Question

Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.

Answer 1

Mitochondria and chloroplasts both have double-membrane-bound. Characteristics of the mitochondria:-Mitochondria have double- membrane-bound structures. It is divided into the inner and outer membranes, The outer membrane is very porous, known as cristae. They are the sites for ATP-generating chemical reactions. The membrane and matrix of a mitochondrion contains specific enzymes meant for aerobic respiration. They have their own DNA and ribosomes. Thus, they are able to make their own proteins. And known as semi-autonomous organelles . Functions of the mitochondria:- (i) They are the sites for cellular respiration. (ii) They provide energy in the form of ATP for all vital activities of living cells. (iii) They have their own DNA and ribosomes. Hence, they are regarded as semi-autonomous organelles. (iv) They have several enzymes, intermediately required for the synthesis of various chemicals such as fatty acids, steroids, and amino acids. Functions of chloroplasts:- (i) They trap solar energy and utilise it for manufacturing food for plants. Hence, they are involved in the process of photosynthesis. (ii) They contain the enzymes required for the synthesis of carbohydrates and proteins. Characteristics of chloroplasts:- Chloroplasts are double-membrane-bound structures. They are divided into outer and inner membranes, further divided into two distinct regions: (i) Grana are stacks of flattened discs containing chlorophyll molecules. The flattened membranous sacks are called thylakoids. The thylakoids of adjacent grana are connected by membranous tubules called stroma lamellae. (ii) Stroma is a homogenous mixture in which grana are embedded. It contains several enzymes that are used for the synthesis of carbohydrates and proteins. It also contains its own DNA and ribosomes and hence semi-autonomous organelle. Pic of Plastid and mitochondria are given bellow-

Answer 2

Plastids and mitochondria are those two organelles which are bounded by double membranes .

Plastids : These are of 3 types. Namely the :

• Chloroplast
• Chromoplast
• Leucoplast

The main function of plastids is to provide different colours to different parts of different organs.

Mitochondria :

They are the house of energy.

Here ATP is formed in the form of energy.

ATP : Adenosine Triphosphate.