Synthesis

Today, we examined synthesis reactions - the process by which the cell makes larger molecules.  This can be used to store food for later, as in the case of synthesizing a polysaccharide like starch or glucose; or, the cell can use synthesis to build functional or structural molecules - for example, synthesizing an enzyme or membrane protein from amino acids, or synthesizing a phospholipid from fatty acid tails, glycerol, and a phosphate.  With synthesis, the cell can build whatever it needs from the raw materials taken in from digestion.  Ian B. made a really good connection to digestion today, pointing out that we humans eat big polymers, break them down into monomers so they are small enough to cross the cell membrane into the cell, and then the cell uses synthesis to reconstruct the polymers inside it.  Pretty cool!

Homework
1) On looseleaf, write a response to the prompt we discussed in class: Explain the role of enzymes, activation energy, and ATP in the synthesis of a disaccharide from two monosaccharides [6].  

2) Your post-interim assignment is due Monday.

Best,
Mr. Hill

Carbs and Lipids

Today, we talked about how the molecular structure of carbs and lipids is related to their properties.  We talked about carbs, looking at the example of the monosaccharide (or simple sugar) glucose:

And we looked at a triglyceride, a molecule of fat composed of glycerol and three fatty acids:

You should be able to discuss the molecule in relationship to their polarity, energy capacity, and readiness to break down via respiration.

Homework

Read textbook pages 138-141 about monosaccharides, disaccharides, and polysaccharides, and answer the following questions in your journal:

1. Name two examples of each of the following: (a)monosaccharide, (b)disaccharide,  (c)polysaccharide
2. What's the difference between a monosaccharide, disaccharide, and polysaccharide?
3. Draw a picture of a condensation (dehydration synthesis) reaction between two monosaccharides to make a disaccharide.  Label the atoms that are removed and the new bond that is formed.
4. When you eat a candy bar, some of the glucose you take in is respired immediately, and some is synthesized into larger chain molecules (polysaccharides).  Why would your cells bother to synthesize a polysaccharide?

NOTE!!  I am missing the "Art of Explanation" unpacking take home quiz from last Friday for the following students:

IAN
JAFAR
GENESIS
BRIAN

If you have this, please hand it in tomorrow otherwise it's a zero!

Anaerobic and Aerobic Cell Respiration

Today, we debriefed cell respiration a little and then learned how cell respiration can be used to explain two phenomena that occur when we are very active: heat and soreness.  In lecture, we revealed two new facets of cell respiration:

1. The energy transfer is inefficient (about 60% efficient, to be precise)
2. Respiration can be aerobic (using oxygen at a higher energy yield) or anaerobic (no oxygen, lower energy yield).

(R6 - we're going to do #2 tomorrow, no worries)

Homework - do on a separate sheet of paper, to be collected

R4 - Respond to the following prompt on a separate sheet of paper, and treat it like a short answer.  This means you should unpack it, and then repack in written form, to get a lot of detail!

Prompt: Explain why anaerobic respiration yields less energy than aerobic respiration. [4]

R6 - Respond to the following prompt on a separate sheet of paper, based on our discussion today.  Treat it like a short answer - meaning you should unpack it, repack it in written form, and give a lot of detail.

Prompt: Explain why activation energy is only required once, at the beginning of cell respiration. [4]

Cell respiration model

Hi all,

Today in class we debriefed your homework and described the structure of ATP, and then went on to model cell respiration.

When you think of cell respiration, think about it as coupled reactions.  The rule of thumb is: break a bond, make a bond.  Meaning, when you break a bond in glucose and release the potential energy stored within it, you have to capture that energy; to do so, you have to make a new bond - for example, a new phosphate bond between ADP and Pi.  Now, that energy is captured and stored again, ready to use for the cell.

Homework
I had planned a lecture for tomorrow, but I'm going to adjust the schedule in order to give us a little more time to discuss what happened in class yesterday.  For tonight, take a break, or continue working on your post-interim assignment, due Friday.

Thanks
Mr. Hill

Great review website - thanks to Genesis

Hi all, check out this great link for interactive biology animations and tutorials.  Thanks to Genesis for pointing this out!  It has many high quality and informative reviews of the topics we have discussed and future topics.  Definitely book mark this for when you are doing your assessment statements.

Interactive Animation for Biology

Potato Chip = Energy

Today, we examined the burning of a potato chip as an example of the transformation of energy that occurs.  Cell respiration, the metabolic reaction that creates energy from food in our cells, is a variation on that same reaction.  The only difference with cell respiration is that in our body, we "burn slow" - meaning we use enzymes to carefully control the reaction so that we can capture the energy in a useable form.  That form, of course, is our good old friend ATP.


Homework
For homework, you will use the following web resources to investigate how the cell manages energy.  After viewing and reading all the resources, please answer the questions that follow in your class journal and be ready to discuss your findings tomorrow.

Resources:
ATP and Energy Storage
Cell Respiration Video


Questions

1. Draw the generalized structure of an ATP molecule.
2. Explain how ATP is like a "rechargeable battery" for the cell.
3. What type of energy is ATP?  (Potential, kinetic, chemical, thermal, nuclear, gravitational, etc).  Explain your answer.
4. Write the equation for cell respiration.
5. Pause the cell respiration video and draw the chemical structure of glucose.  
6. Where does the CO2 released by cell respiration come from?
7. Where does the H2O released by cell respiration come from?
8. The second video says that energy stored in glucose is like "money in the bank" but energy in ATP is "money in your pocket."  Explain what this means.

The Art of Explanation

Hi all,

On Friday, we looked at unpacking, a strategy to maximize the depth of explanation in a short response.  This works best when you see the command term explain on your IB exams.  The goal is to give a lot of depth at the molecular and cellular level about what's going on.  To use this strategy on a short answer:

1. Identify key concepts the question is asking about.
2. Unpack those concepts by brainstorming everything we learned in connection with them.
3. Draw a model of what's happening at the cellular or molecular level.
4. Repack your explanation into a few concise, deep sentences explaining the phenomenon.

For example, in the prompt "Explain the necessity of enzymes in digestion"

I would "unpack" the terms enzyme (biological catalyst, lowers activation energy, speeds up reactions, breaks down bigger molecules into smaller molecules, acts on a substrate, examples are amylase, pepsin, lipase) and digestion (break down of big molecules like polysaccharides, polypeptides, and fatty acids into smaller molecules, absorption into blood stream, smaller molecules diffuse into cells, where they can be respired).  I can use this information to now answer the question in greater depth.

For homework:

"Repack" the examples we looked at in class, writing your deep explanations.  This will go in as a take home quiz grade, so do a good, thorough job.  If you are missing the sheet, the questions are:

1. Explain, with an example, the necessity of enzymes in digestion.
2. Explain the effect of pH on enzyme activity.
3. Explain why the rate of glucose uptake by facilitated diffusion (on the DBQ) levels off after an external concentration of 450.
4. Explain the importance of the tertiary structure of proteins to membrane ion channels.

Below is the graph for #3 for those who may need it.  Thanks to Kai Ni for pointing this out!

On Monday, we're moving onto our next topic: cell respiration (whoo!)

Best,

Mr. Hill

Back in Bio

Hi all,

We're back and we survived our first round of interims!  Congratulations!

Homework
Please complete the interim reflection template and prepare it to hand in, with your interim, tomorrow.

Note that you are only selecting what post-IA assignment you want to do; it will not be due until next Friday.  I am going to look over your decisions over the weekend and approve them.

Virtual Office Hours for Interim

Hi all,

I will be conducting virtual office hours on this Sunday, Nov. 8th, from 7PM-9PM.  Good luck studying for your interim!

For your interim, please remember to bring

1. Your assessment statements to hand in
2. A calculator
3. A ruler
4. A pen and pencil

Best!

Mr. Hill