Question 1. Cell. (or) Cellular organelles.
Answer:
Cellular organelles Definition:
- It is defined as the structural and functional unit of the living body.
Cellular organelles Characteristics:
- Cell needs nutrition and oxygen
- It reproduces by meiosis or mitosis.
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- It produces energy for itself and for repair.
- It eliminates metabolic waste products including carbon dioxide.
- It prevents or invades bacteria from entering into it
Cellular organelles Structure:
- The cell consist of
Question 2. Mitochondria.
Answer:
- Shape: Rod or oval shaped structure.
- Size: Length – 5-12 mm, diameter – 0.5-1 mm.
- Structure: Bilayered membranous organelle.
- Outer membrane.
- It is smooth and encloses the contents of mitochondrion.
- Inner membrane.
- It is formed in the form of cristae.
- Outer membrane.
- Functions:
- Powerhouse of the cell.
- Synthesizes ATP and proteins.
- Initiates apoptosis.
Question 3. Ribosomes.
Answer:
- They are granular and small dot like structures.
Ribosomes Site:
- Some attached to rough endoplasmic reticulum.
- Other are free in cytoplasm.
Ribosomes Function:
- Helps in of proteins synthesis ribosomes attached to rough endoplasmic reticulum synthesizes enzymatic proteins, hormonal proteins, lysosomal proteins and proteins of the cell membrane.
- Free ribosomes synthesizes proteins of haemoglobin, peroxisome and mitochondria.
Question 4. Lysosomes.
Answer:
- They are membrane bound vesicular organelles.
- They are formed by golgi apparatus.
Lysosomes Types:
- Primary lysosome.
- Secondary lysosome.
Lysosomes Functions:
- Degrades macromolecules and worn out organelles
- Secretes melanin and serotonin
- It engulfs bacteria.
Question 5. RNA.
Answer:
- It is formed from DNA.
RNA Structure:
- Consists of a single strand of polynucleotide.
- Each nucleotide is formed by
- Ribose the sugar
- Phosphate
- One of the organic bases.
- Purine adrenine, guanine.
- Pyrimidine-Uracil, cytosine.
RNA Types:
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
Question 6. Apoptosis.
Answer:
Apoptosis Definition:
- It is defined as the programmed cell death under genetic control.
Apoptosis Significance:
- Responsible for regression of duct system during sex differentiation in the foetus.
- Respondible for degeneration and regeneration of neurons.
- Responsible for removal of inappropriate clones of immune cells.
- Responsible for cyclic sheeding of endometrium at the time of menstruation.
- Responsible for cell shed from the tip of the villi in the small intestine.
- Removes auto-aggressive T cells and prevents autoimmune diseases.
- Plays vital role in cellular hoemostasis.
- Useful for removal of a cell that is damaged by a virus or toxin.
Question 7. Components of cell
Answer:
The cell consists of
- Cell membrane – it is protective sheath enveloping the cell body.
- Nucleus – it divides and produces enzymes
- Cytoplasm and its organelles
- Cytoplasm is the fluid present inside the cell
- Endoplasmic reticulum – consists of tubular and microsomal vesicular structures Golgi apparatus shipping department of cell
- Mitochondria-powerhouse of cell
- Lysosomes it is membrane bound vesicular organelle
- Centrosome
- Microtubules and microfilaments
- Ribosomes
- Cytoplasm is the fluid present inside the cell
Question 8. Differences between simple diffusion and facilitated diffusion.
Answer:
Question 90. What is meant by active transport and passive transport across the cell membrane. Give one example for each.
Answer:
Active transport:
- Movement of substances against the chemical or electrical or electrochemical gradient is called active transport.
- It requires energy which is obtained by breakdown of ATP.
- Active transport It includes:
- Primary active transport process
- Transport of sodium and potassium
- Transport of calcium ions
- Transport of hydrogen ions
- Secondary active transport process
- Co transport
- Counter transport
- Carrier type processes – carrier are transport proteins
- Vesicular transport processes – this involves endocytosis and exocytosis.
- Primary active transport process
Passive transport:
- The movement of substances across the cell in this process occurs without the expenditure of energy.
- Example
- Simple diffusion of lipid soluble substances
- Diffusion through protein channels.
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