Life’s Molecules

Carbohydrates

Monosaccharide (Glucose)

Carbohydrates

Polysaccharide (glycogen)

Carbohydrates

Polysaccharides (amylose and cellulose)

Carbohydrates

Lipids

glycerol Three fatty acid tails

Triglyceride

Lipids

Triglycerides are the most common fats in food.

Lipids

Saturated and unsaturated fatty acids

Stearic acid: saturated

Oleic acid: unsaturated

Linoleic acid: polyunsaturated

Lipids

Phospholipid

Lipids

Phospholipids arrange themselves as a bilayer in water. The hydrophilic heads face out, the hydrophobic

tails face inward.

Lipids

Lipids are hydrophobic. Plant leaves are coated withwaxes to keep water inside the plant.

Lipids

One of 20 amino acids (valine). Amino acids vary bythe “R” group they contain.

R group

Carboxyl groupAmino group

Proteins

Amino acids are linked by peptide bondsto form polypeptides

Proteins

A bit of the primary structure (amino acid sequence)of globin.

Proteins

A globin molecule. The arrangement of amino acids in this molecule encourages formation of hydrogen bonds. These bonds cause the molecule to coil helically, giving

rise to its secondary structure (the purple portion).

Protein, Secondary structure

Interactions between R groups at various areas along the spiral cause it to fold and bend. This gives the molecule its tertiary structure (the green portion).

Protein, Tertiary structure

Hemoglobin is an example of the fourth level of protein structure (quaternary structure). In all proteins at this level of organization, two or more polypeptide

chains are joined together. Hemoglobin has four polypeptide chains.

Protein, Quaternary structure

To summarize the four levels of protein structure:

1. Primary structure is the sequence of amino acids in a polypeptide chain.

2. Secondary structure is the coiled or extended shape that the chain assumes owing to hydrogen bonds at short intervals along the chain.

3. Tertiary structure refers to further folding of a coiled chain owing to bend-producing amino acids and interactions among R groups far apart on the chain.

4. Quaternary structure is the linkage of two or more polypeptide chains by hydrogen bonds and other interactions.

Proteins

Nucleic Acids

Nucleotide

Nucleic Acids

DNA: nucleotides bonded by hydrogen bonds

Nucleic Acids

ATP (adenosine triphosphate), the energycurrency of every cell

Nitrogen-containing base

5 carbon sugar

3 phosphate groups

Nucleic Acids

ADP (adenosine diphosphate). When ATP releases itsstored energy, it is converted to ADP + Pi

Nucleic Acids

Enzymes and Reactions

• An enzyme is a protein that accelerates a chemical reaction.

• They may combine, separate or rearrange molecules.• The enzyme and its substrate have a key and lock type

of relationship, one enzyme usually only works with one or two molecules.

Terminology

• - ase• Substrate• Active site• Coenzyme• Metabolic pathway• Metabolism• Activation Energy• Endergonic• Exergonic

Regulation of Enzyme Activity

1. The amount of substrate present regulates the reaction

2. The active site of the enzyme can be blocked by a molecule similar to the substrate. This is called Competitive Inhibition.

3. Allosteric Regulation, the regulation of enzyme activity by means of a molecule binding to a site other than the active site.

- Can decrease or increase enzyme activity.

Lowering the Activation Energy of a Reaction

Lowering the Activation Energy of a Reaction

Electron Carriers transport electrons from one molecule to another.

The

ATP / ADP cycle

Oxidation – Reduction Reactions

OIL RIG

Respiration: Deriving energy from food

C6H12O6 + 6O2 + 36 ADP + 36 Pi -------->

6CO2 + 6H20 + 36ATP

Aerobic respiration

Glucose: the starting point for cellular respiration

Three stages of aerobic respiration

Where does it happen?

Step 1

Glycolysis

Step 1.5

Conversionof Pyruvic

acid to

Acetyl CoA

Step 2

Kreb’s Cycle

Step 3

Electron Transport Cycle

How other foods fit into Cellular respiration

Anaerobic Respiration or Fermentation

• Far less efficient than Cellular Respiration with only

2 ATP generated per Glucose.

• By products are varied : alcohol, lactic acid, acetic acid

Anaerobic respiration or alcoholic fermentation

Anaerobic respiration or lactic acid fermentation

6H2O + 6CO2 ------------> 6O2 + C6H12O6

PhotosynthesisThe process by which certain groups of organisms capture energy from

sunlight and convert this solar energy into chemical energy that is initially stored as a carbohydrate.

sunlight

Two steps in photosynthesis

Photosynthetic terminology

• Leaf, petiole, blade• Epidermis, mesophyll cells, stomata• Chloroplast, vacuole, cell wall• Thylakoids, stroma, granum, inner/outer membrane• Thylakoid membrane, thylakoid compartment• Chlorophyll a, accessory pigments

Light wavelengths absorbed by chlorophylls

Plants reflect green light and absorbs the red and blue light.

Photosystem

• An organized complex of molecules within a thylakoid membrane, that collects solar energy and transforms it into chemical energy.

• Pigment molecules and accessory pigments serve as ‘antennae’ and absorb energy from the sun and pass it onto the reaction center ( a couple of chlorophyll a molecules).– Electrons are moved in two ways

• Physically transferred to the electron acceptor• Metaphorically up the energy hill

The chlorophyll molecules lose electrons to the primary electron acceptor.

This is a redox reaction

• This is the photo of photosynthesis• Photosystem II collects solar energy, its electron moves

to another part of the reaction center, the primary electron acceptor.

• This leaves an energy ‘hole’ which is filled by splitting water into 2 H+ and ½ O2. (Oh, that’s where Oxygen comes from!)

When the energized electrons fall they release energy that is captured as they are transferred through a series of electron transport molecules.

• They then arrive at Photosystem I where they are again boosted by light energy. Again the electrons pass along an electron transport chain and at the end are received by NADP+ where they proceed to the dark reactions.

The light reactions.

Physical movement of electrons

• Started out in the water of the thylakoid compartment.

• Moved into and through the thylakoid membrane• End in stroma, attached to NADPH

• ATP that is produced in the light reactions is used in the dark reactions to produce food.

The Dark Side

• Also called the Calvin Cycle or C3 Cycle.

• This is the synthesis of photosynthesis.

• A process by which CO2 is taken from the atmosphere and joined to a sugar (energized) and stored as a carbohydrate.

• NADPH and ATP are located in the stroma where there Calvin Cycle takes place.

• Fixation, the process where a gas is incorporated into an organic molecule.

• The starting point is RuBP or ribulose biphosphate a type of sugar.– Bring together CO2 and RuBP by enzyme rubisco

– Energize the sugar– Exit of the product– Regeneration of RuBP– Start over

The Calvin CycleThe dark reactions

Summary

• Solar energy is converted to chemical energy in the thylakoids and stored as ATP, NADPH

• Water is required• Oxygen is a byproduct• Stored chemical energy is used in the Calvin

Cycle (in the stroma) to produce a high-energy sugar from CO2 (from the atmosphere, in thru the stromata) and RuBP.

• Dinner is served!

A summary of photosynthesis