Sci Ch-7

Describe the variation in cells in terms of number.

Describe the variation in cells in terms of number.

Organisms may be composed of one cell or many cells. Unicellular organisms consist of a single cell, while multicellular organisms consist of many cells.

Define unicellular organisms and provide examples.

Unicellular organisms are organisms whose body consists of a single cell. Examples include Amoeba, Paramoecium, Euglena, and bacteria.

Describe the vital activities performed by a single cell in a unicellular organism.

In a unicellular organism, a single cell performs all vital activities such as feeding, movement, respiration, and reproduction.

Define multicellular organisms and provide examples.

Multicellular organisms are organisms whose body consists of many cells. Examples include most plants and animals, including human beings.

Describe the variation in cells in terms of shape.

Different cells, carrying out different functions, exist in different shapes.

Describe the different shapes that cells can have.

Cells can be disc-shaped, polygonal, rectangular, branched, or irregular.

What is the specific function of nerve cells?

Nerve cells carry messages between different parts of the body.

How do muscle cells contribute to movement?

Muscle cells help in movement through contraction and expansion.

Explain why skin cells are flat and broad in shape.

Skin cells cover a large area, so they are flat and broad in shape.

What is the variation in size of cells?

Cell size can range from microscopic (a millionth of a meter) to a few centimeters.

Give an example of the smallest cells.

The smallest cells are bacteria, which generally range in size from 0.1 to 0.5 micrometers.

What is the largest cell in terms of size?

The largest cell is the egg of an ostrich, which is 170 millimeters in diameter.

Which cells are believed to be the longest in the human body?

Nerve cells are believed to be the longest cells in the human body.

Describe the difference between prokaryotic and eukaryotic cells.

Prokaryotic cells lack a well-defined nucleus, while eukaryotic cells have a well-defined nucleus.

What is the cell theory?

The cell theory states that all organisms are made of one or more cells and cells arise from pre-existing cells.

Define prokaryotes.

Prokaryotes are organisms that have cells lacking a well-defined nucleus.

How are eukaryotic cells different from prokaryotic cells?

Eukaryotic cells have a well-defined nucleus.

What are the two types of mounts used to view cells under a microscope?

The two types of mounts are dry mount and wet mount.

Describe the process of mounting a specimen on a glass slide.

Mounting is the process of preparing a specimen on a glass slide for viewing under a microscope.

Do viruses fall under the category of prokaryotes or eukaryotes?

Viruses are neither prokaryotes nor eukaryotes.

Describe the structure of a well-defined nucleus.

The well-defined nucleus is a membrane-bound organelle found in eukaryotic cells. It contains the cell's genetic material, including DNA and RNA.

What is the function of a flagellum?

A flagellum is a whip-like structure found in some cells that helps with cell movement.

Define cytoplasm.

The cytoplasm is the gel-like substance that fills the cell and surrounds the organelles.

What is the difference between a dry mount and a wet mount?

A dry mount is used for viewing inanimate objects and does not require water, while a wet mount is used for viewing living specimens and requires water or glycerine.

Describe the process of preparing a wet mount.

To prepare a wet mount, a small piece of the specimen is placed at the center of a slide with one or two drops of water. It is then covered with a coverslip and viewed under a microscope.

What are some commonly used staining dyes in microscopy?

Some commonly used staining dyes in microscopy include iodine solution, safranin, methylene blue, and crystal violet.

What is the function of the cell membrane?

The cell membrane controls the movement of substances in and out of the cell and provides protection and support for the cell.

Describe the structure of a prokaryotic cell of a bacterium.

A prokaryotic cell of a bacterium lacks a well-defined nucleus and other membrane-bound organelles. It has a cell membrane, cytoplasm, and genetic material in the form of a single circular DNA molecule.

What is the aim of observing the structure of a single cell (hen's egg)?

The aim is to study the structure of a single cell, specifically the yolk of a hen's egg, to understand its components and organization.

Describe the structure of a cell.

A cell contains both living and non-living parts, including the cell membrane, cytoplasm, and nucleus.

Who discovered the cell and when?

Robert Hooke discovered the cell in 1664.

What did Robert Hooke observe when examining a slice of cork under a microscope?

He observed that a slice of cork is made up of tiny honeycomb-like compartments, which he called 'cells'.

What is the function of a cell membrane?

The cell membrane is the outermost covering of a cell, protecting it and demarcating it from other cells. It is selectively permeable.

Describe the function of the cell membrane.

The cell membrane allows certain substances to pass through while restricting others.

What is the main difference between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER)?

RER has attached ribosomes, while SER does not.

Define the function of mitochondria in a cell.

Mitochondria are the powerhouses of the cell, responsible for energy production.

Describe the role of plastids in plant cells.

Plastids are organelles that contain pigments and have specific functions, such as chloroplasts for photosynthesis.

What is the function of the cytoplasm in a cell?

The cytoplasm is a viscous jelly-like substance that serves as the site for most of the cell's chemical reactions.

What is the main difference between plant cells and animal cells in terms of the cell wall?

Plant cells have an additional layer called the cell wall, which is made up of cellulose and provides rigidity.

Describe the structure of mitochondria.

Mitochondria are double membrane-bound organelles that are rod-shaped or spherical in structure.

What are the three types of plastids found in plant cells?

The three types of plastids are chloroplasts, chromoplasts, and leucoplasts, each with a specific pigment and function.

Describe the function of chromoplasts.

Chromoplasts contain non-green pigments that give color to flowers and fruits.

What is the function of centrosomes?

Centrosomes initiate and regulate cell division.

Define Golgi apparatus.

The Golgi apparatus is responsible for the packaging and transporting of fats and proteins, and helps in the formation of lysosomes.

What is the function of vacuoles in plant cells?

Vacuoles store excess water, useful minerals, pigments, and other substances, and maintain the shape of the plant cell.

Describe the research contribution of Har Gobind Khorana.

Har Gobind Khorana discovered the manner in which genetic code was carried in nucleic acids and how nucleotides controlled the synthesis of proteins in a cell.

Describe the function of vacuoles in animal cells.

Vacuoles in animal cells are responsible for storing water, nutrients, and waste materials.

What are lysosomes and what is their function?

Lysosomes contain enzymes that digest cells and various materials. In times of emergency, they can burst and destroy the cell.

Define the nucleus and its role in the cell.

The nucleus is considered the brain of the cell. It is surrounded by a double-membrane called the nuclear membrane and contains nucleoplasm and chromatin fibres. It carries genes and transfers characteristics to new cells during cell division.

What is the function of the endoplasmic reticulum?

The endoplasmic reticulum is an interconnected network involved in the synthesis, storage, and transport of cell products. It consists of tubules and channels.

Describe the role of ribosomes in the cell.

Ribosomes are small granular structures found in the cytoplasm. They are the primary sites for protein synthesis and can be attached to the surface of the endoplasmic reticulum.

Describe the structure and function of the nuclear membrane.

The nuclear membrane is a double-layered membrane that surrounds the nucleus of a cell. It acts as a barrier, controlling the movement of substances in and out of the nucleus.

What is the main function of mitochondria?

Mitochondria are responsible for producing energy in the form of ATP through cellular respiration.

Define nucleoplasm.

Nucleoplasm is the viscous jelly-like substance within the nucleus of a cell. It contains various components, including the chromosomes and nucleolus.

Describe the role of the endoplasmic reticulum in a cell.

The endoplasmic reticulum is a network of membranes involved in the synthesis, folding, and transport of proteins and lipids within the cell.

What is the function of ribosomes in a cell?

Ribosomes are responsible for protein synthesis in a cell. They read the genetic information from mRNA and assemble amino acids into proteins.

Describe the materials needed for comparing a plant cell and an animal cell.

Onion, blade, forceps, glass slides, coverslip, glycerine, iodine solution, dropper, blotting paper, and microscope.

What is the function of the cell wall in a plant cell?

Provides structural support and protection.

How can you differentiate a plant cell from an animal cell under a microscope?

Plant cells have large vacuoles and thick cell walls.

What is the function of the Golgi apparatus?

Modifies, sorts, and packages proteins for transport.

Describe the process of preparing an onion peel for observation under a microscope.

Cut out a portion of the onion, separate the fleshy scales, peel out a piece of the onion scale, place it on a glass slide, add a drop of iodine solution, and cover it with a coverslip.

Describe the appearance of a plant cell under a microscope.

Large vacuoles and thick cell walls are visible.

Describe the aim of the activity.

The aim of the activity is to prepare a temporary slide of human cheek cells and observe them under a microscope.

List the materials needed for the activity.

The materials needed for the activity are a plastic spoon, forceps, glass slides, coverslip, distilled water, dropper, blotting paper, and microscope.

Explain the method of preparing the slide.

The method involves gently scraping the inner lining of the cheek with the backside of a plastic spoon, placing a small piece of the scraped lining on a glass slide with distilled water, and covering it with a coverslip.

What can be observed under the microscope when viewing the slide?

Under the microscope, you should be able to see the cell membrane, cytoplasm, and nucleus of the cheek cells.

What leads to an increase in the size of cells?

The food that we eat leads to an increase in the size of cells.

What is the process called when a cell divides into two?

The process is called cell division.

Why does growth occur in the body?

Growth occurs because of an increase in the number of cells in the body as a result of cell division, not because of an increase in the size of cells.

Describe the role of cell division in organisms.

Cell division is responsible for growth in organisms and replaces dead or damaged cells.

Define a cell.

A cell is the smallest structural and functional unit of an organism.

What are unicellular organisms?

Unicellular organisms are organisms whose body consists of a single cell.

Describe prokaryotic cells.

Prokaryotic cells are cells that lack a well-defined nucleus surrounded by a nuclear membrane.

What are organelles?

Organelles are living, membrane-bound bodies that have definite shapes and functions within a cell.