Lecture 1: Introduction & Diffusion Dr McFawn Flashcards
What is Scientific Communication?
Science communication is the practice of informing, raising awareness of science-related topics, and also getting involved with audiences that include, at least in part, people from outside the science community.
Examples of Scientific Communication? (5)
- Oral presentations
- Scientific Posters
- Research Papers (This unit)
- Reviews and books
- Grant applications and research proposals
What are the Main elements of a Scientific Paper? (8)
1 * Title and authors
2 * Abstract (summary of the study)
3 * Introduction (sets up the aim, what is the hypothesis)
4 * Methods (how the aim was tested)
5 * Results (result of the test)
6 * Discussion (use the results to answer the aim)
7 * References
8 * Figures and tables
What should be Part of an INTRODUCTION of a SCIENTIFIC PAPER? (5)
1 * Introduction is the justification for the aim/hypothesis
2 * It makes the argument from known facts (give citations to
references) that the aim/hypothesis is reasonable to test.
3 * NOT a general review of what you know
4 * Keep the focus on moving to the aim
5 * What does the reader need to know to understand the aim
What should be Part of an METHODS AND RESULTS of a SCIENTIFIC PAPER? (7)
METHODS
1 * Methods is how the aim was tested
2 * Written in past tense as it is what you have done
3 * Not a recipe, not like a lab manual
4 * Assume the reader is a competent scientist and is using their own equipment
5 * You cannot assume the reader has seen your equipment or read your lab manual
RESULTS
6 * Results are what happened, the text which tells the story
7 * The results tells the reader in words what the result of the experiment was and refers the reader to the figures and tables.
What should be Part of an DISCUSSION AND REFERENCES of a SCIENTIFIC PAPER? (7)
DISCUSSION
1 * The discussion leads to the conclusion.
2 * Use the data in the paper to answer the aims from the introduction
3 * Keep the focus on YOUR results
4 * When you make a statement of fact, some claim not in your data, you must cite a reference for that fact.
* e.g. “post synaptic parasympathetic nerves release acetylcholine” is a statement of a fact and need a reference
5 * A paper’s introduction and discussion will be dense with citations
REFERENCES
6 * The references is the list of materials cited in the paper
7 * Use Vancouver style (Am J Physiol/ J Appl Physiol)
Elements of Figures in Data and Scientific Report. (5)
1 * Much of the data will be in figure, graphs or diagrams
2 * Each figure must have a legend (caption) that tells the reader
what the figure is about.
3 * Graphs and other figures should be close to publication quality
4 * Notice that every figure has a caption under it.
5 * In Scientific publishing every figure includes a legend which is part of the figure.
- See American Journal of Physiology and Journal of Applied Physiology for examples.
Remembering Diffusion:
How do materials move in and out the membranes of cells?
eg. Transport across Capillary wall
= 4
- Plasma Proteins exist inside the cell - PLASMA PROTEINS GENERALLY CANNOT CROSS THE CAPILLARY WALL
- EXCHANGEABLE PROTEINS ARE MOVED ACROSS BY VESICULAR TRANSPORT
- Small WATER SOLUBLE substances pass through the PORES
eg. Na+, K+, glucose and AMINOACIDS - LIPID-SOLUBLE Substances pass through the endothelial cells.
eg. O2, CO2
Importance of Diffusion?
- Diffusion vital for moving substance across cells
- Many biological processes depend on diffusion
- Exchange across capillaries
- Uptake of oxygen etc - critical for keeping cells alive, neurotransmission, action potentials
Explain the Process of Diffusion: 6
1 * Molecules diffuse from HIGH TO LOW CONCENTRATION
2 * MOVEMENT is RANDOM for each individual molecule
3 * MASS ACTION means more move from the high concentration to low that low to high
4 * Higher concentration difference, larger surface area or
thinner membrane mean faster diffusion
5 *Solubility and the exact molecule involved also change rate
6 *Not linear with distance, going twice as far is 4 times longer
Fick’s Law Diffusion: Elements of the equation
- Amount of substance moving per time is flow (mol/sec).
- Often use flux j (mol/sec/cm2) flow /Area
- Flux from diffusion depends on the concentration gradient dC/ds
- Diffusion constant for that substance and solvent D.
- D increases for small molecular weight
- Membrane thickness is s
LOOK AT THE FORMULA
Fick’s Law diffusion: EXPLAIN WHAT IT IS - 4
1 * Movement of individual molecules is random.
2 * Not very efficient as lots of changes in direction
3 * Over very short distance fast.
4 * Random direction changes make long distance movement slow
5 * Moving 10 times as far takes 100 times as long.
6 * Diffusion at cellular distance scales is fast
s= (2Dt)^1/2
7 * For diffusion in one direction
Cell Membrane Structure, Does diffusion occur? 4
1 * Diffusion into or out of cells.
2 * Cell membrane is a lipid bilayer
3 * Charged phospholipids face out
4 * Hydrophobic tails face
Understanding how diffusion occurs in the Cell Membrane
1 * Diffusion constant now depends on lipid and water solubility.
2 * Distance s is constant (thickness of membrane)
3 * Combine thickness, diffusion constant, area and solubility into permeability P
- J(x) = P x*( [X1] - [X2])
The Summary of Diffusion: 5
1 * Diffusion can move molecules from high to low concentration.
2 * Movement is down a concentration gradient from high to low.
3 * Diffusion is slow over long distance.
4 * Permeability depends on MEMBRANE THICKNESS, SOLUBILITY IN LIPIDS AND WATER ,DIFFUSION IS CONSTANT
5 * Small, LIPID SOLUBLE molecules enter cells FASTER (on average).
