Human biology
Human organization
2. Chemistry of life
NOT PART OF THE EXAM:
- ‘’FROM ATOMS TO MOLECULES’’ (PART 2.1)
1. FROM ATOMS TO MOLECULES
▪ ALL MATTER IS COMPOSED OF ATOMS , WHICH REACT WITH ONE ANOTHER TO FORM MOLECULES
2. WATER AND LIFE
▪ THE PROPERTIES OF WATER MAKE LIFE , AS WE KNOW IT , POSSIBLE
▪ LIVING ORGANISMS ARE AFFECTED ADVERSELY BY WATER THAT IS TOO ACIDIC OR TOO BASIS
3. MOLECULES OF LIFE
▪ CARBOHYDRATES, LIPIDS, PROTEINS AND NUCLEIC ACIDS ARE MACROMOLECULES WITH SPECIFIC
FUNCTIONS IN CELLS
4. CARBOHYDRATES
▪ BLOOD SUGAR IS GLUCOSE , AND HUMANS STORE GLUCOSE AS GLYCOGEN
▪ CELLULOSE IS PLANT MATERIAL , A SOURCE OF FIBER IN THE DIET
5. LIPIDS
▪ FATS AND CELLS ARE LONG -TERM ENERGY STORAGE MOLECULES
▪ THE AMOUNT IN THE DIET HAS AN EFFECT ON OUR HEALTH
▪ OTHER LIPIDS, SUCH AS THE STEROIDS AND PHOSPHOLIPIDS , FUNCTION DIFFERENTLY IN THE BODY
6. PROTEINS
▪ PROTEINS HAVE NUMEROUS AND VARIED FUNCTIONS IN CELLS
▪ THE STRUCTURE OF A PROTEIN DETERMINES ITS FUNCTION
7. NUCLEIC ACIDS
▪ DNA IS THE GENETIC MATERIAL OF LIFE
▪ RNA SERVES AS A HELPER TO DNA
▪ ATP IS AN ENERGY MOLECULE USED BY THE CELL TO DO METABOLIC WORK
2.1 From atoms to molecules
Atoms
• Smallest units of an element
• Physical and chemical properties
• Bond together to form molecules
Isotopes
• Isotopes are atoms that have the same atomic number but have a different atomic mass
because the number of neurons differ
, • Radioisotopes are useful in dating old objects, imaging organs and tissues trough X-rays, and
killing cancer cells
• Radiation can be harmful by damaging cells and DNA and/or causing cancer
→ Figure 12.3: Medical uses for low-level radiation
Bonds
• Ionic bonds – atoms donate or take on electrons
o Most well-known structure
o Most stable structure
o Combination of sodium and chloride
o Positive and negative is attractive; they combine based on their electronic charge
→ Figure 2.5: Formation of an ionic bond
• Covalent bonds – atoms share electrons
o Strong bond
o Combination of oxygen and 2 hydrogen electrons
o The sharing of the electrons means they work together
→ Figure 2.6: Covalent bonds
• Hydrogen bonds – relatively weak bonds
o Polar molecule: positive and negative poles
o They move organized as a result of attractions
▪ Fluid water: freely organized, moving
▪ Ice: atoms become larger ice crystals, less moving, solid organized
o Ice is taking up more volume than fluid water, which is why it is important to not
become frozen (it will burst out and destroy our tissue)
→ Figure 2.7 Hydrogen bonds and water molecules
2.2 Water and life
Properties of water
• Liquid at room temperature
• Does not change temperature quickly: thermal stability
• High heat evaporation
• Frozen water less dense than liquid water
• Water is a solvent (oplossingsmiddel) for polar molecules
Acids and bases
• Acids are substances that dissociate and release hydrogen ions (H+)
• Bases are substances that take up hydrogen ions (H+) or release hydroxide ions (OH-)
pH scale
• Measure of hydrogen ion (H+) concentration
o pH 0-6: more acid, less water
▪ Acidic solutions (high H+ concentrations)
o pH 7: pure water
o pH 8-14: more based, more water
▪ Basic solutions (low H+ concentrations)
→ Figure 2.10: The pH scale
• Buffers help keep the pH within normal limits, because they are chemicals or combinations
of chemicals that take up excess hydrogen ions (H+) or hydroxide ions (OH-)
o Carbonic acid
, • Water dissociates to produce a hydrogen ion with a positive charge and a hydroxide ion with
a negative charge
2.3 Molecules of life
Making and breaking down organic molecules
→ Figure 2.11: The breakdown and synthesis of macromolecules
I. Dehydration reaction – used when a cell constructs a macromolecule, a molecule that
contains many subunits
II. Hydrolysis reaction – used when a cell breaks down a macromolecule, by adding the
components of water during the breaking of the bond between the molecules
Summary of the macromolecules
2.4 Carbohydrates
• Made of subunits called monosaccharides
• Made of C, H and O in which the H and O atoms are in a 2:1 ratio
• Function as short- and long-term energy storage
• Found as simple and complex forms
Simple carbohydrates
• Monosaccharide – 1 carbon ring as found in glucose
o Glucose, fructose
• Disaccharide – 2 carbon rings as found in maltose
o Maltose, sucrose
→ Figure 12.2: The synthesis and breakdown of a disaccharide
Complex carbohydrates
• Polysaccharides are made of many carbon rings (glucose units)
, o Starch, glycogen, cellulose
• Glycogen is the storage form in animals
• Starch is the storage form in plants
→ Figure 2.13: Starch is a plant complex carbohydrate
2.5 Lipids
• Do not dissolve in water
• Used as energy molecules
• Found in cell membranes
• Found as fats and oils, phospholipids and steroids
How are fats and oils different?
• Fats
o Usually animal origin
o Solid at room temperature
o Function for long-term energy storage, insulation form heat loss and cushion for
organs
▪
• Oils
o Usually plant origin
o Liquid at room temperature
Triglyceride (fat)
• Glycerol molecule and 3 fatty acid tails
→ Figure 2.16: Structure of a triglyceride
Waxes
• Molecules made up of one fatty acid combined with another single organic molecule, such as
an alcohol
Understanding fats when reading a nutrition label
• The recommendation for total amount of fat for a 2.000 calorie diet is 65g
• Trans fats: probably harmful
→ Figure 2.17: Comparison of saturated, unsaturated and trans fats
Phospholipid
• The structure is similar to a triglyceride
• One fatty acid is replaced by a polar phosphate group
• Phospholipids are the primary components of cellular membranes
o Nonpolar tails - hydrophobic
o Polar heads - hydrophilic
→ Figure 2.19: Structure of a phospholipid
Steroid
• A steroid is a lipid
• The structure is four fused carbon rings
• Examples are cholesterol and sex hormones
→ Figure 2.20: Examples of steroids
,2.6 Proteins
• Made of subunits called amino acids
• Important for diverse functions in the body including hormones, enzyme, antibodies and
transport
• Can denature, undergo a change in shape that causes loss of function
→ Figure 2.21 The structure of a few amino acids
Levels of protein structure
• All proteins have primary, secondary and tertiary structure
• Only a few have quaternary structure
→ Figure 2.23 Levels of protein structure
2.7 Nucleic acids
• Made of nucleotide subunits
• Function in the cell to make proteins
• Include RNA and DNA
3 parts of a nucleotide
• Sugar
• Phosphate
• Nitrogen-containing base
→ Figure 2.24 Structure of a nucleotide
The structure of DNA
• Adenine (A) and guanine (G) are double-ringed purines
• Cytosine (C), thymine (T) and uracil (U) are single-ringed purines
• In DNA, A pairs with T and G pairs with C
o Base pairing is important because it allows DNA to replicate in a way that ensures the
sequence of bases will remain the same
→ Figure 2.25 The structures of DNA and RNA
Summary of DNA and RNA structural differences
• DNA
o Sugar is deoxyribose
o Bases include A – T and G – C
o Double-stranded
• RNA
o Sugar is ribose
o Bases include A, U, G and C
o Single-stranded
RNA
• mRNA – temporary copy of a gene
• rRNA – works as an enzyme to form peptide bonds
• tRNA – helps to translate amino acid sequence
ATP
• Ribose (sugar)
, • 3 phosphate groups
• Adenine
→ Figure 2.26: ATP is the universal energy currency of cells
