Ch' 6'3 Life substances

1
Ch. 6.3 Life substances

• Objectives
• Classify the variety of organic compounds.
• Describe how polymers are formed and broken down
  in organisms.
• Compare the chemical structures of carbohydrates,
  lipids, proteins, and nucleic acids, and relate
  their importance to living things.
• Identify the effects of enzymes.

2
The Role of Carbon in Organisms

• Organic compounds contain carbon
• A carbon atom has four electrons available for
  bonding in its outer energy level. In order to
  become stable, a carbon atom forms four covalent
  bonds that fill its outer energy level.
• Carbon compounds vary greatly in size.
• When carbon atoms bond to each other, they can
  form straight chains, branched chains, or rings.

3
Cells make a huge number of large molecules from
a small set of small molecules

• Most of the large molecules in living things are
  macromolecules called polymers
• Polymers are long chains of smaller molecular
  units called monomers (building blocks)
• A huge number of different polymers can be made
  from a small number of monomers
• SIZE monomerltpolymerltmacromolecule
• 4 types of macromolecules carbohydrates, lipids,
  proteins, nucleic acids
• (poly many mono one)

4
Making and Breaking of POLYMERS

• Cells link monomers to form polymers by
  dehydration synthesis (building up)

Short polymer
Unlinked monomer
Removal ofwater molecule
Longer polymer
5
Making and Breaking of POLYMERS

• Polymers are broken down to monomers by the
  reverse process, hydrolysis (hydro add water
  lysis to split)

Addition ofwater molecule
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1. CARBOHYDRATES

• composed of carbon, hydrogen, and oxygen with a
  ratio of about two hydrogen atoms and one oxygen
  atom for every carbon atom.

7
The structure of carbohydrates

• The monomer (building block) of a carbohydrate
  is a simple sugar called a monosaccharide (mah
  noh SA kuh ride). (ie. glucose, fructose)
• are the fuels for cellular work
• (Mono one
• sacchar sugar)

8
Cells link single sugars to form disaccharides

• Monosaccharides can join to form disaccharides,
  such as sucrose (table sugar) and maltose
  (brewing sugar)
• di two sacchar sugar

9
Polysaccharides are long chains of sugar units

• polymers of hundreds or thousands of
  monosaccharides linked by dehydration synthesis
• Function as
• Energy storage
• Starch (plants)
• Glycogen (animals)
• Structure
• Cellulose (plants cell walls) (fiber in diet)
• Chitin ( insects)

10
Lipids

• composed largely of carbon and hydrogen
• They are not true polymers
• They are grouped together because they do not
  mix with water (Nonpolar)
• (ie. fats, oils, waxes)

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Lipids include fats,

• Fats are lipids whose main function is long term
  energy storage
• Other functions
• Insulation in higher vertebrates
• shock absorber for internal organs

Fatty acid
Fatty acid
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Saturated Unsaturated fats

• fatty acids of unsaturated fats (plant oils)
  contain double bonds
• These prevent them from solidifying at room
  temperature
• Saturated fats (lard) lack double bonds
• They are solid at room temperature

13
PROTEINS

• essential to the structures and activities of
  life
• Make up 50 of dry weight of cells
• Contain carbon, hydrogen, oxygen PLUS nitrogen
  and sometimes sulfur
• Proteins are involved in
• cellular structure
• Movement (muscles)
• Defense (antibodies)
• Transport (blood)
• Communication
• Monomers are called amino acids

14
The structure of proteins

• 20 common amino acids that can make literally
  thousands of proteins.
• Their diversity is based on different
  arrangements of amino acids
• R variable group- which distinguishes each of
  the 20 different amino acids

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Amino acids can be linked by peptide bonds

• Cells link amino acids together by dehydration
  synthesis
• The bonds between amino acid monomers are called
  peptide bonds

PEPTIDEBOND
Dehydrationsynthesis
Dipeptide
Amino acid
Amino acid
16
A proteins specific shape determines its function

• A protein consists of polypeptide chains folded
  into a unique shape
• The shape determines the proteins function
• A protein loses its specific function when its
  polypeptides unravel

17
Enzymes

• Enzymes are important proteins found in living
  things. An enzyme is a protein that speeds up
  the rate of a chemical reaction.
• (SEE SEPARATE LECTURE.)

18
Nucleic acids

• A nucleic (noo KLAY ihk) acid is a complex
  biomolecule that stores cellular information in
  the form of a code.
• 1. DNA (deoxyribonucleic acid) contains the
  instructions used to form all of an organisms
  proteins.
• 2. RNA (ribonucleic acid) forms a copy of DNA for
  use in making proteins.
• They ultimately control the life of a cell

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NUCLEIC ACIDS

• The monomers of nucleic acids are nucleotides
• Each nucleotide is composed of a sugar,
  phosphate, and nitrogenous base

Nitrogenousbase (A)
Phosphategroup
Sugar