Download Elements in Cells

Elements in Cells
•  The living substance of cells is made up of
cytoplasm and the structures within it.
•  About 96% of cytoplasm and its included
structures are composed of the elements
carbon, hydrogen, oxygen, and nitrogen.
▫  3% from phosphorus, potassium and sulfur
▫  1% from calcium, iron, magnesium, sodium,
chlorine, copper, manganese, cobalt, zinc and
minute quantities of other elements
Elements in Cells
•  When a plant first absorbs these elements from the
soil or atmosphere, or when it breaks down products
within the cell, the elements are in the form of
simple molecules or ions.
•  These simple forms may be converted to very large,
complex molecules through the metabolism of the
cells.
•  The large molecules have “backbones” of carbon
atoms within them and are said to be organic.
•  The countless number of chemical reactions of living
organisms is based on organic compounds.
Carbon-organic Compounds
•  In their outer shells, carbon atoms have four
electrons that can bond with other atoms.
•  When carbon is bonded to hydrogen, which is
common in organic molecules, the carbon atom
shares an electron with hydrogen, and hydrogen
likewise share an electron with carbon.
•  Carbon-hydrogen molecules are referred to as
hydrocarbons.
•  Nitrogen, sulfur, and oxygen also are often joined to
carbon in living organisms.
Building Cells from Four Types of
Molecules
• The cells of all living things, including
plant cells, are primarily made of four
types of big molecules, called
macromolecules:
 Carbohydrates
 Lipids
 Proteins
 Nucleic acids
Carbohydrates
•  Carbohydrates, commonly called sugars, are the
most abundant organic compounds in nature.
•  Carbohydrates contain carbon, hydrogen, and
oxygen in a ratio of 1C:2H:1O.
•  The formula can be multiplied, for example, glucose
has the formula C6H12O6. The basic ratio is the
same.
•  Cells use carbohydrates for:
▫  Storing energy and
▫  Building materials and
▫  To provide structure to the cell.
Carbohydrates
•  Monosaccharides - Simple
sugars with backbones of
three to seven carbon atoms.
(Glucose and Fructose)
•  Glucose fast source of
energy
Carbohydrates
• Monosaccharides may form bonds with each
other to form larger structures.
▫  Disaccharides - Formed when two
monosaccharides (simple sugars) bond
together by dehydration synthesis.
 (glucose + fructose = sucrose)
▫  Polysaccharides - Formed when several to
many (some thousands) of monosaccharides
bond together. (Cellulose)
Carbohydrates
•  Carbohydrates are in nearly every food, not just
bread and pasta, which are know for “carbo loading.”
•  Fruits, vegetables, and meats also contain
carbohydrates.
•  Any food that contains sugars contains
carbohydrates.
•  Most foods are converted to sugars when they are
digested.
•  Plants and animals both store sugars. In animals it is
glycogen
•  The storage form of glucose in plants is starch.
Lipids
•  Lipids are fatty or oily substances that are mostly
insoluble in water. (Fats and Oils)
•  Glycerol (or other alcohol) + three fatty acids
▫  Typically store twice as much energy as
carbohydrates.
  Most consist of chain with 16-18 carbon atoms.
 Saturated - No double bonds, H atoms attached
to every available bond of their C atoms
 Unsaturated - At least one double bond between
carbon atoms.
Glycerol (or other alcohol) +
three fatty acids
Saturated - No double
bonds, H atoms attached to
every available bond of their
C atoms
Unsaturated - At least one
double bond between carbon
atoms.
Lipids
• Lipids serve many important functions.
▫  Store energy
▫  Protection against dehydration and
pathogens
▫  Carry electrons and absorb light
▫  Contribute to structure of membranes
▫  Agricultural commodities important to
the food, medical, and manufacturing
industry
Lipids
•  Because plants can’t control their temperatures,
they contain much more oil than fats.
•  Waxes - Lipids consisting of long-chain fatty
acids bonded to long chain alcohol other than
glycerol.
▫  Example: In plants, waxes, cutin, and suberin
protect against dehydration and pathogens.
•  Phospholipids - Constructed like fats, but one of
the fatty acids is usually replaced by a phosphate
group.
▫  Example: found in cell membranes
Proteins, Polypeptides, and Amino Acids
• Proteins perform essential jobs in cells.
▫  Help chemical reactions
▫  Support the cell
▫  Move materials around
▫  Control information flow
▫  Send signals
Proteins, Polypeptides, and Amino Acids
• Proteins are usually very large and consist of
one or more polypeptide chains.
▫  Polypeptides are chains of amino acids.
▫  20 different amino acids.
 Each amino acid has two functional groups
plus an R group.
 Amino group (-NH2)
 Carboxyl group (-COOH)
Proteins, Polypeptides, and Amino Acids
Proteins, Polypeptides, and Amino Acids
•  Polypeptide Structure- To make a protein amino
acids bond with covalent bonds called peptide bonds
▫  Primary Structure - A sequence of amino acids
fastened together by peptide bonds.
▫  Secondary Structure - Coiling of polypeptide
chains.
▫  Tertiary Structure - Maintained by coils between R
groups.
▫  Quaternary Structure - Occurs when a protein has
more than one kind of polypeptide.
Proteins, Polypeptides, and Amino Acids
• Structural proteins support the cell.
▫  Cytoskeletal proteins provide supportive
scaffolding from the inside of the cell.
▫  Outside the cell, proteins are woven into
the cell wall, a protective layer that encases
a plant cell.
Proteins, Polypeptides, and Amino Acids
• 
Transport proteins move materials into
and within plant cells.
•  Proteins located at the boundary of the
cell help create passageways for
materials.
•  Inside the cells, structures may use
cytoskeletal proteins as tracks that allow
them to move around the cell.
Proteins, Polypeptides, and Amino Acids
• Enzymes are proteins that speed up
chemical reactions.
• Enzymes are mostly large, complex
proteins that function as organic catalysts
under specific conditions.
▫  Work by lowering energy of activation.
 Temporarily bonds with potentially
reactive molecules at a surface site.
 Names end in =ase.
Nucleic Acids
•  Nucleic acids are very large, complex polymers.
▫  Vital to internal communication and cell
functioning.
▫  Two types of nucleic acids.
  Deoxyribonucleic Acid (DNA) and
ribonucleic acid (RNA) are composed of
nucleotides.
  Three parts- nitrogenous base, five-carbon
sugar, and a phosphate.
  DNA does not leave the nucleus of the cell.
Nucleic Acids
•  DNA stores the information that determines the structure
and function of all cells on earth.
•  DNA determines the traits of plants.
•  When cells reproduce, they copy their DNA molecules
and pass them on to the new cells.
•  RNA is similar to DNA in structure, but more flexible in
its functions. Different types perform different functions.
•  Some carry information around the cell.
•  Some help build proteins.
•  Some control when proteins are made.
•  RNAs contain information, but they can move around
and cause things to happen.
Review
•  Attributes of Living Organisms
•  Chemical and Physical Bases of Life
•  Molecules
•  Bonds and Ions
•  Acids and Bases
•  Carbohydrates, Lipids, Proteins
•  Enzymes
•  Nucleic Acids
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