Cell Theory and Plant Cell Components

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Questions and Answers

What is the primary function of the cell wall in plant cells?

Produces energy for the cell

Provides shape and structure to the cell (correct)

Acts as a storage unit for nutrients

Regulates the flow of substances in and out of the cell

Which scientist proposed that all living cells arise from pre-existing cells?

Matthias Schleiden

Rudolf Virchow (correct)

Theodor Schwann

Robert Hooke

What can be observed only under an electron microscope?

Plasma membrane

Basic cell structure

Ultrastructure of a cell (correct)

Cell division process

Which component of the plant cell is responsible for photosynthesis?

Chloroplast Signup and view all the answers

What is the main characteristic of the plasma membrane?

Thin and semi-permeable Signup and view all the answers

What materials primarily make up the plant cell wall?

Cellulose, hemicellulose, and pectin Signup and view all the answers

Which of the following components plays a crucial role in packaging and transport within a plant cell?

Vesicle Signup and view all the answers

Who discovered the nucleus in plant cells?

Robert Brown Signup and view all the answers

What is the primary function of the chloroplasts in plant cells?

To convert light energy into chemical energy Signup and view all the answers

Which structure is primarily responsible for maintaining cell shape and protecting internal contents?

Plasma membrane Signup and view all the answers

What are the distinct regions of chloroplasts?

Grana and stroma Signup and view all the answers

What is the main role of mitochondria in a cell?

To provide energy through ATP synthesis Signup and view all the answers

What key component does the nucleoplasm contain?

Chromatin fibers Signup and view all the answers

Which of the following is a correct statement about the roles of genes?

They transfer hereditary information Signup and view all the answers

What is found within the inner cavity of the mitochondria?

Matrix containing enzymes Signup and view all the answers

What structure contains pores allowing for molecular transport while maintaining a protective barrier?

Nucleus Signup and view all the answers

What differentiates the size and number of vacuoles in plant cells compared to animal cells?

Animal cells have temporary, small vacuoles. Signup and view all the answers

What is the primary function of vacuoles in plant cells?

Maintain osmotic pressure and provide turgidity. Signup and view all the answers

Which statement correctly describes the process of osmosis?

The passage of water through a semipermeable membrane. Signup and view all the answers

What occurs during plasmolysis in plant cells?

Cell contents pull away from the cell wall due to water loss. Signup and view all the answers

In an experiment observing plasmolysis, which solution would be considered hypertonic?

A solution with a higher solute concentration than the cell. Signup and view all the answers

What is the result of a plant cell being placed in a hypotonic solution?

The cell will remain turgid and healthy. Signup and view all the answers

What materials are required to prepare a stained temporary mount of an onion peel?

Cover slip, safranin, and glycerin. Signup and view all the answers

What characteristic of biological membranes is demonstrated by osmosis?

Selective permeability to water molecules. Signup and view all the answers

Study Notes

Cell Theory

All living organisms are made up of one or more cells
All living cells arise from pre-existing cells by division
The cell is the basic unit of structure and function in all living organisms

Plant Cell Components

Cell Wall
- Non-living outer covering of a plant cell
- Can be tough, rigid, sometimes flexible
- Made up of cellulose, hemicellulose, pectin
- May be thin or thick, multilayered
- Functions
  - Provides definite shape, strength, and rigidity
  - Prevents drying up (desiccation) of cells
  - Helps in controlling cell expansion
  - Protects cell from external pathogens
Plasma Membrane
- Extremely delicate, thin, elastic, living, semi-permeable membrane
- Made up of two layers of lipid molecules in which protein molecules are floating
- Can be observed only under an electron microscope
- Functions
  - Maintains the shape and size of the cell
  - Protects the internal contents of the cell
  - Regulates the entry and exit of substances in and out of the cell
  - Maintains homeostasis
Cytoplasm
- Jelly-like material formed by 80% of water
- Present between the plasma membrane and the nucleus
- Contains a clear liquid portion called cytosol and various particles
- Particles are proteins, carbohydrates, nucleic acids, lipids, and inorganic ions
- Also contains many organelles with distinct structure and function
- Some of these organelles are visible only under an electron microscope
Chloroplast
- Double membrane-bound organelles found mainly in plant cells
- Usually spherical or discoidal in shape
- Shows two distinct regions: grana and stroma
- Grana are stacks of thylakoids (membrane-bound, flattened discs)
- Thylakoids contain chlorophyll molecules which are responsible for photosynthesis
- Stroma is a colorless dense fluid
- Functions
  - Convert light energy into chemical energy in the form of food
  - Provide green colour to leaves, stems, and vegetables
Mitochondria
- Small, rod-shaped organelles bounded by two membranes: inner and outer
- The outer membrane is smooth and encloses the contents of mitochondria
- The inner membrane is folded in the form of shelf-like inward projections called cristae
- Inner cavity is filled with matrix which contains many enzymes
- Contains their own DNA, which are responsible for many enzymatic actions
- Functions
  - Synthesize energy-rich compound ATP
  - ATP molecules provide energy for the vital activities of living cells
Nucleus
- Nucleus has a double-layered covering called the nuclear membrane
- The nuclear membrane has pores of diameter about 80-100 nm
- Colorless dense sap present inside the nucleus known as nucleoplasm
- Nucleoplasm contains round shaped nucleolus and a network of chromatin fibers
- Fibers are composed of deoxyribonucleic acid (DNA) and protein histone
- These fibers condense to form chromosomes during cell division
- Chromosomes contain stretches of DNA called genes
- Genes transfer the hereditary information from one generation to the next
- Functions
  - Control all the cell activities like metabolism, protein synthesis, growth, and cell division
  - Nucleolus synthesizes ribonucleic acid (RNA) to constitute ribosomes
  - Store hereditary information in genes
Vacuoles
- Single membrane sacs filled with liquid or sap (water, sugar, and ions)
- In animal cells, vacuoles are temporary, small in size, and few in number
- In plant cells, vacuoles are large and more in number
- May be contractile or non-contractile
- Functions
  - Store various substances including waste products
  - Maintain osmotic pressure of the cell
  - Provide turgidity and rigidity to plant cells

Osmosis

Passage of water from a region of low concentration of solute to a region of high concentration, across a semipermeable membrane
Isotonic: Same solute concentration
Hypotonic: Low solute concentration
Hypertonic: High solute concentration

Plasmolysis

Loss of water from the cell by osmosis
This is evident when the cell contents pull away from the rigid cell wall as the water moves out
Steps of Plasmolysis
- Initial stage: The cell remains in a turgid state
- Plasmolysis begins: The protoplasm starts shrinking
- Continued Plasmolysis: Cytoplasmic contents pull away from the cell wall, causing a space between the cell wall and the protoplasm
- Complete Plasmolysis: The protoplasm is shrunk to a very small size

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Description

Explore the fundamental concepts of cell theory and the essential components of plant cells. This quiz covers the structure, function, and significance of cell walls and plasma membranes in plant biology. Test your knowledge of these critical topics in cellular biology!