IB Biology Higher Level

This subject is broken down into 74 topics in 15 modules:

  1. Cell biology 6 topics
  2. Molecular biology 9 topics
  3. Genetics 5 topics
  4. Ecology 4 topics
  5. Evolution and biodiversity 4 topics
  6. Human physiology 6 topics
  7. Nucleic acids 3 topics
  8. Metabolism, cell respiration and photosynthesis 3 topics
  9. Plant biology 4 topics
  10. Genetics and evolution 3 topics
  11. Animal physiology 4 topics
  12. Option A: Neurobiology and behaviour 6 topics
  13. Option B: Biotechnology and bioinformatics 5 topics
  14. Option C: Ecology and conservation 6 topics
  15. Option D: Human physiology 6 topics
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  • 15
    modules
  • 74
    topics
  • 27,234
    words of revision content
  • 3+
    hours of audio lessons

This page was last modified on 28 September 2024.

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Biology

Cell biology

Introduction to cells

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Introduction to cells

Definitions and Basics

  • Cell is the basic structural and functional unit of life.
  • All organisms are made up of one or more cells. The unicellular organisms, such as bacteria and yeast, are made up of a single cell, while multicellular organisms, such as human and plants, are composed of many cells.
  • All cells originate from pre-existing cells through the process of cell division.

Cellular Structures

  • The cell membrane also referred to as the plasma membrane, controls what enters and leaves the cell.
  • The cytoplasm is the gel-like substance found within the cell membrane which contains all the cell's organelles.
  • The nucleus controls cell activities and contains the cell's DNA.
  • The mitochondria are known as the powerhouses of the cell and produce the cell's energy through a process called respiration.
  • The ribosomes are involved in protein synthesis.
  • The endoplasmic reticulum serves as a pathway for the transport of materials throughout the cell, and is involved in the synthesis of proteins and lipids.
  • The golgi apparatus plays a key role in the modification, sorting, and packaging of proteins for delivery to targeted destinations.

Types of Cells

  • Prokaryotic cells: These cells lack a defined nucleus and do not contain membrane-bound organelles. Examples include bacteria and archaea.
  • Eukaryotic cells: These cells have a defined nucleus enclosed by a nuclear membrane and contain other membrane-bound organelles. Examples include cells of fungi, plants, and animals.

Specialisation of Cells

  • In multicellular organisms, cells tend to be specialised to perform particular functions.
  • There can be many types of specialised cells in an organism, including nerve cells, muscle cells, and red blood cells.
  • Each type of cell has structural adaptions that allow it to perform its function efficiently.

Cell Division

  • There are two main types of cell division, namely, mitosis and meiosis.
  • Mitosis is used for growth and repair and results in two genetically identical cells.
  • Meiosis is used for sexual reproduction and results in four genetically different cells.

Course material for Biology, module Cell biology, topic Introduction to cells

Biology

Metabolism, cell respiration and photosynthesis

Cell respiration

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Cell respiration

Cell Respiration Overview

  • Cell respiration refers to a set of reactions occurring in cells to convert biochemical energy from nutrients into ATP (adenosine triphosphate) and then releases waste products.
  • It is a vital process for all life forms as it provides the energy needed to maintain bodily functions and perform physical activities.

Stages of Cell Respiration

  • Cell respiration consists of three main stages: Glycolysis, Krebs cycle (Citric Acid Cycle), and the Electron Transport Chain.
  • Glycolysis occurs in the cytoplasm where glucose is broken down into two molecules of pyruvate (pyruvic acid), producing a small amount of energy (2 ATP).
  • The Krebs cycle happens in the mitochondria, where pyruvate is further broken down, releasing more energy stored in high-energy electron carriers (NADH & FADH2).
  • Electron Transport Chain (ETC) is the final stage that produces the most ATPs. Electrons transferred from NADH and FADH2 pass through protein complexes, with oxygen being the final electron acceptor creating water.

Types of Cell Respiration

  • There are two types of cell respiration methods: Aerobic and Anaerobic Respiration.
  • Aerobic respiration is the process of creating ATP in the presence of oxygen. It is the most efficient method, yielding approximately 36 ATP molecules per glucose.
  • Anaerobic respiration (including fermentation) happens in the absence of oxygen and produces a relatively small amount of energy (2 ATP from glycolysis).

Importance of Biological Oxygen

  • Oxygen is crucial in cell respiration as it serves as the final electron acceptor in the ETC, facilitating the formation of water.
  • In conditions where oxygen isn't available, glycolysis continues with anaerobic respiration, leading to the production of lactic acid or ethanol (fermentation) in different organisms.

Role of ATP

  • ATP (Adenosine triphosphate) is a high-energy molecule that provides energy for various cellular functions like muscle contraction, impulse propagation, and chemical synthesis.
  • During cell respiration, ATP is synthesized from ADP (adenosine diphosphate) and inorganic phosphate (Pi) in a process called phosphorylation.

Mitochondria and Respiration

  • Mitochondria are termed the 'powerhouse' of the cell because they are the principal sites for aerobic respiration.
  • They are specialised with a double membrane and a matrix that allow for the packaging and concentration of enzymes and substrates necessary for the Krebs cycle and the ETC.

Implications of Faulty Cell Respiration

  • Disruption of the cell respiration processes could result in a variety of human diseases, including cancer, Parkinson's disease, and Type II diabetes.
  • It underlines the significance of understanding cell respiration as it is a fundamental process of life.

Remember to regularly review this content to ensure comprehensive understanding and familiarise yourself with the various stages and components involved in cell respiration. Always relate concepts to real-life biological processes and phenomena when possible.

Course material for Biology, module Metabolism, cell respiration and photosynthesis, topic Cell respiration

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