ch02 cell
DESCRIPTION
CellsTRANSCRIPT
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Human Anatomy, First EditionMcKinley & O'Loughlin
Chapter 2 :
The Cell: Basic Unit of Structure and
Function
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The Cell
Cells:
structural and functional units of all living organisms.
building blocks of the human body.
adult human body contains ~ 75 trillion cells.
Each cell type performs specific functions.
~200 cell types in humans
subcategories of most
2-3
Common Characteristics of Cells
Perform the general functions necessary to sustain life: Obtain nutrients and other materials from its
surrounding fluids. Fuel molecules, O2, building blocks, minerals,etc
Dispose of wastes products Urea (from nitrogen), CO2, metabolic waste
Maintain shape and integrity Size and shape are related to function
Cell division: Mitosis: growth and repair
Meiosis: gamete formation 2-4
Study of Cells
Cytology: study of cells
Microscopic anatomy
Individual cells observable by light microscopy
Subcellular structures observable by electron microscopy.
TEM
SEM
Unit of measure: micrometer (um)
RBC: 7-8um
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Cells
Parts of a cell
Cell Membrane (or plasma membrane)
Cytoplasm
Cytosol
Organelles
Membranous Organelles
Non-membranous Organelles
Inclusions
Nucleus
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Plasma (Cell) Membrane
the outer, limiting barrier
separates the internal
contents of the cell from external materials.
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Cytoplasm
general term for all cellular contents located between the plasma membrane and the nucleus.
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Nucleus
control center of the cell
controls protein synthesis
directs the functional and structural
characteristics of the cell.
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Plasma membrane: composition
Lipids Phospholipids
Head: hydrophilic
Tail: hydrophobic
Form lipid bilayer
Cholesterol
Glycolipids Carbohydrate component
Part of glycocalyx
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Plasma membrane: composition
Protein
Integral membrane proteins
Peripheral membrane proteins
Some serve as enzymes, ion channels or receptors
Glycoproteins
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Plasma membrane: functions
Selectively permeable barrier
Nutrient in
Waste out
Communication
Intercellular connections
Physical barrier
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Transport Mechanisms
Passive Transport
Active Transport
Bulk Transport
Solution= solvent (H2O)+ solute
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Passive Transport
Movement of substances along a concentration gradient [Hi] to [Low]
ATP is not required
Types: Simple Diffusion: solutes
Facilitated Diffusion: solutes
Bulk Filtration: solution
Osmosis: solvent
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Facilitated Diffusion
Requires the participation of specific transport proteins that help specific substances or molecules move across the plasma membrane.
Carrier-mediated
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Bulk Filtration
Involves the diffusion of both solvents and solutes together across the selectively permeable membrane.
Pressure gradients
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Osmosis
Involves the diffusion of a solvent (H2O), across a selectively permeable membrane.
Can cause a volume change
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Active Transport
Movement of a substance across a plasma membrane against a concentration gradient.
Materials must be moved from an area of low concentration to an area of high concentration.
requires cellular energy in the form of ATP (adenosine triphosphate)
uses transport proteins (carrier-mediated)
ATP is continually synthesized by mitochondria
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Ion Pumps
Active transport processes that move ions across the membrane are called ion pumps.
ion pumps allow a cell to maintain its internal concentrations of small molecules or ions
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Bulk Transport - Exocytosis
Used by cells that secrete
Usually movement of large molecules
Movement out of the cell.
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Bulk Transport - Endocytosis
process by which the cell acquires materials from the extracellular fluid: (3 Forms) Phagocytosis:
Cell forms pseudopodia engulfs a particle internalize it into a vacuole
Pinocytosis: incorporation of droplets of extracellular fluid (solution)
Taken into the cell in small vesicles
Receptor-mediated endocytosis: receptors in the cell membrane
Bind with specific molecules
Invagination forms around them to create a cytoplasmic vesicle
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Cytoplasm: cytosol
Matrix; intracellular material
Different in different cell
Mostly water
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Cytoplasm: Organelles
Complex, organized structures
Have unique, characteristic shapes.
Each type performs a different function for the cell.
Are essential for normal cellular structure and activities.
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Membranous Organelles
Include:
Endoplasmic Reticulum
Rough Endoplasmic Reticulum (RER)
Ribosomes
Make protein for export
Peroxisomes made here
Smooth Endoplamic Reticulum (SER)
Lipids and carbohydrates
Detoxification
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Membranous Organelles
Peroxisomes
Vesicles formed from RER
Use oxygen to detoxify
Mediated by specific enzymes
Most abundant in liver
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Membranous Organelles
Golgi Apparatus Modifies, stores and sorts material from
RER
Receiving region (cis-face)
Shipping region (trans-face)
Produces Lysosomes Autophagy: removal of old organelles
Autolysis: destruction of the cell
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Mitochondria
Mitochondria are organelles with a double membrane.
Produce large amounts of ATP.
Are called the powerhouses of the cell.
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Non-Membranous Organelles
Not made of a membrane.
Usually made of protein
Include: Ribosomes: free and fixed
Cytoskeleton Microfilaments
Intermediate fibers
microtubules
Centrosome centrioles
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Ribosomes
Small, dense granules Protein
RNA
Site of protein synthesis.
Each ribosome has a small and a large subunit. small subunit is about one-half the size of
the large subunit.
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The Cytoskeleton
Made of filamentous proteins
Helps give the cell its shape
Coordinates cellular movements.
Three categories:
microfilaments
intermediate filaments
microtubules
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Non-membranous Organelles
Centrioles and the centrosome Centrosome
Area close to the nucleus
Organization site for microtubules
Centrioles (exist as a pair) In the centrosome
Perpendicular to each other
9 sets of microtubule triplets
Important in cell division (spindle)
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Microvilli, Cilia and Flagella
Appendages extending from the surface of some cells. Microvilli:
short, cytoplasmic extensions
For absorption
Cilia: usually occur in large numbers
work together to move materials or fluids along the surface of a cell.
Flagella:
longer than cilia, and usually occur as single appendages.
Move the cell
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The Nucleus
Control center of cellular activities.
Usually, it is the largest structure within the cell
Appears as a single spherical or oval structure.
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The Nucleus
Enclosed by a double membrane called the nuclear envelope.
The nuclear envelope:
controls the entry and exit of materials
between the nucleus and the cytoplasm.
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Nucleolus
The cell nucleus may contain one or more nucleoli.
Nucleoli:
are responsible for making the small and
the large subunits of ribosomes.
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Chromatin and DNA
DNA is the genetic material housed within the nucleus. DNA is a polymer of nucleotides (sugar,
phosphate, nitrogen base)
Is a double helix.
Chromatin: Strands of DNA and histone proteins
Euchromatin: uncoiled; active
Heterochromatin: coiled. inactive
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Insert Figure 2.18
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Chromosome
The chromosome is the most organized level of genetic material.
Each chromosome contains a single, long molecule of DNA and associated proteins.
Chromosomes become visible only when the cell is dividing.
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The Cell Cycle
The life cycle of the cell is called the cell cycle.
New cells must be made continuously in order for an organism to grow and replace its damaged cells.
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Mitosis and Meiosis
There are two types of cell division.
Mitosis: is the cell division process that takes place in somatic cells.
Meiosis: is the cell division process that takes place in gonads to produce gametes.
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Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
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The Stages of Mitosis
Prophase the first and longest stage of mitosis Early prophase chromatin threads condense
into chromosomes Chromosomes are made up of two threads called chromatids
Chromatids are held together by the centromere
Centriole pairs separate from one another
The mitotic spindle forms
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The Stages of Mitosis
Prophase (continued)
Late prophase centrioles continue moving away from each other
Nuclear membrane fragments
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Early Prophase and Late Prophase
Figure 2.21
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The Stages of Mitosis
Metaphase the second stage of mitosis
Chromosomes cluster at the middle of the cell
Centromeres are aligned along the equator
Anaphase the third and shortest stage of mitosis
Centromeres of chromosomes split
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Metaphase and Anaphase
Figure 2.21
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The Stages of Mitosis
Telophase begins as chromosomal movement stops
Chromosomes at opposite poles of the cell uncoil
Resume their thread-like extended-chromatin
form
A new nuclear membrane forms
Cytokinesis completes the division of the cell into two daughter cells
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Telephase and Cytokinesis
Figure 2.21
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Tumor
Normal tissue development exhibits a balance between cell division and cell death.
If this balance is upset and cells multiply faster than they die, abnormal growth results in a new cell mass that is called a neoplasm, or tumor.
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Cancer
Benign neoplasms usually grow slowly and are confined within a connective tissue capsule.
Cells within these tumors dedifferentiatethat is, they revert to a less specialized state, and cause an increase in their own vascular supply to support their growth.
These tumors are usually not lethal, but they have
the potential to become life-threatening if they compress brain tissue, nerves, blood vessels, or airways.
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Cancer
Cancer is the general term used to describe a group of diseases characterized by various types of malignant neoplasms.
unencapsulated
contain cells that dedifferentiate
increase their vascular supply
grow rapidly
spread easily to other organs by way of the blood
or lymph (metastasis)
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Cancer
Cancer cells lose control of their cell cycle.
they divide too frequently and grow out of control
cancer cells lose contact inhibition
they overgrow one another and lack the ability to stop growing and dividing when they crowd other cells
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Cancer Cells
Exhibit dedifferentiation and revert to an earlier, less specialized developmental state.
Produce chemicals that cause local blood vessel formation resulting in increased blood vessels in the developing tumor (angiogenesis).
Have the ability to squeeze into any space (invasiveness) permitting them to leave their place of origin and travel elsewhere in the body.
Acquire the ability to metastasizethat is, spread to other organs in the body.