Organization of the CellOrganization of the Cell

Cell Theory

Cells are the basic living Cells are the basic living units of organization and units of organization and

function in all organisms and function in all organisms and all cells come from other all cells come from other

cellscells

Cells are the basic living Cells are the basic living units of organization and units of organization and

function in all organisms and function in all organisms and all cells come from other all cells come from other

cellscells

Cell TheoryThe players:

Matthias Schleiden- German botanist (1838)

Theodor Schwann- German zoologist (1839)

Rudolph Virchow- German professor of pathology (1855)

The players:

Matthias Schleiden- German botanist (1838)

Theodor Schwann- German zoologist (1839)

Rudolph Virchow- German professor of pathology (1855)

Schleiden and Schwann

The first to point out that all plants and animals are composed of cells.The first to point out that all plants and animals are composed of cells.

1838

Rudolph Virchow

The first to observe cells dividingThe first to observe cells dividing

1855

History of the Microscope

• Robert Hooke examined a thin piece of cork using a compound microscope- noticed the boxes in the thin slice and called them “cells”

• Robert Hooke examined a thin piece of cork using a compound microscope- noticed the boxes in the thin slice and called them “cells”

?

1665

History of the MicroscopeAnton van Leeuwenhoek viewed living cells with 200 magnification single lenses of his own construction. His important discoveries include bacteria, protists, blood cells, and sperm cells.

Anton van Leeuwenhoek viewed living cells with 200 magnification single lenses of his own construction. His important discoveries include bacteria, protists, blood cells, and sperm cells.

1670sDutch ScientistDutch Scientist

Van Leeuwenhoek’s Microscope

1800

1860

1880

1890

1899

1908

1930

1951

1970

2004

Nikon ‘confocal’ microscope and, “No, I don’t know how much it costs.”

Electron Microscope

Invented in 1930s by (believe it or not) German scientists Max Knott and Ernst Ruska

Invented in 1930s by (believe it or not) German scientists Max Knott and Ernst Ruska

Transmission Electron MicroscopeTransmission Electron Microscope

•2-D Image

•Image not living

•10,000X to 100,000X

•Electron beam passes through the specimen

•Specimen is thinly sliced

•2-D Image

•Image not living

•10,000X to 100,000X

•Electron beam passes through the specimen

•Specimen is thinly sliced

Scanning Electron MicroscopeScanning Electron Microscope•3-D imaging

•Image not living

•1,000X-10,000X magnification

•Image is coated with a thin film of metal and the electron beams are collected as they bounce off of the specimen

•3-D imaging

•Image not living

•1,000X-10,000X magnification

•Image is coated with a thin film of metal and the electron beams are collected as they bounce off of the specimen

Prokaryotic Cells

Bacteria are prokaryotic cells. All other known organisms consist of …..

Bacteria are prokaryotic cells. All other known organisms consist of …..

Eukaryotic Cells

Prokaryotic Cells• Structurally simpler than

eukaryotic cells• Nuclear material not

enclosed in a membrane• Ribosomes smaller than

Euk.• Lack of membrane

bound organelles

• Structurally simpler than eukaryotic cells

• Nuclear material not enclosed in a membrane

• Ribosomes smaller than Euk.

• Lack of membrane bound organelles

                                                                

bacteria

Cheek cells

Eukaryotic Cells• Membrane bound organelles• Cell Nucleus• Ribosomes• Endoplasmic reticulum• Golgi complex• Lysosomes• Peroxisomes• Vacuoles• Mitochondria• Chloroplasts

• Membrane bound organelles• Cell Nucleus• Ribosomes• Endoplasmic reticulum• Golgi complex• Lysosomes• Peroxisomes• Vacuoles• Mitochondria• Chloroplasts

Membrane Bound Organelles

The ‘stuff’ outside the nucleus and inside the cell membrane, suspended in cytoplasm

The ‘stuff’ outside the nucleus and inside the cell membrane, suspended in cytoplasm

Membrane Bound Organelles

ribosomesmitochondria

Endoplasmic reticulum

Golgi complexLysosomesPlastids

Just to name a few

Vacuoles

Peroxisomes

Cell Nucleus

Cell Nucleus

Contains nucleolus and chromosomes (DNA)

Contains nucleolus and chromosomes (DNA)

The Nucleus

Cell Nucleus• Typically in the center of the cell

• Most cells have a single nucleus

• Typically in the center of the cell

• Most cells have a single nucleus

Nuclear Envelope• Controls traffic

between the nucleus and the cytoplasm

• Pores in the nuclear membrane allow materials to pass in and out of the

• nucleus

• Controls traffic between the nucleus and the cytoplasm

• Pores in the nuclear membrane allow materials to pass in and out of the

• nucleus

Nucleus – a closer look

Nuclear Envelope

EM View of Envelope

A closer look at the envelope

Nuclear Lamina• Inside the nucleus• Formed by intermediate

filaments• Important in the timing of

the disorganization of the membrane during cell division and the ensuing redevelopment

• Inside the nucleus• Formed by intermediate

filaments• Important in the timing of

the disorganization of the membrane during cell division and the ensuing redevelopment

Lamina

Chromatin

• When dividing, DNA takes the form of chromosomes

• When not dividing, the DNA takes a looser form called chromatin

• When dividing, DNA takes the form of chromosomes

• When not dividing, the DNA takes a looser form called chromatin

Loose Chromatin

Ribosomal Subunits

• Eukaryotic ribosomal subunits are assembled in the nucleolus

• Ribosomes are composed of two subunits

• Eukaryotic ribosomal subunits are assembled in the nucleolus

• Ribosomes are composed of two subunits

Ribosomes

• Ribosomes manufacture proteins

• Ribosomes may be free or may be attached to the endoplasmic reticulum

• Ribosomes manufacture proteins

• Ribosomes may be free or may be attached to the endoplasmic reticulum

Endoplasmic Reticulum

Endoplasmic Reticulum

• Major manufacturing center- proteins

• Extends from the nuclear membrane into the cytoplasm

• Lumen- the space enclosed by the ER- typical intracellular membrane

• Major manufacturing center- proteins

• Extends from the nuclear membrane into the cytoplasm

• Lumen- the space enclosed by the ER- typical intracellular membrane

The Cytosol side of the ER may be studded with ribosomes

Rough ER• Site of protein synthesis

• Proteins formed may be transferred to other sites within the cell in transport vesicles

• Site of protein synthesis

• Proteins formed may be transferred to other sites within the cell in transport vesicles

Transport vesicles

Smooth ER• Lacks

ribosomes• Lipid

production• Detoxifying

chemical agent

• Lacks ribosomes

• Lipid production

• Detoxifying chemical agent

Golgi Complex

• Cis face functions in receiving materials• The Trans face is directed toward the

plasma membrane• Function: processing, sorting and

modifying proteins• The process product is then passed to

other organelles or to the plasma membrane

• Manufactures lysosomes

• Cis face functions in receiving materials• The Trans face is directed toward the

plasma membrane• Function: processing, sorting and

modifying proteins• The process product is then passed to

other organelles or to the plasma membrane

• Manufactures lysosomes

Golgi Complex- Cis and Trans Face

University of texas medical school

Convex shape

Lysosomes

• Compartments for digestion

• Small sacs filled hydrolytic enzymes

• Primary lysosomes bud from the Golgi complex

• Involved in apoptosis (programmed cell death)– Inappropriate apoptosis may be involved in

many different catastrophic illnesses

• Compartments for digestion

• Small sacs filled hydrolytic enzymes

• Primary lysosomes bud from the Golgi complex

• Involved in apoptosis (programmed cell death)– Inappropriate apoptosis may be involved in

many different catastrophic illnesses

Peroxisomes

• Metabolize small organic compounds

• Transfer hydrogen from various compounds to oxygen, forming hydrogen peroxide

• Catalase splits hydrogen peroxide rendering it harmless

• Metabolize small organic compounds

• Transfer hydrogen from various compounds to oxygen, forming hydrogen peroxide

• Catalase splits hydrogen peroxide rendering it harmless

Peroxisomes

• Common in cells that synthesize, store, or degrade lipids

• Plant cells have specialized peroxisomes called glyoxysomes

• Common in cells that synthesize, store, or degrade lipids

• Plant cells have specialized peroxisomes called glyoxysomes

•metabolism of free oxygen radicals; •synthesis of cholesterol and ether lipids; •bile acid formation; •catabolism of long chain fatty acids; •catabolism of purines, prostaglandins, leucotriens; •alcohol detoxification in liver

•metabolism of free oxygen radicals; •synthesis of cholesterol and ether lipids; •bile acid formation; •catabolism of long chain fatty acids; •catabolism of purines, prostaglandins, leucotriens; •alcohol detoxification in liver

Peroxisome Functions:

Some interesting facts about peroxisomes are: •Human congenital diseases associated w/absence of peroxisomes and/or dysfunction of their enzymes•many chemicals (drugs, industrial pollutants) induce a marked proliferation of peroxisomes; •prolonged Tx w/ most proliferators induce malignant hepatic tumors

Some interesting facts about peroxisomes are: •Human congenital diseases associated w/absence of peroxisomes and/or dysfunction of their enzymes•many chemicals (drugs, industrial pollutants) induce a marked proliferation of peroxisomes; •prolonged Tx w/ most proliferators induce malignant hepatic tumors

Vacuoles• Large, fluid filled sacs• Carry out variety of functions

– In plants & fungi, vacuoles carry out many of the functions of the lysosome

– Allow plants to increase in size

• Bound by a membranous tonoplast• May store toxins or pigments• Protists have vacuoles that are involved

in digestions and secretion

• Large, fluid filled sacs• Carry out variety of functions

– In plants & fungi, vacuoles carry out many of the functions of the lysosome

– Allow plants to increase in size

• Bound by a membranous tonoplast• May store toxins or pigments• Protists have vacuoles that are involved

in digestions and secretion

Mitochondria• Energy converting organelle- site of aerobic

respiration• Double membrane bound• Matrix- inside of the inner membrane• Cristae- the foldings of the inner membrane,

providing a large surface area• Mutations in mitochondrial DNA have been

linked to several genetic diseases• Mitochondria also affect health by leaking

electrons, which form free radicals, into the cell

• Energy converting organelle- site of aerobic respiration

• Double membrane bound• Matrix- inside of the inner membrane• Cristae- the foldings of the inner membrane,

providing a large surface area• Mutations in mitochondrial DNA have been

linked to several genetic diseases• Mitochondria also affect health by leaking

electrons, which form free radicals, into the cell

Outer membrane lets manyMolecules through, but inner membrane is very selective

Chloroplasts

• Convert light energy into chemical energy through photosynthesis

• Pigments like chlorophylls are specialized for photosynthesis

• Double membrane bound• Develop from proplastids• Chromoplasts contain pigments and are

common in petals and ripe fruit• Leukoplasts lack pigments and may

store starch

• Convert light energy into chemical energy through photosynthesis

• Pigments like chlorophylls are specialized for photosynthesis

• Double membrane bound• Develop from proplastids• Chromoplasts contain pigments and are

common in petals and ripe fruit• Leukoplasts lack pigments and may

store starch

Contains enzymes

responsible for producing

carbohydrates from carbon dioxide and

water

Fluid filled area

Thylakoids are involved with producing ATP. This is where the chlorophyll is.

Would you recognize these structures as chloroplasts? How?

amyloplasts

Proplastids that will turn into

amyloplasts

Cytoskeleton

• Provides for cell shape and allows movement

• Classifying elements of cytoskeleton by size– Microfilaments- smallest

– Intermediate filaments

– Microtubules- largest

• Provides for cell shape and allows movement

• Classifying elements of cytoskeleton by size– Microfilaments- smallest

– Intermediate filaments

– Microtubules- largest

Hollow cylinders

Microtubules are in green. Actin is in red. DNA is blue.

MTOCMicrotubule Organizing Center- CentrosomeMicrotubule Organizing Center- Centrosome

http://www.cellsalive.com/mitosis.htm

Dynein

Cilia and Flagella

• Composed of microtubules• Cilia- numerous and short• Flagella- longer and fewer in number• Move the cell or move substances over

the surface of the cell• Both have 9+2 arrangement of

microtubules• Basal body and centrioles have 9X3

arrangement

• Composed of microtubules• Cilia- numerous and short• Flagella- longer and fewer in number• Move the cell or move substances over

the surface of the cell• Both have 9+2 arrangement of

microtubules• Basal body and centrioles have 9X3

arrangement

9 + 2 arrangement of cilia

Microfilaments

microtubules

actin

Extracellular Matrix

• ECM

• Secreted gel surrounding cell

• Composed of collagen which forms very tough fibers

• Integrins- main membrane receptors for the ECM

• Help the cell cell signaling pathways and help regulate various functions of the cell

• ECM

• Secreted gel surrounding cell

• Composed of collagen which forms very tough fibers

• Integrins- main membrane receptors for the ECM

• Help the cell cell signaling pathways and help regulate various functions of the cell

Glycocalyx- Cell Coat

• Surround most eukaryotic cells

• Formed by polysaccharide side chains

• May act as recognition sites

• Surround most eukaryotic cells

• Formed by polysaccharide side chains

• May act as recognition sites

Junctions between Cells• Form strong connections• Prevent passage of materials• Establish communication • Animal cell junctions

– Anchoring (desmosomes and adhering junctions– Tight junctions– Gap junctions

• Plant Cell junction– plasmodesmata

Des

mos

omes

• Points of attachment for some animal cells

• Hold cells subject to mechanical stress together

• Composed of intermediate filaments, which span the gap between two cells

Cell Walls

• Surround plant, fungal, and bacterial cells

• Primary cell wall can expand as the cell grows

• Secondary cell wall forms between the primary cell wall and the cell membrane

• Middle lamella glues adjacent plant cells together

• Surround plant, fungal, and bacterial cells

• Primary cell wall can expand as the cell grows

• Secondary cell wall forms between the primary cell wall and the cell membrane

• Middle lamella glues adjacent plant cells together

Middle Lamella