Human AnatomyBio 22

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Human Anatomy-Bio 22 Lecture 2 Cells The Living
Units 2-3-05
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Cell Theory

• The cell is the basic structural and functional
  unit of life
• There are 3 Main Regions of the Cell
• Plasma Membrane
• 2. Cytoplasm
• 3. Nucleus

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General Structure of an Animal (Human) Cell
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Plasma Membrane
Separates intracellular fluids from extracellular
fluids Plays a dynamic role in cellular
activity Glycocalyx is a glycoprotein area
abutting the cell that provides highly specific
biological markers by which cells recognize one
another
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Plasma Membrane
Plasma Membrane is composed of a lipid
bilayer Proteins are integrated into the lipid
bilayer to allow the passage of various molecules
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Plasma Membrane Surfaces
Plasma Membrane surfaces differ in the kind and
amount of lipids they contain -glycolipids
-phospholipids -cholesterol Glycolipids are
found only in the outer membrane surface 20 of
all membrane lipid is cholesterol
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Plasma Membrane Specializations
Microvilli-hair-like extensions of plasma
membrane. found on intestinal and kidney tubule
cells Tight junction impermeable junction
that encircles the cell Desmosome anchoring
junction scattered along the sides of
cells Gap junction a nexus that allows
chemical substances to pass between cells
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Plasma Membrane Transport Processes
1. Passive Processes A. Diffusion-net
movement of particles along their concentration
gradient a. this is the means by which fats,
oxygen, carbon dioxide, glucose,
some ions B. Osmosis a. Movement of water
into and out of the cells via integral
proteins called aquaporins C.
Filtration a. Movement of water, nutrients and
gases through a capillary wall formation of
kidney filtrate
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Plasma Membrane Transport Processes
1. Active Processes A. Active Transport a.
transport of substances against
concentration or electrochemical gradient
across plasma membrane by a pump-uses
ATP
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Plasma Membrane Transport Processes
1. Active Processes B. Vesicular
Transport a. Exocytosis the ejection of
substances via a vesicle which blebs out of
PM b. Endocytosisthe taking in of substances
via a vesicle which squishes into the PM
phagocytosis- eating of
particles pinocytosis- drinking of
particles
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Anatomy of the Cell
1. Cytoplasmlocated between the plasma
membrane and the nucleus. Has 3 major
components A. Cytosolviscous fluid in which
all other cytoplasmic components are
suspended B. Cytoplasmic Organellesthe
machinery of the cell, each has specific
functionsmore later C. Inclusions chemica
l substances
present/absent depending on cell type
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Anatomy of the Cell
2. Mitochondrion (pl. Mitochondria) sausage or
kidney bean shaped organelles. enclosed by 2
membranes -outer membrane smooth -inner has
many folds, cristae contain their own
DNA and RNA POWERHOUSE of the cell the
density of mitochondria in a cell reflects
cell activity
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Anatomy of the Cell
3. Endoplasmic Reticulum (ER) Interconnected
tubes and parallel membranes enclosing cisternae
continuous with the nuclear membrane Two
varieties rough ER and smooth ER
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Anatomy of the Cell
Rough ER External surface studded with
ribosomes Manufactures all secreted proteins, so
abundant in secretory cells Responsible for the
synthesis of integral membrane proteins and
phospholipids for cell membranes
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Anatomy of the Cell
Smooth ER Tubules arranged in a looping
network Catalyzes the following reactions in
various organs of the body In the liver lipid
and cholesterol metabolism, breakdown of glycogen
and, along with the kidneys, detoxification of
drugs In the testes synthesis of steroid-based
hormones In the intestinal cells absorption,
synthesis, and transport of fats In skeletal and
cardiac muscle storage and release of calcium
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Anatomy of the Cell

• Golgi Apparatus
• Stacked and flattened membranous sacs
• Functions in modification, concentration, and
  packaging of proteins
• Transport vessels from the ER fuse with the cis
  face of the Golgi apparatus
• Proteins then pass through the Golgi apparatus to
  the trans face
• Secretory vesicles leave the trans face of the
  Golgi stack and move to designated parts of the
  cell

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Anatomy of the Cell
Golgi Apparatus
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Anatomy of the Cell
Golgi Apparatus Functions
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Anatomy of the Cell
Lysosomes
Spherical membranous bags containing digestive
enzymes Digest ingested bacteria, viruses, and
toxins Degrade nonfunctional organelles Breakdow
n glycogen and release thyroid hormone Breakdown
nonuseful tissue Breakdown bone to release
Ca2 Secretory lysosomes are found in white
blood cells, immune cells, and melanocytes