Extended Response Questions Topic 1 2 and 4 Flashcards
(a) Outline the sequence of events that occurs during mitosis. [5]
During Prophase DNA supper coils and the chromosomes condense. Additionally centrioles will move to the opposite sides of the cell and form microtubule spindle fibers and the nuclear membrane breaks up.
During Metaphase the spindle fibers connect to the centromere of chromatids and chromosomes will align across the center of the cell.
Duing Anaphase contraction of the spindle fibers which causes genetically identical sister chromatids to separate and move to opposite poles of the cell. Once chromatids separate they are considered individual chromosomes.
During Telophase the spindle fibers dissolve and nuclear membranes form around each set of chromosomes.
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Describe the processes that occur in the nucleus of a cell during interphase. [7]
Interphase is the longest phase in the cell cycle where DNA replication, organelle duplication, Cell growth, Transcription and Translation, Obtaining nutrients, and cellular respiration take place.
DNA replication is when DNA is copied during the S phase of interphase and results in identical copies of DNA in daughter cells. It involves the enzyme helicase which unwinds the double helix and the enzyme DNA polymerase which makes new strands of DNA using the two unwinded strands as a template.
Transcription is when the RNA sequence is produced from a DNA template. The RNA molecule will then follow the complementary base pairing rules of DNA and the RNA sequence will be synthesized.
Translation is protein synthesis where the genetic information encoded in mRNA is transferred into a sequence of amino acids on a polypeptide chain. mRNA is exported and moves to the cytoplasm.
(c) Explain how the presence of a Y chromosome in the cells of a human embryo causes it to develop as a male. [3]
The Y chromosomes in the cells of a human embryo will carry the protein TDR(Testis Determining Factor) which triggers development of testis and production of testosterone. TDR will regulate the transcription of geenes involved in the differentiation of the gonads into testis. Once testis have developed they start to produce testosterone which triggers the development of male genitalia.
(a) Describe the organelles and other structures in animal cells that are visible in electron micrographs. [7]
The organelles and other structures in animal cells that are visible in electron micrographs are the nucleus, Smooth ER, Rough ER (endoplasmic reticulum) Golgi Complex, mitochondria, vesicles, and lysosomes. The nucleus controls the activities of the cells and allows for the reproduction of unicellular organisms. The Smooth ER produces and stores lipids. The Rough ER transports proteins produced by ribosomes to the Golgi complex. The Golgi Complex processes and packages proteins which are released in the Golgi vesicles. The mitochondria are the site of cellular respiration where ATP is generated. The Vesicles are small sacs that transport and release substances byfusing with the cell membrane. The Lysomes contain enzymes and play roles in destroying microbes engulfed by white blood cells and destroying old cellular organelles.
(b) Explain how animal cells produce the ATP that they need. [5]
Cellular respiration is the controlled release of energy from organic compounds to produce ATP. during cellular respiration energy is released from glucose, lipids, and proteins. Anaerobic respiration does not require oxygen and involves a partial breakdown of glucose to produce ATP. Aerobic respiration requires oxygen to completely break down glucose to produce a larger yield of ATP. During Aerobic respiration carbon dioxide and water are produced in addition to ATP. Cellular respiration takes place in the mitochondria.
(c) Distinguish between reptiles and amphibians in terms of their recognition features. [3]
Reptiles are covered in scales made of keratin and have internal fertilisation meaning they lay soft eggs. Reptiles also breathe through lungs and are ectothermic. Amphibians have moist skins which is permeable to gasses and reproduce through external fertilisation. Amphibians also breathe through skin and are ectothermic.
