Bioknowledgy
questioning, investigating and understanding
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  • IB Biology
    • Syllabus
    • General Resources
    • Practical scheme of work >
      • Practical activities (Labs)
      • Individual investigation
      • IB Write
  • Core
    • 1. Cell biology >
      • 1.1 Introduction to cells
      • 1.2 Ultrastructure of cells
      • 1.3 Membrane structure
      • 1.4 Membrane transport
      • 1.5 The origin of cells
      • 1.6 Cell division
    • 2. Molecular biology >
      • 2.1 Molecules to metabolism
      • 2.2 Water
      • 2.3 Carbohydrates and lipids
      • 2.4 Proteins
      • 2.5 Enzymes
      • 2.6 Structure of DNA and RNA
      • 2.7 DNA replication, transcription and translation
      • 2.8 Cell respiration
      • 2.9 Photosynthesis
    • 3. Genetics >
      • 3.1 Genes
      • 3.2 Chromosomes
      • 3.3 Meiosis
      • 3.4 Inheritance
      • 3.5 Genetic modification and biotechnology
    • 4. Ecology >
      • 4.1 Species, communities and ecosystems
      • 4.2 Energy flow
      • 4.3 Carbon cycling
      • 4.4 Climate change
    • 5. Evolution and biodiversity >
      • 5.1 Evidence for evolution
      • 5.2 Natural selection
      • 5.3 Classification of biodiversity
      • 5.4 Cladistics
    • 6. Human physiology >
      • 6.1 Digestion and absorption
      • 6.2 The blood system
      • 6.3 Defence against infectious disease
      • 6.4 Gas exchange
      • 6.5 Neurons and synapses
      • 6.6 Hormones, homeostasis and reproduction
  • Additional higher level (AHL)
    • 7. Nucleic acids >
      • 7.1 DNA structure and replication
      • 7.2 Transcription and gene expression
      • 7.3 Translation
    • 8. Metabolism, cell respiration and photosynthesis >
      • 8.1 Metabolism
      • 8.2 Cell respiration
      • 8.3 Photosynthesis
    • 9. Plant biology >
      • 9.1 Transport in the xylem of plants
      • 9.2 Transport in the phloem of plants
      • 9.3 Growth in plants
      • 9.4 Reproduction in plants
    • 10. Genetics and evolution >
      • 10.1 Meiosis
      • 10.2 Inheritance
      • 10.3 Gene pools and speciation
    • 11. Animal physiology >
      • 11.1 Antibody production and vaccination
      • 11.2 Movement
      • 11.3 The kidney and osmoregulation
      • 11.4 Sexual reproduction
  • Options
    • A. Neurobiology and behaviour >
      • A.1 Neural development
      • A.2 The human brain
      • A.3 Perception of stimuli
      • A.4 Innate and learned behaviour (AHL)
      • A.5 Neuropharmacology (AHL)
      • A.6 Ethology (AHL)
    • B. Biotechnology and bioinformatics
    • C. Ecology and conservation >
      • C.1 Species and communities
      • C.2 Communities and ecosystems
      • C.3 Impacts of humans on ecosystems
      • C.4 Conservation of biodiversity
      • C.5 Population ecology (AHL)
      • C.6 Nitrogen and phosphorus cycles (AHL)
    • D. Human physiology
  • Giving back - BioKQQAnswers

Essential idea: The structure of biological membranes makes them fluid and dynamic.

Above is are models of a plasma membrane showing how it's fluidity allows lipid soluble molecules to move directly through the membrane.

Understandings, Applications and skills:

1.3.U1 Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules. [Amphipathic phospholipids have hydrophilic and hydrophobic properties.]
1.3.U2 Membrane proteins are diverse in terms of structure, position in the membrane and function.
1.3.U3 Cholesterol is a component of animal cell membranes.
1.3.A1 Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.
1.3.S1 Drawing of the fluid mosaic model. [Drawings of the fluid mosaic model of membrane structure can be two dimensional rather than three dimensional. Individual phospholipid molecules should be shown using the symbol of a circle with two parallel lines attached. A range of membrane proteins should be shown including glycoproteins.]
1.3.S2 Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model.
1.3.S3 Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model.
[Text in square brackets indicates guidance notes]

Starters

The cell membrane rap by Mr W
Drawing the structure of the plasma membrane
a good knowledge check for the start of lessons, use the video to check your understanding and test yourself


Presentation and notes

The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the develop of student notes to aid revision.
Download presentation

Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
Download notes

Labs

Membrane integrity
Investigating the effect of temperature on beetroot membranes
n.b. this outline was written for the old syllabus, the document needs updating, but the lab is still a valid one.

Concept mapping activity

Try out this mapping activity on membrane structure from BiologyForLife:

  • After the sheets have been printed cut out the phrases
  • Now build your map
  • Draw lines to show how the phrases link together
  • Annotate the lines to explain the linkages

hint: one strategy is to first try to separate the phrases into small groups with obvious links, then link together the groups slowly making the map larger until all the cards are used.

example of a completed map

Quick Quiz

Quick quiz Use the BioK Quick Quiz on 1.3 Membrane structure (as directed) to check your understanding of the topic.

Weblinks:

Membrane structure
Phospholipid bilayer by the College of Siskiyous
Membrane structure tutorial by Davidson College
Construction of the cell membrane by Wisconsin online
Membrane structure and the fluid mosaic model by Candle light productions
Phospholipid membranes by Carnegie Mellon

A series of helpful animation concerning biological membranes by Carnegie Mellon

Membrane fluidity

Membrane fluidity from Learn.Genetics
Animated plasma membrane, by John Kyrk
Membrane fluidity from John Gianni

Origin of cells
Exploring Life's Origins - the importance of membranes lipids to the development of cells is
discussed in this well written article - this article links nicely with 1.5 Origin of cells
_
Here's a fun musical interlude from the Standford biologists

Nature of science:

Using models as representations of the real world—there are alternative models of membrane structure. (1.11)
Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9)

(both NoS points are well dealt with in the presentation)

Theory of knowledge:

The explanation of the structure of the plasma membrane has changed over the years as new evidence and ways of analysis have come to light. Under what circumstances is it important to learn about theories that were later discredited?
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