The Fundamental Unit of Life

Prokaryotic cells lack a membrane-bound nucleus and most membrane-bound organelles, while eukaryotic cells have both

Step 1: The key difference between prokaryotic and eukaryotic cells lies in the presence or absence of a membrane-bound nucleus. Step 2: Prokaryotic cells (like bacteria) have a nucleoid region – a poorly defined nuclear area with no nuclear membrane around the DNA. Step 3: Eukaryotic cells have a well-defined nucleus surrounded by a double-layered nuclear membrane. Step 4: Additionally, prokaryotic cells lack membrane-bound organelles such as mitochondria, ER, and Golgi apparatus. Step 5: Option A is wrong because plant cells (eukaryotic) DO have cell walls. Option C is wrong because eukaryot

Smooth Endoplasmic Reticulum (SER) synthesises lipids and Rough Endoplasmic Reticulum (RER) synthesises proteins – both contribute to membrane formation

Step 1: The plasma membrane is made up of lipids and proteins. Step 2: The Smooth Endoplasmic Reticulum (SER) is responsible for synthesising fat molecules (lipids) required for cell membrane formation. Step 3: The Rough Endoplasmic Reticulum (RER) has ribosomes on its surface that synthesise proteins needed for the membrane. Step 4: Both these components – lipids from SER and proteins from RER – come together to build new membrane material. This process is called MEMBRANE BIOGENESIS. Step 5: The Golgi apparatus helps in modification and packaging but does not make membrane components by itsel

When there is severe disturbance in cellular metabolism due to physical or chemical damage to the cell

Step 1: Lysosomes are membrane-bound sacs containing powerful digestive enzymes capable of breaking down all organic materials. Step 2: Under normal conditions, the lysosomal membrane keeps these enzymes safely contained and they perform routine tasks like digesting foreign materials and worn-out organelles. Step 3: When a cell undergoes severe stress – such as physical damage, chemical poisoning, or metabolic disturbance – the lysosomal membrane may rupture. Step 4: Once the membrane bursts, the powerful digestive enzymes are released into the cytoplasm and begin to digest the cell's own cont

Diffusion – both gases move from regions of higher concentration to regions of lower concentration

Step 1: Diffusion is the spontaneous movement of a substance from a region of HIGH concentration to a region of LOW concentration – it requires NO energy. Step 2: CO₂ builds up to a HIGH concentration inside the cell (as a waste product of respiration). The concentration of CO₂ outside the cell is LOW. Therefore CO₂ diffuses OUT of the cell. Step 3: O₂ is consumed inside the cell for respiration, so its concentration inside becomes LOW. The concentration outside is HIGH. Therefore O₂ diffuses INTO the cell. Step 4: Osmosis (Option D) specifically refers to the diffusion of WATER molecules only