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Inquiry into LifeEleventh Edition

Sylvia S. MaderChapter 3

Lecture Outline

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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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. – 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– 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