Inquiry into Life

Eleventh Edition

Sylvia S. Mader

Chapter 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 1-2

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 1-3

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 1-4

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 1-5

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 1-6

• Fig. 3.2

Animal cell anatomy

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• Fig. 3.3

Plant cell anatomy

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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 1-9

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 1-11

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 1-12

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 1-14

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 1-16

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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• Fig 3.8

Chloroplast structure

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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 1-20

• Fig. 3.9

Mitochondrion structure

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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 1-22

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 1-23

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 1-25

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 1-29

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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