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Cell - The Cell Interior - A Coordinated W orking System

Grade 9CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The cell interior is composed of the cytoplasm and various cell organelles that work together as a coordinated system to perform vital life processes.

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The Endoplasmic Reticulum (ER) is a large network of membrane-bound tubes and sheets. Rough ER (RER) has ribosomes attached for protein synthesis, while Smooth ER (SER) helps in the manufacture of fat molecules, or lipids, and detoxification of poisons.

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The Golgi Apparatus, first described by Camillo Golgi, consists of a system of membrane-bound vesicles (cisterns). Its functions include the storage, modification, and packaging of products in vesicles.

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Lysosomes are the waste disposal system of the cell. They contain powerful digestive enzymes capable of breaking down all organic material. They are often called 'suicide bags' because if the cell gets damaged, lysosomes may burst and the enzymes digest their own cell.

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Mitochondria are known as the 'powerhouse of the cell'. They have two membrane coverings. The inner membrane is deeply folded to increase the surface area for ATPATP (Adenosine Triphosphate) generating chemical reactions.

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Plastids are present only in plant cells. There are two types: Chromoplasts (colored plastids like Chloroplasts containing chlorophyll) and Leucoplasts (white or colorless plastids used for storage of starch, oils, and protein granules).

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Vacuoles are storage sacs for solid or liquid contents. They are small-sized in animal cells while plant cells have very large vacuoles that provide turgidity and rigidity to the cell.

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Coordinated functioning: Proteins synthesized by RER and lipids by SER are packaged by the Golgi apparatus and sent to various targets inside and outside the cell.

📐Formulae

Cellular Respiration: C6H12O6+6O2→6CO2+6H2O+Energy (ATP)\text{Cellular Respiration: } C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}

Photosynthesis: 6CO2+6H2O→Light, ChlorophyllC6H12O6+6O2\text{Photosynthesis: } 6CO_2 + 6H_2O \xrightarrow{\text{Light, Chlorophyll}} C_6H_{12}O_6 + 6O_2

ATP⇌ADP+Pi+Energy\text{ATP} \rightleftharpoons \text{ADP} + P_i + \text{Energy}

💡Examples

Problem 1:

Why is the inner membrane of mitochondria deeply folded into cristae?

Solution:

The inner membrane of mitochondria is folded into cristae to create a large surface area for chemical reactions. Specifically, it provides more space for the enzymes involved in the production of ATPATP molecules.

Explanation:

Mitochondria produce energy through aerobic respiration. By increasing the surface area (AA), the cell can host more electron transport chains and ATPATP synthase complexes, maximizing energy output.

Problem 2:

What would happen to the life of a cell if there was no Golgi apparatus?

Solution:

If the Golgi apparatus were absent: 1. Packaging and dispatch of materials synthesized by the ER would stop. 2. Storage and modification of cellular products would not occur. 3. Lysosomes would not be formed, leading to the accumulation of waste and worn-out organelles.

Explanation:

The Golgi apparatus acts as a shipping and receiving department. Without it, the proteins (PP) and lipids (LL) produced would not reach their functional destinations.

Problem 3:

A cell has a high concentration of CO2CO_2 inside (CinC_{in}) and low concentration outside (CoutC_{out}). How will CO2CO_2 move?

Solution:

CO2CO_2 will move from inside to outside the cell through the process of diffusion.

Explanation:

Diffusion occurs along a concentration gradient. Since Cin>CoutC_{in} > C_{out}, the net movement of molecules is towards the exterior until equilibrium is reached.