IB Biology Topic 2 : Molecular Biology

How many bonds can carbon make

carbon can make four covalent bonds

Four most common compounds

- carbon
-hydrogen
-nitrogen
-oxygen

what is life based on

carbon compounds

metabolism

metabolism- chemical processes in the body, synthesis & breakdown of substances in living organisms.
anabolism- the synthesis of complex molecules (simple to complex) (condensation reaction)
catabolism- the breakdown of complex molecules into simpler macr

Importance of the artificial creation of urea

vitalism - states that organic compounds can come from living things, so the creation on urea in a lab disproved this

international problems with water

Water is not readily available to all countries. And even within countries there are distribution problems

What does polar and non polar mean?

polar means that there is a positive and negative charge and its an equal sharing of electrons, while non-polar means that there is an unequal sharing

what kind bonds do water molecules make with each other

hydrogen bonds

Hydrogen Bonds

Hydrogen bonds are the weakest because they are positive

Covalent Bonds

covalent bonds are strongest because they share a pair of electrons.

Properties of Water

Water molecules are polar (forms hydrogen bonds), because of the pull of electrons towards oxygen.
Cohesion - when water sticks to itself. Allows surface tension to occur.
Adhesion- when water sticks to to other substances. The ability for water to stick

Hydrophobic

- not attracted to water
- insoluble in water

Hydrophilic

- attracted to water
- dissolves well in water
- form molecular bonds with water molecules

What are the four main macromolecules?

-lipids
-carbohydrates
-nucleic acids
-proteins

Carbohydrates

- Sugars
- Made of of C, H, and O
- main functions are quick energy, storage, raw/structural material
- Monosaccharides, disaccharides, polyssacharides

Monosaccharides

- sugars that consist of a single sub-unit (monomer)
- only contains carbon, hydrogen & oxygen with a ration of 1:2:1
eg. glucose (C6H12O6) and fructose

Disaccharides

- a pairs of monosaccharides linked together by condensation
eg. maltose ( glucose + glucose - used for food when plants break down their starch stores), lactose ( glucose + galactose - nursing and milk), sucrose ( fructose + glucose - table sugar)

Polysaccharides

- complex carbohydrates
- chain of many monosaccharides
- extremely soluble so a good source of quick energy
eg. starch, glycogen, chitin, and cellulose

How are sugars classified?

the number of carbons

Lipids

- carbon compounds
- non polar hydrophobic organic molecules
Types of lipids:
- triglycerides (eg. fats & oils)
- phosopholipids
- steroids (eg. testosterone & estrogen)

Function of lipids

- twice as much energy as carbohydrates but a slower release
- insulation
- framework for cell membrane

Health risks for trans/saturated fat

- Trans fats increase the "bad" cholesterol which raises the risks of coronary heat disease.
- Diets that are high in trans-fat unnecessarily increase the chance that you will consume more than your body needs, because they are energy dense.

BMI Equation

bmi = weight of body / (height in meters ^2)

Fatty Acids

Types:
- Saturated: All atoms in the chain are connected by single bonds
- Unsaturated: chain contains one or more double bonds
- Monounsaturated: only one double bond
- Polyunsaturated: two or more double bonds
- Cis-unsaturated: H bonded to C on the sam

Polypeptides

- chain of amino acids
- the amino acid sequence of a polypeptide is coded for by a gene. The DNA sequence determines the sequence of amino acids in the polypeptide.
- a protein consists of either a single or multiple polypeptides linked together.

Denaturation

proteins have a delicate structure that can be damaged by substances or conditions: this is called denaturation
- heat causes denaturation
- change in pH causes denaturation

Function of proteins

wide range of functions
Eg:
- Rubisco is an enzyme that catalyses the photosynthesis reaction
- Insulin is a hormone that lowers the body's blood glucose concentration

Enzymes

- biological catalysts
- they speed up chemical reactions and metabolism
- a reactant is an enzyme catalysed reaction called a substrate
-substrates bind to the active site of the enzyme and the products are released.

Factors affecting enzymes

1) Temperature
- temperature increases enzyme activity
- when temperatures are high, enzymes are denatured and stop working.
2) pH
- enzyme activity decreases pH decreases from optimum.
- above a certain pH, the a;lalinity denatures the enzyme
3) Substrat

Production of lactose free milk (for lactose intolerant people)

- lactose is the sugar in milk
- it can be hydrolysed into glucose and galactose by the enzyme lactase

DNA

- nucleic acid
- consist of nucleotides
- nucleotide: sugar, phosphate, and nitrogenous base
(bases: adenine, thymine, guanine, cytosine)

Structure of DNA

RNA

- single stranded (DNA is double stranded)
- thymine is replaced by uracil

Proteome

the combination of all proteins in an organism, everyone's is unique

Amino acids

have a central carbon atom with 4 different atoms linked to it:
- R group (R)
- amine group (N - Hx2)
- carboxyl group (C=o, C-OH)
- hydrogen atom (H)

Peptide bonds

bonds that link amino acids to form polypeptides. you take way the OH and one of te H's from the H2 of the amine group

primary, secondary, tertiary, and quaternary

1. order of amino acids
2. reactions with amino acids near each other
3. reacts with farther apart amino acids, the reaction of the R groups which them determines the quaternary structure
4. arrangement of multiple proteins

The importance of the R group

This group determines the function of the protein and thus instructs how the it will interact with other amino acids ( which instructs how the amino acid chains are folded)

Activation energy

the energy it takes to begin a reaction

Active site

the place where the substrate binds to the enzyme; where the reaction occurs