Download Biol 115 DNA, the Thread of Life

Biol115
The Thread of Life
Lecture 13
A panoramic tour of the cell
It is the cells which create and maintain in us, during the
span of our lives, our will to live and survive, to search and
experiment, and to struggle.
~Albert Claude
Objectives
• Describe key elements of cell theory.
• Explain why cells are limited in size.
• Compare and contrast light and electron microscopes.
• Compare and contrast eukaryotic and prokaryotic cells.
• Identify and discuss functions of prokaryotic cellular structures.
• Relate the forms of different cell structures to their functions.
• Compare and contrast the structure and function of organelles found
in animal and plant cells.
• Explain how microtubules cause flagellar movement.
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Objectives
Keywords: light microscopy, cell theory, cell wall, cilia, cytoplasm,
cytosol, endosymbiotic theory, eukaryote, extracellular matrix (ECM), flagellum,
fluorescence microscopy, magnification, organelle, phase-contrast
microscopy, plasma membrane, scanning electron microscopy (SEM),
autophagy, vacuole, chlorophyll, chloroplast, contractile vacuole, cristae,
endomembrane system, endoplasmic reticulum (ER), endosymbiotic theory,
food vacuole, Golgi apparatus, granum (plural: grana), lumen, lysosome, matrix,
mitochondria, nuclear envelope, nuclear pore, nucleolus, peroxisome,
phagocytosis, photosynthesis, rough endoplasmic reticulum (RER), smooth
endoplasmic reticulum (SER), stroma, vacuole, vesicle, cytoskeleton,
depolymerisation, doublet, dynein, kinesin, motor proteins, microtubule,
polymerization, tubulin
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Principles of Biology
• Chapter Cells.
• Chapter Eukaryotic cells
• Chapter Cytoskeleton
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Overview: the fundamental units of life
• All organisms are made of cells.
• The cell is the simplest collection of matter
that can live.
• Cell structure is correlated to cellular function.
• All cells are related by their descent from earlier cells.
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Cells compose organisms or can be
organisms
• Unicellular organisms (bacteria, protists)
perform all functions in a single cell.
• Multicellular organisms have specialized cells
for different functions, but cells have same
basic structure.
Cell theory
1. Cells are the basic unit of life.
2. Cells come from other cells.
Why aren’t there giant cells?
• Large cells have less surface area per unit volume.
• Large cells less capable of transporting materials across plasma
membrane.
How do we observe cells?
light microscopy
scanning electron microscopy
transmission electron microscopy
fluorescence microscopy
Eukaryotes
(protists, fungi,
plants, animals)
have complex
membranes
around
organelles.
Eukaryotic cells have internal membranes
that compartmentalise their functions
• The basic structural and functional unit of every organism is one of two types
of cells:
• prokaryotic, or
• eukaryotic.
• Eukaryotic cells are characterised by having:
• DNA in a nucleus that is bounded by a membranous nuclear envelope,
• membrane-bound organelles,
• Eukaryotic cells are generally much larger than prokaryotic cells.
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Components of the eukaryotic cell
• The evolution of compartmentalization allowed eukaryotes to
exploit new food sources.
• Compartments are organelles bound by semi-permeable
membrane.
• Several linear chromosomes within a double membrane
nucleus.
The nucleus
• Control center of the cell. Contains chromosomes made up of DNA.
Endomembrane system
• Nuclear envelope: retains DNA.
• Smooth endoplasmic reticulum: lipid synthesis and breaking down toxins.
• Rough endoplasmic reticulum: contains ribosomes, which synthesize
proteins.
• Vesicle: transports synthesized proteins.
• Golgi apparatus: modifies, stores and exports proteins from the cell.
A cell (amoeba) ‘eating’ a yeast particle
Mitochondria: powerhouses of the cell
• Transform chemical energy via cellular respiration by breaking down glucose
and converting it to ATP.
• Possess separate type of DNA (mtDNA).
• Likely arose from an endosymbiosis with prokaryotic cells.
Chloroplasts
Photosynthesis: Conversion of light energy, carbon dioxide (CO2) and
water into carbohydrates.
Peroxisomes
Peroxisomes:
eliminate waste by
converting it to
hydrogen peroxide
and then to water.
Vacuoles
Vesicles for transporting
food and waste.
Cytoskeleton — complex protein network
•
•
•
•
Structural support
Locomotion
Intracellular anchor
Involved in mitosis
Cytoskeletal components
Microfilaments, Intermediate filaments (not covered in Biol115)
Microtubules
-motility (cilia, flagella), cell division
-made of tubulin
Eukaryotic flagellum
Flagella & cilia bend
Endosymbiotic theory
Eukaryotic organelles (mitochondria, chloroplasts) arose from
symbiosis with prokaryotes:
- Divide independent from nucleus.
- Contain DNA that differs from nuclear DNA but similar to
bacterial DNA.
- Contain ribosomes smaller and more similar to bacterial
ribosomes.
The cell: a living unit greater than
the sum of its parts
• Cells rely on the integration of structures and organelles in order
to function.
• For example, the destruction of bacteria by a macrophage involves the
whole cell, coordinating components such as the cytoskeleton,
lysosomes, and plasma membrane.
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Fig. 6-33
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You should now be able to:
1.
Distinguish between the following pairs of terms:
•
prokaryotic and eukaryotic cell;
•
free and bound ribosomes;
•
smooth and rough ER.
2.
Describe the structure and function of the components of the
endomembrane system.
3.
Briefly explain the role of mitochondria, chloroplasts, and
peroxisomes.
4.
Describe the functions of the tubulin cytoskeleton, using the cilia or
flagella as an example.
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You should now be able to:
5. Compare the structure and functions of microtubules,
microfilaments, and intermediate filaments.
6. Explain how the ultrastructure of cilia and flagella relate to their
functions.
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