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Topic  3:  The  Chemistry  of  
Life  
 

3
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Sulphur,  iron,  calcium,  phosphorus,  iron  and  sodium  are  chemical  elements  that  
are  needed  by  living  organisms
...
 
In  some  vitamins
...
 
Co-­‐factor  for  
enzymes
...
 
In  some  vitamins
...
 
Reacts  with  muscle  
fibre  contraction,  
blood  clotting  and  
synapses
...
 
Synthesis  of  
Synthesis  of  
nucleotides
...
 
ATP
...
 
Constituent  of  bones
...
g
...
g
...
 
cytochromes,  haem  
Chlorophyll  synthesis
...
 
Involved  with  
potassium  in  
membrane  function
...
 

In  some  amino  acids  
and  proteins
...
 
Co-­‐factor  for  
enzymes
...
 
Synthesis  of  
nucleotides
...
 
Constituent  of  
electron  transport  
molecules
...
 
Involved  with  
potassium  in  
membrane  function
...
 
Due  to  this  water  molecules  carry  an  unequal  distribution  of  electric  charge,  this  
property  makes  water  a  polar  molecule
...
 This  forms  weak  bonds  
known  as  hydrogen  bonds
...
 
The  polarity  of  water  allows  it  
to  dissolve  and  interact  with  
other  polar  molecules
...
 
 
Water  has  a  high  boiling  point  
compared  with  other  solvents  
because  large  amounts  of  

Water  can  form  continuous  
columns  when  travelling  in  
the  xylem  of  plants
...
 CO2  is  dissolved  in  
the  water  of  the  blood  and  
maintains  the  appropriate  PH  
of  the  blood
...
 
The  temperatures  of  
organisms  tend  to  change  
slowly  -­‐  fluids  such  as  blood  
can  transport  heat  around  the  
body  easily
...
 
 
Water  evaporates  as  hydrogen  
bonds  are  broken  and  heat  
from  the  water  is  used
...
 
 
Sweating  and  transpiration  
enable  plants  to  lose  heat,  so  
water  acts  as  a  coolant
...
2  Carbohydrates,  Lipids  and  Proteins  

 
 
 
Organic  compounds  are  compounds  that  consist  of  carbon  and  are    
...
 
 
 
 
 
 
The  chemical  formula  of  glucose  is  C6H12O6
...
 There  are  two  forms  of  glucose:  
alpha  glucose  and  beta  glucose
...
 The  second  carbon  in  beta  glucose  has  
the  hydroxide  at  the  top  and  hydrogen  at  the  bottom
...
 It  is  a  
pentose  sugar  (sugar  containing  5  carbons)
...
 The  acid  
part  of  the  name  comes  from  the  carboxylic  group,  
which  ionises  to  form  hydrogen  ions,  weak  acids
...
   

 
 
Amino  acids  have  both  an  amino  group  (NH2)  and  a  
carboxyl  group  (COOH)
...
 

 

  
Form  of  
Carbohydrate  

 
 
Examples  

Use  in  Plants  

Use  in  Animals  

Monosaccharides  

Glucose  
Galactose  
Fructose  

Disaccharides  

Maltose    
Lactose  
Sucrose  

Glucose  is  a  source  of  
energy  in  cell  
respiration  and  then  
the  digestion  of  
carbohydrate  foods  
obtains  it
...
 

Polysaccharides  

Glycogen  
Starch    
Cellulose  

Fructose  is  a  
component  of  fruit,  
making  them  sweet  
and  attracting  animals  
to  eat  them,  thereby  
dispersing  the  seeds
...
 
Cellulose  is  the  
structural  component  
of  cell  walls
...
 

Glycogen  is  the  
storage  carbohydrate  
of  animals  and  is  
found  in  the  liver  and  
muscles
...
 The  bond  
produced  (H_O_H)  is  called  a  glycosidic  bond
...
 The  reaction  that  splits  up  the  disaccharide  into  two  
monosaccharides  and  breaks  the  glycosidic  bond,  this  is  known  as  a  hydrolysis  
reaction
...
 
 

 
 
Triglycerides  are  formed  in  condensation  reactions;  this  is  done  when  the  
carboxyl  group  of  the  fatty  acid  reacts  with  the  hydroxide  of  glycerol
...
 This  reaction  is  repeated  three  times  when  reacting  one  fatty  
acid;  a  monoglyceride  is  formed  first,  when  repeated  diglyceride  is  produced,  
and  the  after  the  third  repeat  triglyceride  is  formed
...
 
 
 
 
 

The  condensation  reaction  of  two  amino  acids  produces  a  dipeptide
...
 Water  is  produced  as  
a  bi-­‐product
...
 Lipids  can  form  tissue  
layers  around  vital  organs,  providing  them  protection  against  physical  injuries
...
 
 
 
 
 

Lipids  molecules  contain  more  energy  per  gram  than  carbohydrate  molecules
...
 
Animals  use  carbohydrates  for  short-­‐term  energy  storage,  while  lipids  are  used  
for  long-­‐term  energy  storage
...
 Lipids  are  stored  as  fats  in  animals  
and  oils  in  plants
...
   Lipids  have  less  effect  on  
osmotic  pressure  within  a  cell  than  complex  carbohydrates
...
3  DNA  Structure  

 
 
Nucleotides  compose  of  a  phosphate  group,  a  deoxyribose  sugar  and  a  nitrogenous  base
...
 
 

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2
1

There  are  four  different  nitrogenous  bases:  
 
adenine,  thymine,  guanine  and  cytosine
...
 The  phosphate  ion,  which  is  attached  to  
the  5th  carbon  (5'  -­‐C)  of  the  deoxyribose  sugar,  attaches  to  the  third  carbon  (3"-­‐
C)  of  the  neighbouring  deoxyribose  sugar
...
 Successive  
condensation  reactions  result  in  a  long  single  
strand
...
   
 
Thymine  and  adenine  are  joined  with  two  hydrogen  bonds
...
 In  order  for  the  bases  to  join,  the  twos  
strands  must  run  in  opposite  directions

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