the plasma membrane
o Consists largely of water
o Contains cell organelles
o Cytoplasm
 Contains three major elements
 Cytosol
 Fluid that suspends other elements
 Organelles
 Metabolic machinery of the cell
 “Little organs” that perform functions for the cell
 Inclusions
o Chemical substances such as stored nutrients or cell
products
Cytoplasmic Organelles
o Mitochondria
o “Powerhouses” of the cell
 Similar in size to bacteria
 Endosymbiotic theory
 Replicate independently
 Change shape continuously
 Carry out reactions where oxygen is used to break down food
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 Provides ATP for cellular energy
Ribosomes
o Made of protein and RNA
o Sites of protein synthesis
o Found at two locations
o Free in the cytoplasm
Endoplasmic reticulum (ER)
o Fluid-filled tubules for carrying substances
o Two types of ER
 Rough endoplasmic reticulum
 Studded with ribosomes
 Synthesizes proteins
 Smooth endoplasmic reticulum
 Functions in lipid metabolism and detoxification of drugs and pesticides
 Rough Endoplasmic Reticulum
 Cytoplasmic Organelles
Golgi apparatus
o Modifies and packages proteins
o Produces different types of packages
Secretory vesicles
Lysosomes
o Contain enzymes that digest worn-out or nonusable materials within the cell
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Peroxisomes
o Membranous sacs of oxidase enzymes
o Detoxify harmful substances such as alcohol and formaldehyde
o Break down free radicals (highly reactive chemicals)
o Replicate by pinching in half
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Cytoskeleton
o Network of protein structures that extend throughout the cytoplasm
o Provides the cell with an internal framework
o Three different types of elements
o Microfilaments (largest)
o Intermediate filaments
o Microtubules (smallest)
Centrioles
o Rod-shaped bodies made of microtubules
o Direct the formation of mitotic spindle during cell division
o May be involved in the development and function of cilia
Cellular Projections
o Not found in all cells
o Used for movement
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Cilia move materials across the cell surface
Located in the respiratory system to move mucus
Flagella propel the cell
The only flagellated cell in the human body is sperm
Similar to spirochettes (a bacteria) in structure.