Ch 3 - biological molecules Flashcards
carbohydrates, fats and proteins
definition of carbohydrates
Carbohydrates are organic molecules made up of the elements carbon, hydrogen and oxygen
what is the ratio of hydrogen to oxygen atoms in carbs?
2:1
What can carbohydrates be classified as?
Sugars and Complex carbohydrates
what can sugars be classified into?
-single sugars
- double sugars
What are the different types of complex carbohydrates?
- starch
- cellulose
- glycogen
What are the different types of sugars?
-glucose
- froctose
what are the different types of double sugars?
-maltose
-sucrose
What is the benefit of sugar?
sugars provide us with energy to do work and carry out activites
basic unit of carbohydrates
a single sugar is the basic unit of carbohydrates
do fructose and glucose have the same chemical formula?
yes
How are glucose and fructose different?
their atoms are arranged differently, affecting the sugars chemical and biological properties
Where can glucose be found
animals and plants
where can fructose be found?
plants
animals(rarely)
what is the structuse of a glucose molecule?
a hexagon but flattened a bit –> 6 sides
what is the structure of a fructose molecule?
pentagon –> 5 sides
What is a double sugar?
It is when 2 single sugars are joined together
where can maltose be found?
in germinating grains
what is a maltose molecule made up of?
2 glucose
what is a sucrose made up of?
1 glucose + 1 fructose
What are the different types of reducing sugars?
glucose, fructose and maltose
How can we test for the presence of reducing sugars?
Benedict’s test
What is the procedure of a Benedict’s test?
- place the substance into a test-tube
- add benedict’s solution to the test tube and shake the mixture
- place in boiling water-bath for 2-3 mins
What can be observed if reducing sugar is present?
a red precipitate is formed
What are complex carbohydrates?
a complex carbohydrate is made up of many similar molecules of single sigar joined together for form a large molecule.
Which molecules are the complex carbohydrates made up of?
it is made up of numerous glucose molecules
What makes starch, glycogen and cellulose different?
The glucose molecules are linked up in different ways.
How are starch, glycogen and cellulose different?
They have different chemical and biological properties and have different roles to play.
What is the structure of a starch molecule?
a starch molecule is made up of several thousand glucose molecules joined together
What is the role of a starch molecule?
Starch is ths storage form of carbohydrates in plants. When needed, it can be digested to glucose to provide energy for the cell
where is starch found
in storage organs of plants
what is the structure of cellulose?
a starch molecule is made up of many glucose molecules joined together. The bonds between glucose units are different from that in starch.
What is the role of a cellulose?
- the cellulose cell wall protects plant calls from bursting or damage
- cellulose serve as dietary fibre that prevents constipation
Where is cellulose found?
In cells walls of plants
What is the structure of a glycogen molecule?
Glycogen is a branched molecule. It is made of many glucose molecules joined together
what is the role of glycogen?
it is a storage form of carbohydrates in mammals. When needed, it is digested to glucose to provide energy for cell activites
Where can glycogen be found?
it is found in the liver and muscles of mammals
What happens to the starch when consumed?
the starch is digested into glucose, which is then stored in animals as glycogen.
What makes glycogen and starch suitable as storage materials in cells?
- insoluble in water, do not change water potential in the cells
- they are large molecules that cannot diffuse through cell membranes, not lost from cell
- easily broken down to glucose when needed
- their molecules have compact shapes, occupy less space
Where is the starch we eat digested?
alimentary canal
What is starch digested into?
Starch is digested to maltose by the enzyme amylase
What is maltose digested to?
Maltose is digested to glucose molecules by the enzyme maltase
What are the different functions of carbohydrates?
- needed as a substrate for respiration, to provide energy for cell activities
- needed to form supprting structures
- needed to be converted to other organic compounds such as amino acids and fats
- needed for the formation of nucleic acids like DNA
- needed to synthesise lubricants,like mucus, which consists of a carbohydrate and a protein
- to synthhesise the nectar in some flower
How to test for starch
Iodine test
procedure of the iodine test
add a few drops of iodine to the substance
what should be observed if starch is present?
The iodine turns from brown to blue-black upon contact with the food sample
definition of fats
fats are organic molecules makde up of the elements carbon, hydrogen and oxygen.
Does fats contain more or less oxygen when compared to hydrogen?
less
are fats a lipid
yes
what are the 2 types of fats
animal fats, plant fats
What is the common function of fats?
Fats are used as a store of energy, especially in animals
what are fats broken into?
glycerol and fatty acids
what is the exact number of glycerol and fatty acids 1 fat molecule is broken into?
1 glycerol + 3 fatty acids
examples on sources of fats
butter, cheese, fatty meat, olives, many kinds of nuts, peas, beans, seeds of castor oil and palm oil, herring and salmon
what are the function of fats?
- source and long term storage of energy
- fats are an insulating material that prevents excessive heat loss
- fats are a solvent for fat-soluble vitamins and many other vital substances
- important part in cells, especially in cell membranes
- fats are a way to reduce water loss from the skin surface because of glands in the skin secreting an oily substance
why are fats suitable for storing energy?
fats have a higher energy value compared to carbohydrates
what is an example of of how fats are insulating?
animals such seals have a thick layer of fat beneath the skin, which helps to reduce loss of body heat
how does the glands in iur skin secreting oil benefit?
an oily substance forms a thin layer the skin, reducing the rate of evaporation of water. The oily substance alsoo reduces the rate of heat loss from thhe skin
Test for presence of fats
ethanol emulsion test
procedure of the ethanol emulsion test on liquid samples
- add ethanol to a drop of liquid sample in a test tube ans shake
- add water to the mixture and shake
procedure of the ethanol emulsion test on solid samples
- crush the sample using a motar and a pestle
- place the pieces into a test tube
- add ethanol into the test tube and shake
- add water to another test tube
- after the solid particles settle, decant the ethanol into test tube with water and shake
What should be observes if there is a presence of fats?
A white emulsion is formed
Definition of proteins
Proteins are organic molecules made up of the elements carbon, hydrogen, oxygen and nitrogen. Sulfur may also be present.
Can proteins be found in all cellls?
YES
‘Proteins’s molecules are the smallest of all the food substances’ . This sentence is wrong. What is the correct version?
Proteins’s molecules are the largest and most complicated of all the food substances
What is the building blocks of proteins?
Amino acids
what are the 3 things an amino acid made up of?
an amino group, an acidic group, a side chain
What causes the different amino acids differ?
the different R groups
’ amino acids are combined in 2 ways to form 2 different protein molecules’. Is this statement true? if not, what is the correct statement?
amino acids are combined in various ways to form millions of different protein molecules
What is a polypeptide?
Many amino acid molecules are joined in a linear manner to form a polypeptide
can different polypeptides be linked up to form a longer chain?
YES
What does one or more ‘linked polypeptides’ chain folded together like a 3-D shape make up?
a protein molecule
sources of proteins?
milk, eggs, seafood, chicken, lean beef. soya beans, nuts, grains, vegetables like French beans
Functions of proteins?
Proteins are used in the:
- sunthesis of new cytoplasm, for growth and repair of worn-out body cells
- synthesis of enzymes and some hormones
- formation of antiibodies to combat diseases
how to test for proteins?
the biuret test
what colour is the biuret solution?
blue
What is the biuret solution made up of?
sodium hydrooxide and copper(II) sulfate
procedure of biuret test?
- an eyual volume of biuret solution and food sample to be shked well
- let the mixture stand for 5 mins
what is the observation made if there is a presence of proteins?
the blue to biuret solution turns violet
what is the observation if the test is negative?
the blue biuret solution turns clear
