Chapter 7 Section 1: Cell Discovery and Theory Flashcards - Learn and Test Yourself

Chapter 7 Section 1 Cell Discovery And Theory Study Guide Answerszip

Are you looking for a comprehensive guide on chapter 7 section 1 cell discovery and theory? If so, you have come to the right place. In this article, we will cover everything you need to know about this topic, from the invention of the microscope and the discovery of cells to the structure and function of the plasma membrane to the comparison between prokaryotic and eukaryotic cells. By the end of this article, you will have a clear understanding of the concepts and facts related to cell biology.

Chapter 7 Section 1 Cell Discovery And Theory Study Guide Answerszip

The Invention of the Microscope and the Discovery of Cells

The study of cells would not be possible without one important tool: the microscope. A microscope is an instrument that magnifies objects that are too small to be seen by the naked eye. The invention of the microscope opened up a whole new world for scientists who wanted to explore the structure and function of living things.

Robert Hooke and His Observation of Cork Cells

One of the first scientists who used a microscope to observe cells was Robert Hooke (1635-1703), an English physicist and naturalist. In 1665, he published a book called Micrographia, in which he described his observations of various objects under a compound microscope, which uses two or more lenses to magnify an image. One of the objects he examined was a thin slice of cork, which is the bark of a tree. He noticed that the cork had tiny holes or pores that looked like honeycombs. He called these structures "cellulae" or "small rooms", because they reminded him of the cells or rooms that monks lived in. He did not know that these cells were actually the dead remains of plant cells, and that living cells were much more complex and diverse.

Anton van Leeuwenhoek and His Observation of Living Cells

Another pioneer in the field of microscopy was Anton van Leeuwenhoek (1632-1723), a Dutch cloth merchant and amateur scientist. He used a simple microscope, which has only one lens, to observe various types of living cells. He made his own microscopes by grinding and polishing tiny glass spheres, which he mounted on metal plates. He was able to achieve a magnification of up to 300 times, which was much higher than the compound microscopes at that time. He observed many kinds of living cells, such as bacteria, protozoa, blood cells, and sperm cells. He called them "animalcules" or "little animals", and wrote detailed descriptions and drawings of them. He was the first person to see and document the existence of microorganisms, which are living things that are too small to be seen by the unaided eye.

The Development of the Cell Theory

The observations of Hooke and Leeuwenhoek laid the foundation for the development of the cell theory, which is one of the most important principles in biology. The cell theory states that:

• All living things are composed of one or more cells.

• Cells are the basic units of structure and function in living things.

• New cells are produced from existing cells.

The cell theory was formulated by several scientists over the course of the 19th century. Some of the major contributors were:

• Matthias Schleiden (1804-1881), a German botanist who stated that all plants are made of cells.

• Theodor Schwann (1810-1882), a German zoologist who stated that all animals are made of cells.

• Rudolf Virchow (1821-1902), a German physician who stated that all cells come from pre-existing cells.

The cell theory revolutionized the understanding of life and its diversity. It also led to the discovery of many other aspects of cell biology, such as cell division, cell differentiation, cell metabolism, and cell communication.

The Structure and Function of the Plasma Membrane

One of the most important features of a cell is its plasma membrane, which is the boundary between the cell and its environment. The plasma membrane separates prokaryotic and eukaryotic cells from the watery environment in which they exist. It also regulates what enters and exits the cell, thus maintaining homeostasis, which is the process of keeping a stable internal condition.

The Composition and Properties of the Plasma Membrane

The plasma membrane is made up of a phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol. A phospholipid is a molecule that has a glycerol backbone, two fatty acid chains, and a phosphate-containing group or compound. The fatty acid chains are hydrophobic, meaning they repel water, while the phosphate group is hydrophilic, meaning it attracts water. The phospholipids arrange themselves in such a way that their hydrophobic tails face inward and their hydrophilic heads face outward, forming two layers. This allows the plasma membrane to form a barrier between the inside and outside of the cell.

The plasma membrane also contains various proteins that perform different functions, such as transporting substances across the membrane, receiving signals from other cells, attaching to other cells or structures, or catalyzing chemical reactions. Some proteins are embedded within the phospholipid bilayer, while others are attached to either side of it. The plasma membrane also has carbohydrates attached to some proteins or lipids, which act as markers or identifiers for the cell. They help the cell recognize other cells or molecules that are friendly or harmful. Additionally, the plasma membrane has cholesterol molecules interspersed within the phospholipid bilayer, which help stabilize and maintain its fluidity.

The Fluid Mosaic Model of the Plasma Membrane

The plasma membrane is not a rigid or static structure, but rather a dynamic and flexible one. It is constantly changing and adapting to the needs of the cell and its environment. The phospholipids and proteins in the plasma membrane can move laterally within the bilayer, creating a fluid-like behavior. This allows the plasma membrane to adjust its shape and size, as well as to form vesicles or small sacs that transport substances in and out of the cell. The plasma membrane also has a mosaic-like appearance, with different types and patterns of proteins and carbohydrates embedded in it. This gives the plasma membrane a variety of functions and properties, depending on the location and type of cell.

The Role of Transport Proteins in the Plasma Membrane

One of the main functions of the plasma membrane is to transport substances across it. Some substances can easily pass through the phospholipid bilayer by simple diffusion, which is the movement of molecules from an area of higher concentration to an area of lower concentration. For example, oxygen and carbon dioxide can diffuse across the plasma membrane because they are small and nonpolar molecules. However, other substances cannot pass through the phospholipid bilayer by simple diffusion because they are too large, polar, or charged. For example, glucose, amino acids, ions, and water cannot diffuse across the plasma membrane because they are either too big or have an uneven distribution of electrons. These substances need the help of transport proteins to cross the plasma membrane.

Transport proteins are specialized proteins that facilitate the movement of substances across the plasma membrane by passive transport or active transport. Passive transport does not require energy from the cell, while active transport does require energy from the cell. There are different types of transport proteins that perform different types of passive or active transport.

Some examples of passive transport are:

• Osmosis: The diffusion of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. A solute is a substance that is dissolved in a solvent, such as salt in water. Osmosis helps cells maintain their water balance and volume.

• Facilitated diffusion: The diffusion of molecules across a selectively permeable membrane with the help of transport proteins. These transport proteins act as channels or carriers that allow specific molecules to pass through. For example, glucose can enter the cell by facilitated diffusion using a glucose transporter protein.

Some examples of active transport are:

• Endocytosis: The process of taking in large substances or particles into the cell by forming a vesicle from the plasma membrane. The vesicle then moves into the cytoplasm and fuses with other organelles, such as lysosomes, that break down or process its contents. There are different types of endocytosis, such as phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis (specific uptake).

• Exocytosis: The process of releasing large substances or particles out of the cell by forming a vesicle from within the cell. The vesicle then moves to the plasma membrane and fuses with it, releasing its contents to the outside. Exocytosis is used for secretion or export of substances, such as hormones, enzymes, or waste products.

The Comparison Between Prokaryotic and Eukaryotic Cells

Another important aspect of cell biology is the comparison between prokaryotic and eukaryotic cells. Prokaryotic and eukaryotic cells are two major types of cells that differ in their structure and function. Prokaryotic cells are simpler and smaller than eukaryotic cells, while eukaryotic cells are more complex and larger than prokaryotic cells.

The Characteristics of Prokaryotic Cells

Prokaryotic cells are cells that lack a nucleus and membrane-bound organelles. They have a single circular chromosome that contains their genetic material (DNA), which is located in a region called the nucleoid. They also have small circular pieces of DNA called plasmids that can be transferred between cells or provide extra functions. They have ribosomes that synthesize proteins, but their ribosomes are smaller and simpler than those in eukaryotic cells. They have a plasma membrane that encloses their cytoplasm, which is a fluid-like substance that contains various molecules and enzymes. They may also have a cell wall that provides support and protection, and a capsule that covers the cell wall and helps the cell adhere to surfaces or evade the immune system. Some prokaryotic cells have appendages, such as flagella (long whip-like structures) or pili (short hair-like structures), that help them move or attach to other cells. Prokaryotic cells are mostly unicellular, meaning they exist as single cells. However, some prokaryotic cells can form colonies or biofilms, which are groups of cells that stick together and communicate with each other. Prokaryotic cells are divided into two domains: bacteria and archaea. Bacteria are the most common and diverse prokaryotes, while archaea are more ancient and extreme prokaryotes that live in harsh environments.

The Characteristics of Eukaryotic Cells

Eukaryotic cells are cells that have a nucleus and membrane-bound organelles. They have multiple linear chromosomes that contain their genetic material (DNA), which is enclosed by a double membrane called the nuclear envelope. They also have ribosomes that synthesize proteins, but their ribosomes are larger and more complex than those in prokaryotic cells. They have a plasma membrane that encloses their cytoplasm, which is a fluid-like substance that contains various molecules and organelles. Organelles are specialized structures that perform specific functions within the cell. Some of the most important organelles are:

• Mitochondria: The powerhouses of the cell that produce energy (ATP) by breaking down glucose and oxygen in a process called cellular respiration.

• Chloroplasts: The sites of photosynthesis in plant cells and some algae cells that convert light energy into chemical energy (glucose) by using carbon dioxide and water.

• Endoplasmic reticulum (ER): A network of membranes that transport materials within the cell and synthesize lipids and proteins. The ER can be rough (with ribosomes attached) or smooth (without ribosomes attached).

• Golgi apparatus: A stack of flattened membranes that modify, sort, and package proteins and lipids for export or use within the cell.

• Lysosomes: Sacs of enzymes that digest or recycle unwanted or damaged materials within the cell.

• Vacuoles: Sacs of fluid that store water, nutrients, waste products, or other substances within the cell. Plant cells have a large central vacuole that helps maintain their shape and turgor pressure.

• Cytoskeleton: A network of protein fibers that provide support, shape, movement, and organization to the cell and its organelles.

Eukaryotic cells are either unicellular or multicellular, meaning they can exist as single cells or as part of a larger organism. Multicellular eukaryotes can have different types of cells that perform different functions and form tissues, organs, and organ systems. Eukaryotic cells are divided into four kingdoms: protists, fungi, plants, and animals. Protists are diverse and mostly unicellular eukaryotes that can be autotrophic (make their own food) or heterotrophic (consume other organisms). Fungi are heterotrophic eukaryotes that decompose organic matter and absorb nutrients from their environment. Plants are autotrophic eukaryotes that have cell walls made of cellulose and chloroplasts for photosynthesis. Animals are heterotrophic eukaryotes that lack cell walls and chloroplasts and ingest their food.

The Similarities and Differences Between Prokaryotic and Eukaryotic Cells

Prokaryotic and eukaryotic cells have some similarities and differences in their structure and function. Some of the similarities are:

• Both types of cells have a plasma membrane, cytoplasm, ribosomes, DNA, and can break down molecules to generate energy.

• Both types of cells use the same genetic code to store and transmit information.

• Both types of cells share a common ancestor and evolutionary history.

Some of the differences are:

• Prokaryotic cells are smaller and simpler than eukaryotic cells.

• Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have them.

• Prokaryotic cells have a single circular chromosome, while eukaryotic cells have multiple linear chromosomes.

• Prokaryotic cells divide by binary fission, while eukaryotic cells divide by mitosis or meiosis.

or multicellular.

• Prokaryotic cells belong to two domains (bacteria and archaea), while eukaryotic cells belong to four kingdoms (protists, fungi, plants, and animals).

Conclusion

In this article, we have covered the main points of chapter 7 section 1 cell discovery and theory. We have learned about the invention of the microscope and the discovery of cells by Robert Hooke and Anton van Leeuwenhoek. We have learned about the development of the cell theory by Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. We have learned about the structure and function of the plasma membrane and its components, such as phospholipids, proteins, carbohydrates, cholesterol, and transport proteins. We have learned about the comparison between prokaryotic and eukaryotic cells and their characteristics, similarities, and differences. We hope that this article has helped you understand the concepts and facts related to cell biology.

Thank you for reading this article. If you have any questions or comments, please feel free to contact us. We would love to hear from you.

FAQs

Here are some frequently asked questions and answers about chapter 7 section 1 cell discovery and theory:

• What is the difference between a compound microscope and a simple microscope?A compound microscope uses two or more lenses to magnify an image, while a simple microscope uses only one lens to magnify an image.

• What are the three principles of the cell theory?The three principles of the cell theory are: all living things are composed of one or more cells; cells are the basic units of structure and function in living things; new cells are produced from existing cells.

• What is selective permeability?Selective permeability is the quality of a plasma membrane that allows some substances to pass through while blocking others.

• What are the two types of passive transport?The two types of passive transport are osmosis and facilitated diffusion.

• What are the two types of active transport?The two types of active transport are endocytosis and exocytosis.

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