Bio211

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Mariebs Human Anatomy and Physiology Ninth
Edition
Marieb w Hoehn
Chapter 3 Cells The Living Units Lecture 5
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Lecture Overview

• Specialization and differentiation of cells
• General characteristics of cells
• The cell membrane
• Movement of substances into and out of the cell
• Osmotic pressure and tonicity
• Overview of cellular organelles

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Cells Are Specialized
Figure from Martini Ober, Visual Anatomy
Physiology, Human AP, 1st edition, 2010
Differentiated 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

Figure From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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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
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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A Transmembrane Protein
Figure from Alberts et al., Essential Cell
Biology, Garland Publishing, 1998
Hydrophilic channel
Membrane Lipids
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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
Figure from Holes Human AP, 12th edition, 2010
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 solute 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

• 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
Figure from Holes Human AP, 12th edition, 2010
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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
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Osmosis

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

A special case of passive diffusion
Figure from Holes Human AP, 12th edition, 2010
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Osmotic Pressure/Tonicity
Osmotic Pressure ability of osmosis to generate
enough pressure to move a volume of water
Osmotic pressure increases as the number of
nonpermeable solutes particles increases
Figure from Holes Human AP, 12th edition, 2010

• 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
• separates large from small molecules
• hydrostatic pressure important in fluid
  movement
• molecules leaving blood capillaries

Think sprinkler hose
Figure from Holes Human AP, 12th edition, 2010
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Active Transport

• carrier molecules transport substances across a
  membrane from regions of lower solute
  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, e.g., ATP
Figure From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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The Cellular Electrochemical Gradient
Cells maintain a transmembrane potential, with
the inside of the cell being slightly negative
relative to the outside. - Slight excess of
positive charges immediately outside the cell
membrane - Slight excess of negative charges
immediately inside the cell membrane The cell
membrane maintains the transmembrane potential
by - Selective permeability - Active
transport Different types of cells have different
resting potentials between -10mV and -100mV -
Neurons -70mV - Skeletal muscle -85mV
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Transmembrane Potential
Dependent upon active transport
Cells maintain a transmembrane potential, with
the inside of the cell membrane being slightly
negative relative to the outside
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Endocytosis

• 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

Figure from Holes Human AP, 12th edition, 2010
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Endocytosis
Figures from Holes Human AP, 12th edition, 2010
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Exocytosis

• reverse of endocytosis
• substances in a vesicle fuse with cell membrane
• contents released outside the cell
• release of neurotransmitters from nerve cells

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

• endocytosis followed by exocytosis
• transports a substance rapidly through a cell
• HIV crossing a cell layer

Figure from Holes Human AP, 12th edition, 2010
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Cytoplasmic OrganellesEndoplasmic Reticulum
Figure from Holes Human AP, 12th edition, 2010
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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
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.)
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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Cytoplasmic Organelles - Endoplasmic Reticulum

• Endoplasmic Reticulum
• connected, membrane-bound sacs, canals, and
  vesicles
• transport system
• smooth ER
• lipid and cholesterol synthesis
• breakdown of drugs
• rough ER
• studded with ribosomes
• protein and lipid synthesis

• Ribosomes
• free floating or connected to ER
• site of protein synthesis

Figure From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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Cytoplasmic OrganellesMitochondria and Golgi
Apparatus
Figure from Holes Human AP, 12th edition, 2010
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Golgi Apparatus

• Golgi apparatus
• group of flattened, membranous sacs (cisternae)
• modifies, packages, and transports proteins

Figure From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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Cytoplasmic Organelles Transport from Nucleus ?
Membrane
Figure From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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Lysosomes
Figure from Holes Human AP, 12th edition, 2010
Lysosomes - Spherical membranous sacs
containing digestive enzymes (proteins) -
"suicide sacs" which safely destroy anything the
cell no longer wants or needs - Autolysis is
the process by which worn cell parts are digested
by autophagy
TEM (falsely colored) 14,100x
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Peroxisomes
Peroxisomes - Membranous sacs containing
oxidase enzymes - Function detoxification of
harmful or toxic substances (i.e.
alcohol, formaldehyde, oxygen free radicals) -
H2O2 (hydrogen peroxide) ----gt water.
Figure from Alberts et al., Essential Cell
Biology, Garland Publishing, 1998
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Centrosomes

• Centrosome
• two rod-like centrioles
• used to produce cilia and flagella
• forms mitotic spindle that distributes
  chromosomes during cell division

Figures From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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Microfilaments/Microtubules

• Microfilaments and microtubules form
  cytoskeleton of cell
• thin rods and tubules
• support cytoplasm
• allows for movement of organelles

Figures From Marieb Hoehn, Human Anatomy
Physiology, 9th ed., Pearson
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Microfilaments/Microtubules
Figure from Holes Human AP, 12th edition, 2010
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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 four major components
  in common
• Nucleus
• Cell membrane
• Cytosol
• Organelles
• Inclusions

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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
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.)
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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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