biology- biomolecules

biomolecules

Biomolecules are chemicals that are made inside a living thing.

What are the four biomolecules found in food?

• Carbohydrates

• Lipids (fats and oils)

• Proteins

• Nucleic acids

Why is food important to living organisms?

• Provides energy

• Allows for growth and repair of body structures

What are the elements present in food?

• Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur

What five elements are found in dissolved salts?

•  Sodium, chlorine, potassium, magnesium, calcium 

Trace elements

• Trace elements are elements that are only required by living things in tiny amounts.

• Examples: iron, copper, zinc and iodine

  
  

What is the chemical composition of carbohydrates?

• Contain the elements carbon (C), hydrogen (H) and oxygen (O).

• These elements are usually present in the ratio C_x(H₂O)_y. 

• There is always a fixed ratio of twice as much hydrogen as oxygen in a carbohydrate. 

• Glucose is an example of a carbohydrate in which y and x are both 6. The formula for glucose is C₆H₁₂O₆.

What are the three main types of carbohydrates?

• Monosaccharides

• Disaccharides

• Polysaccharides

What are the basic units of a carbohydrate?

Monosaccharides

Structure of a monosaccharide:

• Consists of a single sugar unit 

• Sweet to taste

• Soluble in water

Examples of monosaccarides: 

• Glucose is: 

• Made by plants in photosynthesis.

• Broken down in respiration to release energy.

• Fructose is much sweeter than glucose.

• Ribose is a sugar used to form RNA.

Structure of a disaccharide:

• Consists of two sugar units joined together

• Sweet to taste

• Soluble in water

Examples of disaccharides:

• Maltose is composed of two glucose molecules joined together.

• Sucrose is composed of a glucose and a fructose joined together.

• Lactose is composed of glucose and galactose joined together. 

Structure of a polysaccharide:

• Consists of many sugar units joined together

• Not sweet to taste

• Insoluble or only slightly soluble in water

Examples of polysaccharides:

• Starch:

  • Is easily digested.

  • Provides energy.

• Glycogen is:

  • Stored in the muscles and liver.

• Cellulose is:

  • Difficult to digest, so it is used as a source of fibre to stimulate the intestines.

  • A structural carbohydrate as it forms the cell wall in plants.

Nutritional sources of carbohydrates

• Bread, potatoes, rice, pasta, sugars

Metabolic roles of carbohydrates

• Glucose is broken down in respiration to release energy (catabolic role).

• Glucose is made during photosynthesis (anabolic role).

What is the chemical composition of lipids? 

• Contain the elements carbon, hydrogen and oxygen.

How do lipids differ from carbohydrates?

• Carbohydrates have a fixed ratio of elements.

• Lipids have no fixed ratio of elements. 

How do fats differ from oils? 

• Fats are lipids that are solid at room temperature (normally taken to be 20°C).

• Oils are lipids that are liquid at room temperature.

What is the basic unit of a lipid?

Triglyceride

Structure of a triglyceride

• Made up of one glycerol molecule and three attached molecules of fatty acids.

Nutritional sources of lipids

• Butter, oil, cream, fat on meat

Metabolic roles of lipids

• Lipids can be used in respiration to release energy (catabolic role).

Structure of a phospholipid

• Made up of a glycerol molecule, two attached molecules of fatty acids and a phosphate group.

What is the difference between a triglyceride and a phospholipid?

• In a phospholipid, a phosphate group replaces a fatty acid.

Where would you find a phospholipid in a cell? 

biological membranes

What is the chemical composition of proteins? 

• Contain the elements carbon, hydrogen, oxygen and nitrogen

• Sometimes contain sulfur or phosphorus

What are the basic units of a protein?

amino acids

What is the difference between an amino acid and a protein?

• Amino acids are the basic unit of proteins.

• A protein is a chain of many amino acids joined together.

Proteins:

• Proteins are made up of 20 common amino acids. 

• A peptide is a short chain of amino acids (up to 50 amino acids).

• A polypeptide consists of a long chain of amino acids bonded together (more than 50 amino acids).

• A protein is a long chain of polypeptides. 

TYPES OF PROTEINS:

• fibrous

• globular

-Fibrous proteins show very little folding.

Examples: 

• Keratin in hair and nails

• Myosin in muscles

-Globular proteins show a lot of folding to form a rounded 3-D shape.

Examples: 

• Haemoglobin in red blood

• Enzymes

Nutritional sources of protein

• Meat, fish, eggs, nuts, milk

Metabolic roles of proteins

• Enzymes are made of proteins and they control reactions. These reactions may be anabolic (e.g. photosynthesis) or catabolic (e.g. respiration).

• Many hormones are protein-based and they regulate processes, e.g. insulin regulates the amount of sugar in our blood.

• Antibodies are made of protein and they inactivate and help to destroy viruses and bacteria.

Metabolic roles of proteins

• Proteins are essential to the structure and functions of membranes: 

  • Channel proteins form the pores in membranes.

  • Channel proteins act as receptors to recognise molecules.

  • If the molecules have the correct shape, the channel proteins allow their transport through pores across the membrane. (If they have the wrong shape, they are prevented from crossing the membrane.)

Minerals

Minerals are inorganic nutrients that plants and animals require in small amounts.

Why are minerals needed? 

• To control the pH in cells and organs (mainly sodium, potassium and chlorine).

• To help control enzyme systems (by controlling pH in the body, which impacts enzyme activity). 

• Muscle contraction requires calcium and magnesium.

How are minerals used in the formation of structures?

• Iron is involved in the formation of haemoglobin. 

• Magnesium is involved in the formation of chlorophyll. 

• Calcium is involved in the formation of teeth and bones. 

Where do animals source their minerals? 

• Calcium is found in dairy products.

• Sodium and chlorine are found in table salt.

• Magnesium is found in whole grains and green vegetables.

• Iron is found in meat, eggs, wholegrains and green vegetables.

Where do plants source their minerals? 

The roots of plants absorb minerals from the soil by active transport.

vitamins

Vitamins are complex biomolecules that are not made in the body but are needed in tiny amounts.

What are the two categories of vitamins? 

• Water-soluble, e.g. vitamins B and C

• Fat-soluble, e.g. vitamins A, D, E and K

Good sources of vitamin C

• Vegetables

• Fresh fruit

Biological role of vitamin C

Vitamin C is important for:

• The formation of collagen, which is found in connective tissue (holds body structures together)

• Growth and maintenance of bone and teeth

• Helping wounds to heal

• Immune function

What disease is associated with a deficiency of vitamin C?

• Scurvy

• Symptoms of scurvy: 

  • Tiredness

  • Aching joints

  • Poor healing of skin

  • Bleeding under the skin

  • Bleeding gums with loose teeth

Good sources of vitamin D

• Oily fish

• Egg yolks

Biological role of vitamin D

• Allows the small intestines to absorb calcium.

• Calcium is needed for healthy bone and tooth formation

What disease is associated with a deficiency of vitamin D?

• Rickets

• Symptoms of rickets: 

  • Weak and soft bones that tend to deform easily, often resulting in bowed legs.

Why is water important to living organisms? 

• Main component of cytoplasm and body fluids

• Good solvent

• Maintains neutral pH

• Participates in chemical reactions (e.g. respiration and photosynthesis)

• Moves easily through membranes (allows cells to have shape and structure)

• Helps to regulate temperature

experiments needed

• Testing for the presence
  or absence of starch

• Testing for the presence or
  absence of reducing sugars

• Testing for the presence or
  absence of protein

• Testing for the presence
  or absence of lipids

• To investigate quantitatively the
  level of reducing sugars in a range of food samples

To investigate quantitatively the
level of reducing sugars in a range of food samples

Procedure

• Dissolve food sample in water in test tube and add an equal volume of Benedict’s (or Fehling’s) quantitative solution (which is blue).

• In a second test tube, mix equal volumes of water and Benedict’s (or Fehling’s) quantitative solution (this acts as a control).

• Place both test tubes in a very hot water bath for 5 minutes.

Results

• If reducing sugar is absent, the solution remains blue.

• A green colour indicates very little reducing sugar is present.

• A yellow colour indicates a low concentration of reducing sugar.

• An orange colour indicates a medium concentration of reducing sugar. 

• A red colour indicates a high concentration of reducing sugar.