The Cell And Its Functions

The phosphate end of the phospholipid is hydrophilic because it contains a charged phosphate group that can interact with water molecules. On the other hand, the fatty acid portion is hydrophobic because it is made up of long hydrocarbon chains that do not interact well with water. This arrangement of hydrophilic and hydrophobic regions allows phospholipids to form a bilayer in aqueous environments, such as cell membranes, with the hydrophilic heads facing outward towards the water and the hydrophobic tails facing inward away from the water.

Fat cells, also known as adipocytes, do not contain water. They are specialized cells that store fat in the form of triglycerides. These cells have a large lipid droplet occupying most of their volume, which displaces other cellular components, including water. This lack of water content contributes to the low density of fat tissue compared to other tissues in the body.

The plasma membrane is a thin, pliable, elastic structure that envelops the cell. It is approximately 7.5-10 nanometers thick.

Especially important lipids are phospholipids and cholesterol, which together constitute only about 2 percent of the total cell mass. The significance of phospholipids and cholesterol is that they are mainly insoluble in water and therefore are used to form the cell membrane and intracellular membrane barriers that separate the different cell compartments.

The correct answer is 70-85. This suggests that the cell contains between 70% and 85% water.

Pinocytosis is a process by which cells engulf extracellular fluid and small particles. Macrophages are specialized immune cells that are highly efficient in phagocytosis, including pinocytosis. They play a crucial role in engulfing and destroying pathogens, dead cells, and other debris in the body. Therefore, macrophages have a high rate of pinocytosis compared to other cell types such as monocytes, blood cells, and lymphocytes.

Membrane proteins are mainly glycoproteins because they are composed of both proteins and carbohydrates. These glycoproteins play crucial roles in various cellular processes such as cell signaling, transport of molecules across the cell membrane, and cell adhesion. The presence of carbohydrates on the surface of these proteins helps in cell recognition and interaction with other cells or molecules. Therefore, glycoproteins are essential components of the cell membrane and are responsible for its proper functioning.

Lysosomes are formed by the Golgi apparatus. The Golgi apparatus is responsible for packaging and modifying proteins and lipids into vesicles. These vesicles, called lysosomes, contain digestive enzymes that break down waste materials and cellular debris. The Golgi apparatus processes these enzymes and packages them into lysosomes, which are then transported to different parts of the cell to carry out their functions.

The correct answer is endoplasmic matrix. The endoplasmic reticulum is a network of tubules and vesicles within the cell. The space inside these structures is filled with a gel-like substance called the endoplasmic matrix. This matrix contains various molecules, including enzymes, proteins, and other substances necessary for the functioning of the endoplasmic reticulum. It provides a medium for the movement and transport of molecules within the organelle.

The basic lipid bilayer is composed of three main types of lipids: phospholipids, sphingolipids, and cholesterol. Phospholipids are the primary component of the bilayer and form a barrier that separates the internal and external environments of the cell. Sphingolipids are also present in the bilayer and contribute to its stability and fluidity. Cholesterol is another important lipid that is embedded within the bilayer and helps regulate its fluidity and permeability. Together, these three types of lipids make up the basic structure of the lipid bilayer.

The passage states that there are carbohydrate compounds called proteoglycans, which are mainly carbohydrate substances bound to small protein cores, loosely attached to the outer surface of the cell. It also mentions that the entire outside surface of the cell often has a loose carbohydrate coat called the glycocalyx. Therefore, the correct answer is "proteoglycans, glycocalyx."

Phospholipids, cholesterol, and triglycerides are all lipids. Lipids are a diverse group of molecules that are insoluble in water but soluble in organic solvents. Phospholipids are a major component of cell membranes and play a crucial role in maintaining their structure and function. Cholesterol is a type of lipid that is essential for the production of hormones, bile acids, and vitamin D. Triglycerides are the main form of fat storage in the body and serve as a source of energy.

The plasma membrane is selectively permeable, allowing only certain substances to pass through. Ions, glucose, and urea are all substances that require specific transport mechanisms to cross the plasma membrane. Oxygen and carbon dioxide, on the other hand, are small molecules that can diffuse freely across the membrane due to their size and nonpolar nature. Alcohol, being a small molecule, can also diffuse across the membrane to some extent.

The term "glycocalyx" refers to the negatively charged carbohydrate layer on the outer cell surface. This layer is composed of carbohydrate chains that protrude from glycolipids and integral glycoproteins. It plays a crucial role in cell adhesion, protection against mechanical stress, and recognition by other cells and molecules. The negatively charged nature of the glycocalyx helps repel negatively charged particles, preventing them from binding to the cell surface.

Large numbers of actin filaments frequently occur in the outer zone of the cytoplasm, called the ectoplasm, to form an elastic support for the cell membrane. The ectoplasm is a region of the cytoplasm that is located just beneath the cell membrane. Actin filaments, which are a type of protein filament, provide structural support and help maintain the shape and integrity of the cell membrane. The abundance of actin filaments in the ectoplasm allows for the formation of an elastic network that can withstand mechanical forces and provide stability to the cell membrane.

Proteins are a vital component of cells and are involved in various functions such as structure, regulation, and signaling. The statement suggests that protein normally makes up a certain percentage of the cell mass. The answer options provided are 10 and 20, indicating that protein can constitute anywhere between 10 to 20 percent of the cell mass. This range allows for variability in different cell types and conditions, as protein content can vary depending on the specific needs and functions of the cell.

Proteins can be classified into two main types: structural proteins and functional proteins. Structural proteins provide support and shape to cells and tissues. They help in maintaining the structural integrity of cells and are involved in building and maintaining the extracellular matrix. Examples of structural proteins include collagen, keratin, and elastin. On the other hand, functional proteins perform specific functions in the body. They include enzymes, antibodies, and hormones, which play roles in various biological processes such as metabolism, immune response, and cell signaling.

Integral proteins can act as receptors, ligands, pores, and channels. Receptors are proteins that bind to specific molecules, such as hormones or neurotransmitters, and initiate a cellular response. Ligands are molecules that bind to receptors and activate or inhibit their function. Pores are openings in the protein structure that allow the passage of small molecules or ions across the cell membrane. Channels are proteins that form a passageway for the selective transport of ions or molecules across the cell membrane. Therefore, integral proteins can perform multiple functions depending on their structure and location within the cell membrane.

Lysosomes are organelles responsible for the breakdown of cellular waste and foreign substances. They contain bactericidal agents that help in destroying bacteria. Lysozyme is an enzyme that can break down the cell walls of bacteria, making it an effective bactericidal agent. Lysoferrin is a compound that binds to iron, which is essential for bacterial growth, thereby inhibiting bacterial growth. Additionally, lysosomes maintain an acidic environment, with a pH of about 5.0, which further aids in the destruction of bacteria. Therefore, the correct answer includes lysozyme, lysoferrin, and acid at a pH of about 5.0.

Pinocytosis is a process by which cells engulf fluids and solutes from their surroundings. It requires energy to occur, which is provided by ATP. ATP is the main energy currency of the cell and is necessary for various cellular processes. Additionally, pinocytosis involves the rearrangement of the cell membrane, which requires calcium ions. Calcium ions play a crucial role in many cellular processes, including membrane fusion and vesicle formation. Therefore, both ATP and calcium ions are required for pinocytosis to take place.

Phagocytosis is a process in which cells engulf and digest foreign particles or pathogens. Macrophages and white blood cells are both types of immune cells that are capable of phagocytosis. Macrophages are specialized phagocytic cells that reside in tissues and play a crucial role in immune response by engulfing and destroying pathogens. White blood cells, also known as leukocytes, include various types such as neutrophils, monocytes, and lymphocytes. While lymphocytes do not typically engage in phagocytosis, monocytes can differentiate into macrophages and perform phagocytosis. Therefore, macrophages and certain types of white blood cells are involved in phagocytosis.

Protoplasm is the living substance found within cells, and it is primarily composed of water, electrolytes, proteins, lipids, and carbohydrates. Water is essential for maintaining the structure and function of cells, as it acts as a solvent and participates in various metabolic reactions. Electrolytes, such as ions of sodium, potassium, calcium, and chloride, are crucial for maintaining the balance of fluids within cells and for transmitting electrical impulses. Therefore, the presence of water and electrolytes in protoplasm is necessary for the proper functioning of cells.

The correct answer is "residual body." In endocytosis, the digestive vesicle undergoes various processes to break down and digest substances. However, there may be some substances that are unable to be digested. These indigestible substances are left behind in the residual body, which represents the remnants of the digestive vesicle after digestion has occurred.

Hyaluronic acid and chondroitin sulfate are synthesized by the Golgi Apparatus and serve multiple functions. They are major components of proteoglycans secreted in mucus and other glandular secretions, as well as the ground substance in the extracellular matrix. They act as fillers between collagen fibers and cells, and are principal components of the organic matrix in cartilage and bone. Additionally, they play a role in cell activities such as migration and proliferation.

Membrane proteins can be classified into two types: integral proteins and peripheral proteins. Integral proteins are embedded within the lipid bilayer of the cell membrane, spanning across it and often protruding on both sides. They play crucial roles in transporting molecules across the membrane and transmitting signals. On the other hand, peripheral proteins are attached to the surface of the membrane, either on the inner or outer side. They are not embedded within the lipid bilayer and are usually involved in cell signaling, enzymatic activity, or structural support.