Cell membrane function and difference-digieduco

on
  Functions of cell membrane : (a) The proteins and enzymes present in the cell membrane helps in the transport of certain substances like sugar, sodium and other ions etc. across the cell membrane. (b) Cell membrane protects the internal structures of the cell and different organelles of the cytoplasm. (c) It maintains the shape of the cell. (d) It acts as a selective permeable membrane because it allows to pass certain substances while others are not, hence it helps in the transport of selective materials from and to the cells. (e) The membranes on the cytoplasmic organelles and nucleus most probably formed from the plasma membrane. (f) Other important functions of cell membrane of the cells are endocytosis and exocytosis . Endocytosis is the process by which materials are transported into the cells by the formation of vesicles. It includes two processes-phagocytosis (cell eating) and pinocytosis (cell drinking). The reverse process of endocytosis is exocytosis. During th...
0

SECRETORY MATERIALS-digieduco

on
Some useful products are formed from the living substance of the protoplasm during the metabolic activity. Those substances are called secretory and they are not concerned with the nutrition of the plant.

Secretory materials are :--(a) plant pigments, (b) enzymes and (c) nectar.

(a) Plant pigments-Different types of colouring matters are found in plants. The bright colour of the petals of nowers and skins of fruits is due to the presence of those pigments.

Plant pigments are -
(i) Chlorophylls--It is the green pigment of the plant. The green colour of stem, leaves and other aerial plant parts is due to the presence of the chlorophyll. Chlorophyll is essential in the plant cells for the manufacture of carbohydrate food. Chlorophyll is formed by the combination of four pigments, viz. chlorophyll a, chlorophyll b, carotene and xanthophyll.

(ii) Carotenoids :-The two pigments carotene and xanthophyll are together called carotenoids. These are found in the petals of flowers and skins of fruits. Their colour ranges from orange to yellow.

(iii) Anthocyanin :--Anthocyanin is another pigment which is present in dissolved state within the cell sap of the vacuole of the epidermal cells. Blue, violet, red and pink colours of the petals of flowers are due to the presence of anthocyanin pigments.

Carotenoid and anthocyanin pigments attract insects which bring about pollination.

(b) Enzymes-Enzymes are the active substances like catalysts present in the living cells which only control the rate of reactions but without being used up, they remain unchanged at the end of reactions. Due to the action of enzymes, complex substances break down into simpler soluble forms. These are nitrogenous substances secreted by the living substance protoplasm. Diastase, protease, lipase etc. are the examples of some enzymes.

(c) Nectar-The petals of flowers contain some glands called nectar glands which secrete a sugary fluid. The sweet tasting sugary substance secreted from the glands is the nectax which attracts insects. 

Comments

Post a Comment