Life Processes

Introduction

How to define living?

The best way to define ‘living’ is through movement , but visible movement alone is not enough and we must take into consideration movement at the molecular level while defining what is living

Are viruses dead or alive?

Since viruses do not show any molecular movement until they infect another cell there is controversy regarding whether they are dead or alive.

Why is movement needed?

Living organisms are complex made of tissues , cells and organs that work together in order , when that order breaks down and in general maintenance and repair is need to keep the organism alive in maintaining their structures. These structures are made up of molecules hence movement of molecules is needed.

Nutrition

Since the body requires energy and that energy must come from somewhere , nutrition is the process by which energy is obtained from outside sources for use in the body.

Respiration

Processes of obtaining oxygen from outside the body and using it to break down food sources into simpler forms is called respiration.

Why single celled organisms don’t have cellular respiration and separate organs?

As their entire body surface is in contact with the outside world they do not need cellular respiration or separate organs.

Why is simple diffusion not enough for complex organisms?

As all of their cells are not in contact with the environment more sophisticated methods are needed such as respiratory system.

Modes of Nutrition

Autotrophic - In this mode of nutrition organisms can produce their own food. It includes photosynthetic organisms like green plants and some bacteria. Autotrophs convert complex organic molecules into simple organic molecules into complex inorganic compounds (Anabolic process)

Heterotrophic Nutrition - These organisms obtain nutrition from other living or dead organisms and cannot produce their own food.

  1. Holozoic - Heterotrophic nutrition in which they consume food as a whole and digest it using enzymes. Example - human , tiger and goat

  2. Saprotrophic - They feed on dead and decaying organic matter and convert complex inorganic compounds into simple organic matter. Example - bacteria , mushrooms

  3. Parasitic - They depend on other living organisms called hosts for their food. They do not kill the hosts but harm them. Example - cuscuta , tapeworm , ringworm , leech

Photosynthesis

Steps for Photosynthesis

  1. Absorption of sunlight by chlorophyll.

  2. Conversion of light energy energy into chemical energy to break down water into oxygen and hydrogen. Oxygen is released as breathable hydrogen

  3. Reduction of carbon dioxide to form carbohydrate (glucose)

Stomata

Only the guard cells have chlorophyll. The guard cells swell up when water enters opening the stomata and they close when they loose water,

  1. It performs the exchange of carbon dioxide and oxygen

  2. Transpiration and Loss of excess water

  3. Photosynthesis

Importance of Transpiration

  1. Removing waste and excess water

  2. Cooling of plant

  3. Transpirational pull

Photosynthesis in desert plants

  1. Stomata is closed during day and opens at night to prevent water loss

  2. When stomata opened at night exchange of gases takes placed for formation of intermediary

  3. During daytime with sunlight intermediate is converted into carbohydrate or simple sugars

Human Digestion

Mouth

  1. Salivary glands produce salivary amylase beginning the process of breaking down carbohydrates

  2. Saliva mixes with food , wetting food and forming bolus

  3. Tongue helps mix saliva with the food

  4. Teeth help in chewing the food called mechanical digestion.

Stomach

  1. J shaped muscular bag which helps in the churning of food

  2. Produces HCl which kills germs and increases pH to activate pepsin

  3. Mucus protects the inner wall lining of the stomach

  4. Pepsin begins the digestion of proteins

  5. Product of stomach is called the chyme

Small Intestine

  1. Food enters the small intestine throught the pyralic sphincter

  2. Bile juice is secreted here from the liver , which creates an alkaline pH for pancreatic jusice and emulsifies fats to form small globules

  3. Pancreas secerete pancreatic juice which contains

    1. Pancreatic amylase - breaks down carbohydrates into glucose

    2. Trypsin - breaks down proteins into amino acids

    3. Lipase - breaks down emulsified fats into glycerol and fatty acid