Transcript
The Chemicals of Living Cells
The chemicals of life
All living organisms are made up of chemical substances
Reactions between these substances keep the cytoplasm(and the organism) alive. They are living processes.
The chemical substances described in the next seriesof slides are carbohydrates, proteins and lipids.
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Carbohydrates
Carbohydrates contain the elements carbon, hydrogen and oxygen
Familiar carbohydrates are sugar and starch
Glucose, fructose, maltose and sucrose are sugars
Glucose and fructose have the same formula, C6H12O6
Sucrose and maltose have the same formula, C12H22O11
Carbohydrates provide the main source of energy forrespiration in living organisms
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Glucose C6H12O6
C
C
C
C
C
C
HO
HO H
HO H
H OH
H OH
H2OH
A glucose molecule as a straight chain
5 of the carbon atoms maybe arranged in a ring
This molecule is often represented simply as a hexagon
C O
C C
C C
C
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Classification of sugars• MONOSACCHARIDES: with a single carbon ring.
- glucose and fructose• DISACCHARIDES: 2 carbon rings.
- maltose (glucose – glucose)
- sucrose ( glucose – fructose)• POLYSACCHARIDES:
- Glycogen (animal cells)
- Starch ( plant cells)
- Cellulose ( cell wall of plant cells)
Other carbohydrates2 molecules of glucose canjoin together to form a molecule of maltose
maltose
sucrose is formed whena molecule of glucose anda molecule of fructose combine
Starch and cellulose are formed from hundreds ofglucose molecules joinedto form a long chain
part of a starch molecule
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ProteinsProteins are made up of carbon, hydrogen and oxygenmolecules but with the addition of nitrogen
-Carbohydrates are made up of glucose units.-Proteins are made up of units called amino acids
-There are about 20 different amino acids. Examples are glycine (Gly), alanine (Ala), valine (Val) and cysteine (Cyst)
-Proteins make up the structure of cells; cytoplasm, nucleus cell membranes and enzymes, haemoglobin, antibodies, hormones, fibrin.
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Protein structure and shapeThe way the amino acids join up, gives a protein molecule a particular shape, which is different for every protein
Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly
Val- Cyst-Ala-Ala-Ser-Gly
This is a small, imaginary protein molecule showing howit acquires a shape
High temperatures or certain chemicals can cause theprotein molecule to lose its shape and its properties.
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Lipids
Lipids are fats and oils
They are made up from glycerol and fatty acids
Examples of fatty acids are stearic acid, oleic acid and palmitic acid
stearic acid
oleic acid
palmitic acid
C
C
H
H2
H2 C
O
O
O
glycerol fatty acids
A simple lipid
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FOOD TESTS
• Scientists often need to know wether or not a particular type of molecule is present in a solution.
• For e.g, a doctor might try to detect glucose in a urine sample (if it is present suggests the patient has diabetes)
• Simple chemical tests can be carried out on biological solutions.
Test for lipids: The emulsion test
• Ethanol is added to the unknown solution, and the mixture is gently shaken.
• The mixture is poured into a test tube containing an equal volume of water.
• If a lipid is present, a milky- white emulsion is formed.
A milky emulsion shows that a lipid is present
Salts and water
In addition to proteins, carbohydrates and lipids, cytoplasm contains salts and water
Water makes up the bulk of cytoplasm
All the chemical reactions in cytoplasm take place in solution, i.e. in water
Water itself takes part in many of these chemical reactions
Salts of sodium, potassium and calcium and many othersplay an important part in these reactions
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Question 1
The correct formula for glucose is
(a) C12H22O11
(b) C5H10O5
(c) C4H8O4
(d) C6H12O6
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Question 2
Which is the most accurate description of a carbohydrate?
A carbohydrate contains
(a) carbon and oxygen
(b) carbon, oxygen and nitrogen
(c) carbon, hydrogen and oxygen
(d) carbon and hydrogen
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Question 3
When two molecules of glucose combine, they form
(a) maltose
(b) sucrose
(c) fructose
(d) ribose
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Question 4
Which is the most accurate description of a protein
Proteins contain
(a) carbon, hydrogen and oxygen
(b) carbon, hydrogen, oxygen and nitrogen
(c) carbon, hydrogen and nitrogen
(d) carbon, nitrogen and oxygen
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Question 5
Which statements are correct?
Proteins are present in
(a) cell membranes
(b) cell walls
(c) cytoplasm
(d) nucleus
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Question 6
High temperatures damage proteins by
(a) decomposing them
(b) changing their chemical composition
(c) changing their shape
(d) making them soluble
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Question 7
A protein is made up of a series of
(a) glucose units
(b) fatty acids
(c) amino acids
(d) carbohydrates
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Question 8
Lipids are made up of
(a) glycerol and amino acids
(b) glycerol and fatty acids
(c) protein and fatty acids
(d) starch and fatty acids
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