Transcript HB Cell Structure

Human Biology
CELL STRUCTURE
&
FUNCTION
Instructor Terry
Wiseth
CELL MEMBRANE
Cell membrane made up
of:
1) Phospholipids
2) Sterols
3) Proteins
4) Glycoproteins
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PHOSPHOLIPIDS
cell membrane - semi-permeable lipid bilayer
two layers of Phospholipids
STEROLS
common sterols of cell membranes
Cholesterol (animal cells)
prevent packing of lipid cells in the
cell membrane
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PROTEINS
Proteins are embedded into the cell
membrane
These proteins serve a variety of cell
membrane functions
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GLYCOPROTEINS
proteins are embedded in the bilayer
glycoproteins - sugar-protein combinations
sugars extend out to the extracellular fluid
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CELL MEMBRANE
FLUID MOSAIC
MODEL
membrane bilayer shows fluid behavior
molecules of the bilayer are in constant
motion
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FLUID MOSAIC
MODEL
membrane is composite of molecules allowing
a “mosaic description”
cell survival depends on fluidity characteristics
of the cell membrane
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FLUID MOSAIC
MODEL
extracellular fluid temperature decreases
cause a stiffening of the cell membrane
disrupts membrane protein function
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CELL THEORY
Smallest entity that retains the characteristics
of life
1) Complex organization
2) Metabolic activity
3) Reproduction
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CELL SIZE
Most cannot be seen without the
aid of a microscope
Larger cells
”Yolk” of bird eggs
Fish eggs “caviar”
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CELL SIZE
Human eyes able to see about 100 microns
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LIGHT
MICROSCOPE
The light microscope has a limit of resolution
of about 200 nm (0.2 microns)
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TEM
The Transmission Electron Microscope (TEM)
has a limit of resolution of about 2 nm
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SEM
The Scanning Electron Microscope
(SEM) also has a limit of 2 nm
Sperm & Egg
Bronchiole cilia
WBC engulf bacteria
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GENERALIZATIONS OF
CELL THEORY
Cells vary in size, shape and activities
All cells have:
1) Plasma membrane
2) DNA region
3) Cytoplasm
4) Organelles
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PLASMA MEMBRANE
Outer membrane
maintains the
integrity of the cell
Membrane does
not however
isolate the cell
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PLASMA MEMBRANE
Cell membrane
“Lipid bilayer”
Boundary that bars free passage of water
soluble substances in and out of the cell
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NUCLEUS
DNA is localized in the cell nucleus
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CYTOPLASM
Everything enclosed by the plasma membrane
except the DNA semi-fluid
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CYTOPLASMIC
STREAMING
Cytoplasm is not stagnant but rather is
constantly moving (streaming)
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ORGANELLES
Organelles--internal sacs which have a
specific metabolic function
Essential in keeping chemical reactions in
the cytoplasm separate from each other
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CELL MACHINERY
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CELL MACHINERY
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NUCLEUS
Nucleus sequesters DNA
1) Separates DNA from chemical reactions
in cytoplasm
2) Nuclear membranes control access
between nuclear material and cytoplasm
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NUCLEUS
Nuclear envelope has pores to allow passage
of messenger units of nucleic acid
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NUCLEUS
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NUCLEOLUS
1) Assembly of RNA and
ribosomes
2) Storage of RNA and
ribosomes
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DNA
Instructions for building proteins (enzymes)
are contained in DNA
Instructions of heredity are distributed in
several DNA molecules of various lengths
Humans = 46 DNA molecules
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DNA
DNA is threadlike
prior to cell division the DNA molecules
duplicate
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CHROMOSOMES
DNA folds and twists into condensed
structures called chromosomes
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CYTOMEMBRANE
SYSTEM
Series of organelles through which lipids and
proteins, produced on cytoplasmic
ribosomes, pass through in becoming
packaged for export
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CYTOMEMBRANE
SYSTEM
1) Endoplasmic reticulum (ER)
2) Golgi bodies
3) Vesicles
4) Lysosomes
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ENDOPLASMIC
RETICULUM
1) Rough endoplasmic reticulum
Ribbon like structure with ribosomes attached
Arranged as flat, stacked sacs
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ENDOPLASMIC
RETICULUM
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RIBOSOMES
Ribosomes are small spherical shaped
structures
Serve as the “working table” for assembling
proteins
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RIBOSOMES
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ENDOPLASMIC
RETICULUM
2) Smooth endoplasmic reticulum
Lacks ribosomes
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SMOOTH ENDOPLASMIC
RETICULUM
Appears like a system of pipes
1) Lipid synthesis
Ex: endocrine glands produce steroid
hormones
2) Inactivate harmful
by-products of
metabolism and drugs
Ex: liver cells
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GOLGI BODIES
Resemble stacks of pancakes
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GOLGI BODIES
Flattened sacs in which lipids and protein
molecules are modified
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GOLGI BODIES
Modifications allow for sorting and packaging
for transport
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GOLGI
MODIFICATIONS
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GOLGI
MODIFICATIONS
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VESICLES
Sacs which transport or store enzymes, lipids
and proteins
1) Peroxisomes
2) Lysosomes (microbodies)
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VESICLES
1)
Peroxisomes
Contain enzymes to break down fatty
acids and amino acids
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VESICLES
2) Lysosomes
Vesicles of intracellular digestion
Contain enzymes which can break down any
polysaccharide, protein, nucleic acid and
some lipids
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LYSOSOMES
Important in proper function of white
blood cells (immunity)
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LYSOSOMES
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CYTOMEMBRANE
SYSTEM
Raw materials (amino acids and lipids) are
dissolved in the cytoplasm
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CYTOMEMBRANE
SYSTEM
Under the instructions
of the DNA molecule
polypeptide chains of
proteins are
assembled from the
dissolved raw
materials
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CYTOMEMBRANE SYSTEM
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MITOCHONDRIA
Contains a series of inner membranes folded
repeatedly (cristae)
Increases the total surface area available
for reactions
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MITOCHONDRIA
Use oxygen to assist in liberating energy
stored in sugars (aerobic respiration)
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MITOCHONDRIA
Energy is used to form ATP molecules which
is used for protein synthesis and transport
ATP-molecule is able to store and transport
energy for short periods of time
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MITOCHONDRIA
Most numerous in high energy demanding
cells
Ex: muscles, liver
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MITOCHONDRIA
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CYTOSKELETON
Interconnected system of bundled fibers,
threads and lattices
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CYTOSKELETON
Extend from the cell membranes, organelles
and nucleus
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CYTOSKELETON
Supply internal organization, shape, ability to
move, reinforce the cell membrane and hold
proteins in place
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CELL SURFACE
SPECIALIZATIONS
Gap Junctions
channels of exchange in animal cells
ex: liver, heart
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CELL SURFACE
SPECIALIZATIONS
Junction Proteins
hold cells together in forming tissues
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END
Cell