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Chemistry of Cells Chapter 2, Section 3
I.
Carbon Compounds are found in living things.
Organic compounds contain carbon atoms that are covalently bonded to other elements – mainly hydrogen,
oxygen, and other carbon atoms. Four classes of organic compounds are found in living things:
carbohydrates, lipids, proteins, and nucleic acids.
A.
Carbohydrates
a. Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen atoms in the
proportion of 1:2:1.
b. Key source of energy and found in most found foods.
c. Monosaccharides (single sugars) – the building blocks of carbohydrates
i. Examples – glucose and fructose
d. Disaccharides (double sugars) – example is sucrose made of glucose and fructose
e. Polysaccharides – chains of three or more monosaccharides
i. Example – starch is made of many glucose molecules
ii. Some polysaccharides store energy
1. Starch – made by plants
2. Glycogen – made by animals
3. Cellulose – provides structural support for plants but cannot be digested by
humans
B. Lipids
a. Lipids are nonpolar molecules that are not soluble in water
b. Examples are fats, phospholipids, steroids, and waxes.
c. Lipids are Important to
i.
cell membranes – phospholipid in bilayer
ii. Steroids include cholesterol
iii. Plant pigment chlorophyll
d. FATS
i. Lipids that store energy – because of the bond between carbon and hydrogen
1. Saturated fatty acid – saturated with hydrogen –single bonds between carbons
and hydrogens – draw example
 Most animal fats – in butter, lard, and grease from cooked meats
 Straight molecules and solid at room temperature
2. Unsaturated fatty acid – some carbon bonds contain a double covalent bond so
it is not bonded to as many hydrogens, producing kinks in the comecule
 Most plant oils – olive oil and some fish oils
 Liquid at room temperature
 Hydrogenated vegetable oils -- artificially saturated by adding hydrogen
atoms – so margarine and vegetable shortening are solid at room temp.
C. Proteins
a. A protein is a chain of molecules called amino acids linked together like pearls on a necklace.
i. Amino Acids are the building blocks of proteins.
1. 20 different amino acids found in proteins
2. Some amino acids can be polar, others are non polar
3. Some are electrically charged others are not
4. Amino acids determine how the protein folds into shape
ii. Enzymes – promote chemical reactions
iii. Collagen – found in your skin, ligaments, tendons, and bones – most abundant protein
in your body.
iv. Examples of other from page 36 – record
D. Nucleic Acids
a. Nucleic Acids are long chains of smaller molecules called nucleotides.
b. Nucleotide has three parts – a sugar, a base and a phosphate group (phosphorus and oxygen)
c. Two Types – DNA and RNA
i. DNA – deoxyribonucleic acid – two strands of nucleotides that spiral around each other,
held together by hydrogen bonds between bases across from one another.
1. Chromosomes consist of very long strands of DNA, which stores hereditary
information.
2. RNA – ribonucleic acid—consists of a single strand of nucleotides – helps to
manufacture proteins
E. ATP
a. ATP – adenosine triphosphate – a single nucleotide with two extra energy storing phosphate
groups
b. This is the main energy currency of cells
c. When carbs are broken down, some of the energy in the molecules is stored temporarily in ATP.
Some of the energy is used by the cell, they need it to function.
Energy – define
Can be stored or released by chemical reactions (when a bond is broken or
formed)
Chemical Reactions absorb or release energy –When bonds are broken or formed
Metabolism – all chemical reactions that occur within an organism.
We get energy from the chemical reactions that take place after the food we
eat is digested.
Energy is needed to start a chemical reaction – activation energy – it pushes the
chemical reaction to take place
Enzymes – promote chemical reactions – help biochemical reactions occur –
increase the speed of chemical reactions
They are catalysts – they reduce the activation energy of a
chemical reaction
“It takes more activation energy to start a chemical reaction
if the enzyme is not present”
Enzymes help maintain homeostasis
Enzymes affect specific substances –
Substrate –
Active site
Copy fig. 2-15
Factors that affect enzyme activity – these will change the shape
of the enzyme
Temperature
pH