Structure & function: Cells
Major Concepts (from lecture 2) •  Cell structure (including organelles) correlates with func:on •  More complex biology requires more specializa:on – trade-­‐
offs (e.g. mul:cellular organisms have more steps that can be regulated, but also more steps that can go wrong) •  There are 3 types of cytoskeleton filaments which play diverse roles in the cell •  Energy can be transformed from one type to another •  Cells respond to signals in their environment •  Signals are perceived by receptors •  Ac:vated receptors ac:vate intracellular signaling molecules which in turn alter cell ac:vity (e.g. cell movement) 1
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Chemistry of Life Take home points: Molecules are atoms bonded together The rela:ve electronega:vity of the atoms determines the type of bond formed You can learn a lot about a molecule from the organiza:on and arrangement of atoms that it is made of. 2
Basic Signal Transduc:on Pathway 3
To understand complex cellular processes we need to understand the chemical nature of cellular components For example:
Why do some cell signals bind to receptors inside the cell while others
bind receptors at the cell membrane?
Fig. 8.13
Fig. 8.14
Figure 2.3
The Structure
Atoms Found
In Organisms
Distribu-on of of
electrons in elements is key Which are the most common atoms found in organisms?
Elements commonly found in living organisms have What do you notice is in common
unfilled outermost shells among
these atoms?
Hydrogen
How many bonds can carbon form?
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
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In Class Ac:vity: Biological Molecules •  Work in groups of 3 to complete the exercise •  We will ask clicker ques:ons as you work through the exercise •  Ask a TA/instructor if you do not understand the ques:ons 6
Why is H20 such an important molecule? 7
What Does the Intracellular Environment Look Like?
Molecules in Cells Exist in
an Aqueous Environment
5 million fold magnification
Illustration from Machinery of Life by David Goodsell
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REVIEW AT HOME: You should be familiar with everything in Table 2.3
Carbon forms 6 major functional groups that “flavor” biological molecules
Test yourself: Predict whether each functional group is polar or nonpolar
based on the electronegativities of atoms involved.
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Key Concepts •  Chemical bonding exists on a con:nuum from nonpolar to ionic (see fig. 2.7) •  Electronega:vity is a measure of the power of an atom to aZract electrons to itself O>N>C=H (memorize this!) •  The types of bonds determine whether a molecule is primarily hydrophobic or hydrophilic •  The closer to equal sharing of electrons, the more energy a bond contains (chemical energy) •  H2O is probably the most important small molecule for life 10
You should be able to: Recognize polar vs nonpolar bonds and relate this to poten-al energy Relate bond type and hydrophobicity/hydrophilicity VOCABULARY
Electronegativity, hydrophobic, hydrophilic, polar, nonpolar
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