4. Biological Molecules Flashcards
What 3 categories do most molecules in living organisms fall into?
carbohydrates, proteins and lipids
What do all organic molecules contain?
Carbon
What chemical elements do carbohydrates include?
carbon
oxygen
hydrogen
What chemical elements do proteins include?
All contain C, O2, H2 and nitrogen
- some contain small amounts of other elements such as sulphur
What chemical elements do lipids include?
C, O2, H2
What is the structure of carbohydrates?
Long chains of simple sugars
What type of sugar is glucose?
a monosaccharide
What is formed when 2 glucose molecules join together?
maltose is formed (a disaccharide)
What happens when lots of glucose molecules join together? Examples?
When lots of glucose molecules join together starch, glycogen or cellulose can form (a polysaccharide)
What are most fats made up of?
Most fats (lipids) in the body are made up of triglycerides
What is 1 basic unit of triglycerides made up of?
1 glycerol molecule chemically bonded to 3 fatty acid chains
What are lipids divided into?
Lipids are divided into fats (solids at room temperature) and oils (liquids at room temperature)
What are proteins?
Long chains of amino acids
How are enzymes’ shapes different?
Enzymes have an area in them known as the active site – this is important as this is the place where another molecule fits into the enzyme in order for a reaction to take place
What happens if the shape of the active site does not match the shape of the molecule?
If the shape of the active site does not match the shape of the molecule that fits into it, the reaction will not take place
Do active sites in enzymes differ?
Every enzyme has a different shaped active site
What are antibodies?
Antibodies are proteins produced by certain types of white blood cell to attach to antigens on the surface of pathogens
What must the shape of the antibody match?
The shape of the antibody must match the shape of the antigen so that it can attach to it and signal it for destruction
What gives rise to different shapes of protein and what does this give proteins?
- The different sequences of amino acids cause the polypeptide chains to fold in different ways and this gives rise to the different shapes of proteins
- In this way every protein has a unique 3-D shape that enables it to carry out its function
What test is used for testing for reducing sugars?
Benedicts test
Describe the procedure for a test for reducing sugars/glucose
- Add Benedict’s solution into sample solution in test tube
- Heat at 60 – 70 °c in water bath for 5 minutes
- Take test tube out of water bath and observe the colour
- A positive test will show a colour change from blue to orange or brick red
What safety precautions are necessary with the Benedict’s test?
- handle test tube with tongs
- wear safety googles and heatproof gloves
What test can be used to test for starch?
Iodine test
Describe procedure for a test for presence of starch
- Add drops of iodine solution to the food sample
- A positive test will show a colour change from orange-brown to blue-black
What test is used to test for protein?
Biuret test
Describe procedure for a test for presence of protein
- Add drops of Biuret solution to the food sample
- A positive test will show a colour change from blue to violet / purple
What test is used to test for lipids?
emulsion test
Describe procedure for a test for presence of lipids
- Food sample is mixed with 2cm3 of ethanol and shaken
- The ethanol is added to an equal volume of cold distilled water
- A positive test will show a cloudy emulsion forming
Describe procedure for a test for presence of vitamin C
- Add 1cm3 of DCPIP solution to a test tube
- Add a small amount of food sample (as a solution)
- A positive test will show the blue colour of the dye disappearing
(DCPIP goes from blue to colourless if positive)
What does DNA stand for?
deoxyribonucleic acid
Definition of DNA
molecule that contains the instructions for growth and development of all organisms
What is the structure of DNA?
It consists of two strands of DNA wound around each other in what is called a DOUBLE HELIX
What are the individual units of DNA called?
NUCLEOTIDES
What similarities do nucleotides have and what one difference?
All nucleotides contain the same phosphate and deoxyribose sugar, but differ from each other in the base attached
What are the 4 different bases?
Adenine (A), Cytosine (C), Thymine (T) and Guanine (G)
How are the bases joined?
The bases on each strand pair up with each other, holding the two strands of DNA in the double helix
In what way do the bases pair up?
- Adenine always pairs with Thymine (A-T)
- Cytosine always pairs with Guanine (C-G)
What forms the backbone of the DNA?
The phosphate and sugar section of the nucleotides form the ‘backbone’ of the DNA strand (
Overall summary of the structure of the DNA helix
The DNA helix is made from two strands of DNA held together by hydrogen bonds
What holds the code for the formation of proteins?
It is this sequence of bases that holds the code for the formation of proteins
Why is water important (generally)?
Water is important for all living organisms as many substances are able to dissolve in it (it is a solvent)
This makes it incredibly useful and essential for all life on Earth
What is water’s role with dissolved substances?
Dissolved substances can be easily transported around organisms – eg xylem and phloem of plants and dissolved food molecules in the blood
What is water’s role with digested food molecules?
Digested food molecules are in the alimentary canal but need to be moved to cells all over the body – without water as a solvent this would not be able to happen
What is water’s role with toxic substances?
Toxic substances such as urea and substances in excess of requirements such as salts can dissolve in water which makes them easy to remove from the body in urine
What is water’s role with cytoplasm?
Water is also an important part of the cytoplasm and plays a role in ensuring metabolic reactions can happen as necessary in cells
