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Biological Molecules Can Have Complicated Structures PowerPoint PPT Presentation

Biological Molecules Can Have Complicated Structures DNA Protein How complicated are living things? Even a bacterium is made up of at least 10,000 different kinds of molecules. But these fall into 4 classes of organic molecules. 4 Kinds of Organic Molecules

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Biological Molecules Can Have Complicated Structures

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Biological molecules can have complicated structures l.jpg

Biological Molecules Can Have Complicated Structures

DNA

Protein


How complicated are living things l.jpg

How complicated are living things?

Even a bacterium is made up of at least 10,000 different kinds of molecules.

But these fall into 4 classes of organic molecules.


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4 Kinds of Organic Molecules


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Properties of organic molecules:

  • Carbon skeletons as backbones

  • Side chains bear functional groups that

    are chemically active

  • polymers: chains of subunits


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Organic molecules are built around carbon skeletons


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Functional Groupschemically active side branches


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Organic molecules are polymers


Dehydration condensation synthesis polymer elongation l.jpg

Dehydration (Condensation) Synthesis - Polymer Elongation


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Hydrolysis - Polymer Disassembly


Structures are built of large molecules which are built of small molecules l.jpg

Structures are built of large molecules which are built of small molecules


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Carbohydrates

  • carbohydrates are sugar polymers

  • used for:

    • energy storage

    • structural features


Sugars are characterized by size the kinds of functional groups and their position l.jpg

Sugars are characterized by size, the kinds of functional groups and their position


Another example l.jpg

Another example


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Linear carbon chains often become cyclic


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Synthesis and breakdown of carbohydrate polymers


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Disaccharides


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Polysaccharides


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Polysaccharides held together by weak bonds are used for energy storage (e.g., starch), whereas those held together by strong bonds are used or structural purposes (e.g., cellulose)


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Cellulose


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Lipids

  • One end is hydrophilic, the other hydrophobic

  • Often polymers (few large instead of many small subunits, fatty acid derivatives)

  • Used for:

    • Energy storage, e.g., fats and oils

    • Chemical messengers (hormones) , e.g., steroids

    • Chemical defenses , e.g., terpenes

    • Membranes , e.g., phospholipids


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Fatty Acids

Note: carbon and hydrogen have similar electronegativities and will form non-polar covalent bonds


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A simple lipid - triglyceride


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Saturated fat


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Unsaturated fat


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other lipids:

Terpene (citronellol)

Prostaglandin

(PGE)

Steroid

(cholesterol)


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Phospholipid


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Phospholipids function in membranes


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Membranes - more than lipids

Glycoproteins

(proteins with carbohydrate antennae)

Membrane

(lipid bilayer)

lipid monolayer

proteins


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membrane systems can be extensive

nuclear envelope

ribosomes

golgi apparatus

rough endoplasmic reticulum

smooth endoplasmic reticulum


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Proteins

  • Every protein = an unbranched chain of amino acids

  • Each kind of protein has a unique amino acid sequence

  • Each amino acid sequence confers a specific 3D shape

  • Each kind of protein is coded for by a single gene

  • Proteins have many functions


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Amino acids - 20 kinds


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Acidic and basic amino acids


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Non-polar amino acids


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Polar amino acids


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Peptide bond formation

The peptide bond is surrounded by two important charges

+

-


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A short protein - 4 amino acids


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four levels of protein structure

primary

secondary

tertiary

quartenary


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Secondary Structure and Hydrogen Bonds


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Quartenary Structure in Hemoglobin

Quartenary structure:

4 proteins (chains)


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Hemoglobin and Sickle Cell Anemia:a single amino acid substitution can make a big difference

under oxygen stress

MUTATION:

valine replaces glutamate

hemoglobin polymerizes, forming long rods that distort the cell


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Four levels of protein structure


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Proteins differ in their 3D shapes


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3D shapes have specific cavities on their surfacethese cavities allow “lock and key” fits with other molecules with which the protein interact


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Enzymes Control Chemical Activity


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Molecules are modified in pathways, in numerous small controlled steps


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Biochemical Pathways


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Catalysts Control Chemical Activity


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What is the significance of complicated shapes?Numerous weak bonds among complementary complex surfaces allow molecular recognition and catalysis.


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Nucleic Acids: RNA & DNA

  • Nucleic acid molecules consist of polynucleotide strands

  • DNA has two complementary strands, RNA has one strand

  • Both DNA & RNA can replicate and store information

  • Nucleotide sequences code for amino acid sequences …DNA genes code for RNA and protein structure

  • Like proteins, RNA is single stranded and can fold up into complex 3D shapes ….RNA catalysts are ribozymes


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Nucleotides have three subunits

P

S

B


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Four kinds of DNA nucleotides


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RNA is composed of a single polynucleotide strand


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DNA is double stranded


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DNA can replicate

  • DNA unzips

  • Single strands act as templates

  • Complementary nucleotides added

    to form new complementary

    second strands


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Replication


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DNA Synthesis - Replication


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RNA Synthesis - Transcription


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DNA structure is too monotonous to serve catalytic functions,but single stranded RNA can assume complicated shapes

DNA is double stranded

cannot be catalytic

RNA is single stranded

can be catalytic (ribozymes)


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Protein, RNA and DNA Roles

Single strandedness can confer complicated 3D shapes that permit catalytic roles

Heredity

-

Catalysis

-

Protein

RNA

DNA


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How does DNA store information for RNA and protein structure?

each kind of molecule is an unbranched sequence of subunits

nucelotide sequences are colinear with the amino acid sequences that they code for


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Central Dogma of Biology


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