Chapter-8 cell structure and function

Explanation:

Cytoplasm can be comprehended as the jelly-like substance that fills the cell and surrounds its organelles. It comprises water, salts, organic molecules, and various proteins and performs various cellular processes, including protein synthesis, energy production, and cell division.

Explanation:

As the sketch displays, a human nerve cell, also known as a neuron, has a cell body, dendrites, and an axon. Nerve cells function to transmit electrical and chemical signals throughout the body, allowing for communication between different cells and organs. They play a crucial role in the nervous system, controlling and coordinating the body's responses to internal and external stimuli.

Explanation:

Nucleus, a membrane-bound organelle, contains the cell's genetic material, organized into chromosomes. The nucleus has several parts, including the nuclear envelope, nucleolus, and chromatin. The nuclear envelope is a double membrane surrounding the nucleus, while the nucleolus is a region within the nucleus producing ribosomes. Chromatin is the material that makes up the chromosomes and consists of DNA, RNA, and protein.

Explanation:

Plant and Animal cells share many similarities, such as having a cell membrane, cytoplasm, and genetic material. However, there are several key differences between plant and animal cells:

Cell Wall: Plant cells have a cell wall made of cellulose, which provides support and protection to the cell, while animal cells do not have a cell wall.

Chloroplasts: Chloroplasts contain chlorophyll and enable photosynthesis, while animal cells do not have chloroplasts.

Vacuoles: Plant cells have large central vacuoles that store water and other materials, while animal cells have smaller vacuoles.

Shape: Plant cells are generally rectangular or square-shaped, while animal cells are more irregular in shape.

Mitochondria: Mitochondria, which produce energy for the cell, are more numerous in animal cells than in plant cells.

Lysosomes: Lysosomes, which are organelles that contain digestive enzymes, are more common in animal cells than in plant cells.

Explanation:

The nucleus is a membrane-bound organelle found in eukaryotic cells. It contains the cell's genetic material, which is organized into chromosomes. The nucleus regulates gene expression, controls cell growth and division, and maintains the integrity of the genetic material. The nucleus has several parts, including the nuclear envelope, nucleolus, and chromatin.

Explanation:

The cytoplasm is part of the cell that contains organelles, including the mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, and cytoskeleton.

Explanation:

Difference between eukaryotes and prokaryotes are listed below:

• Eukaryotes contain a membrane-bound nucleus and other complex membrane-bound organelles, while prokaryotes are organisms whose cells lack a nucleus and other membrane-bound organelles. 

• Eukaryotes include all plants, animals, fungi, and protists, while prokaryotes include bacteria and archaea. 

• Eukaryotic cells are generally larger in size and are more complex than prokaryotic cells.

  
  

Explanation:

Chromosomes are found in the nucleus of eukaryotic cells and the nucleoid region of prokaryotic cells. Their function is to carry and organize the cell's genetic material, which is essential for regulating cell growth and division, as well as the inheritance of traits from one generation to the next.

Explanation:

Cells are the fundamental building blocks of living organisms. They are the smallest units that can carry out all the necessary functions of life, such as metabolism, reproduction, and response to their environment.

Explanation: Chloroplasts are specialized organelles that are responsible for photosynthesis in plants. They are found only in plant cells because photosynthesis is a process unique to plants, and chloroplasts are essential for this process.

Explanation:

This statement is incorrect. The basic living unit of an organism is the cell, not the organ. Organs are made up of different types of cells working together to perform a specific function, but without individual cells, organs cannot exist or function properly.

Explanation:

Differences are listed below:

• Unicellular organisms consist of only one cell, while multicellular organisms comprise many cells.

• Unicellular organisms perform all life functions within a single cell, while multicellular organisms have specialized cells that perform different functions.

• Unicellular organisms reproduce asexually, while multicellular organisms can reproduce sexually and asexually.

• Unicellular organisms have a simpler structure and organization, while multicellular organisms have a more complex structure and organization

Explanation:

Cells were not observed before the 17th century due to the lack of advanced technology such as microscopes. The first microscope was invented in the 16th century, but it was not until the 17th century that improvements in lens technology enabled scientists to observe and study cells.

Explanation:

Hooke had to take thin slices of cork to observe the material's structure under his primitive microscope. The slices allowed him to view the individual cells of the cork, which appeared as small, box-like structures that he called "cells" due to their resemblance to the small rooms or "cells" of a monastery.

Explanation:

The only cells visible to the naked eye are the egg cells (ovum) of certain large animals, such as ostrich. These cells are typically several centimeters in diameter and can be observed without needing a microscope.

Explanation:

The four basic elements that constitute 90% of protoplasm are carbon, hydrogen, oxygen, and nitrogen (abbreviated as CHON). These elements are the building blocks of organic molecules, such as proteins, carbohydrates, lipids, and nucleic acids, which are essential for living cells' structure, function, and metabolism.

Explanation:

Protoplasm is a term used to describe the entire living substance within a cell, including the cytoplasm, nucleus, and other organelles. Cytoplasm refers to the gel-like substance that fills the cell and surrounds the organelles, excluding the nucleus. In other words, the cytoplasm is a component of protoplasm.

Explanation:

Yes, some unicellular organisms, such as certain species of protists, algae, and bacteria, can be seen with the naked eye, although most are too small to be seen without a microscope. Some species may form colonies or aggregates visible to the naked eye.

Explanation:

The Golgi apparatus, also known as Golgi bodies, is a stack of flattened membrane-bound sacs found in eukaryotic cells. Major function of Golgi bodies is to modify and package proteins and lipids produced by the endoplasmic reticulum for transport to their final destination within or outside the cell.

Explanation:

The organelle responsible for cell division in animal cells is the centrosome, which consists of a pair of centrioles and plays a crucial role in organizing the microtubules that form the spindle fibers during mitosis. 

Explanation:

Genes are located on the chromosomes in the nucleus of a cell. Chromosomes are long, coiled-up strands of DNA and proteins that carry genetic information from generation to generation. DNA is the molecule that encodes genetic information used to build and maintain all living organisms.

Explanation:

Mitochondria and chloroplasts are two organelles found in eukaryotic cells that contribute to the cell's energy metabolism in different ways. Mitochondria is the powerhouse of the cell. They are responsible for cellular respiration, a process that aids cells to convert glucose and oxygen into ATP. Chloroplasts are found in plant cells and are responsible for the process of photosynthesis: converting sunlight into energy in the form of glucose.

Explanation:

Ribosomes are responsible for protein synthesis, which is building proteins from amino acids. They read the genetic code in messenger RNA (mRNA) and use it to link together specific sequences of amino acids.

Explanation:

Peroxisomes are organelles responsible for detoxifying harmful substances in the cell, such as hydrogen peroxide. They also play a role in lipid metabolism by breaking down fatty acids for energy production.

Explanation:

The endoplasmic reticulum (ER) plays a crucial role in protein synthesis and modification by providing a platform for protein synthesis, folding, and modification. The rough ER is studded with ribosomes that synthesize proteins, which are then folded and modified in the ER lumen.

Explanation:

Cell division is the process by which cells reproduce and is essential for growth, development, and repair in all living organisms. The process involves several stages, including the interphase, mitosis, and cytokinesis. Each stage is essential for the proper replication and division of cells.

Explanation:

Cells communicate with each other through a process called intercellular signaling. This process involves a range of mechanisms that allow cells to send and receive information, which is critical for coordinating physiological processes and maintaining homeostasis.

One common mechanism for intercellular signaling is using chemical messengers, such as hormones, neurotransmitters, and cytokines. These molecules are secreted by cells and travel through the bloodstream to reach their target cells.

Other mechanisms include direct contact between cells, such as through gap junctions and the use of signaling pathways that activate receptors on the cell surface. These pathways can trigger a cascade of intracellular signaling events that ultimately lead to gene expression or cellular behavior changes.

In summary, cells communicate through various mechanisms, including chemical messengers, direct contact, and signaling pathways. This communication is essential for maintaining proper cellular function and homeostasis in multicellular organisms.