Grade 9 Biology Practice Questions PDF

Hamdan Bin Zayed School C2&C3 Grade 9 Biology Prac ce Ques ons 1. Iden fy the four major families of biological macromolecules and describe their func ons in living organisms. o Answer: 1. Carbohydrates: Provide...

Hamdan Bin Zayed School C2&C3 Grade 9 Biology Prac ce Ques ons 1. Iden fy the four major families of biological macromolecules and describe their func ons in living organisms. o Answer: 1. Carbohydrates: Provide energy and structural support. 2. Lipids: Store energy, provide insula on, and make up cell membranes. 3. Proteins: Serve as enzymes, structural components, and transport molecules. 4. Nucleic Acids: Store and transmit gene c informa on (DNA and RNA). 2. Draw and label the structure of the plasma membrane.  3. Why is selec ve permeability crucial for the survival of cells? Answer: Selec ve permeability means the plasma membrane allows certain substances to pass while restric ng others. This property is crucial because it enables the cell to absorb essen al nutrients, expel waste, and prevent harmful substances from entering, ensuring the cell’s survival and efficient func oning. 4. Explain how the development of the cell theory changed our understanding of biology. Why is cell theory considered a founda onal concept in biology? Answer: The cell theory revolu onized biology by establishing three key principles: 1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of structure and organiza on in living organisms. 3. All cells arise from pre-exis ng cells. This understanding unified the study of life by emphasizing that all living organisms share a common cellular structure and origin. It shi ed focus to observable, testable cellular phenomena, providing a founda on for modern biology, including gene cs, medicine, and biotechnology. 5. Compare and contrast prokaryo c and eukaryo c cells. What are the main structural differences, and how do these differences allow eukaryo c cells to perform more specialized func ons? Answer Key: Similari es: Both types of cells have a plasma membrane, cytoplasm, DNA, and ribosomes. Differences: Prokaryo c Cells: o Lack a nucleus; DNA floats in the cytoplasm (nucleoid region). o Do not have membrane-bound organelles. o Smaller and simpler in structure. o Example: Bacteria and archaea. Eukaryo c Cells:  o Have a nucleus where DNA is stored. o Contain membrane-bound organelles (e.g., mitochondria, endoplasmic re culum). o Larger and more complex. o Example: Animal, plant, fungal, and pro st cells. 6. Describe how advances in microscope technology contributed to our knowledge of cell structure and func on. Which types of microscopes have been most impac ul in cell biology and why? Answer: Advances in Light Microscopy: The inven on of the light microscope allowed scien sts like Robert Hooke to observe cells for the first me and led to the discovery of cell structures. Improvements in magnifica on and resolu on made it possible to study organelles like the nucleus. Electron Microscopes (TEM and SEM): o Transmission Electron Microscope (TEM): Provides detailed images of internal cell structures by passing electrons through thin sec ons of the specimen. This revealed organelles like mitochondria and the endoplasmic re culum. o Scanning Electron Microscope (SEM): Produces three-dimensional images of cell surfaces, helping us understand cell morphology. 7. Explain the difference between passive and ac ve transport in cells. Provide an example of each. o Answer: Passive transport is the movement of molecules across the cell membrane without the use of energy, moving from an area of high concentra on to low concentra on. An example is the diffusion of oxygen into cells. Ac ve transport, on the other hand, requires energy in the form of ATP to move molecules against their concentra on gradient, from low concentra on to high concentra on. An example is the sodium-potassium pump, which moves sodium ions out of the cell and potassium ions into the cell. 8. Explain why the sodium-potassium pump is considered an example of ac ve transport.  o Answer: The sodium-potassium pump is an example of ac ve transport because it moves sodium and potassium ions against their concentra on gradients. This process requires energy in the form of ATP to move sodium ions out of the cell and potassium ions into the cell, maintaining the necessary concentra on gradients for cell func on. 9. If a red blood cell is placed in a hypertonic solu on, what will happen to it? Explain your answer. o Answer: If a red blood cell is placed in a hypertonic solu on, water will move out of the cell by osmosis, causing the cell to shrink and become crenated. This happens because the concentra on of solutes outside the cell is higher than inside, so water flows out to balance the concentra ons.