CELLS: UNITS OF LIFE

Chapter 4Hyperlink is the 3rd one that says

component of cells – same as above, but narrated!

CELLS: UNITS OF LIFE

The Discovery of CellsAll organisms consist of cells

The Discovery of CellsCells – the place where

biochemical activity occurs

The Discovery of CellsCells – have ALL characteristics of

lifeAll made of cells – and have levels of organization

All grow, develop, and reproduceAll use energyAll adaptAll respond to stimuliMaintain internal constancy

The Discovery of CellsCells – cell membrane –

separates living matter from the environment and limits size of organism

The Discovery of CellsOrganelles – structures where

life processes occur to keep cell alive

The Discovery of CellsCellular Cytoplasm- remainder of

interior of cell besides organelles

The Discovery of CellsCells can specialize (examples :

muscle cells, leaf cells, root cells)

The Discovery of CellsStem cells –

from which all cells differentiate in many celled organism

Lenses Reveal the World of the Cell13th Century – world

recognized glass magnifies

Lenses Reveal the World of the Cell16th Century – began using paired

lenses (Jansen and church spire)

Lenses Reveal the World of the Cell• Robert Hooke (1660)

• 1st person to see the outlines of cells• Spun glass and looked at bee stingers, fish scales, fly

legs, insects and CORK• Antonie van Leeuwenhoek (1673)

• developed over 500 high magnification lenses• 1st record of microorganisms- he called

“animalcules” found in tooth tartar

The Cell Theory Emerges – not till 19th Century Robert Brown – discovered

cellular nucleus Houses DNA

Schleiden Cells were basic unit of

plants Schwann

Cells were basic unit of animals

Together Cells were elementary

particles of all organisms, the unit of structure and function

VirchowAll cells come

from pre-existing cells

Believed abnormal cells cause diseases

The Cell Theory Emerges – not till 19th Century

Cell Theory1. All living things are composed

of cells. [Schleiden & Schwann]

2. All cells come from preexisting cells. [Virchow]

Cell Theory still evolving: Organelles have precise locations

in cells

C. Types of Cells3 basic types:• Bacterial• Archaean

Prokaryotic

• Eukaryotic

Variations on the Cellular Theme

Review surface area to volume relationship – Large volume justifies the need to have organelles

Variations on the Cellular Theme

Variations on the Cellular ThemeFolding membranes also increase surface

area for reactions

1. Bacterial cells • 1-10 m in diameter • NO membrane-bound organelles• Some photosynthetic – use pigment only• Some cause illness some don’t• Vital to life on earth• 1 circular DNA molecule located in nucleoid region

• MAKE PROTEINS RAPIDLY DUE TO CLOSE LOCATION OF ORGANELLS

• plasma membrane, cytoplasm & ribosomes• most have a cell wall (peptidoglycan)

• Many antibiotics interfere with cell wall construction

• may have a polysaccharide capsule to protect or attach

• Film on teethn morningEx. bacteria & cyanobacteria

Bacterial ShapesCocciBacilliSpirillaFibrios fusiform

Gram-stainingDistinguishes 2 types of bacteria •Gram – negative – thin cell wall•Gram positive – thick cell wall

Structure of a Gram-Negative Cell Wall Gram positive cell wall

Archaean cells represent a distant ancestor???• 1-10 m in diameter• Use carbon dioxide and

hydrogen to make methane (methanogens)

• Have co-enzymes that make methane

• NO membrane-bound organelles• cell walls lack peptidoglycan• have characteristics of both

bacteria & eukaryotic cells• Half of genes are same as

bacteria, other half totally different

• mRNA and tRNA are different than in other domains

Methanogen

Archaean Extremophiles, con’t

Ex. Extremophiles: extreme environments: temp, pressure, pH, salinity

methanogens, extreme halophiles & extreme thermophiles

Live in Swamps, rice paddies and oceans

Extreme halophile

3. Eukaryotic cells• 10-100 m in diameter • Includes plants, animals, fungi and protists• nucleus & other membrane-bound organelles• Nucleus

• Protects and organizes the cell’s linear DNA• DNA combined with protein forming chromosomes

• plasma membrane, cytoplasm & ribosomes• some have a cell wall (cellulose or chitin) • Animal cells: half the volume of a cell is organelles• Plant cells: 90% may be water (found in vacuole)• Cytoskeleton – rods and tubules within cells to give

cell shape or appendages to move

Introduction to Organelles Organelles –

improve efficiency, protect contents, secrete substances, derive energyDegrade debrisreproduce

Introduction to Organelles Organelles Synthesize and Process Proteins

Enzymes – key to determining function of cell

Endomembrane system Rough endoplasmic reticulum

Compartments use enzymes that assist with protein production and transportation

Smooth endoplasmic reticulumLipids synthesized, modified and

toxins neurtalized

Generalized Generalized Animal Cell Plant Cell

Introduction to Organelles’s cont Golgi apparatus

Sorts proteins for exports out of cell or into lysosomes

links simple carbohydrates together to form starch

links simple carbohydrates to proteins (glycoprotein) or lipids (glycolipid)

completes folding of proteins temporarily stores secretions

(milk)

Organelle interaction in a mammary gland cell.

Introduction to Organelles’s cont Lysosomes (suicide sacs)

Contain digestive enzymes – 40 types Function to recycle damaged organelles,

break down cellular by products & destroy invading microbes

The Nucleus Exports RNA instructions

Genes: instructions on DNA are copied onto mRNA

mRNA exits nucleus through nuclear pores (found in nuclear envelope Not just holes Channels with 100 types of proteins

(importins and exportins)

The Cytoplasm Site of Protein synthesis and other

reactions mRNA binds to ribosomes

A complex of MANY proteins surrounding an rRNA

rRNA + proteins are assembled in the nucleolus then exit the nucleus through pores

Remainder of section completes milk production example

Lysosomes and Peroxisomes: Cellular Digestion Centers – and more

Lysosomes are cellular recycling centers Lyse – cut apart Enzymes within organelle – lyse targets

Dismantle bacteria Dismantle worn out organelles and debris Break down large nutrients into useable

monomers Fuse with vesicles carrying debris Made in rough ER Function in very acidic environment

Lysosome’s con’t Numbers very based on cell function

White blood cells have many Liver have MANY – process cholesterol

Human cells have more than 40 enzyme types

Balance of enzyme related to health Too many, causes storeage problems in

cell – crowds other organelles Tay Sachs – missing an enzyme in a

lysosome

Tay Sachs events

PeroxisomesFacilitate oxidative Reactions

Contain enzymes that oxidize other molecules

Enzymes made in the cytoplasm – then transported to vesicles

Environmental toxins: cause explosion of peroxisome production Toxins are oxidized and removed

Synthesize bile acids

Peroxisomes, con’t Break down lipids Degrade rare biochemicals Metabolize free radicals Some produce hydrogen peroxide

Produces free radicals So contain catalase – removes oxygen

from hydrogen peroxide to make water Found in leaves Adrenoleukodystrophy (Lorenzo’s disease) –

two proteins missing in peroxisomes outer membrane pg 59

Leopard spot retinal pigmentation

Mitochondria – organelle of energy Mitochondria Extract Energy from

nutrientsNumbers vary from few to 1000’sCristae – inner folds contain

enzymesSite of cellular respiration (ATP)

Converts glucose into ATP energy

Has own genetic material (DNA) Inherited only from female

Chloroplast – organelle of energy Chloroplasts provide plant cells with nutrients

(THEREFORE ENERGY) Chloroplast

carry out photosynthesis Form glucose or other carbohydrates Have stroma – space inside chloroplast for

reactions Thylakoids – membrane system of stacked

sacks called grana where reactions take place Has own DNA See Table pg 60

Origin of Complex Cells Endosymbiont theory – large celled critters

engulfed smaller simpler cells. Simple cells became organelles in the larger critter Structure and DNA sequences provide

evidence Evidence in FAVOR of EST

Resemblance between mitochondria and chloroplasts to certain kinds of bacteria

» Size» Shape» Membrane structure» Presence of pigments» Reproduction method» Relative relationship of DNA, RNA and ribosomes

Origins of Complex Cells, con’t Technology Evidence DNA evidence – bacteria and archaea

contributed Theory: archaean cells enveloped

bacterial cells that became mitochondria and chloroplasts

Theory: bacteria share genes with bacteria and vice versa

Ricettsia

Endosymbiant Theory

Origins of Complex Cells, cont

How Endosymbiosis May have worked, pg 61

2. Endoplasmic reticulum (ER)• interconnected network of membranes extending from nucleus to plasma membrane

3. Golgi apparatus • stacks of membrane-enclosed

sacs

4. Lysosomes (suicide sacs)• vesicles containing > 40 types of

digestive enzymes

• function to recycle damaged organelles, break down cellular byproducts & destroy invading microbes

5. Perixisomes• vesicles containing several types

of enzymes (produced in cytoplasm)• found in all eukaryotic cells• function to help cell use oxygen

& metabolize potentially toxic compounds

• hydrogen peroxide is produced as a by-product of peroxisome activity

• the enzyme catalase converts hydrogen peroxide to water

• #/cell varies• contain DNA• inherited from female parent• site of cellular respiration

(production of ATP)

6. Mitochondria• double-

membrane• outer is smooth• inner is highly

folded (cristae)

7. Chloroplasts• possess 3 membranes

• outer/inner membranes surround stroma• 3rd membrane system folded into flattened

sacs (thylakoids)

• #/cell varies • contain DNA• found in plants & protists• function in

photosynthesis

E. The Endosymbiont TheoryProposes that chloroplasts and

mitochondria evolved from once free-living bacteria engulfed by larger archaea.

Based on fact that mitochondria & chloroplasts resemble certain bacteria (size, shape, membrane structure & method of making proteins).