Explain why lysosomes store acidic enzymes, including one way in which this storage process benefits the cell. (2 marks)
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Explain why lysosomes store acidic enzymes, including one way in which this storage process benefits the cell. (2 marks)
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→ Lysosomes store acidic enzymes because these type of enzymes are most effective in helping the organelle perform its major role of breaking down waste and cellular debris.
→ This storage process plays a crucial role in protecting the cell by keeping these enzymes contained.
→ If the acidic enzymes were released into the cytoplasm, they would lower the pH in the cytosol, adversely affecting other enzymes and potentially damaging other cellular components.
→ Lysosomes store acidic enzymes because these type of enzymes are most effective in helping the organelle perform its major role of breaking down waste and cellular debris.
→ This storage process plays a crucial role in protecting the cell by keeping these enzymes contained.
→ If the acidic enzymes were released into the cytoplasm, they would lower the pH in the cytosol, adversely affecting other enzymes and potentially damaging other cellular components.
Products of an enzyme-controlled reaction can sometimes inhibit the enzyme that produced them.
Discuss how this process can be advantageous for cellular metabolism. (3 marks)
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→ When products of an enzyme-controlled reaction inhibit the enzyme that produced them, it regulates the cell’s metabolism (in a process known as feedback).
→ This process prevents the accumulation of excess products, ensuring that resources like ATP and raw materials are used efficiently.
→ By controlling the enzyme activity, the cell can balance production according to its needs, conserving energy and maintaining metabolic stability.
→ When products of an enzyme-controlled reaction inhibit the enzyme that produced them, it regulates the cell’s metabolism (in a process known as feedback).
→ This process prevents the accumulation of excess products, ensuring that resources like ATP and raw materials are used efficiently.
→ By controlling the enzyme activity, the cell can balance production according to its needs, conserving energy and maintaining metabolic stability.
Discuss how the structure of the phospholipid bilayer contributes to the selective permeability of a cell membrane. (3 marks)
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→ The phospholipid bilayer’s structure, with hydrophilic heads facing outward and hydrophobic tails facing inward, forms a barrier that allows only small, nonpolar molecules to pass through easily, while blocking larger or charged molecules.
→ This selective permeability is further controlled by embedded proteins, which act as channels or carriers to facilitate the movement of ions and larger molecules that cannot cross the bilayer on their own.
→ This structure helps the cell regulate the entry and exit of specific substances, maintaining internal balance.
→ The phospholipid bilayer’s structure, with hydrophilic heads facing outward and hydrophobic tails facing inward, forms a barrier that allows only small, nonpolar molecules to pass through easily, while blocking larger or charged molecules.
→ This selective permeability is further controlled by embedded proteins, which act as channels or carriers to facilitate the movement of ions and larger molecules that cannot cross the bilayer on their own.
→ This structure helps the cell regulate the entry and exit of specific substances, maintaining internal balance.
The diagram below illustrates a model depicting how an enzyme functions.
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a. \(\text{X}\) – enzyme, \(\text{Y}\) – substrate, \(\text{Z}\) – products
b. Role of enzymes:
→ Enzymes are crucial because they accelerate chemical reactions, allowing vital processes such as digestion and respiration to occur quickly enough to sustain life.
→ By lowering the activation energy needed for reactions, enzymes ensure that cells operate efficiently and maintain balance within biological systems.
→ Without enzymes, these reactions would be too slow to support cellular function, leading to poor cellular health and even death.
a. \(\text{X}\) – enzyme, \(\text{Y}\) – substrate, \(\text{Z}\) – products
b. Role of enzymes:
→ Enzymes are crucial because they accelerate chemical reactions, allowing vital processes such as digestion and respiration to occur quickly enough to sustain life.
→ By lowering the activation energy needed for reactions, enzymes ensure that cells operate efficiently and maintain balance within biological systems.
→ Without enzymes, these reactions would be too slow to support cellular function, leading to poor cellular health and even death.
Which of the following best distinguishes cellular waste from cellular secretions?
\(B\)
→ Cellular waste includes substances like carbon dioxide or urea, which result from metabolic processes and must be removed.
→ Secretions, on the other hand, are purposeful substances like hormones or enzymes that are actively produced and released by cells for specific roles in the body.
\(\Rightarrow B\)
Explain how cells remove waste products to maintain proper function and provide an example of a specific waste product that cells eliminate. (3 marks)
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→ Cells remove waste products through exocytosis, where waste is trapped within vesicles inside the cell.
→ These vesicles then fuse with the cell membrane, releasing the waste to the outside environment.
→ Examples of a waste product: could include carbon dioxide, lactic acid or urea (and other nitrogen based waste compounds).
→ Cells remove waste products through exocytosis, where waste is trapped within vesicles inside the cell.
→ These vesicles then fuse with the cell membrane, releasing the waste to the outside environment.
→ Examples of a waste product: could include carbon dioxide, lactic acid or urea (and other nitrogen based waste compounds).
Which process is primarily responsible for removing waste materials from a cell?
\(C\)
→ Exocytosis is the process by which cells expel waste materials and other substances by transporting vesicles to the cell membrane, where they fuse and release their contents outside the cell.
\(\Rightarrow C\)
Compare the movement of a lipid-soluble substance and water across the cell membrane.
In your answer, explain how the structure of the membrane affects the transport of these molecules. (2 marks)
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→ Lipid-soluble substances can pass directly through the phospholipid bilayer by simple diffusion because the cell membrane contains lipids.
→ In contrast, water is unable to penetrate the cell through the phospholipid bilayer.
→ Instead, water molecules must pass through special protein channels (pores) in the cell membrane.
→ Lipid-soluble substances can pass directly through the phospholipid bilayer by simple diffusion because the cell membrane contains lipids.
→ In contrast, water is unable to penetrate the cell through the phospholipid bilayer.
→ Instead, water molecules must pass through special protein channels (pores) in the cell membrane.
Discuss how concentration gradients affect the transport of molecules across the cell membrane? (3 marks)
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→ Concentration gradients determine the direction of molecule movement across the cell membrane.
→ Molecules naturally move from areas of high concentration to low concentration in processes like diffusion and osmosis (passive transport). The higher the gradient, the faster the movement.
→ In contrast, active transport requires energy to move substances against the gradient, from low to high concentration. The higher the gradient, the more energy that is required.
→ These gradients are crucial for maintaining cellular balance and function.
→ Concentration gradients determine the direction of molecule movement across the cell membrane.
→ Molecules naturally move from areas of high concentration to low concentration in processes like diffusion and osmosis (passive transport). The higher the gradient, the faster the movement.
→ In contrast, active transport requires energy to move substances against the gradient, from low to high concentration. The higher the gradient, the more energy that is required.
→ These gradients are crucial for maintaining cellular balance and function.
"The surface area to volume ratio is crucial for efficient cellular transport."
Evaluate the above statement, providing an example of how cells adapt their shape to maintain an effective ratio. (3 marks)
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→ The surface area to volume ratio is vital for efficient cellular transport because a higher ratio allows for quicker exchange of materials, such as nutrients and waste, across the cell membrane.
→ As cells grow larger, their volume increases faster than their surface area, reducing efficiency.
→ To compensate, some cells increase surface area without significantly adding volume.
→ An example is red blood cells that have adapted to be biconcave in shape. This maximises surface area relative to volume to enhance oxygen exchange.
→ The surface area to volume ratio is vital for efficient cellular transport because a higher ratio allows for quicker exchange of materials, such as nutrients and waste, across the cell membrane.
→ As cells grow larger, their volume increases faster than their surface area, reducing efficiency.
→ To compensate, some cells increase surface area without significantly adding volume.
→ An example is red blood cells that have adapted to be biconcave in shape. This maximises surface area relative to volume to enhance oxygen exchange.
In active transport, how does the cell maintain a steep concentration gradient across the membrane?
\(B\)
→ Active transport requires energy (ATP) to move ions or molecules against their concentration gradient, often with the help of carrier proteins.
→ This process helps cells maintain steep concentration gradients essential for functions like nerve impulse transmission and muscle contraction.
\(\Rightarrow B\)
Which of the following best describes movement of molecules in passive transport with respect to concentration gradients?
\(B\)
→ Passive transport relies on molecules moving naturally from an area of high concentration to an area of low concentration without the need for energy.
→ This process includes diffusion and osmosis, allowing molecules to equalise concentration across membranes.
\(\Rightarrow B\)
Describe how active transport and passive transport differ in their mechanisms for moving substances into and out of cells, and give an example of each. (2 marks)
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→ Active transport requires energy (usually in the form of ATP) to move or create the passage for substances into or out of cells.
→ Endocytosis and exocytosis are examples of active transport (only one example required).
→ In contrast, passive transport does not require energy to move substances into or out of cells.
→ Diffusion and osmosis are examples of passive transport (only one example required).
→ Active transport requires energy (usually in the form of ATP) to move or create the passage for substances into or out of cells.
→ Endocytosis and exocytosis are examples of active transport (only one example required).
→ In contrast, passive transport does not require energy to move substances into or out of cells.
→ Diffusion and osmosis are examples of passive transport (only one example required).
Which of the following best describes the process of endocytosis?
\(B\)\
→ Endocytosis is a process by which the cell membrane folds inward to form a vesicle, bringing large molecules like nutrients or particles into the cell.
\(\Rightarrow B\)
Explain how lysosomes maintain cellular homeostasis and describe what happens when their function is impaired. (2 marks)
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→ Lysosomes maintain cellular homeostasis by breaking down waste materials, damaged organelles, and cellular debris using enzymes.
→ This prevents the accumulation of harmful substances.
→ When lysosomal function is impaired, waste products and damaged components build up, leading to cellular dysfunction and potentially contributing to diseases that impair cellular efficiency and overall health.
→ Lysosomes maintain cellular homeostasis by breaking down waste materials, damaged organelles, and cellular debris using enzymes.
→ This prevents the accumulation of harmful substances.
→ When lysosomal function is impaired, waste products and damaged components build up, leading to cellular dysfunction and potentially contributing to diseases that impair cellular efficiency and overall health.
Explain how the cell arrangement supports the role and specific functions of the following cellular structures
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a. Cytoplasm:
→ The cytoplasm is a gel-like substance that fills the cell, providing a medium in which organelles are suspended.
→ It facilitates the movement of materials within the cell and allows biochemical reactions to occur efficiently.
b. Ribosomes:
→ Ribosomes can be found either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum.
→ Their arrangement allows them to efficiently translate mRNA into proteins, with free ribosomes synthesising proteins for use within the cell and membrane-bound ribosomes manufacturing proteins for export or use in the cell membrane.
a. Cytoplasm:
→ The cytoplasm is a gel-like substance that fills the cell, providing a medium in which organelles are suspended.
→ It facilitates the movement of materials within the cell and allows biochemical reactions to occur efficiently.
b. Ribosomes:
→ Ribosomes can be found either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum.
→ Their arrangement allows them to efficiently translate mRNA into proteins, with free ribosomes synthesising proteins for use within the cell and membrane-bound ribosomes manufacturing proteins for export or use in the cell membrane.
Which of the following correctly describes the roles of lysosomes and the Golgi apparatus?
\(C\)
→ Lysosomes contain digestive enzymes that break down cellular waste and debris.
→ Golgi apparatus is responsible for modifying, sorting, and packaging proteins for secretion or use within the cell.
\(\Rightarrow C\)
Which of the following correctly compares the structure and function of the mitochondria and the chloroplast?
\(C\)
→ Mitochondria are responsible for producing ATP through the process of cellular respiration.
→ Chloroplasts, found in plant cells, convert light energy into glucose via photosynthesis.
→ Both organelles have distinct functions related to energy conversion in cells.
\(\Rightarrow C\)
Describe the structure and role of phospholipids in the cell membrane based on the fluid mosaic model. (3 marks)
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→ In the fluid mosaic model, phospholipids form a bilayer that acts as the fundamental structure of the cell membrane.
→ Each phospholipid has a hydrophilic head that faces outward and a hydrophobic tail that faces inward, creating a barrier that separates the cell’s internal and external environments.
→ This bilayer is semi-permeable, allowing selective substances to pass through while blocking others.
→ In the fluid mosaic model, phospholipids form a bilayer that acts as the fundamental structure of the cell membrane.
→ Each phospholipid has a hydrophilic head that faces outward and a hydrophobic tail that faces inward, creating a barrier that separates the cell’s internal and external environments.
→ This bilayer is semi-permeable, allowing selective substances to pass through while blocking others.
According to the fluid mosaic model of the cell membrane
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a. The phospholipid bilayer:
→ Consists of two layers of phospholipids.
→ One layer involves hydrophilic (water-attracting) heads facing outward toward the water-based environment while the opposite layer has hydrophobic (water-repelling) tails facing inward, away from water.
b. Proteins:
→ are embedded in the double phospholid layer and play a role in the cell structure and communication.
a. The phospholipid bilayer:
→ Consists of two layers of phospholipids.
→ One layer involves hydrophilic (water-attracting) heads facing outward toward the water-based environment while the opposite layer has hydrophobic (water-repelling) tails facing inward, away from water.
b. Proteins:
→ are embedded in the double phospholid layer and play a role in the cell structure and communication.
Describe the progression of microscopy technologies and discuss how these advancements have enhanced our knowledge of cell structure and function. (4 marks)
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→ The progression of microscopy technologies has revolutionised our understanding of cell structure and function.
→ Early light microscopes allowed scientists to observe basic cell components, such as the nucleus, but were limited in resolution.
→ The invention of the transmission electron microscope brought a major leap, enabling the detailed 2-D visualisation of organelles like mitochondria and the endoplasmic reticulum.
→ The development of the scanning electron microscope created high resolution 3-D images of cells. This allowed for the study of bacteria and cell-surface structures such as cilia.
→ More recently, confocal and fluorescence microscopy have allowed researchers to study living cells in real-time, providing dynamic insights into cellular processes.
→ These advancements have deepened our knowledge of cell biology, revealing intricate structures and functions previously unseen.
→ The progression of microscopy technologies has revolutionised our understanding of cell structure and function.
→ Early light microscopes allowed scientists to observe basic cell components, such as the nucleus, but were limited in resolution.
→ The invention of the transmission electron microscope brought a major leap, enabling the detailed 2-D visualisation of organelles like mitochondria and the endoplasmic reticulum.
→ The development of the scanning electron microscope created high resolution 3-D images of cells. This allowed for the study of bacteria and cell-surface structures such as cilia.
→ More recently, confocal and fluorescence microscopy have allowed researchers to study living cells in real-time, providing dynamic insights into cellular processes.
→ These advancements have deepened our knowledge of cell biology, revealing intricate structures and functions previously unseen.
Describe how the development of electron microscopy has improved our understanding of cell structure and function.
In your answer, compare the capabilities of transmission electron microscopes (TEM) and scanning electron microscopes (SEM), and give examples of how each is used in biological research. (4 marks)
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→ The development of electron microscopy has significantly enhanced our understanding of cell structure and function by providing much higher resolution images than light microscopes.
→ Transmission electron microscopes (TEM) allow scientists to view internal structures of cells in great detail by transmitting electrons through thin slices of specimens, revealing organelles like the mitochondria and endoplasmic reticulum.
→ In contrast, scanning electron microscopes (SEM) produce three-dimensional images by scanning the surface of a specimen with electrons, which is useful for studying cell surfaces and structures such as cilia or bacterial shapes.
→ Both TEM and SEM have been pivotal in biological research, allowing the discovery of cellular organelles and understanding of cell interactions at the microscopic level.
→ The development of electron microscopy has significantly enhanced our understanding of cell structure and function by providing much higher resolution images than light microscopes.
→ Transmission electron microscopes (TEM) allow scientists to view internal structures of cells in great detail by transmitting electrons through thin slices of specimens, revealing organelles like the mitochondria and endoplasmic reticulum.
→ In contrast, scanning electron microscopes (SEM) produce three-dimensional images by scanning the surface of a specimen with electrons, which is useful for studying cell surfaces and structures such as cilia or bacterial shapes.
→ Both TEM and SEM have been pivotal in biological research, allowing the discovery of cellular organelles and understanding of cell interactions at the microscopic level.
Which of the following correctly explains why a scanning electron microscope is advantageous in studying living cells?
\(A\)
→ Scanning electron microscopes capture detailed three-dimensional images of living cells, allowing researchers to observe cellular processes in real time with high resolution.
→ Unlike electron microscopes, this technology can be used to study live cells without extensive sample preparation that might kill the cells.
\(\Rightarrow A\)
Which of the following technologies was pivotal in discovering the internal structure of organelles such as mitochondria and the endoplasmic reticulum?
\(B\)
→ The transmission electron microscope (TEM) allows for the visualisation of internal cell structures at high resolution by passing electrons through thin sections of a sample.
→ This technology was crucial in discovering detailed organelle structures like mitochondria and the endoplasmic reticulum, which are not visible with light microscopes.
\(\Rightarrow B\)
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a. Answers could include any two of the following:
→ Nucleus – the nucleus contains the cell’s genetic material and regulates gene expression.
→ Mitochondria – generates ATP through cellular respiration, providing energy for the cell’s functions.
→ Endoplasmic reticulum (ER) – helps synthesise proteins (rough ER) and lipids (smooth ER), contributing to various cell processes.
b. → Specialised organelles allow eukaryotic cells to compartmentalise tasks.
→ This increases metabolic efficiency and enables complex processes to occur within the cell.
→ In contrast, prokaryotic cells, lacking organelles, must perform all functions in the cytoplasm, limiting their ability to handle as many simultaneous or specialised activities as eukaryotic cells.
a. Answers could include any two of the following:
→ Nucleus – the nucleus contains the cell’s genetic material and regulates gene expression.
→ Mitochondria – generates ATP through cellular respiration, providing energy for the cell’s functions.
→ Endoplasmic reticulum (ER) – helps synthesise proteins (rough ER) and lipids (smooth ER), contributing to various cell processes.
b. → Specialised organelles allow eukaryotic cells to compartmentalise tasks.
→ This increases metabolic efficiency and enables complex processes to occur within the cell.
→ In contrast, prokaryotic cells, lacking organelles, must perform all functions in the cytoplasm, limiting their ability to handle as many simultaneous or specialised activities as eukaryotic cells.
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a. Structural and functional differences:
→ Prokaryotic cells lack membrane-bound organelles and a true nucleus, with their DNA free-floating in the cytoplasm.
→ Eukaryotic cells, on the other hand, have a membrane-bound nucleus and various organelles such as mitochondria, which allow compartmentalisation of functions.
→ This structural difference enables eukaryotes to perform more complex processes, while prokaryotes are limited to simpler metabolic activities.
b. → Eukarytic organisms can manage multiple, specialised functions simultaneously.
→ This supports greater complexity in multicellular organisms and leads to highly organised systems with differentiated tissues and organs.
→ Prokaryotic organisms remain unicellular or simple multicellular forms, with all functions occurring in the same space.
a. Structural and functional differences:
→ Prokaryotic cells lack membrane-bound organelles and a true nucleus, with their DNA free-floating in the cytoplasm.
→ Eukaryotic cells, on the other hand, have a membrane-bound nucleus and various organelles such as mitochondria, which allow compartmentalisation of functions.
→ This structural difference enables eukaryotes to perform more complex processes, while prokaryotes are limited to simpler metabolic activities.
b. → Eukarytic organisms can manage multiple, specialised functions simultaneously.
→ This supports greater complexity in multicellular organisms and leads to highly organised systems with differentiated tissues and organs.
→ Prokaryotic organisms remain unicellular or simple multicellular forms, with all functions occurring in the same space.
Which of the following accurately explains why prokaryotic cells are generally smaller than eukaryotic cells?
\(B\)
→ Prokaryotic cells lack membrane-bound organelles, which limits their ability to compartmentalize functions.
→ This results in lower metabolic efficiency, constraining their size compared to eukaryotic cells.
\(\Rightarrow B\)
Which of the following structures is present in both prokaryotic and eukaryotic cells?
\(C\)
→ Both prokaryotic and eukaryotic cells contain ribosomes, which are responsible for protein synthesis.
→ Prokaryotes lack membrane-bound organelles like mitochondria or the Golgi apparatus.
\(C\)
Which of the following is a key structural difference between prokaryotic and eukaryotic cells?
\(B\)
→ Prokaryotic cells lack a membrane-bound nucleus, whereas eukaryotic cells have a well-defined nucleus that encloses their DNA.
\(\Rightarrow B\)