Month: June 2020

 

For each of the following, know where they are made and where they are used  (The light cycle or Calvin Cycle): ATP, NADPH, NADP+, Oxygen, Carbon Dioxide, Sugars,  Part of the table is filled in for you. Can you fill in the rest?  

Compound	Light Cycle	Calvin Cycle
ATP	Made	Used
NADPH
NADP+
Oxygen	Made	Not made or used
Carbon Dioxide
Sugars

 

The link below is an exercise to put steps of photosynthesis in order

Photosynthesis Order

 

Be able to interpret an action spectrum and distinguish it from an absorbance spectrum

Plants move toward light. The image below shows how the relationship between the wavelength of light and the degree of movement. This is an action spectrum, because it measures a plant response as a function of wavelength. This can be compared to an absorbance spectrum which measures absorbance of light as a function of wavelength (like our first lab). What would you predict about the absorbance spectrum of a pigment that was responsible for the response in the graph below? What would be a good title for this graph?

Action Spectrum for phototropism

 

Be able to label a chloroplast and show where the Calvin cycles and light cycles take place.

 

Be able to compare respiration with photosynthesis. Which processes and components do they have in common?

 

 

 

To understand the basic energy rules, view the slideshow

Energy Rules

Here is a video on thermodynamics and perpetual motion machines

Perpetual Motion machines and Thermodynamics

Enzymes:  First watch this video

Enzyme Video

Know what substrates are and how they relate to enzyme catalyzed reactions.

Example what is the substrate in this enzyme catalyzed reaction

Lactose→Glucose + Galactose?

The enzyme in this reaction is lactase

Know how enzymes catalyze biological reactions, specifically their effects on activation energy. 

Another concept in how enzymes speed up reactions is activation energy. Imagine you have a homework assignment due next week. You could do it now, or you could put it off until right before it is due.  The activation energy is the energy needed to get the process started. Note that the homework might take you an hour whether you do it now or later. The activation  energy is just what it takes to get started. Enzymes decrease activation energy as shown in the diagram in the link

Activation Energy

 

Note that that the ΔG (The overall energy) does not change whether or not the enzyme is present. Enzymes also have no effect on the equilibrium of a reaction; adding an enzyme does not shift the reaction to the left or right.  It does change how quickly the reaction reaches equilibrium.

Understand how compounds that bind to the active site or allosteric site can alter enzyme function

Many drugs can inhibit enzyme function by binding to the active site. Here is an example

HIV Drug Action

The key point here is that the inhibitor binds very strongly to the active site preventing the substrate from binding. Because both the inhibitor and substrate bind to the same site, the binding is said to be competitive.  If the concentration of substrate increases, the inhibitor is less effective.

We have already mentioned active sites, they bind to the substrate(s) of a reaction. Some enzymes also have allosteric sites. These do not bind to substrates but they bind to compounds that can turn on (activators) or turn off (inhibitors) an enzyme as shown in this video

Allosteric regulation of enzymes

Non-competitive inhibitors bind to the allosteric site.  Adding more substrate has no effect on allosteric inhibitors since the inhibitor changes the active site to be “closed”.

Know what feedback inhibition is and how it can be used to control amino acid synthesis.

Feedback inhibition

Here is an example of how this works to control amino acid levels

Feedback inhibition o f amino acid synthesis