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ENTIRE topic 5 - A level Biology (AQA) Learn or revise the WHOLE topic to get you exam ready

Miss Estruch・27 minutes read

Miss Estri provides comprehensive resources and videos for AQA biology students, covering topics like photosynthesis, aerobic and anaerobic respiration, energy transfer in ecosystems, nutrient cycles, and the impact of fertilizers on water sources. It is important to understand key concepts like the Calvin cycle, oxidative phosphorylation, and the nitrogen and phosphorus cycles to grasp the complexities of biology.

Insights

  • Photosynthesis involves two main stages: light-dependent reactions on the thylakoid membrane and light-independent reactions in the stroma, utilizing ATP and reduced NADP to produce hexose sugars.
  • Energy transfer in ecosystems starts with producers, leading to energy loss between trophic levels; understanding biomass, GPP, and NPP is crucial for comparing productivity, while nutrient cycles like nitrogen and phosphorus are essential for life, with fertilizers replenishing nutrients but potentially causing environmental issues like eutrophication.

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Recent questions

  • What topics does Miss Estri cover in her biology resources?

    Miss Estri covers topics like photosynthesis, respiration, nutrient cycles.

  • What are the two stages of photosynthesis?

    The two stages of photosynthesis are light-dependent and light-independent reactions.

  • How does aerobic respiration differ from anaerobic respiration?

    Aerobic respiration requires oxygen, while anaerobic respiration does not.

  • How do limiting factors affect the process of photosynthesis?

    Limiting factors like light intensity, carbon dioxide concentration, and temperature can affect photosynthesis.

  • Why are nutrient cycles important in ecosystems?

    Nutrient cycles are vital for life as they ensure the availability of essential elements like nitrogen and phosphorus.

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Summary

00:00

"Biology Teacher Provides AQA Exam Resources"

  • Miss Estri, a biology teacher, offers resources and videos for biology students.
  • Her notes contain theory, key points, and exam techniques for AQA biology.
  • Topic 5 covers photosynthesis, starting with the structure of a chloroplast.
  • Photosynthesis involves two stages: light-dependent and light-independent reactions.
  • Light-dependent reactions occur on the thylakoid membrane, producing ATP and reduced NADP.
  • Photolysis, photoionization of chlorophyll, and chemiosmosis are key steps in the light-dependent reactions.
  • Light-independent reactions, or the Calvin cycle, occur in the stroma and use ATP and reduced NADP.
  • The Calvin cycle involves carbon dioxide, ATP, and reduced NADP to create hexose sugars.
  • Limiting factors like light intensity, carbon dioxide concentration, and temperature affect photosynthesis.
  • Aerobic respiration consists of glycolysis, the link reaction, Krebs cycle, and oxidative phosphorylation.

17:50

Cellular Respiration and Nutrient Cycles in Ecosystems

  • For every glucose molecule, the citric acid cycle occurs twice due to the production of two acetyl CoA, resulting in a doubling of ATP and carbon dioxide values.
  • Oxidative phosphorylation, the final step, is similar to the light-dependent reaction in photosynthesis, where most ATP is generated in the mitochondrial Matrix through the release of hydrogen from reduced Co enzymes, leading to the creation of an electrochemical gradient.
  • The electrons from the hydrogen are transported along the electron transfer chain, releasing energy used to move protons into the intermembrane space, creating an electrochemical gradient for ATP synthesis.
  • Oxygen acts as the final electron acceptor, combining with electrons and protons to form water, while anerobic respiration occurs without oxygen, producing ethanol and carbon dioxide in plants and microbes, and lactate or lactic acid in animals.
  • Anerobic respiration reoxidizes NAD to allow glycolysis to continue, with pyruvate being reduced to lactate in the absence of oxygen, ensuring ATP production.
  • Energy transfer in ecosystems begins with producers like green plants, who photosynthesize to create organic compounds, with energy lost between trophic levels due to respiration and excretion.
  • Biomass, the mass of carbon within an organism, is crucial for comparing productivity, with terms like GPP (gross primary production) and NPP (net primary production) quantifying energy stored and energy available for biomass production.
  • The nutrient cycles, including the nitrogen cycle, are vital for life as nitrogen is essential for proteins, ATP, and nucleic acids, with processes like ammonification, nitrification, nitrogen fixation, and denitrification ensuring nitrogen availability.
  • The phosphorus cycle, crucial for DNA, RNA, ATP, and phospholipids, involves phosphate ions in sedimentary rocks, with micro rizy fungal associations aiding in plant growth and phosphate ion absorption.
  • Fertilizers, both natural and artificial, are used to replenish nutrients removed during crop harvesting, with artificial fertilizers providing precise mineral proportions but leaching into water sources, causing eutrophication by stimulating algae growth and depleting oxygen levels.

35:53

"Deadly Consequences of Oxygen Depletion in Water"

  • Lack of dissolved oxygen in water leads to the death of aquatic animals like fish due to the absence of oxygen for respiration.
  • To delve deeper into this topic, viewers are encouraged to click on the playlist for more detailed explanations.
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