The Chemistry of Life

DP BioMs Wilson

9/12

3.1 Chemical elements and water

• 4 elements most commonly found in living things (as we know them!)– Carbon– Hydrogen– Oxygen– Nitrogen

• What else do living things need? Why?

Water

• Thermal properties– High specific heat (can absorb or release a lot of heat without

changing temp – temp stabilizer)– High heat of vaporization (cooling mechanism)

• Cohesive properties– Forms droplets– Surface tension (Jesus Christ lizard)– Moves as a column in plants– HSH and HHV

• Solvent properties– Glucose, amino acids, fibrinogen and hydrogencarbonate ions

(transport CO2) in blood

3.2 Carbs, lipids and proteins

• Carbohydrates – monosaccharides• Lipids – glycerol and fatty acids• Proteins (polypeptides) – amino acids• Nucleic acids – nucleotides

• Why are models of these molecules used? What do the molecules actually look like?

Functions of carbs:

• Animals:• Glucose (mono-)

– Chemical fuel for cell respiration

• Lactose (di-)– Makes up some of the solutes

in milk• Glycogen (tri-)

– Stores glucose in liver and muscles

• Plants:• Fructose (mono-)

– Found in many fruits• Sucrose (di-)

– Often transported from leaves of plants to other locations in plants by vascular tissue

• Cellulose (tri-)– One of the primary

components of plant cell walls

Lipids

• Why are they important?– Insulation– Adipose cells hold more or less– Energy storage – think about this primitively– Phospholipid – what is that?

Hydrolysis and Condensation

• Hydrolysis: water “splitting” as part of reaction• Figure 3.7

Condensation

• Condensation: water is a product• Figure 3.8

3.3 DNA Structure• Nucleotide: a phosphate group O=P, a deoxyribose sugar and a

nitrogenous base• 4 Nitrogenous bases

– Adenine– Thymine– Guanine– Cytosine

• Nucleotides are covalently bonded• Complementary pairs are hydrogen bonds (T and C are much smaller than

A and G)– C-----G– A-----T

• Check out heinemann.co.uk/hotlinks; ex code 4242P and click on Weblink 3.4

3.4 DNA Replication

• Hydrogen bonds undone so DNA can be copied– Helicase is an enzyme that does this

Formation of 2 complementary strands

• Free nucleotides also present – can bond to end of strand– These covalent bonds are catalyzed by DNA

polymerase

3.5 Transcription and Translation

Transcription

• Produces RNA using free nucleotides in nucleoplasm

• Only 1 strand of DNA is copied• mRNA is single stranded and shorter than DNA

(only 1 gene)• DNA has thymine and deoxyribose• RNA has uracil

• Figure 3.15 \/

Genetic Code

• Written in 3’s…every 3 base pairs can code for any of the 20 amino acids (Called a codon)

• mRNA: a comp. copy of DNA, can code for a gene

• rRNA: makes up ribosomes with ribosomal protein

• tRNA: transfers 1/20 aa’s to ribosome, contains anticodon to mRNA

• TRANSLATE TRANSLATION with a partner!

3.6 Enzymes

• Enzymes: proteins (long chain of aa’s) forming very specific shape; “–ase”

• Require a certain temperature unless they denature (sometimes permanent)

• Require pH 7 or lower• Lactose intolerance is…– Inability to produce lactase (mono’s are absorbed more

easily) – Pills for lactase available– Very very common

3.7 Cell Respiration• Used by all cells to produce ATP• 1st step: Glycolysis

– Glucose enters cell, eventually becomes pyruvate, 2 ATP molecules needed for glycolysis (net gain of 2)

• Anaerobic respiration– AKA fermentation: yeast undergoes glycolysis to produce pyruvate, CO2

and ethanol– Lactic acid fermentation: when exercise exceeds O2 supply, glycolysis,

pyruvate to lactate and back with O2 available• Aerobic is most efficient (because glucose is completely oxydized)

– Mitochondria go through glycolysis and get 2 pyruvate molecules which are metabolized in mitochondria

• Pgs 70-73

3.8 Photosynthesis

• Light to energy in just plant cells?

• Read about photosynthesis in your book on pgs 74-78

• Study hard! Exam next Wed. chapters 1-3!!