Transcript Inquiry into Life, Eleventh Edition

Inquiry into Life
Eleventh Edition
Sylvia S. Mader
Chapter 3
Lecture Outline
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Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
3.1 Cellular level of organization
• Cells are the smallest unit of life
– Exhibit all characteristics of life
– All cells are highly organized
– Many cells become specialized for complex functions
• Cell theory
– All organisms are composed of one or more cells
– Cells are the basic unit of structure and function in organisms
– All cells come only from other cells. They are derived from
previously existing cells
• Discovery of cells
– Antonie van Leeuwenhoek- invented the light microscope
– Robert Hooke- first observed cells in cork
– Schleiden and Schwann-proposed cell theory
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Cellular level of organization, cont’d.
• Cell size
– Most cells are smaller than 1 mm in diameter
– Surface/volume ratio determines cell size
• Volume increases as the cube of the radius while surface
area increases by the square of the radius
• Therefore small cells have a greater surface/volume ratio
than larger cells
• Nutrients from the environment must cross the surface of the
cell to enter
• Cells must be small in order for the surface area to be
adequate to supply nutrients
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3.2 Eukaryotic cells
• Eukaryotic cells have a membrane-bound
nucleus
– Nucleus contains genetic material
– All plant and animal cells are eukaryotic
• Plasma membrane-outer boundary of cell
– Phospholipid bilayer-note arrangement of
hydrophilic and hydrophobic ends
– Embedded proteins
– Associated glycolipids and cholesterol
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Eukaryotic cells, cont’d.
• Functions of the cell membrane
– Functions as a barrier between the cell and its environment
– Plays a role in regulation of transport of substances into and out
of the cell
– Contains receptors that determine how a cell will respond to
stimuli in the environment
– Contains proteins that are important in immune responses
– It is a very dynamic, fluid structure
– Plant cells have an outer cell wall in addition to the plasma
membrane which is composed of cellulose for rigidity
• Some plant cells have a secondary cell wall which is composed of
lignin
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Eukaryotic cells, cont’d.
• Organelles-subcellular structures which
perform specific life functions for the cell
• Many organelles are found in both animal
and plant cells
• Some are found exclusively in plants or
animals
– Only in Plants- cell wall , chloroplasts, and
large central vacuole
– Only in Animals-centrioles
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Animal cell anatomy
• Fig. 3.2
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Plant cell anatomy
• Fig. 3.3
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Eukaryotic cells, cont’d.
• Nucleus
– Contains the genetic material DNA
– Nucleoplasm-semifluid within nucleus
– Chromatin-threadlike DNA which has a grainy
appearance
– Nucleolus-dark regions of chromatin which
produce rRNA which composes ribosomes
– Nuclear membrane- double layered,
surrounds nucleus and has large pores
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The nucleus and nuclear envelope
• Fig 3.4
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Eukaryotic cells, cont’d.
• Ribosomes– site of protein assembly
– Composed of RNA subunits
– Exist either as free ribosomes or bound to
endoplasmic reticulum
• Endomembrane system– Includes nuclear membrane, endoplasmic
reticulum (er), Golgi apparatus, and vesicles
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Eukaryotic cells, cont’d.
• Endomembrane system cont’d.
– Rough endoplasmic reticulum (rer)
• Complex system of membranous channels and saccules
studded with Ribosomes.
• Serves as site of assembly of proteins for export
• Assembled proteins enter channels for processing
– Addition of sugar chains to form glycoproteins
• Released in vesicles
– Smooth endoplasmic reticulum (ser)
• Synthesizes lipid products such as phospholipids and
steroids which are released in vesicles
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The endoplasmic reticulum
• Fig 3.5
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Eukaryotic cells, cont’d.
• Golgi apparatus
– Receives protein and lipid-filled vesicles from the
Endoplasmic Reticulum and packages, processes,
and distributes them.
– Vesicles fuse with Golgi and products are released
inside
– Further modification of glyoproteins occurs
– Products are packaged into secretory vesicles and
released to the cell membrane
– Golgi also produces lysosomes-protein containing
vesicles within cells
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The endomembrane system
• Fig 3.6
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Eukaryotic cells, cont’d.
• Lysosomes
– Contain hydrolytic enzymes and are involved in
intracellular digestion
– Fuse with vesicles from cell membrane containing
macromolecules
– Digestion occurs and nutrients released to cell
– Also may be involved in programmed cell death”suicide sacs”
• Lysosomal membranes in old or damaged cells
rupture and enzymes digest the cell
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Peroxisomes
• Fig 3.7
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Eukaryotic cells, cont’d.
• Energy related organelles
– Chloroplasts- site of photosynthesis - Produces food
in plant cells.
• Capture light energy and convert it to chemical
energy in the form of food molecules
• Double outer membrane surrounds fluid-filled
stroma
• Membranous system of thylakoids
• Regions of stacked thylakoids are called grana
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Chloroplast structure
• Fig 3.8
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Eukaryotic cells, cont’d.
• Mitochondria-another energy related organelle
- Produces energy in animal and plant cells.
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–
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Site of aerobic cell respiration-production of ATP
Outer double membrane surrounds fluid-filled matrix
Inner folded membrane-folds are called cristae
Cristae provide increased surface area for the
production of ATP
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Mitochondrion structure
• Fig. 3.9
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Eukaryotic cells, cont’d.
• Interrelationship between mitochondria and chloroplasts
– Chloroplasts convert light energy to chemical energy in the form
of organic food molecules (carbohydrates) which can be used by
all organisms in cell respiration to make ATP
– Only plants and algae have chloroplasts
– All cells, plant and animal, contain mitochondria
– Photosynthesis can be summarized by the following:
• Light energy + carbon dioxide + water  carbohydrate + oxygen
– Cell respiration can be summarized below:
• Carbohydrate + oxygen  carbon dioxide + water + energy (ATP)
– It can be seen that the chemicals required by cell respiration are
produced in photosynthesis, and vice versa
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Eukaryotic cells, cont’d.
• The cytoskeleton
– Maintains cell shape
– Allows cells and organelles to move
– Components include actin filaments, intermediate filaments, and
microtubules
– Actin filaments interact with motor molecule myosin in muscles
– Intermediate filaments support the nuclear membrane
– Microtubules protrude from the centrosome and form centrioles,
cilia, and flagella
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The cytoskeleton
• Fig. 3.10
• Fig 3.11
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Eukaryotic cells, cont’d.
• Centrioles
– Short tubules with 9+0 pattern of microtubule triplets
– In animal cells, centrosome is composed of 2
centrioles
– Believed to be involved in microtubule formation
including mitotic spindle
• Cilia and flagella
– Hair-like projections, cilia generally multiple and
flagella single or double
– 9+2 pattern of microtubules
– Whip-like action involved with movement
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Actin and intermediate filaments
• Fig 3.12
• Fig 3.13
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Centrioles
• Fig. 3.14
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Structure of cilia and flagella
• Fig. 3.15
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3.3 Prokaryotic cells
• Archae and bacteria are prokaryotes
– Lack a nucleus
– Smaller than eukaryotes
• Prokaryotic cell structures
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–
–
–
–
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Cell wall-contains peptidoglycans
Capsule present in some
Plasma membrane
Nucleoid-region which contains a single chromosome
Ribosomes
Thylakoids-in photosynthetic cyanobacteria
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Bacterial cells
• Fig 3.16
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3.4 Evolution of eukaryotic cells
• Endosymbiotic hypothesis-prokaryotes engulfed
by larger cells which became eukaryotic cells
with prokayotes becoming Chloroplasts and
Mitochondria inside.
• Mitochondria and Chloroplasts
- Both resemble bacteria
- Both have double membrane-outer could be from engulfing
vesicle, inner from original cell membrane
- Contain DNA and are self-replicative
- Contain their own ribosomes
- RNA base sequences suggest relationship with bacteria
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Evolution of eukaryotic cells
• Fig 3.17
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