Unformatted text preview: 2/1/17 Lecture 7 Lipids Lipids, Membranes, and the First Cells • Organic molecules • Insoluble or only slightly soluble in H20 • Structures vary widely BIOL 225
Prof. Liz Allison
February 1, 2017 1. Fats and O ils “Triglyceride” Glycerol Fatty acids An adipose (fat) cell in which lipid droplets (green)
and mitochondria (red) have been stained with two different fluorescent dyes. Properties of f at are determined by: • Length of fatty acid chain
• Number of double bonds
Hydrocarbon chains The fatty acids chains are hydrocarbons.
Ester linkages are not bonds she highly
emphasizes. The fatty acid composition determines a
fats state at room temperature. Fats with
double bonds cannot tightly pack together,
lowering their melting point. Saturated have
a linear structure, with no double bonds.
Unsaturated have double bonds and a kinked
structure, making them liquid at room temp. 1 2/1/17 3. Steroids
2. Waxes • Highly insoluble in H2O • Long chain fatty acids linked to long chain alcohols • Protective coating Cholesterol Scale insects on a lemon tree branch These are impermeable to another level- 4. Phospholipids
The key to the structure of cell membranes in Bacteria and Eukarya
Hydrophilic or hydrophobic?
bilayers Phospholipids are both hydo phobic and philic, this is
how a membrane bilayer is spontaneously formed (or
a sphere like shape forms) • Cell membrane component
• Precursor of vitamin D and sex steroid hormones Steroids include things like testosterone and
progesterone. Even Cholesterol, which is the
precursor to the various steroid hormones, and an
important aspect of the cell membrane (increase
fluidity). Membranes are vital • Separate the cell from the outside world • Separate compartments inside the cell But…cells need to communicate with their environment and other cells, acquire and utilize energy, etc… Membranes keep things in and out, the cells still
need to communicate with the outside world 2 2/1/17 Selective Permeability of Lipid Bilayers
High permeability Permeability scale (cm/sec) 100 Small,
molecules O2, CO2, N 2 10−2
molecules H 2O,
10 −12 Low permeability Large,
Na + Ions Lipid
bilayer Animation: Diffusion Phospholipid bilayer The lipid bilayer is selectively permeable. The
permeability scale is cm / sec. Non-polar molecules
cross rapidly due to their lack of charge. Water and
glycerol, too can pass thru relatively easily. Red Blood Cell in Isotonic Solution Net water movement via osmosis: •Double the number of solute molecules on the left side of the membrane. IN, OUT, or NO CHANGE?
Red Blood Cell in Hypertonic Solution Red Blood Cell in Hypotonic Solution •At equilibrium, would the water level on the left side be higher or lower than what is shown here? The movement/diffusion of water is called osmosis.
Water moves to where there is a higher solute
concentration. In cells, the concentration matters
ISOTONIC : concentration the same within and
without the membrane (no net movement)
HYPERTONIC: There is more solute outside of the
membrane, water moves out of the cell
HYPOTONIC: Lower concentration of solute outside
of the cell, water moves into the cell
This is a relative term, when using it always define
one to the other. 3 2/1/17 Research Box Project What is a primary r esearch paper? Due no later than Monday May 1, 2017 at 1:00 pm • A primary research paper can be distinguished from secondary sources—such as review articles, textbooks, and magazine articles—by looking for key characteristics. • Choose a recent primary research paper (from 2015, 2016, or 2017) on a topic that falls within material covered in Chapters 2-21 of the text.
• Select one figure (or part of a multi-part figure) in the Results section and construct a Research Box that represents findings of an experiment.
• Use the same format as the Research Boxes in your textbook (see Template under Course Information). • Turn in a hard copy of your Research Box and the primary research paper, ISC 2117 • A primary research paper includes a detailed description of methods and results, written by the researchers who did the work. • A typical paper contains a Title, Abstract, Introduction, Materials and Methods (or Experimental Design), Results and Discussion, although the order and name of the sections varies from journal to journal. Example from Chapter 6
Where can you find primary research papers?
• You can get an electronic copy of most articles through online databases such as PubMed, ScienceDirect, or Google Scholar, or through the library. d/ But first, some background information…. 4 2/1/17 Permeability is a function of temperature and… Lipid bilayer
hydrocarbon tails Higher
and fluidity Lipid bilayer
hydrocarbon tails Lower
and fluidity Example from Chapter 6 Hypothesis: A testable statement to explain a phenomenon or a set of observations. A null hypothesis specifies what should be observed when the hypothesis being tested isn’t correct. Note the added labels and color-coding of graph to make it easy to understand. Prediction: a measurable or observable result that must be correct if a hypothesis is valid. 5 2/1/17 • I am happy to provide feedback on rough drafts of your project.
Recommended reading from the textbook
Chapter 6 (p. 119-130)
BioSkill 16: Reading and Citing the Primary Literature
• The last day to submit a rough draft for review is April 17, 2017 at 5:00 pm. 6 ...
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