Chemistry of Life PDF

# Atoms, Minerals and Compounds All living organisms are made up of atoms from different elements (think of the periodic table of elements). An atom is the smallest part of an element and cannot be chemically broken down into smaller components. - Some of these elements (atoms) are necessary for...

# Atoms, Minerals and Compounds All living organisms are made up of atoms from different elements (think of the periodic table of elements). An atom is the smallest part of an element and cannot be chemically broken down into smaller components. - Some of these elements (atoms) are necessary for the functioning of life- these are called **minerals**. - When **TWO or more** of these elements combine they form **molecules.** These are also important for the functioning of life. - When molecules are made up of **different types of elements** (atoms) they are called **compounds**. There are two types of compounds- **organic** and **inorganic.** ## Minerals Minerals are **inorganic**. **Inorganic definition:** Molecules that do not contain carbon-hydrogen bonds. Some minerals are considered to be **Micro elements** and others are considered to be **Macro elements**. - **Micro** elements (Micro= small) are only needed in **small quantities**. Examples: Sodium, Potassium, Calcium and Chloride - **Macro** elements (Macro= large) are needed in **Large quantities**. Examples: Zinc, Iodine, Copper and Iron **NOTE!** Macro and micro in this case does **NOT** refer to the size of the minerals! ## Inorganic Compounds Many of the minerals mentioned before are not able to be used by living organisms in their original form. They are combined together to make **compounds**. Water and mineral salts are the main inorganic molecules required by living organisms. If there are **NO** Carbon - Hydrogen bonds, then they are considered **Inorganic Molecules**. Examples: - Water (H2O) - Carbon dioxide (CO2) - Aluminium chloride (AICI3) These are not organic as they do not contain any Carbon-Hydrogen bonds. ## Examples of Mineral Salts - MnSO4 - CuSO4 - NiCl2 - FeSO4 - FeCl3 - Fe2O3 ## Water - Water is the only substance that exists naturally on Earth in all three states (Solid, Liquid and gas). - 70-95% of cells are made of water. That makes the human body 60% - 75% water! Water is important, without it life on Earth could not exist. Its importance in the body include: 1. Forms saliva (digestion) 2. Keeps mucus membranes moist 3. Allows body's cells to grow reproduce and survive 4. Flushes body waste, mainly in urine 5. Lubricates joints 6. Major component of most body parts 7. Needed by brain to manufacture hormones and neurotransmitters 8. Regulates body temperature (sweating and respiration) 9. Acts as shock absorber for brain and spinal cord 10. Converts food to components needed for survival - digestion 11. Helps deliver oxygen all over the body ## Plant Nutrients In order to grow, plants need various nutrients from the air and soil. Usually, natural **decomposition** occurs and nutrients from dead plants are put back into the soil. When plants are grown and harvested frequently, there may not be enough time for natural decomposition to take place and the soil becomes **nutrient poor**. Sometimes farmers artificially add these nutrients to the soil in the form of **fertilizers**. These contain mostly nitrates, calcium and phosphates. This can result in **eutrophication**. ## Eutrophication 1. **Excessive** fertilizers are used on crops by farmers 2. **Leaching** (nutrients) enter rivers and lakes due to **(a process whereby minerals are washed away, out of the soil)** and run off 3. This causes algae and other plants to grow rapidly, also known as an **Algal bloom** 4. This overabundance of algae blocks the **sunlight** from reaching the plants below and they **die** 5. **Decomposing bacteria** population increases to decompose dead plants. 6. The bacteria use up all the **oxygen** in the water causing it to become **anoxic** (no oxygen). 7. **Fish** and other **organisms** die due to the lack of oxygen. 8. This results in even more **nutrients** accumulating in the water body and the **cycle continues**. ## Organic Compounds As mentioned before, organic compounds are made up of Carbon-Hydrogen bonds and usually, (but not always) Oxygen. Organic compounds you need to know are: - Carbohydrates - Lipids - Proteins - Nucleic acids - Vitamins ## Carbohydrates Consists of the elements C, H and O. The ratio of H:O atoms = 2:1. Made up of ring-shaped units called **saccharides**. There are three types of saccharides: - Monosaccharide - Disaccharide - Polysaccharides ### Monosaccharide - **one** ring, six-sided structure. - **simple** sugars. - Examples: glucose and ribose. ### Disaccharide - Disaccharides form when **two** monosaccharides join together. - **double** ring structure. - E.g. Glucose + glucose = **Maltose**, Glucose + fructose = **sucrose**. ### Polysaccharide - When **three** or more monosaccharides join together. - **large** complex structures. - E.g. **Starch**, **glycogen**, **cellulose** and ## Why are Carbohydrates important? - Used during **cellular respiration** to release energy when required - **Store** energy e.g. starch and plants / glycogen / animals - Used to form **certain cell structure** e.g. cellulose to form cell walls ## Lipids (Fats and Oils) They are also made of C, H and O. The ratio of H:O is far greater than 2:1. They may, however also contain other elements such as phosphorous. Lipids are made up of two kinds of smaller molecules: Glycerol and fatty acids. One glycerol molecule combines with three fatty acid molecules to make one fat molecule. 1 glycerol + 3 fatty acids ----> lipid + water ## Fats You get two main types of fats- saturated and unsaturated. - **Saturated fats** are solid at room temperature while **unsaturated fats** are liquids at room temperature. ## Examples of food containing saturated fat: - Beef - Pork - Eggs ## Examples of food containing unsaturated fat: - Avocado oil - Almond oil - Sunflower oil ## Why are fats important? - Important source of **reserve energy** : fats yield more energy (gram for gram) than any other organic compound. - **Insulation** of heat. - Protection from **shock** (shock-absorber). - Phospholipids form part of the **cell membrane** and thus control the entry /exit of substances into and out of the cell. ## Proteins Consist of the elements carbon (C), hydrogen (H), oxygen (O), Nitrogen (N) and sometimes phosphorus (P) and sulphur (S). Proteins are made up of **amino acids** joined together with **peptide bonds**. - Two amino acids joined together is called a **dipeptide**. - More than three amino acids combine to form a **polypeptide** - A **protein** is a polypeptide chain with at least 50 amino acids and has a particular shape. - ***monomers** - building blocks* ## There are 20 different types of amino acids. The type of protein created depends on: - The number of amino acids - The type of amino acids used. - The sequence of amino acids. ## Why are proteins important? - For growth and repair of tissue. - A special type of protein carries oxygen in the red blood cells - Antibodies are composed of proteins and provide the body with immunity to germs. - Enzymes are made of proteins and are needed to speed up chemical reactions. - Proteins are a reserve source of energy (although not as much as lipids) ## Proteins are very sensitive to: - **excessive heat** and **extreme pH change**. These cause the proteins to **denature (change shape)** and therefore are **no longer able to perform their original functions ever again**. Proteins exposed to cold temperatures do not denature, they become **inactive**. This means they stop functioning temporarily, but do not lose their shape. Once a protein is **denatured** it will never function again. However, if a protein is **inactive** it may begin to function once returned to a warmer temperature. - Extremely high temperature= **denatured** - Extremely high pH= **denatured** - Extremely low pH= **denatured** - Extremely low temperature = **inactive** ## Proteins- Enzymes Enzymes are protein molecules that **speed up metabolic reactions** in our bodies. ## There are two types of metabolic reactions: 1. **Anabolic reactions**: * building up larger molecules * forming chemical bonds 2. **Catabolic reactions**: * breaking down larger molecules * breaking chemical bonds Enzymes work by binding to molecules called 'substrates'. 1. The **substrates** bind to an area on the enzyme called the ' **active site** ' 2. It holds them in such a way that the chemical bond-breaking and bond-forming processes take place more quickly. 3. The molecules produced at the end of the reaction are called the **products**. In the **lock - and - key** model, the active site of an enzyme is precisely shaped to hold specific substrates. Therefore each enzyme is specifically designed to do its function and if denatured, will lose its specific shape and function. ## Nucleic Acids Nucleic acids play an important role in controlling the **structure and functions** of the cell. They contain the elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and phosphorous (P). They are made up of building blocks called **nucleotides**. - **Ribonucleic Acid (RNA)** - **Deoxyribonucleic Acid (DNA)** ## Food testing There are different tests which can be done to detect carbohydrates, proteins and lipids. They involve adding a reagent to a food sample which changes colour depending on what biological molecules are present. Sometimes it may be necessary to crush the food or add water to the food before adding the reagent. The table below is a summary of food tests that you will need to study. | Food sample | Reagent | Method | Initial colour | Colour of positive result | |---|---|---|---|---| | Reducing sugar | Benedict's | Add Benedict's reagent to the food and boil in a water bath. | Blue | Brick red precipitate | | Starch | Iodine | Add iodine reagent to the food. | Yellow-brown | Blue-black | | Protein/amino acids | Biuret (a mixture of sodium hydroxide and copper sulfate). | Add Biuret reagent to the food. | Blue | Lilac/purple | | Fat | Ethanol | Add ethanol to the food to dissolve the fat then add water. | Colourless | White emulsion |