biology paper 1 six markers Flashcards
Describe the differences between prokaryotic and eukaryotic cells.
-Prokaryotic cells are simpler and smaller than eukaryotic cells.
-Prokaryotic cells do not have a true nucleus; DNA is free in the cytoplasm.
-Prokaryotic cells may have plasmids (small loops of DNA).
-Eukaryotic cells have a nucleus where DNA is enclosed by a membrane.
-Eukaryotic cells contain membrane-bound organelles (e.g., mitochondria, ribosomes).
-Examples: Bacteria are prokaryotic; animal, plant, and fungal cells are eukaryotic.
Describe how to prepare a slide of an onion cell and view it using a light microscope.
-Peel a thin layer of onion epidermis.
-Place it flat on a clean microscope slide.
-Add a drop of iodine solution to stain the cells.
-Carefully lower a coverslip to avoid trapping air bubbles.
-Use the lowest magnification lens first and coarse focus to find the image.
-Use fine focus to sharpen the image, then increase magnification if needed.
Explain the importance of mitosis in the life of an organism.
-Mitosis allows organisms to grow by increasing the number of cells.
-It repairs damaged tissues by replacing dead or damaged cells.
-It enables asexual reproduction in single-celled organisms.
-The process produces genetically identical daughter cells.
-It ensures each cell has an exact copy of the parent cell’s DNA.
-It maintains the chromosome number across generations of cells.
Explain how stem cells could be used in medicine and why there are objections to their use.
-Stem cells can differentiate into any cell type and replace damaged cells.
-They can be used to treat diseases like diabetes and spinal cord injuries.
-Therapeutic cloning produces embryos genetically identical to patients to prevent rejection.
-Some people object because it involves the destruction of embryos (potential human life).
-Ethical concerns arise regarding the status of embryos.
-There are risks such as tumour development and unknown long-term effects.
Explain how root hair cells and alveoli are adapted to maximise the movement of substances.
-Root hair cells have long projections to increase surface area for absorption.
-Root hair cells have thin walls to shorten diffusion distance.
-Alveoli provide a large surface area for gas exchange.
-Alveoli have thin walls for a short diffusion distance.
-Alveoli are surrounded by a rich blood supply maintaining concentration gradients.
-Alveoli have a moist lining allowing gases to dissolve and diffuse more easily.
Explain the process of active transport and why it is necessary in both plants and animals.
-Active transport moves substances against a concentration gradient.
-It requires energy from respiration.
-In plants, it enables mineral ions to be absorbed from low concentrations in the soil into root hair cells.
-Mineral ions are necessary for healthy plant growth.
-In animals, it allows glucose to be absorbed from the gut into the blood, even when concentrations are lower in the gut.
-This ensures that no glucose needed for respiration is wasted.
