Lecture02_-Water_Macromolecules_sv.ppt.pdf

8/17/2019 Lecture02_-Water_Macromolecules_sv.ppt.pdf

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Lecture 2

Water and Macromolecules

! Life on earth began in waterand evolved for 3 billion

years

! all life remains tied to water

! water is important for

chemical reactions

! cells are 70-95% water

! water’s behavior depends on

its structure



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! Surface tension: ameasure of howdifficult it is tobreak the surfaceof water

! Water has highspecific heat – dueto H-bonds

!

Moderation oftemperature bywater

! Evaporative cooling

! H-bonds have tobe broken beforeliquid water turnsinto vapor



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! water in 2 states:

! ice floats

biologicalsignificance?

!

the solvent of life

Large molecules:



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contain C, H, O

Include:

Some sources of carbohydrates?

1. Monosaccharides

– Consist of one subunit

2. Disaccharides

– Consist of two subunits

Formed by adehydration

reaction

Glucose

Sucrose

Chemical formula: C6H12O6



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Polysaccharides

- consist of long chains of sugars

• Examples:

Starch

Glycogen

Cellulose

Fructosemonomer

Glucose

monomer

Glucose

monomer

(a) Corn syrupcontaining

fructose

(b) starch (c) glycogen

Polysaccharides

not considered a nutrient – why?



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Function?

Outsideof cell

Insideof cell

Glycoprotein

Glycoproteins (carbohydrates joined to proteins) are keymolecules in cell-cell recognition and cell-cell signaling



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!

building blocks in the synthesis of other

molecules

! nutrients: source of energy

! polysaccharides: structure, support, protection

! glycoproteins: cell identity

! Made up of amino

acids

• amino acids have acentral carbon atomthat bonds to:

! H2N (amino group)

! COOH (carboxyl)

! H

! R (side group)



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each protein has a unique structure that is

specific for its functionFibrin

Silk

Keratin

is its unique linearsequence of amino

acids

! results from hydrogen bonding between thecarboxyl oxygen of one amino acid and theamino hydrogen of another



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Tertiary structure: determined

by interaction of R groups

Quaternary structure: 2 or

more polypeptides,

interaction between thechains

! important nutrients; foods contain protein

! plant proteins are considered incomplete becausethey generally lack one or more of the essential

amino acids



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! all are available in milk,

eggs, meat, but not in

all vegetables

! can be combined to make them complete

Lysine Valine

(a) Lentils are high in lysine and low in valine. (b) Rice is low in lysine and high in valine.

Lysine Valine

The side groups oflysine and valineare different.

form reflects function



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-

Stanley Prusiner: Nobel Prize

Scientists at the University of California, have

discovered that Multiple System Atrophy

(MSA), a rare Parkinson’s disease-like

disorder is caused by a prion (Aug 31, 2015,

Proceedings of the National Academy of Sciences).



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! polymers of nu leotides that are each composed ofa phosphate group, a sugar, and a nitrogenous

base! provide direction for building proteins

- sugars

! ribose (RNA)

! deoxyribose (DNA)

- nitrogenous bases:

! purines

! pyrimidines

! The two DNA strands are held together by weak

hydrogen bonds between complementary base pairs

! A and T

! C and G

ATACGCATIf the sequence on one strand isThe other ’s sequence must be TATGCGTA

RNA – uracil replaces thymine

! is the use of information in DNA to direct the production

of proteins

! occurs in two stages

Genotype produces a phenotype (physicaltraits we see), that are the product of the

proteins produced (eg., different coat color)



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Genetic Code

Translation: converts the order of the nucleotides of a gene into the order of amino acidsin a protein mRNAs are “read” in three-base sequences, termed codons (4 bases are UCAG)

= first base= second base

= third base

shared by all organisms, suggesting it arose early in evolutionand passed on to all living organisms

! The sequence of DNA can be altered:

Point mutations:

! a single base change, can have 3 effects

1) Missense mutation

base substitution or replacement; changes one amino

acid for another

2) Nonsense mutation

change in base produces a stop codon (translation is

terminated prematurely and protein is shortened)

! The sequence of DNA can be altered:

3) Silent mutation

change in base does not change the amino acid (as a

result of redundancy of code)

Mutations: can be neutral, beneficial, or deleterious

Frame-shift mutationinsertion or deletion alter the reading frame of the

genetic message



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Mutations:

Lecture02_-Water_Macromolecules_sv.ppt.pdf

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