The Living CellThe Living Cell

Lecture 11Lecture 11

UNIV301 – Great Ideas of ScienceUNIV301 – Great Ideas of Science

Great Idea: Life is based on chemistry, and chemistry takes place

in cells

CellsCells All living things are made of cells, which All living things are made of cells, which

are like chemical factoriesare like chemical factories Every cell has an Every cell has an ““insideinside”” and an outside, and an outside,

separated by a cell membraneseparated by a cell membrane Every cell uses raw materials and energy to Every cell uses raw materials and energy to

produce new chemicalsproduce new chemicals Every cell must contain information on how Every cell must contain information on how

to operate and how to make new cellsto operate and how to make new cells

Observing Cells: Observing Cells: The MicroscopeThe Microscope

Observing Cells: Observing Cells: The MicroscopeThe Microscope

The Cell TheoryThe Cell Theory Robert Hooke (1635-1702)Robert Hooke (1635-1702)

Cells are like small Cells are like small compartmentscompartments

Matthais Scheiden – plants, 1838Matthais Scheiden – plants, 1838 Theodor Schwann – animals, 1839Theodor Schwann – animals, 1839

The Cell Theory, 1839The Cell Theory, 1839 All living things are composed of cellsAll living things are composed of cells The cell is the fundamental unit of lifeThe cell is the fundamental unit of life All cells arise from previous cellsAll cells arise from previous cells

Two Kinds of CellsTwo Kinds of Cells

Prokaryotes (Prokaryotes (““before nucleusbefore nucleus””))

Eukaryotes (Eukaryotes (““true nucleustrue nucleus””))

Cellular Cellular ArchitectureArchitecture OrganelleOrganelle: Any specialized cell structure: Any specialized cell structure

Cell membrane Cell membrane ((cell wall cell wall in plants)in plants) NucleusNucleus MitochondriaMitochondria and and chloroplastschloroplasts (power plants) (power plants)

Plant CellsPlant Cells

Animal CellsAnimal Cells

LipidsLipids

Cell MembranesCell Membranes Cell MembranesCell Membranes

Isolate the cellIsolate the cell Separate cell partsSeparate cell parts

TransportTransport Individual moleculesIndividual molecules Channels for specific Channels for specific

materialsmaterials ReceptorsReceptors

Bind moleculesBind molecules EncapsulateEncapsulate

Cell Wall (plants) Cell Wall (plants)

The NucleusThe Nucleus NucleusNucleus

Contains DNAContains DNA ProkaryotesProkaryotes

No nucleusNo nucleus EukaryotesEukaryotes

Nucleus Nucleus The nucleus has a double membrane. The nucleus has a double membrane.

Why?Why?

Nucleus

CytoskeletonCytoskeleton

CytoskeletonCytoskeleton Gives cell shapeGives cell shape AnchorsAnchors Allows movementAllows movement Transport systemTransport system within cellwithin cell

StructureStructure Strong filamentsStrong filaments Complex webComplex web

How Is Energy Obtained?How Is Energy Obtained?Plants – make sugar in the presence of the Plants – make sugar in the presence of the

Sun by the process of Sun by the process of photosynthesisphotosynthesis

Energy (light) + COEnergy (light) + CO22 + H + H22O O Glucose + O Glucose + O22

Carbohydrates (sugars)Carbohydrates (sugars)

Carbon

Hydrogen

Oxygen

Cellulose and StarchCellulose and Starch

How Is Energy Obtained?How Is Energy Obtained? Plants and animals convert sugar Plants and animals convert sugar

into small energy-rich molecules into small energy-rich molecules by the process of by the process of glycolysisglycolysis..

Glucose Glucose 2 Pyruvic Acids + ATP 2 Pyruvic Acids + ATP

ATP ATP ADP + PO ADP + PO44 + energy + energy

ATP: The CellATP: The Cell’’s Energy s Energy CurrencyCurrency

Adenosine triphosphate (ATP)Adenosine triphosphate (ATP) Provides energy Provides energy

StructureStructure 3 phosphate groups3 phosphate groups Sugar molecule: riboseSugar molecule: ribose adenineadenine

FunctionFunction Removal of phosphate group provides energyRemoval of phosphate group provides energy

How Is Energy Obtained?How Is Energy Obtained?

Some animals obtain Some animals obtain energy by the process of energy by the process of

respirationrespiration::

Glucose + OGlucose + O22

Energy + COEnergy + CO22 + H + H22O O

The Final Stages of The Final Stages of RespirationRespiration

Glucose is broken downGlucose is broken down COCO22 is produced is produced

ATP is produced to serve as ATP is produced to serve as energy-carrying moleculesenergy-carrying molecules

Result: 36-38 ATPResult: 36-38 ATP

How Is Energy Obtained?How Is Energy Obtained?

Many organisms obtain Many organisms obtain additional energy from additional energy from

pyruvic acid by the pyruvic acid by the process of process of fermentationfermentation::

Pyruvic Acid Pyruvic Acid

small molecules + ATPsmall molecules + ATP

Vinegar, alcohol, carbonic acidVinegar, alcohol, carbonic acid

The Energy Organelles: The Energy Organelles: Chloroplasts and Chloroplasts and MitochondriaMitochondria

ChloroplastsChloroplasts Plant cells onlyPlant cells only Energy transformationEnergy transformation

chlorophyllchlorophyll

Double membraneDouble membrane

MitochondriaMitochondria Plants and AnimalsPlants and Animals Produces the cellProduces the cell’’s ATPs ATP Double membraneDouble membrane Has its own DNAHas its own DNA

MitochondriaMitochondriaWhere ATP is manufacturedWhere ATP is manufactured

Mitochondria (mtDNA) = maternally inheritedMitochondria (mtDNA) = maternally inheritedUnaltered from your motherUnaltered from your mother

Genetic material from common ancestorGenetic material from common ancestorGenetic anthropologyGenetic anthropology

Genetics: The Genetic Genetics: The Genetic CodeCode

KEY IDEA: All living things share the KEY IDEA: All living things share the same genetic codesame genetic code

Classical genetics – the observation Classical genetics – the observation of organismsof organisms

Cellular genetics – the observation of Cellular genetics – the observation of cell division and chromosomescell division and chromosomes

Molecular genetics – the study of DNA Molecular genetics – the study of DNA and RNAand RNA

Two great mysteries of lifeTwo great mysteries of life

1.1. Like begets likeLike begets like

2.2. You begin life as a single cellYou begin life as a single cell

Three Stages Three Stages of Genetics Researchof Genetics Research

1. Classical Genetics1. Classical Genetics

2. Cellular Genetics2. Cellular Genetics

3. Molecular Genetics3. Molecular Genetics

Gregor Mendel (1822-1884)Gregor Mendel (1822-1884) Pea plant – breeding experimentsPea plant – breeding experiments

Two-characteristic variationsTwo-characteristic variations Established pure-breeding stocksEstablished pure-breeding stocks Studied cross breeding Studied cross breeding

OffspringOffspring’’s traits are derived s traits are derived

from parentsfrom parents

Classical GeneticsClassical Genetics

Gregor MendelGregor Mendel’’s Lawss Laws Pea plant experimentsPea plant experiments PurebredPurebred HybridHybrid

ResultsResults First generation all hybrid tallFirst generation all hybrid tall

If you cross a pure bred tall pea plant If you cross a pure bred tall pea plant with a pure bred short pea plant, all with a pure bred short pea plant, all offspring are tall.offspring are tall.

T T

t tT tT

t tT tT

Classical GeneticsClassical Genetics

Gregor MendelGregor Mendel’’s Lawss Laws Pea plant experimentsPea plant experiments PurebredPurebred HybridHybrid

ResultsResults First generation all hybrid tall.First generation all hybrid tall. Cross breed those hybrids.Cross breed those hybrids. Second generation is ¾ tall Second generation is ¾ tall

and ¼ short!and ¼ short!

If you cross two hybrid pea plants, If you cross two hybrid pea plants, ¾ will be tall and ¼ will be short.¾ will be tall and ¼ will be short.

T t

T TT Tt

t tT tt

Classical GeneticsClassical GeneticsMendel LawsMendel Laws

1.1.Genes exist (Genes exist (““atoms of inheritanceatoms of inheritance””))

2.2.Each parent contributes half.Each parent contributes half.

3.3.Some are dominant and some are Some are dominant and some are recessive.recessive.

If you cross a pure bred tall pea plant If you cross a pure bred tall pea plant with a hybrid pea plant, what would the with a hybrid pea plant, what would the first generation of offspring look like?first generation of offspring look like?

T T

T TT TT

t tT tT

Gregor MendelGregor Mendel’’s s Three Laws of HeredityThree Laws of Heredity

1.1. There exist There exist ““atoms of inheritanceatoms of inheritance”” or genesor genes

2.2. Each parent contributes halfEach parent contributes half

3.3. Some genes are dominant, others Some genes are dominant, others are recessiveare recessive

4.4. Genes are expressed independently Genes are expressed independently of each other (WRONG)of each other (WRONG)

Cellular GeneticsCellular Genetics

Use microscope to observe cells dividingUse microscope to observe cells dividing ChromosomesChromosomes – elongated colored objects – elongated colored objects

Cellular GeneticsCellular Genetics

Use microscope to observe cells dividingUse microscope to observe cells dividing ChromosomesChromosomes – elongated colored object – elongated colored object MitosisMitosis (one cell becomes two) (one cell becomes two)

Most cellular division in your bodyMost cellular division in your body

Humans 23 pairs (before division 46 pairs)Humans 23 pairs (before division 46 pairs) 2 daughter cells same as parent2 daughter cells same as parent

MeiosisMeiosis (one becomes 4 gametes) (one becomes 4 gametes) Crossing-Over (reshuffle = end of meiosis)Crossing-Over (reshuffle = end of meiosis) Recombination yields different mix of genesRecombination yields different mix of genes

MitosisMitosis Mitosis is cell divisionMitosis is cell division

(Not sexual reproduction)(Not sexual reproduction) Observe chromosomesObserve chromosomes Multi-step ProcessMulti-step Process

1. Copy chromosomes1. Copy chromosomes2. Spindle fibers2. Spindle fibers3. Migration of chromosomes3. Migration of chromosomes4. Nuclear membrane reforms4. Nuclear membrane reforms

MitosisMitosis

MeiosisMeiosisMeiosis is sMeiosis is sexual reproductionexual reproduction

1 cell forms 4 gametes1 cell forms 4 gametesGametes are genetically uniqueGametes are genetically unique

Multi-step processMulti-step process1. Copy chromosomes1. Copy chromosomes2. Crossing over2. Crossing over

MeiosisMeiosisMeiosis is sMeiosis is sexual reproductionexual reproduction

1 cell forms 4 gametes1 cell forms 4 gametesGametes are genetically uniqueGametes are genetically unique

Multi-step processMulti-step process1. Copy chromosomes1. Copy chromosomes2. Crossing over2. Crossing over3. Segregation3. Segregation4. Segregation again4. Segregation again

Result: Result: 4 daughter cells, each 4 daughter cells, each with ½ normal number of with ½ normal number of chromosomes. Each chromosomes. Each chromosome is unique!chromosome is unique!

Molecular GeneticsMolecular Genetics

What chemical carries the genetic What chemical carries the genetic message?message?

How is that molecular message How is that molecular message translated into the chemicals of translated into the chemicals of life?life?

The Discovery of DNAThe Discovery of DNA

Oswald Avery (1877-1955)Oswald Avery (1877-1955)

DNA is composed of deoxyribose (5-DNA is composed of deoxyribose (5-carbon sugar), phosphate, and one of carbon sugar), phosphate, and one of four bases (ATGC).four bases (ATGC).

A = T; G = CA = T; G = C

Sugar=Phosphate=Base (1:1:1 ratio)Sugar=Phosphate=Base (1:1:1 ratio)

Nucleotides: The Building Nucleotides: The Building Blocks of Nucleic AcidsBlocks of Nucleic Acids

Nucleotides are madeNucleotides are madeof three moleculesof three molecules

1. Sugar1. SugarDNA: deoxyriboseDNA: deoxyriboseRNA: riboseRNA: ribose

2. Phosphate ion2. Phosphate ion3. Base 3. Base

Adenine (A)Adenine (A)Guanine (G)Guanine (G)Cytosine (C)Cytosine (C)Thymine (T) Thymine (T)

DNADNA’’s Double Helixs Double Helix

Nucleotide: Building blocks in nucleic acids

(A phosphate linked to a sugar linked to a base)

DNA StructureDNA Structure Join nucleotides by Join nucleotides by

alternating phosphate alternating phosphate and sugarand sugar

DNADNA 2 strands of nucleotides2 strands of nucleotides Joined by base pairsJoined by base pairs

Bonding patternBonding pattern Adenine:ThymineAdenine:Thymine Cytosine:GuanineCytosine:Guanine

DNA Base PairingDNA Base Pairing

Adenine:ThymineAdenine:Thymine

Cytosine:GuanineCytosine:Guanine

The Replication of DNAThe Replication of DNA

DNA replication occurs DNA replication occurs before mitosis & meiosisbefore mitosis & meiosis

ProcessProcess1. DNA double helix splits1. DNA double helix splits2. New bases bond to 2. New bases bond to

exposed basesexposed bases3. Results in two identical 3. Results in two identical

DNA strandsDNA strands

Proteins – EnzymesProteins – Enzymes

Amino AcidsAmino Acids

Amino groupAmino group Carboxyl groupCarboxyl group Side-group (20 Side-group (20

different things)different things)

Protein – sequence of Protein – sequence of amino acidsamino acids

Primary – chain of Primary – chain of amino acidsamino acids

Secondary – folding of Secondary – folding of chainchain

TertiaryTertiary QuaternaryQuaternary

How Does DNA Make Protein?How Does DNA Make Protein?

1. 1. ChromosomesChromosomes (DNA) carry the (DNA) carry the genetic messagegenetic message

2. 2. Messenger RNA Messenger RNA copies the genetic copies the genetic messagemessage

3. 3. Transfer RNA Transfer RNA holds an amino acidholds an amino acid

4. 4. Ribosomal RNA Ribosomal RNA assembles a proteinassembles a protein

RNA StructureRNA Structure

1. Single strand of 1. Single strand of nucleotidesnucleotides

2. The sugar is ribose2. The sugar is ribose

3. Thymine is replaced 3. Thymine is replaced by uracil (U), which by uracil (U), which bonds with adeninebonds with adenine

DNA to ProteinsDNA to Proteins Protein pulls apart DNA Protein pulls apart DNA Make one Messenger RNA (mRNA) Make one Messenger RNA (mRNA)

Single stranded molecule carries one geneSingle stranded molecule carries one gene 64 combinations of bases64 combinations of bases

Codons (3 DNA letters) copied to mRNA Codons (3 DNA letters) copied to mRNA Transfer RNA (tRNA)Transfer RNA (tRNA)

Codon at top matches to mRNA codon Codon at top matches to mRNA codon Associated Amino Acid attachedAssociated Amino Acid attached

Ribosomes Ribosomes Machine that makes proteinsMachine that makes proteins Two units (small & large) – reads mRNATwo units (small & large) – reads mRNA Attaches amino acids from tRNA (creates a protein)Attaches amino acids from tRNA (creates a protein)

From DNA to ProteinFrom DNA to Protein1.1. Transcription: Use DNA to make mRNA Transcription: Use DNA to make mRNA

2.2. Attach mRNA to ribosomeAttach mRNA to ribosome

3.3. Translation: RNA to amino acidsTranslation: RNA to amino acids

4.4. Fold amino acids into proteinFold amino acids into protein