Human Biology - 4HB1 PearsonEdexcel

Cell Structure And DNA

Muhtasari

Every decision your body makes, from building a new skin cell after a graze to fighting off a cold, starts with an instruction written in a molecule barely two nanometres wide. That molecule is DNA, and it is coiled inside the nucleus of almost every one of your cells, carrying the complete set of instructions needed to build and run a human being.

In this lesson you will learn the structures a light microscope and an electron microscope reveal inside a human cell, discover how DNA's double helix lets it copy itself with astonishing accuracy, and follow the two-step journey, transcription then translation, that turns a gene into a working protein.

Malengo

  1. Recognise cell structures as seen with a light microscope and electron microscope (TEM images only), including nucleus, chromosomes, cell membrane, mitochondria, endoplasmic reticulum and ribosomes
  2. Describe the functions of the cell structures: nucleus, chromosomes, cell membrane, mitochondria, endoplasmic reticulum, ribosomes
  3. Describe the structure of a DNA molecule as two strands coiled to form a double helix, containing nucleotides, strands linked by complementary bases, complementary bases linked by hydrogen bonds
  4. Describe DNA replication as the separation of DNA strands and the formation of a new strand by complementary base pairing of nucleotides, including the role of DNA polymerase
  5. Understand that a gene is a length of DNA containing a sequence of bases that code for a specific protein
  6. Know that RNA is a second type of nucleic acid that is single stranded, contains ribose, contains uracil and is used to take information from DNA in the nucleus to the ribosomes for the synthesis of proteins
  7. Understand that a DNA mutation involves a change in the sequence of bases that could lead to a change in the amino acid sequence and phenotype of an individual
  8. Describe protein synthesis as transcription (the formation of mRNA in the nucleus), the transfer of mRNA to ribosomes in the cytoplasm, translation of the genetic code by tRNA from mRNA codons, and the formation of a polypeptide chain using amino acids

Maelezo ya Somo

A human cell is a working factory, and its instruction manual is kept in a single room: the nucleus. Everything else the cell needs, energy, building materials, transport routes, is organised around structures that a microscope can reveal. Some of these structures are visible with an ordinary light microscope; others are so small that only an electron microscope can resolve them.

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Tathmini ya Somo

Hongera kwa kukamilisha somo la Cell Structure And DNA. Sasa kwa kuwa umechunguza dhana na mawazo muhimu, ni wakati wa kuweka ujuzi wako kwa mtihani. Sehemu hii inatoa mazoezi mbalimbali maswali yaliyoundwa ili kuimarisha uelewaji wako na kukusaidia kupima ufahamu wako wa nyenzo.

Utakutana na mchanganyiko wa aina mbalimbali za maswali, ikiwemo maswali ya kuchagua jibu sahihi, maswali ya majibu mafupi, na maswali ya insha. Kila swali limebuniwa kwa umakini ili kupima vipengele tofauti vya maarifa yako na ujuzi wa kufikiri kwa makini.

Tumia sehemu hii ya tathmini kama fursa ya kuimarisha uelewa wako wa mada na kubaini maeneo yoyote ambapo unaweza kuhitaji kusoma zaidi. Usikatishwe tamaa na changamoto zozote utakazokutana nazo; badala yake, zitazame kama fursa za kukua na kuboresha.

  1. Which structure can only be seen in detail using an electron microscope, not a light microscope? A) Nucleus B) Cell membrane outline C) Internal structure of a mitochondrion D) Cytoplasm Answer: C
  2. In a DNA molecule, adenine always pairs with: A) Guanine B) Cytosine C) Thymine D) Uracil Answer: C
  3. Which enzyme joins new nucleotides together during DNA replication? A) RNA polymerase B) DNA polymerase C) DNA ligase D) Amylase Answer: B
  4. Where in the cell does transcription take place? A) Ribosome B) Mitochondrion C) Nucleus D) Cell membrane Answer: C
  5. Which of these is a difference between RNA and DNA? A) RNA contains uracil instead of thymine B) RNA is double stranded and DNA is single stranded C) RNA contains deoxyribose and DNA contains ribose D) RNA is found only in mitochondria Answer: A

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