Cell The Unit Of Life - Class 11 Medical Biology - Extra Questions

Lysosomes are vascular cell-organelles which contain hydrolytic enzymes called Lysozyme. Lysozyme is a special enzyme found in tears, saliva, sweat, and other body fluids. Other mucosal linings, such as the nasal cavity, also contain lysozyme. It destroys bacteria that attempt to enter our body through this passageways. Lysosomes help in keeping the cell clean. If the cell gets damaged, then one of the lysosomes bursts, releasing those digestive enzymes. The released enzymes then digest their own cell and ultimately the cell dies. Hence, lysosomes are called suicide bags of the cell.

 Explanation :

One function of Rough endoplasmic reticulum –

They have the presence of ribosomes which help the formation of protein.

One function of smooth endoplasmic reticulum  -

They are involved in the synthesis of lipids, phospholipids and steroids.

1.       The single membrane-bound organelles that are found only in eukaryotes include vacuoles, lysozymes, endoplasmic reticulum, Golgi apparatus etc. They can be differentiated on the basis of their structure, functions, as well as secretions.

1. It contains ribophorins for providing attachment to ribosomes.
2. It bears enzymes in the region of pores for modifying polypeptides synthesised by attached ribosomes, e.g., glycosylation.
3. It synthesises serum proteins, membrane proteins and a number of other proteins.
4. Proteins and enzymes synthesised by ribosomes enter the channels of RER both for intracellular use as well as secretion.
5. It provides enzymes precursors for the formation of lysosomes by Golgi complex.
6. SER can develop from RER by discarding ribosomes.

1. It is responsible for synthesis of fats inside the cells of adipose tissue, formation of sphaerosomes, synthesis of glycogen as well as glycogenolysis in liver cells, synthesis of sterol, etc.
2. As sarcoplasmic reticulum, it stores $$Ca^{2+}$$ for release during muscle contraction.
3. It takes part in detoxification of toxic chemicals with the help of cytochrome P-450.
4. Synthetic products of RER pass on to Golgi complex through SER.

1. All glandular cells depend upon Golgi complex for concentrating and packaging their products inside a soluble protein coat visible as dark staining under electron microscope.
2. Golgi complex brings about membrane transformation, that is, converting one type of membrane into other types.
3. Proteins synthesised by the rough endoplasmic reticulum and lipids synthesised by smooth endoplasmic reticulum reach the cisternae of the Golgi apparatus. Here, they combine with carbohydrates to form glycoproteins and glycolipids.

Answer:

$$\textbf{ Solution: }$$

$$\bullet$$A cell is the smallest unit of an organism containing a nucleus.

$$\bullet$$This cell is made up of biomolecules such as nucleic acids, proteins, carbohydrates, and lipids.

$$\bullet$$Cell is the unit forming tissue of an animal muscle. 

$$\bullet$$The main parts of the cell are the cell membrane, the nucleus, and the cytoplasm.

a) Ribosomes – protein synthesis

(b) lysosome – suicidal bags

(c) chromosome – inheritance

• As per the fluid mosaic model and the bilipid layar of plasma membrane, the cell membrane of the cell is made up of 2 layers of lipid with the hydrophilic head and hydrophobic tail. 
• Also interval and peripheral proteins are present in between the lipod layers. These proteins work as transporters for many molecules and receptors for many. 
• The molecules that are soluble in lipid are easily able to pass through the plasma membrane without any resistance whereas small molecules such as hydrogen, oxygen etc are also albel to pass through the space present between the lipid molecules. 
• The uncharged molecules which are smaller in size can also be passed either without the help of transporter proteins or with their help. 
• All of the above characters describe the lipoprotein and semi permeable layer of plasma membrane. 

1. Diffusion is the movement of molecules from higher to lower concentration, it occurs in both gases as well as liquids. 
2. Osmosis is the movement of water from higher to lower concentration, against the concentration gradient through the semi-permeable plasma membrane.
3. Impermeable means not allowing the substance to pass through it.
4. Differentially impermeable is a selectively permeable membrane which is almost impermeable to solutes but completely permeable to solvents.
5. The fluid mosaic model is the modern model of the plasma membrane in which proteins are embedded in the layers of lipid.
6. The micellar theory states that protoplasts and some of its contents are only primarily and are micellar ( a unit structure made up of many molecules or ions ).
7. Endocytosis is the process of engulfing food by the invagination of the membrane and forms a vacuole.
8. Exocytosis is the process of removal of food by the cell, it requires energy.
9. Passive transport is the movement of ions and substances across the membrane without the use of energy.
10. Active transport is the movement of ions and molecules across the plasma membrane against the concentration gradient and needs energy.
11. Microvilli are the small finger-like projections on the surface of the membrane to increase the surface area for absorption.
12. Desmosomes are the structure that attaches two adjacent cells to each other.
13. Chemoreception is a physiological process where the organisms respond to chemical stimuli.

• The plasma membrane or cell membrane is a lipid bilayer membrane in which proteins are embedded that separates the cytoplasm of the cell from the extracellular spaces.
• It is selectively permeable that regulates the transportation of molecules.
• The transportation of molecules across the membrane can be active or passive.

• Responsible for separation of contents from its immediate surroundings
• Maintenance of shape of the animal cell
• Checks the entrance of ions and solutes