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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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Presentation Transcript
how complicated are living things
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.

properties of organic molecules
Properties of organic molecules:
  • Carbon skeletons as backbones
  • Side chains bear functional groups that

are chemically active

  • polymers: chains of subunits
carbohydrates
Carbohydrates
  • carbohydrates are sugar polymers
  • used for:
    • energy storage
    • structural features
slide18

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)

lipids
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
fatty acids
Fatty Acids

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

other lipids
other lipids:

Terpene (citronellol)

Prostaglandin

(PGE)

Steroid

(cholesterol)

membranes more than lipids
Membranes - more than lipids

Glycoproteins

(proteins with carbohydrate antennae)

Membrane

(lipid bilayer)

lipid monolayer

proteins

membrane systems can be extensive
membrane systems can be extensive

nuclear envelope

ribosomes

golgi apparatus

rough endoplasmic reticulum

smooth endoplasmic reticulum

proteins
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
peptide bond formation
Peptide bond formation

The peptide bond is surrounded by two important charges

+

-

four levels of protein structure
four levels of protein structure

primary

secondary

tertiary

quartenary

quartenary structure in hemoglobin
Quartenary Structure in Hemoglobin

Quartenary structure:

4 proteins (chains)

hemoglobin and sickle cell anemia a single amino acid substitution can make a big difference
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

slide43

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

slide48

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

nucleic acids rna dna
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
dna can replicate
DNA can replicate
  • DNA unzips
  • Single strands act as templates
  • Complementary nucleotides added

to form new complementary

second strands

slide58
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)

protein rna and dna roles
Protein, RNA and DNA Roles

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

Heredity

-

Catalysis

-

Protein

RNA

DNA

how does dna store information for rna and protein structure
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