Question

Qn 5. The cellular structure that is directly responsible for maintaining cell shape as well as contributing to cell movement is                                                                            . (1 mark)

1. Ribosomes
2. Golgi apparatus
3. Smooth endoplasmic reticulum
4. Microfilaments and microtubules

Qn 6. In bone, calcium phosphate and the extracellular matrix rich in glycosaminoglycans are secreted by                                                                 (1 mark)

1. Osteoblasts
2. Chondrocytes
3. Fibroblasts
4. Osteoclasts

Qn 11. Which of the following statements is INCORRECT (FALSE) in regard to bone tissue? (1 mark)

1. Bone tissue may store and release calcium depending on the metabolic status of the animal
2. Osteocytes compact and spongy bone are biologically viable cells
3. Deposition of calcium salts into bone tissue is a function of osteoblasts
4. Mobilization of bone calcium is mediated by osteoblasts

Answer 1

Question 5.

The cellular structure that is directly responsible for maintaining cell shape as well as contributing to cell movement is :

Answer : D) microfilaments and microtubules.

Explanation: Cytoskeleton of a cell is a network of protein filaments which connects the nucleus of the cell to the cell membrane and helps in maintaining the shape of the cell as well as the movements of the intracellular organelles. It is made up of microfilaments, microtubules and intermediate filaments.

Microfilaments are a network of proteins made up of individual protein units called actin. It forms the contractile element of the muscles and core of the microvilli of the cells. It is essential element for the contraction of the muscles.

Microtubules are protein network composed of individual protein units called as tubulin. They are essential elements in the formation of mitotic spindles which helps in cell division. Microtubules also form the core of cilia and flagella which helps in movements of the cells.

Intermidiate filaments are protein network which are present in the cytoplasm of the cell, nuclear lamina and in the skin epithelium as keratin. They provide mechanical strength to the cells and link the cells together.

Other options:

Ribosomes - It is an organelle which is concerned with protein synthesis inside the cell. It helps in the translation phase of protein synthesis i.e. formation of proteins from mRNA.

Golgi apparatus - Proteins synthesized in the rough endoplasmic reticulum are packaged into vesicles and transported to their destination through Golgi apparatus.

Smooth endoplasmic reticulum - It helps in synthesis of lipids, steroids and detoxification of harmful substances inside the cell. Hence, liver cells have abundant smooth endoplasmic reticulum as liver is concerned with detoxification of harmful substances.