Biology Matters GCE 'O' Level Textbook - Comprehensive Notes

Biology Matters GCE 'O' Level Textbook Notes

About the Biology Matters Author Team

  • Lam Peng Kwan:

    • More than 40 years of experience teaching Biology at secondary and junior college levels.

    • First prize winner of the Creative Science Teachers' Award.

    • Authored several Biology textbooks and workbooks.

    • Specialist writer in Biology for the Curriculum Development Institute of Singapore.

  • Eric Lam Y K:

    • Graduated with First Class Honours in Molecular Biology from the National University of Singapore.

    • An internationally recognised expert in STEM learning, inquiry-based pedagogies, formative assessments and eLearning.

    • Pioneered an award-winning method of inquiry-based teaching using interactive technologies.

    • Co-authored Biology textbooks and workbooks.

About This Book

  • Aligned with the latest GCE 'O' Level Biology syllabus by the Ministry of Education.

  • Designed for effective concept development and reinforcement

  • Includes tasks and activities for students to apply critical and creative thinking skills.

  • Uses real-life contexts, infographics and integrated videos and simulations to enhance learning.

  • Chapter Opener:

    • Introduces the topic with engaging real-life contexts and trigger questions.

  • What You Will Learn:

    • Provides an overview of the sections to be covered in the chapter in the form of inquiry questions

  • Learning Outcomes:

    • List the learning objectives at the start of each section to keep students focused.

  • Biology Connect:

    • Allows students to scan the QR codes to access complimentary digital resources* such as videos and simulations that are interesting and informative, making science truly come alive.

  • Tech Connect:

    • Showcases cutting-edge technology used for the benefit of life, society and the environment

  • Link forward/backward:

    • Shows connections across chapters and sections by linking back to students' prior learning and linking forward to prepare them for related chapters they will learn later.

  • Link to Physics/Chemistry:

    • Allows students to appreciate the interconnectedness of concepts among the various science subjects.

  • Worked Example:

    • Guides students on how to interpret a question and work out the solution.

  • Let's Practise:

    • Prompts immediate checks on understanding at the end of the section and facilitates the reinforcement of key concepts.

  • Concept Cartoon:

    • Challenges students' ideas, triggers discussions and aids in clearing misconceptions.

  • Helpful Note:

    • Highlights misconceptions, tips and additional information to support students' learning.

  • Let's Investigate:

    • Reinforces concepts through investigative procedures or hands-on activities.

  • Problem-based Learning Activity:

    • Hones problem-solving skills by encouraging students to develop solutions to a real-life problem.

  • Cool Career:

    • Showcases a career related to the topic to inspire students and show them the relevance of science in the workplace

  • Disciplinary Ideas:

    • Highlight the overarching ideas of Biology that can be applied to explain real-life problems or phenomena. The Disciplinary Ideas include:

      • The Cell - Diverse life forms are similar in that their basic unit are cells.

      • Structure and Function - Structure and function of organisms from the molecular to the organ system levels are related to each other.

      • Systems - Biological systems interact among themselves and with the environment resulting in the flow of energy and nutrients.

      • Energy - To ensure survival, living organisms obtain, transform and utilise energy from the external world.

      • Homeostasis, Co-ordination and Response - Living organisms detect changes both from the surrounding environment and within themselves so that they are able to respond to these changes to maintain a constant internal environment needed for sustaining life.

      • Heredity - Genetic information is passed on from parents to offspring during reproduction to ensure the continuity of life.

      • Evolution - The diversity of living organisms is achieved through a process of evolution, driven by mechanisms such as natural selection.

  • Past to Present:

    • Inspires the spirit of scientific inquiry through examples of scientific innovation and the evolution of scientific developments over time, demonstrating the nature of science.

  • Let's Map It:

    • Summarises the relationships among key concepts in the chapter through a visual concept map.

  • Word Alert:

    • Provides language support by explaining certain difficult words in context or giving information on word forms.

  • Let's Review:

    • Provides questions at the end of the chapter for students to review their understanding of concepts.

  • The following features are also included at the end of the book:

    • Answer Key lists the answers to Let's Practise, Let's Investigate and Let's Review.

    • Quick Revision Guide consolidates key definitions and concepts at the back of the book for easy revision.

    • Index provides a list of key words with page reference for easy searching.

Contents

*Cells and the Chemistry of Life
* Cell Structure and Organisation
* What are cells?
* How Are Cells Adapted to Their Functions?
* Movement of Substances
* What Is Diffusion?
* What Is Osmosis?
* What Is Active Transport?
* Biological Molecules
* What Are Carbohydrates?
* What Are Fats?
* What Are Proteins?
* Enzymes
* What Are Enzymes?
* What Are the Characteristics of Enzymes?
*The Human Body - Maintaining Life
* Nutrition in Humans
* What Is Nutrition?
* What Is Digestion?
* What Is Absorption?
* What Happens to the Absorbed Nutrients?
* What Are the Effects of Alcohol Consumption?
* Transport in Humans
* What Are the Main Components of Blood?
* What Are Blood Groups?
* How Are Blood Vessels Adapted to Their Functions?
* How Does Blood Circulate in the Human Body?
* What Is Coronary Heart Disease?
* Respiration in Humans
* Why Do Living Things Respire?
* How Does Gas Exchange Occur in Humans?
* How Do We Breathe?
* What Effects Does Tobacco Smoke Have on Human Health?
* Excretion in Humans
* Why Is Excretion Necessary?
* What Makes Up the Human Urinary System?
* How Is Urine Formed?
* What Is Osmoregulation?
* What Happens When the Kidneys Fail?
* Homeostasis and Hormonal Control
* Why Is Homeostasis Necessary?
* How Do Hormones Control the Human Body?
* How Does the Body Maintain a Constant Body Temperature?
* The Nervous System and the Eye
* What Makes Up the Human Nervous System?
* What Is the Structure of the Human Eye?
* How Do We See?
* Infectious Diseases in Humans
* What Are Infectious Diseases?
* What Are the Structures of a Bacterial Cell and a Virus?
* How Can Infectious Diseases Be Prevented and Managed?
*Living Together - Plants, Animals and Ecosystems
* Nutrition and Transport in Flowering Plants
* What Are the Leaf Structures and Their Functions?
* What Are the Functions of Xylem and Phloem?
* What Is Photosynthesis?
* How Can We Study the Movement of Substances in Plants?
* How Does Water Enter a Plant?
* How Does Water Move Up a Plant?
* Organisms and Their Environment
* How Does Energy Flow Through an Ecosystem?
* What Are Ecological Pyramids?
* How Are Nutrients Recycled Through an Ecosystem?
* What Are Carbon Sinks?
* How Do We Affect the Ecosystem?
* Why Is There a Need for Conservation?
*Continuity of Life
* Molecular Genetics
* What Is DNA?
* What Are Genes?
* How Can Genes Be Transferred Between Organisms?
* What Are the Considerations Surrounding Genetic Engineering?
* Modes of Reproduction
* What Is Asexual Reproduction?
* What Is Sexual Reproduction?
* Reproduction in Plants
* What Are the Parts of a Flower?
* What Is Pollination?
* What Happens After Pollination?
* Reproduction in Humans
* What Makes Up the Human Reproductive System?
* What Is the Menstrual Cycle?
* What Happens During and After Fertilisation?
* What Is HIV/AIDS?
* Inheritance
* What Is the Mechanism of Inheritance?
* What Is Some Basic Knowledge Needed for Studying Inheritance?
* How Are ABO Blood Groups Inherited?
* How Is Sex Determined?
* What Is Variation?
* What Is Natural Selection?

Cell Structure and Organisation

  • Imagining Cells as Chemical Factories

    • Cells are the building blocks of life; the simplest structural and functional units.

    • Cells take in raw materials, process them to make new molecules, and transport these molecules.

    • Organelles like mitochondria and chloroplasts perform different roles, increasing efficiency.

  • How Did Cells Get Their Name?

    • Robert Hooke coined the term 'cells' in 1667 after observing cork slices under a microscope.

  • How Can We Study the Parts of the Cell?

    • Light microscopes magnify objects up to 1000x.

    • Electron microscopes magnify objects to more than 200 000x.

    • Micrographs are pictures taken using microscopes.

    • Sections of cells can be made in transverse (T.S.) or longitudinal (L.S.) planes for clearer observation.

  • What Does a Cell Consist of?

    • A cell consists of protoplasm: cell membrane, cytoplasm, and nucleus.

    • Protoplasm is a complex jelly-like substance where chemical activities occur.

  • Cell Membrane

    • Made of lipids and proteins.

    • Partially permeable controlling movement of substances in and out of cell.

  • Cell Wall

    • Present in plant cells, made of cellulose.

    • Protects and gives fixed shape to the cell.

    • Fully permeable.

  • Cytoplasm

    • Jelly-like substance enclosed by the cell membrane.

    • Contains organelles, each specialized for a specific function.

  • Nucleus

    • Surrounded by nuclear membrane.

    • Contains genetic information in the form of chromosomes.

    • Controls cell activities and is essential for cell division.

  • Chromosomes

    • Long thread-like structures in the nucleus made of proteins and DNA.

    • DNA carries instructions for cell activities.

    • Condense and shorten during cell division becoming thick and rod-shaped.

  • Rough Endoplasmic Reticulum (RER)

    • Network of flattened spaces lined with a membrane.

    • Ribosomes are attached to its outer surface, making it appear rough.

    • Continuous with the nuclear membrane.

  • Ribosomes

    • Small round structures attached to the RER or lying freely in the cytoplasm.

    • Synthesise proteins.

    • Ribosomes attached to RER make proteins transported out of the cell.

    • Ribosomes lying freely in the cytoplasm make proteins used within the cell.

  • Smooth Endoplasmic Reticulum (SER)

    • More tubular than RER and does not have ribosomes attached.

    • Synthesises fats and steroids.

    • Converts harmful substances into harmless ones (detoxification).

  • Golgi body

    • Consists of a stack of flattened spaces surrounded by membranes.

    • Modifies substances made by ER, stores, and packages these into vesicles for secretion.

  • Mitochondria

    • Small, oval, or sausage-shaped organelles.

    • Site of aerobic respiration, breaking down food to release energy.

  • Chloroplasts

    • Oval structures found in plant cells containing chlorophyll.

    • Chlorophyll is essential for photosynthesis.

  • Vacuoles

    • Fluid-filled spaces enclosed by a partially permeable membrane.

    • Store substances within the cell.

    • Plant cells have a large central vacuole with cell sap; animal cells have many small, temporary vacuoles.

  • Differences Between Plant and Animal Cells

    • Plant cells have a cell wall, large central vacuole, and chloroplasts; animal cells do not.

    • Tissues, organs, and organ systems are levels of organization beyond the cell.

  • How Are Cells Adapted to Their Functions?

    • Specialized cells develop unique structures (differentiation).

    • Examples include:

      • Red blood cells' biconcave shape and lack of nucleus for efficient oxygen transport.

      • Muscle cells' elongated shape and many mitochondria for energy.

      • Root hair cells' extension to increase surface area for water and mineral absorption.

  • Different cells structures leads to differences in functions between plants and animals

Movement of Substances

  • What Is Diffusion?

    • Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

    • It plays a role in nutrient uptake and gaseous exchange.

    • Concentration gradient is the difference in concentration between two regions.

  • Factors That Affect the Rate of Diffusion:

    • Concentration gradient: a steeper gradient results in a faster rate of diffusion.

    • Diffusion distance: shorter distances result in higher diffusion rates.

    • Surface area-to-volume ratio: a greater ratio promotes higher diffusion rates.

  • What Is Osmosis?

    • Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane.

    • Water potential measures the tendency of water molecules to move.

  • How Does Osmosis Affect Living Organisms?

    • In a solution with higher water potential, a plant cell becomes turgid, and an animal cell may burst.

    • In a solution with the same water potential, there is no net change.

    • In a solution with lower water potential, a plant cell becomes flaccid (plasmolysis), and an animal cell shrinks (crenation).

  • Turgor is important in plants for maintaining shape and movements of certain plant parts.

  • What Is Active Transport?

    • Active transport is the process in which energy is used to move particles across a membrane against a concentration gradient.

Biological Molecules

  • The Need for Food and Water

    • Living organisms need food for nutrients (water, carbohydrates, fats, and proteins).

  • Carbohydrates

    • Organic molecules made of carbon, hydrogen, and oxygen (2:1 ratio).

    • Classified as single sugars (glucose, fructose), double sugars (maltose, sucrose), or complex carbohydrates (starch, cellulose, glycogen).

    • Sugars are sweet, soluble, and provide energy.

    • Single sugars (glucose, fructose) are the basic units.

    • Double sugars (maltose, sucrose) are formed from two single sugars.

    • Starch, glycogen, and cellulose are complex carbohydrates made of numerous glucose molecules.

      • Starch is a storage form of carbohydrates in plants.

      • Cellulose is present in plant cell walls.

      • Glycogen is a storage form of carbohydrates in mammals.

  • Breakdown of Starch

    • Starch is digested by amylase to form maltose.

    • Maltose is hydrolysed by maltase to form glucose.

  • Test for Reducing Sugars

    • Add Benedict's solution and boil; a red precipitate indicates reducing sugars (glucose, fructose and maltose are also known as reducing sugars).

  • Test for Starch

    • Add iodine solution; a blue-black color indicates starch.

  • Functions of Carbohydrates

    • Substrate for respiration, supporting structures, conversion into other organic compounds, formation of nucleic acids, synthesis of lubricants, synthesis of nectar.

  • Fats

    • Organic molecules made of carbon, hydrogen, and oxygen (less oxygen than carbohydrates).

    • Broken down into fatty acids and glycerol.

    • Can be animal or plant-based.

    • Functions: source and long-term storage of energy, insulation, solvent for fat-soluble vitamins, cell membranes, reduce water loss.

  • Test for Fats

    • The ethanol emulsion test is a test for the presence of fats. A white emulsion is formed when ethanol and water are added to fats.

  • Proteins

    • Organic molecules containing carbon, hydrogen, oxygen, and nitrogen.

    • Building blocks are amino acids with an amino group (-NH2), an acidic group (-COOH) and variable side chain.

  • Chain of amino acids is a polypeptide; polypeptides and proteins are joined to form even longer chains.

  • Functions of Proteins

    • Synthesis of new cytoplasm.

    • Synthesis of enzymes and some hormones.

    • Formation of antibodies.

  • Test for Proteins

    • The biuret test is a test for the presence of proteins. the solution will turn violet (deep purple) when proteins are present.

Enzymes

  • Biological Catalysts

    • Enzymes are proteins that act as biological catalysts, speeding up chemical reactions without being changed themselves.

    • Enzymes lower activation energy, the energy needed to start a reaction.

  • What Reactions Do Enzymes Catalyze?

    • Enzymes break down large food molecules into smaller, soluble ones for absorption.

    • Digestive enzymes include amylase, maltase, protease, and lipase.

    • Enzymes also build up complex substances from simpler ones (anabolic reactions) or break down complex substances to simple substances (catabolic reactions).

  • **Enzymes are classified according to the chemical reactions they catalyse such as carbohydrases, proteases or lipases.

  • Characteristics of Enzymes

    • Enzymes Speed Up Chemical Reactions

    • Enzymes Are Specific in Action

    • Enzymes Are Required in Minute Amounts and Remain
      Unchanged at the End of Reaction

    • Enzymes Are Affected by Temperature

      • Each enzyme works best at a certain temperature called the optimum temperature.

      • Higher temperatures lead to denaturation (change in shape) of the enzyme.

    • Enzymes Are Affected by pH

      • Each enzyme has the best effect in a solution that is at its individual optimumpH. As the solution becomes more acidic or alkaline, the effect of the enzyme reduces.

  • How Does an Enzyme Work?

    • 'Lock-and-key' hypothesis: the active site (grooves or pockets) of an enzyme fits the substrate molecule, forming an enzyme-substrate complex.

    • The products are released, and the unchanged enzyme is free to catalyze another reaction.

Transport in Humans

  • What Are the Main Components of Blood?

    • Plasma: transports blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins

    • Red blood cells: Contain haemoglobin for oxygen transport; have a biconcave shape for large surface area and volume ratio. The oxygen is transported from the lungs to the other parts of the body in the form of oxyhaemoglobin.

    • White blood cells: Function in phagocytosis, antibody formation, and tissue rejection

    • Platelets: Contribute to blood clotting (e.g., Fibrinogen to fibrin)

  • Human store their food to see them through store their food to see them through. Unfortunately, bacteria and fungi attack stored food and make it go bad. One way of preventing this is to store food in strong salt solutions (brine) or sugar solutions (syrups).

  • In human systems, osmosis has water molecules that may require active energy for transport against a concentration gradient this is different to that of active transport.

Human Respiratory system

  • What Effects Does Tobacco Smoke Have on Human Health?

    • Harmful Effects on the Digestive System:

      • stimulates acid secretion in the stomach. Excess stomach acid increases the risk of gastric ulcers. In turn, these problems may lead to poor appetite and digestion

    • Harmful Effects on the Nervous System:

      • Alcohol is a depressant. It slows down some brain functions. Its effects vary from one perso