7) Structure, properties and ecological role of lichens.

Lichens is a symbiosis between a fungus and an alga. A symbiosis is a lifeform where all the partners benefit together.

Lichens are very good bio-indicators for assessing air pollution.

The types of lichen

The "body" of a lichen is termed the thallus, and its general shape enables us to group lichens into four broad categories.

• Foliose lichens have a flat, leaf-like structure.

• Fruticose lichens have an erect or pendulous, bushy structure .

• Crustose lichens produce a flat crust on or beneath rock or tree surfaces.

Properties of lichens:

• They grow very slowly, 0.1 - 1mm a year.

• Lichens are able to survive extreme conditions.

• There are 20,000 species of lichens

Ecological role of lichens:

• Lichens account for approximately 8 percent of the vegetation covering Earth's surface.

• In certain environments, such as regions of tundra, they cover vast areas of land.

• Lichens delay global warming by consuming significant amounts of carbon dioxide (CO2) during photosynthesis.

• When they cover the ground, they prevent soil from drying out.

• In desert areas they are able to capture and conserve the moisture present in fog and dew.

• Lichens release nutrients, such as nitrogen and phosphorus, which are important in regions with nutrient-poor soils as the nutrients aid tree growth.

• Lichens are also an important food source for many species of animals.

• Lichens play an important role colonising new surfaces.

Also as a medicine lichens used to have more importance.

• Lungmoss (Lobaria pulmonaria) wasued against lung diseases.

• Leather moss (Peltigera sp.) was a treatment for rabies.

• Icelandic moss (Centraria islandica) is still processed for cough remedies.

• Evernia prunastri and Pseudevernia furfuracea areused in parfume.

• Umbilicaria esculenta is on the banquet-menu in Japan.

• The skull lichen supposedly treated epilepsy.

8) Structure and functions of proteins.

Proteins are fundamental components of all living cells. They are made up of C,H,O,S and N. The development of an organism from a zygote and the formation of its organ systems are entirely dependent on proteins. Proteins contain 20 different amino acids.

Structure of proteins:

The structure of a protein is characterized in four ways:

• The primary structure is the order of the different amino acids in a protein chain.

• The secondary structure consists of the geometry of chain segments in forms such as helices or sheets.

• The tertiary structure describes how a protein folds in on itself.

• The quaternary structure of a protein describes how different protein chains hook up with each other.

Functions of proteins:

• Our body uses protein to make hemoglobin.

• Proteins are used to build cardiac muscle.

• Proteins sustain the osmotic balance between the intracellular and the extracellular environment.

• Enzymes and hormones and other compounds in the body are made of protein.

• Protein is used to make hair, skin and nails.

• They are responsible for the growth and repair of body cells and tissues.

• They combine with each other to make energy.

• Transport molecules.

• Produces hormones such as insulin and antibodies.