Post on 14-Jan-2016
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Cell 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
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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
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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 dedifferentiate—that
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 metastasize—that is, spread to other organs in the body.