Unit 4- Biochemistry, Energy, &
Enzymes
4a- Chemistry + Carbon Compounds
Chemistry Review
• What makes an atom stable?
– 8 valence electrons; full outer
energy level, or shell
• What can an atom do to
become stable?
– Form bonds with other atoms
Chemistry Review
• Two types of bonds?
– Ionic Bonds: attraction of oppositely charged ions
– Covalent Bonds: form by sharing electrons; causes the
outer energy levels to overlap
Chemistry Review
• Bonds between atoms are built and broken causing
substances to combine and recombine as different
molecules during chemical reactions.
• Essential functions of a cell involve chemical
reactions that take place between many different
types of molecules
– All of the chemical reactions within a cell are referred to
as the cell’s metabolism.
Building Blocks of Cells
• Living things are organized…
• All organisms are composed of
organic molecules
–
Organic Molecules- contain
carbon atoms
The Role of Carbon
• A carbon atom has 4 electrons in its valence shell.
• Carbon can form covalent bonds with as many as 4
other atoms.
– Can also bond with other carbon atoms to form a single,
double or triple bond (sharing 1, 2, or 3 electrons)
– Allows carbons to form straight chains, branched chains,
or rings
Large Carbon Molecules
(Biomolecules, Macromolecules)
• Most organic molecules are made of smaller units
(monomers) that bond to form larger molecules (polymers)
– Energy is stored in the bonds that link these units together
– The amount of energy varies with the type of molecule formed.
• Polymer: a molecule that consists of repeated, linked units.
– Units may be identical or structurally related
Large Carbon Compounds
• Example: Starches are complex carbohydrates
formed by long chains of simple sugars, like glucose
– Glucose= monomer; Starch= polymer
Molecules of Life
• There are four types of organic compounds
necessary for life (aka biomolecules)
–
–
–
–
Carbohydrates
Lipids
Proteins
Nucleic Acids
Carbohydrate Structure
• Contain: Carbon, Hydrogen, & Oxygen
• Structures:
– Monosaccharides – 1 ring (simple sugars)
• Glucose (cell’s primary source of energy)
– Disaccharides – 2 rings
• Sucrose (table sugar)
– Polysaccharides – 3 or more rings (complex
carbohydrates)
• Amylose (component of starch)
• Cellulose (structural carbohydrate in plants)
Role of Carbohydrates
• In Plants
– Carbohydrates are synthesized during the
process of photosynthesis
– The plants then:
• Use them as a source of energy
• Store them in the cells.
Role of Carbohydrates
• In Animals
– Consumed as sugars, starches, and fiber
– When complex carbohydrates are consumed, digestion breaks
the bonds between the larger carbohydrate molecules so that
individual simple sugars can be absorbed into the
bloodstream through the walls of the intestines.
• The bloodstream carries the simple sugars to cells
throughout the body
• Once inside the cells, they are used as fuel in the process of
cellular respiration, releasing energy that is stored as ATP.
– If an organism has a greater supply of carbohydrates than
needed for its energy requirements, the extra energy is
converted to fats and stored by the body.
Functions of Carbohydrates
• Energy Source
– Glucose in cells is the primary source of energy fuel for cellular respiration
• Energy Storage (short term)
– Glycogen in the liver of animals
– Starch in the structures of plants
• Structural Support
– Cellulose forms cell walls in plants
• An important source of fiber for animals to stimulate the digestive system
• The C, H, & O that make up carbohydrates serve as raw
materials for the synthesis of other small organic
molecules, such as amino acids & fatty acids.
Lipids
• Contain: Carbon, Hydrogen, &
Oxygen
• Includes fats (triglycerides),
phospholipids, steroids, &
waxes
• A triglyceride is a lipid made up
of a glycerol & 3 fatty acids
• The high number of C-H bonds
makes lipids very energy rich.
glycerol
three fatty acids
Role of Lipids
• Fats
– Important to organisms for energy when carbohydrates
are scarce, but when there is no shortage of food, stored
fat accumulates.
– Functions:
• providing long-term energy storage
• cushioning of vital organs
• insulation for the body
– Fats are insoluble in water.
Role of Lipids
• Phospholipids
– Major component of cell
membranes.
• Steroids
– Can serve as raw materials
necessary for the production
of some vitamins, some
hormones, and cholesterol
• Waxes
– Lipids that form waterproof
coatings for plants and animals
Proteins
• Proteins are molecules composed of chains of amino
acids
– Contain: Carbon, Hydrogen, Oxygen, & Nitrogen &
sometimes Sulfur
• 20 different amino acids
– 10 amino acids are made in the human body
– Humans need to consume the other 10 amino acids from
sources such as nuts, beans, or meat.
• Failure to obtain enough of even 1 of the 10 essential AA’s results
in degradation of the body’s proteins.
Protein Structure
• Two amino acids bond to form a dipeptide.
– This covalent bond is called a peptide bond
• Polypeptide: long chain of amino acids
• Proteins are composed of one or more
polypeptides.
– The sequence of amino acids determines the proteins
shape & function.
• ~100,000 different proteins in the human body
Role of Proteins
• Proteins are the major structural & functional material of body
cells. (workhorse molecules)
– Because of the variety of shapes & structures of protein molecules,
proteins have a wide variety of functions
– Involved in almost every function in the human body
• Functions:
– Structural proteins- used for support such as connective tissue & keratin
that forms hair & finger nails.
– Transport proteins- move many substances throughout the body
• Example: hemoglobin transports oxygen from the lungs to the other parts of
the body to be used by cells in cellular respiration.
– Hormone proteins- coordinate body activities
• Example: insulin regulates the amount of sugar
in the blood.
– Contractile proteins- help control movement
• Example: proteins in the muscles which help
control contraction.
– Enzymatic proteins- accelerate the speed of
chemical reactions
• Example: digestive enzymes break down food
in the digestive tract.
Nucleic Acids
• Nucleic Acids are long chains of nucleotides
– Nucleotides contain: Carbon, Hydrogen, Oxygen,
Nitrogen, & Phosphorus
– Nucleotides are made up
of three parts
• Five carbon sugar
• Phosphate group
• Nitrogen base
Function of Nucleic Acids
• Carry and transmit genetic information
– Two Types:
• DNA – holds genetic code for an organism
• RNA – makes a copy of DNA in order to make a protein
Calorie Comparison
• Energy stored in organic molecules
determines the caloric value
• Lipids have the greatest chemical
bond energy over carbohydrates &
proteins
• Calorie comparisons:
– Proteins
4 Calories per gram
– Lipids
9 Calories per gram
– Carbohydrates 4 Calories per gram