Visual Anatomy

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Visual Anatomy PhysiologyFirst
EditionMartini Ober

• Chapter 3
• Cellular Level of Organization
• Lecture 5

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Lecture Overview

• Specialization and differentiation of cells
• General characteristics of cells
• The cell membrane
• Cellular organelles (summary table)
• Cell death necrosis and apoptosis
• Stem cells and progenitor cells
• Cancer
• Movement of substances into and out of the cell

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Cells Are Specialized

• vary in size
• vary in shape
• vary in function
• measured in micrometers

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A Composite Cell

• hypothetical cell
• major parts
• nucleus
• cytoplasm
• cell membrane

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Cell Membrane

• outer limit of cell isolates cell

• controls what moves in and out of cell -
  selectively permeable

• self-sealing

• phospholipid bilayer
• water-soluble heads form outer surfaces
• water-insoluble tails form interior
• permeable to lipid-soluble substances only

• cholesterol stabilizes the membrane

• proteins
• receptors
• pores, channels, carriers
• enzymes
• CAMS
• self-markers

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Cell Membranes
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A Transmembrane Protein
Hydrophilic channel
Membrane Lipids
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Cellular Organelles
Table 1 of 2
CELL COMPONENT DESCRIPTION/ STRUCTURE FUNCTION(S)
CELL MEMBRANE Bilayer of phospholipids with proteins dispersed throughout cell boundary selectively permeable (i.e. controls what enters and leaves the cell membrane transport)
CYTOPLASM jelly-like fluid (70 water) suspends organelles in cell
NUCLEUS Central control center of cell bound by lipid bilayer membrane contains chromatin (loosely colied DNA and proteins) controls all cellular activity by directing protein synthesis (i.e. instructing the cell what proteins/enzymes to make.
NUCLEOLUS dense spherical body(ies) within nucleus RNA protein Ribosome synthesis
RIBOSOMES RNA protein dispersed throughout cytoplasm or studded on ER protein synthesis
ROUGH ER Membranous network studded with ribosomes protein synthesis
SMOOTH ER Membranous network lacking ribosomes lipid cholesterol synthesis
GOLGI Stack of Pancakes cisternae modification, transport, and packaging of proteins
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Cellular Organelles
Table 2 of 2
CELL COMPONENT DESCRIPTION/ STRUCTURE FUNCTION(S)
LYSOSOMES Membranous sac of digestive enzymes destruction of worn cell parts (autolysis) and foreign particles
PEROXISOMES Membranous sacs filled with oxidase enzymes (catalase) detoxification of harmful substances (i.e. ethanol, drugs, etc.)
MITOCHONDRIA Kidney shaped organelles whose inner membrane is folded into cristae. Site of Cellular Respiration Powerhouse of Cell
FLAGELLA long, tail-like extension human sperm locomotion
CILIA short, eyelash extensions human trachea fallopian tube to allow for passage of substances through passageways
MICROVILLI microscopic ruffling of cell membrane increase surface area
CENTRIOLES paired cylinders of microtubules at right angles near nucleus aid in chromosome movement during mitosis
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Cell Death

• Two mechanisms of cell death
• Necrosis
• Programmed cell death (PCD or apoptosis)
• Necrosis
• Tissue degeneration following cellular injury or
  destruction
• Cellular contents released into the environment
  causing an inflammatory response
• Programmed Cell Death (Apoptosis)
• Orderly, contained cell disintegration
• Cellular contents are contained and cell is
  immediately phagocytosed

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Necrosis vs. Apoptosis
Necrosis
Apoptosis
Figure from Alberts et al., Essential Cell
Biology, Garland Press, 1998
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Cellular Pathways of Apoptosis
Figure from http//www.ambion.com/tools/pathway/p
athway.php?pathwayCellular20Apoptosis20Pathway
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Cellular Pathways of Apoptosis
Figure from http//www.ambion.com/tools/pathway/p
athway.php?pathwayCellular20Apoptosis20Pathway
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Failure of Apoptosis - Syndactyly
Photo from http//en.wikipedia.org/wiki/Apoptosis
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Stem and Progenitor Cells

• Stem cell
• can divide to form two new stem cells
• can divide to form a stem cell and a progenitor
  cell
• totipotent can give rise to any cell type
  (Embryonic stem cells)
• pluripotent can give rise to a restricted
  number of cell types

• Progenitor cell
• committed cell
• can divide to become any of a restricted number
  of cells
• pluripotent

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Figure from Holes Human AP, 12th edition, 2010
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Cancer

• Two types of tumors
• benign usually remains localized
• malignant invasive and can metastasize
  cancerous

• Genes that cause cancer
• oncogenes activate other genes that increase
  cell division
• tumor suppressor genes normally regulate
  mitosis if inactivated they will not regulate
  mitosis

Oncology is the study of tumors
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Cancer is a Genetic Disorder
Figure from Holes Human AP, 12th edition, 2010
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Cancer
Cancers are due to
Figure from Holes Human AP, 12th edition, 2010
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Cancer
Metastasis is the spread of a cancer from its
site of origin to other areas of the body
Figure from Holes Human AP, 12th edition, 2010
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Movements Into and Out of the Cell

• Passive (Physical) Processes
• require no cellular energy
• simple diffusion
• facilitated diffusion
• osmosis

• Active (Physiological) Processes
• require cellular energy
• active transport
• endocytosis
• exocytosis
• transcytosis

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Simple Diffusion
Solutes will evenly disperse in a solvent with
time by diffusion. This is the lowest energy
state.
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Simple Diffusion

• movement of substances from regions of higher
  concentration to regions of lower concentration
  (a physical process)

Figure from Holes Human AP, 12th edition, 2010
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Where Would You Rather Be?
Spread out, would ya!?
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Facilitated Diffusion
Figure from Holes Human AP, 12th edition, 2010

• diffusion across a membrane with the help of a
  channel or carrier molecule
• e.g, transport of glucose across cell membrane

BUTstill from a region of higher concentration
to a region of lower concentration
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Factors Influencing Diffusion Rates

• Distance (shorter is faster)
• Gradient size (bigger difference in concentration
  is faster)
• Molecule size (smaller is faster)
• Temperature (warmer is faster)
• Electrical forces (repulsion is better)

In the body, diffusion distances are typically
limited to a maximum of about 125 µm
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Diffusion and the Cell Membrane
Carrier/channel proteins required for all but
fat-soluble molecules and small uncharged
molecules
oxygen, carbon dioxide and other lipid-soluble
substances diffuse freely through the membrane
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Osmosis (Special case of passive diffusion)

• movement of water (solvent) through a
  selectively permeable membrane from regions of
  higher water concentration to regions of lower
  water concentration
• water moves toward a higher concentration of
  solutes

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Osmotic Pressure/Tonicity
Osmotic Pressure (Osmolarity) ability of solute
to generate enough pressure to move a volume of
water by osmosis
Osmotic pressure increases as the number of
nonpermeable solutes particles increases

• isotonic same osmotic pressure as a second
  solution
• hypertonic higher osmotic pressure
• hypOtonic lower osmotic pressure

0.9 NaCl5.0 Glucose
Crenation
The O in hypotonic
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Filtration

• smaller molecules are forced through porous
  membranes
• hydrostatic pressure important in the body
• molecules leaving blood capillaries

Think sprinkler hose
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Active Transport

• carrier molecules transport substances across a
  membrane from regions of lower concentration to
  regions of higher concentration, i.e., against a
  concentration gradient
• sugars, amino acids, sodium ions, potassium
  ions, etc.

Active transport is a physiological process since
it requires cellular energy
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Endocytosis and Exocytosis

• cell engulfs a substance by forming a vesicle
  around the substance
• three types
• pinocytosis substance is mostly water
• phagocytosis substance is a solid
• receptor-mediated endocytosis requires the
  substance to bind to a membrane-bound receptor

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Lecture Review

• The cell is
• The structural and functional unit of all living
  matter
• Smallest body structure that can perform the
  functions of life
• Cells must specialize and differentiate, e.g.,
  neurons (nerve cells) and muscle cells
• All eukaryotic cells have several major
  components in common
• Nucleus
• Cell membrane
• Cytosol
• Organelles
• Inclusions

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Lecture Review
TRANSPORT PROCESS IS ENERGY NEEDED? CONCEN- TRATION GRADIENT GENERAL DESCRIPTION EXAMPLE IN HUMANS SIGNIFICANCE
SIMPLE DIFFUSION NO HIGH TO LOW spreading out of molecules to equilibrium O2 into cells CO2 out of cells. Cellular Respiration
FACILITATED DIFFUSION NO HIGH TO LOW Using a special cm carrier protein to move something through the cell membrane (cm) Process by which glucose enters cells
OSMOSIS NO HIGH TO LOW water moving through the cm to dilute a solute maintenance of osmotic pressure of 0.9. Same
FILTRATION NO HIGH TO LOW using pressure to push something through a cm (sprinkler hose) manner in which the kidney filters things from blood removal of metabolic wastes
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Lecture Review
TRANSPORT PROCESS IS ENERGY NEEDED? CONCEN- TRATION GRADIENT GENERAL DESCRIPTION EXAMPLE IN HUMANS SIGNIFICANCE
ACTIVE TRANSPORT YES LOW TO HIGH opposite of diffusion at the expense of energy K-Na-ATPase pump maintenance of the resting membrane potential
ENDOCYTOSIS YES LOW TO HIGH bringing a substance into the cell that is too large to enter by any of the above ways Phagocytosi cell eating Pinocytosis cell drinking. Phagocytosed (foreign) particles fuse with lysosomes to be destroyed help fight infection
EXOCYTOSIS YES LOW TO HIGH expelling a substance from the cell into ECF Exporting proteins dumping waste Same