Chapter 4 cell structure and function pdf writer
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- Lakhmir Singh Science Class 8 Solutions Chapter 8 Cell Structure and Functions
- Book: General Biology (Boundless)
- Cell (biology)
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This video is taught at the high school level. Topics:- 3 Main sections- Cytoplasm
Chromosome , the microscopic threadlike part of the cell that carries hereditary information in the form of genes. A defining feature of any chromosome is its compactness. The structure and location of chromosomes are among the chief differences between viruses, prokaryotes , and eukaryotes.
Lakhmir Singh Science Class 8 Solutions Chapter 8 Cell Structure and Functions
These solutions for Cell Structure And Functions are extremely popular among Class 8 students for Science Cell Structure And Functions Solutions come handy for quickly completing your homework and preparing for exams.
All questions and answers from the Living Science Book of Class 8 Science Chapter 8 are provided here for you for free. A unicellular organism is composed of a single cell. This single cell performs all the biological processes required for the maintenance of life activities of a cell. Thus, in case of unicellular organisms, all life activities are performed by a single cell. In a multicellular organism, all cells have the capability to perform all life functions.
Do you agree? Give reasons. Multicellular organisms are composed of large number of cells and every cell is destined for a specific function.
For example, a Red Blood Cell RBC can transport oxygen across the body, but it can not perform the functions of a nerve cell.
Thus, in case of multicellular organisms, all cells do not have the capability of performing all life functions. Cell is the smallest and fundamental unit of life. All living organisms are essentially made up of cells and the functions carried out by cells is responsible for the perpetuation of life.
Nucleus of a cell is also referred to as the brain of the cell. This is because nucleus regulates all the processes within the cell and it also controls all the cellular activities. A cell requires water, minerals and other substances to stay alive. But the cell is covered with a cell membrane.
How do these things reach inside the cell? The cell membrane forms a selective barrier around a cell and restricts the entry of many substances. However, cell membrane allows entry of water, minerals and other substances, which are essential for the survival of a cell. The cells in a tissue have identical shapes and perform identical functions. Cells that constitute tissues generally have similar structure and function.
This is because the concerted functioning of these cells is required for the proper functioning of a tissue. Thus, it can be asserted that cells in the tissues have identical shapes and perform identical functions. How does growth in an organism occur- by growth in the size of cells or by growth in the number of cells? Growth in an organism occurs by the process of cell division. In this process, the cells divide to increase the number of cells.
Organelles that contain a green pigment are only found in plants and not in animals. What are the organelles and the green pigment called? The organelles that contain a green pigment and are selectively found in plants are called chloroplasts. These organelles contain chlorophyll pigment, which allows them to capture solar energy to prepare food. Which of these is multicellular? Mushroom is a multicellular organism. All the other organisms mentioned here, are unicellular.
It divides repeatedly and differentiates into various tissues to develop into a chicken. Which of these is not present in an animal cell? Chloroplasts are present in green plants and serve as the sites of photosynthesis in plants. Which of these is the control centre of the cell? The nucleus contains chromosomes, which divide during cell division. Which organelles are responsible for energy production in a cell? Which of these is not stated by the cell theory?
Cell theory states that all cells are similar in their basic structure and function but not identical. In which of these does a single cell NOT perform all life functions?
Which of these unicellular organisms has no definite shape? It keeps changing its shape. The cell membrane which surrounds the cell does not allow anything to pass through it. True or false? The cell membrane, which surrounds the cell, is porous and allows the passage of specific molecules both inward and outward of the cell.
Chromosomes present in the nucleus act as a storehouse for information needed by the cell to function. In animal cells, vacuoles are usually small in size. Cells are the building blocks of life. They are called so because large number of cells assemble to make the body of a multicellular organism.
Unicellular Organism Multicellular Organism A unicellular organism is made up of a single cell. A multicellular organism is made up of more than one cell. All the functions of the organism such as respiration, digestion and reproduction are preformed by a single cell.
Different organs are present to perform different functions of the organism. Cytoplasm is the basic component of the cell. It is a jelly-like substance present between the cell membrane and nucleus. Various organelles of cell such as mitochondria, ribosomes, and Golgi complex are present in the cytoplasm. Protoplasm is the entire content of a living cell. It includes the cytoplasm and the nucleus of a cell. A tissue is a group of one or more type of cells and their intercellular substance that performs a particular function.
Organelles are organised cell components present in the cytoplasm. Each organelle has a specific function to perform inside the cell. Examples: Ribosomes, mitochondria, vacuoles, etc. What are the lower levels of organization in a multicellular organism? Are these levels also present in unicellular organisms?
The lower levels of organisation in a multicellular organism are as follows: a Cellular level b Tissue level c Organ level d Organ system level These levels are not present in unicellular organisms because their body is made up of a single cell. Plant Cell Animal Cell Cell wall is present. Cell wall is absent. Plastids are found in plant cell. Plastids are absent in animal cell. A mature plant cell has a large central vacuole. An animal cell has many small vacuoles. Cell division is the process of formation of new cells from parent cells.
Cell division is necessary for the growth and development of a multicellular organism because new cells are needed to replace the old and dead cells. Following are the main points of the cell theory of life: a All living organisms are composed of cells and their products. What are the functions of the following in a cell? Cell membrane also protects the cell from injury. Nucleus controls the overall cell metabolism and other activities.
All the hereditary information is located in the genes. Chromosomes control the cell division and cell growth. Vacuoles store food, waste and water. Generally, cells are round, spherical or elongated in shape. Some cells such as nerve cells are quite long and have extensive branching. Some cells such as Amoeba has no fixed shape.
White blood cells in humans can also change its shape. The cell membrane provides shape to the cells of animals and plants. There is a wide variation in the size of the cells also. Most of the cells cannot be seen with naked eye. The smallest cell a bacterium is 0. Longest cells of human body are the nerve cells, which may reach a length of 90 cm.
In general, cell sizes are not related to the size of an organism. However, will there be a difference in the length of the nerve cells in a rat and a giraffe? It is not necessary that nerve cells, which are the longest cells in the body of a multicellular organism, have difference in the length in a rat and a giraffe. White blood cells WBC can squeeze through walls of blood vessels and get into intercellular spaces to fight against germs.
Which property of WBCs allows them to do this? White blood cells like Amoeba can change their shape. This property allows them to squeeze through the walls of blood vessels and get into intercellular spaces to fight against germs.
Book: General Biology (Boundless)
Scientists believe that prokaryotic cells were some of the first life forms on Earth. These cells are still abundant today and can be divided into bacteria and archaea. Prokaryotic cells are fundamental to mastering high school cell biology. Read on to learn about about the various cellular components of prokaryotes. Prokaryotes tend to be simple, single-celled organisms without membrane-bound organelles or a nucleus. Eukaryotes have these structures. Billions of years ago, prokaryotes may have evolved from membrane-bound organic molecules called protobionts.
Question 1. Which instrument was essential for the study of cells? Answer: Microscope was essential for the study of cells. Question 2. What is the basic similarity among all the living organism plants and animals? Answer: The basic similarity among all the living organisms is that they all are made up of cells. Question 3.
The cell from Latin cella , meaning "small room"  is the basic structural, functional, and biological unit of all known organisms. Cells are the smallest units of life, and hence are often referred to as the "building blocks of life". The study of cells is called cell biology , cellular biology, or cytology. Cells consist of cytoplasm enclosed within a membrane , which contains many biomolecules such as proteins and nucleic acids. Organisms can be classified as unicellular consisting of a single cell such as bacteria or multicellular including plants and animals.
The cell theory the cell theory states that all living organisms are made of one or more cells, cells are the basic units of structure and function, and cells come only from pre existing cells. This comprehensive bundle on cells and cell organelles contains everything you need to teach a unit on cell structure and function. The cell smallest unit of life can survive on its own or has potential to do so is highly organized for metabolism senses and responds to environment has potential to reproduce. Chapter 3 cellular structure and function worksheets opening image by sebastian kaulitzki,
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