Thursday, September 30, 2010

Sex cells......Meiosis!

SO....once in a while an organism needs to reproduce.

Some organisms can make copies of their own cells that will become separate organisms that live separate from their parent.  Reproduction without any other contribution is asexual.

However some organisms create special cells known as gametes that only have 1/2 the normal amount of chromosomes as other body cells in that organism's structure.  Sexual reproduction is a process that requires these gametes and there is a specialized process to create these particular cells known as meiosis.

Meiosis is cellular division that creates gametes aka sex cells aka reproductive cells aka in humans called sperm and eggs.

A cell going through meiosis only takes place in the gonads of a human.  Each cell that will form gametes goes through the following stages:

1. Interphase: before meiosis begins, the chromatin (DNA) must replicate just like in interphase prior to mitosis.

2. Meiosis I begins!

a. prophase 1

Chromosomes appear as they do in mitosis, except a very special event is taking place.  Homologous chromosomes (chromosomes that have similar gene loci  ex. both contain different versions of the same blood type gene) pair up in a tetrad.  The pairing is known as a tetrad because there are 4 individual chromatids in the grouping and "tetra" means 4.   Tetrads form so that they can exchange little pieces of DNA.

Imagine that you are back in elementary school and it's lunchtime.  You pull out your sandwich and sigh because you have turkey. AGAIN!  You peer into your friend's bag and become jealous because they have a peanut butter and grape jelly sandwich that sounds SO much better than yours.  After some quick negotiation, you trade your sandwich for theirs and everyone is happy.

This exchange of sandwiches is much like the exchange of DNA during crossing over.  The section of DNA that is exchanged between nonsister chromatids is from the same gene (i.e. eye color isn't exchanged for blood type).

Once crossing over has occurred, the chromosome head towards the center still in their tetrads.

b. metaphase 1

Each tetrad lines up on the center plate between the centrioles instead of lining up in a straight line as the chromosomes do in mitosis.

Each set of homologous pair remains together like holding hands with a buddy and standing in line.

c. anaphase 1

Because each homologous chromosome is pulled to an opposing side, each cell is on its way to being haploid.  Remember diploid means having both members of each set of homologous chromosomes.

d. telophase 1

Each resulting cell now has 1/2 the chromosomes (n) as the original cell (sometimes called the parent cell).
3. Meiosis II begins and proceeds pretty much just like mitosis.

a. prophase II

In each cell the single homolog prepares to separate into gametes

b. metaphase II

Each homolog lines up in a straight line along the metaphase plate and centrioles attach spindle fibers to the centromere in order to now separate each chromatid from their sister.

c. anaphase II

Each chromosome in each of the two cells is split from its sister chromatid and head toward opposing poles.

d. telophase II

The nucleus reforms around the 1/2 set of DNA and the cell prepares for cytokinesis.

At the end of this process, we have 4 gametes that each have 1/2 the set of chromosomes that were in the original cell as opposed to the 2 clone cells that mitosis produces.

To review, click on the link below to watch an animation that should make this process clear.

Meiosis YouTube Review Video

Be sure that you look at the differences and similarities between mitosis and meiosis.  Below I have posted some diagrams and other helpful tools to guide you in your review.
Nova has a great comparison website that is interactive and puts each phase side by side.  Click on the link below and enjoy!

Nova comparison website

Below is a link to a great comparison chart.  Click away my pretties!

Comparison chart

Watch this cute old man biology teacher as he helps you hash out the differences between the two processes!

Video comparison

I hope all this information is wrinkling into your brains!  See you in the a.m.!


Tuesday, September 28, 2010

The Cell that Divides

Have you ever wondered how your cuts and bruises heal, how sperm and eggs are formed, or how cancerous cells go out of control????


There are 2 types of cell division: mitosis and meiosis.  They are each a part of a larger process called the cell cycle.

The cell cycle has 3 stages or steps:

1. Interphase - during this step the cell is growing, organelles are replicating, and the DNA is copying its code.  It takes the majority of cell cycle's time.

2. Mitosis or Meiosis - during this stage the cell's nuclear material (DNA) is divided equally among resulting cells.

3. Cytokinesis - during this quick stage, the cell's cytoplasm divides and the cell membrane pinches or cleaves to finally form 2 separate cells.

Now lets get more detailed information about mitosis.  There are 4 stages of mitosis: prophase, metaphase, anaphase, and telophase.

Once a cell has entered mitosis, it already has a duplicate copy of each strand of DNA that was created during interphase.

1. Prophase
a. chromosomes become visible as sister chromosomes that look like a series of Xs
b. nuclear envelope disintegrates
c. nucleolus also disintegrates
d. centrioles begin to migrate towards opposite poles and to form spindle fibers.
 2. Metaphase
a. each pair of sister chromatids (1 chromosome at this point) lines up in a straight line down the equator (i.e. center of the cell) much like we line up in a line for a movie or to get a meal at a fast food joint.

b. Centrioles that are now at opposing poles attach their spindle fibers to each centromere to prepare to pull each sister chromatid to their respective poles.
3. Anaphase
a. centrioles pull each sister chromatid away from its partner and toward opposing poles
4. Telophase
a.Cell boundaries start to reform
b.2 new nuclei from around their new DNA package in separate areas.
c. Cell begins to look pinched as it prepares for cytokinesis
After mitosis, the cell splits its cytoplasm, closes up its cell membrane, and presto we have 2 cells.

Below is a summary of the cell cycle using a special kind of microscope that relies on fluorescence

Finally, as a total review of mitosis click on the link below to watch a WONDERFUL mitosis video.

Mitosis YouTube Review Video

Tomorrow we will review meiosis which is the process by which an organism forms gametes or sex cells each having half the set of chromosomes as the original cell.

Until then....may your cells divide with a quickness that heals all your worries and woes and makes you appreciate each day we are given to study biology!

Love ya! Mean it!

Friday, September 24, 2010

So to Recap.......a Little Review From Me to You

Below are some review tools to help prepare for the assessment on Monday/Tuesday.

1. Illuminating photosynthesis!

The images below are a guided webquest to help break down what happens in this website.  Combined poems and helpful animation should shine some light on any last minute confusion about photosynthesis.

2. Review Packet for Energy
If you can answer the questions below, then you are well prepared for our test of energetic reactions in living organisms.

Thursday, September 23, 2010

Just Breathe --- Or You Can't Break Down Your Food -- at Least Not All the Way

So..we discussed respiration yesterday.  I wanted to expand further on the differences between aerobic and anaerobic respiration.

Anaerobic respiration takes place solely in the cytoplasm and requires no oxygen to process the glucose molecule.  Anaerobic respiration only provides 2 ATP per 1 glucose molecule, but those organisms that rely only on this method of energy production are single celled organisms that don't need much energy to maintain homeostasis.

Eukaryotic organisms take this process further by shuffling the now broken sugar molecule into the mitochondria.  Inside the mitochondria, the sugar is further broken down to release more energy.  As a result of 1 glucose molecule being processed in the presence of oxygen, the cell receives 36 to 38 ATP as compared to only 2 ATP in anaerobic respiration.

As far as anaerobic respiration (aka fermentation) goes, there are 2 outcomes for sugar.

1. Alcohol fermentation - When an organism processes sugar in this manner, it produces alcohol and ethyl alcohol and of course ATP.

Follow the link below to watch a video about fermentation.....maybe you can even try to make the ginger soda they demonstrate.

Alcoholic fermentation

2. Lactic acid fermentation - When an organism processes sugar in this manner, it only produces lactic acid and of course ATP.

So no matter what the nucleus situation a cell has they are able to release the energy in their food by cellular respiration.

Wednesday, September 22, 2010

Now Break it Down!

That's right.....we talked about making the food, now we focus on breaking that food down to release the energy that was stored.

Cellular respiration is the process by which food molecules are broken down (i.e. their bonds are snapped) to release energy.

All cells need energy; therefore all cells have to process food to release that energy.  We tend to assume that this process happens solely in the mitochondria, but that isn't the case.  Otherwise organisms that lack mitochondria wouldn't be able to process food and release energy.  The first step happens in the cytoplasm without the presence of oxygen.  The first step (glycolysis) happening outside the mitochondria doesn't make a lot of ATP, but it does allow bacteria to process their food.  

The next 2 steps (citric acid cycle and the electron transport chain)  happen in the presence of oxygen within the double membrane of the mitochondria.

In comparison with photosynthesis, the input of cellular respiration is the output of photosynthesis.  What this means is instead of taking in carbon dioxide and water, cellular respiration minimally needs a carbon compound (namely sugars and lipids) to start the process of releasing energy.

The first time sugar is split in the cytoplasm no oxygen is required.  The lack of oxygen is known as anaerobic respiration.

Aerobic respiration occurs when an organism further breaks down the split sugar within a mitochondria.

Aerobic respiration only releases 2 ATP while aerobic respiration can release 36-38 ATP per the same glucose molecule.

Here is a picture to review the structure of the mitochondria!  Enjoy!

May the ATP with you!

Tuesday, September 21, 2010

The Anacharis and the Light

To understand better the ingredients and environment necessary for photosynthesis, we started an experimental setup using an aquatic plant called Anacharis.  We added water and carbon dioxide bubble to a snippet of the aquatic plant.  Then we put one set of flasks in the light and other in a drawer.

We will see what happens tomorrow as our plants sit in their flasks.

Bromothymol blue is an indicator that lets us know the approximate pH (how acidic) of a solution.  When we bubble carbon dioxide through the water, the pH is lowered because we are creating carbonic acid. 

As you can see, we lowered the pH of our flasks from around 8-10 down to around a 6.

Let's see what happens tomorrow!!


Monday, September 20, 2010

Who Needs Energy??? I Do! I Do!

All cells guessed it!!!   ENERGY!

This week we venture into the processes of photosynthesis and cellular respiration.

We will first speak about how inorganic molecules (carbon dioxide and water) are combined using the energy gathered from the sun to create organic molecules for that organisms and others to break down later for energy.

This fancy process is known as photosynthesis because light (photo) is used to combine (syn) the inorganic molecules to make organic molecules.

There is a similar process called chemosynthesis that uses the energy from chemicals as the combining factor, but we will focus on the process involving light.

Photosynthesis depends on chlorophyll whether it is housed in the chloroplast like in a plant or free floating in the cytoplasm of a bacterial cell.

We will focus on the process that involves the chloroplast.  This green pigment traps light energy and converts it into ATP (chemical energy) that cells can use to combine the carbon dioxide and water to make simple sugars like glucose.

Just to review the structure of the cholorplast:

1. Inside there are stacked membranes.  Each "tire" is a thylakoid filled with chlorophyll.  Each "stack of tires" is known as a grana.  The area around these stacks is known as the stroma.
2. Own set of DNA that allows the choroplast to self replicate when needed.
3. Double membrane.

Just to review the function of the cholorplast:

1. Each thylakoid filled with chlorophyll collects sunlight and converts it to ATP.
2. The area around the thylakoids (stroma) is where the food is made.
We will continue our discussion of cellular energy tomorrow as we look at the importance of light in the process of photosynthesis by denying some aquatic plants light while exposing others.

Finally below is a link for a review exam for both cell anatomy and plasma membrane structure and function.

Until we meet again!!!  Bode 

Sunday, September 19, 2010

May the Force be with You!

So we discussed passive transport on Thursday!

Those processed require no energy or special accommodation, but that is not always the case when it comes to moving substances across the plasma membrane.

Even when no energy is required, sometimes a particle is too big to wiggle through the phospholipids and must take an alternate route.  Membrane proteins that span the entire bilayer provide passage ways for larger molecules to pass through without exertion of energy.  Using a protein to pass through the membrane is known as facilitated diffusion.

However sometimes particles need to enter a cell that are too large to even use a membrane protein or they are trying to go against the concentration gradient (from L to H).  Transport that requires energy is known as active transport.

When the cell brings in a large particle or expels one, they can use the membrane to form a vesicle around the object.

Exocytosis: uses the membrane to spit objects out of the cell.

Endocytosis: the membrane encloses items to bring them into the cell.

Thursday, September 16, 2010

High to Low That's All You Need to Know!

We continue on into the workings of the plasma membrane by taking a moment to discuss the amazing properties of water.  Because living organisms are mostly water (70 to 95%) it only makes sense to understand some of its important characteristics.

1. Water is polar meaning because of its chemical composition, there are oppositely charged regions arranged at opposing ends of the molecule.

2. Water molecules combine via the attraction of hydrogen to an oxygen on another water molecule.

3. Water resists changes in temperature allowing living organisms time to acclimate to their environment.
The cone on the left catches on fire more quickly than the one with a small amount of water in its base.

4. Water expands when it freezes which protects life that lives under water.

Once we knew a little more about water, we were ready to speak about the process of diffusion.  It is a passive transport that requires no energy.  

Substances move by random collisions subsequently pushing further and further apart until they are evenly distributed in their container. Particles tend to flow with the concentration gradient from high to low concentration.
Tomorrow we will continue our discussion by looking at several types of diffusion and then investigating transport that requires energy.


Our eggs did a little shrinking last night.  Because there was a high concentration of vinegar on the inside of the egg when placed in the corn syrup, the vinegar passed over the egg's membrane and back into the beaker to try to even out the difference in concentration.  We saw the evidence of the transport when our amount of fluid remained the same or even was a little more than 200 mL.  Also our beakers of corn syrup now smelled like vinegar!

Stay tuned for tomorrow when we see what happened to our eggs that soaked in water overnight!

Bode out.

Wednesday, September 15, 2010

Fluid Mosaic Model!

We have begun our discovery about cellular transport by exploring the components of the cell membrane.  The main components are phospholipid that have 3 regions: phosphate head, glycerol backbone, and 2 fatty acids chains. 
The phosphate head region is polar.  Polar substances have a slight negative and positive charge that allows them to chemically interact with a variety of substances.

The fatty acid chains are non-polar meaning they have little to no charge and don't interact with those substances that do have a charge.

 Two layers of these phospholipids are sandwiched back to back (i.e. fatty acid to fatty acid) to form what is known as the phospholipid bilayer.

In this layer there are several items that are stuck in to allow further access and provide recognition.

Cell Membrane Components

Follow this link to a review of the cell membrane in general and then click on highlighted words to follow the trail for new information.

Make sure that you look into the membrane proteins, cholesterol, and carbohydrates that are a part of the cell membrane. 

Osmosis Eggs

In other news, we observed our osmosis eggs after soaking in vinegar overnight.  We noticed that our eggs were without their shell and swollen with vinegar.  We also measured our vinegar remaining and saw that 10-60 mL were missing.  Since the egg is swollen and the vinegar level is down, we concluded that the vinegar passed into the egg and out of the beaker.  If you would like to look at pictures, then click the link above.

See you guys tomorrow!!!

Friday, September 10, 2010

More Cell Parts! Oh My!

We further reviewed our cell parts and function today!  Here are some links to offer more practice for our test TUESDAY SEPTEMBER 14th!

Cells Alive

An amazing website that lets you look at an animal or plant cell.  Drag your cursor over each organelle and it is highlighted in the diagram.  Then click on the organelle name and a screen comes up to give you information about its structure and function!

Cell Organelles and Descriptions

Another site where you can click on various organelles and learn more about their structure and function.  This website also has several short animations to demonstrate the function of particular organelles.

Biology 4 Kids

A good website for any topic we cover this semester, but there are some specific portions that relate to cell structure and function.  Also, you can take a quiz to test your knowledge.

Organelle identification practice

Review each structure and function.  Then you will be asked to identify each organelle as it is highlighted.

Prokaryotes versus Eukaryotes

Here is a 6 minute lecture on the similarities and differences between these two main groups of cells!

Plant vs. Animal Cell

A little more advanced.  You can make the cell membrane transparent or opaque and you move your scope over the cell to seek out organelles to learn more about.  With a click of a button, the cell transforms into a plant cell and the differences are highlighted and explained.

Cell theory

A time line and a summary of cell theory.

Hope all these resources help you in your quest for cells over the weekend!  See you bright and early on Monday!

Thursday, September 9, 2010

Is That a Fried Egg or My Cheek Cell??

So we have been working on the parts of the cell this week.  Like we discussed in the last blog, microscopes were the technological advance into the world of microorganisms.  In order to better understand just how small cell are we took some cheek smears and had a look under the microscope.

The link below will take you to a page for a simulation to practice the parts of the microscope and how to focus and find items on a slide.

Microscope Simulation

There is a 7 minute video that you can watch to introduce you to the microscope and the simulation.  Once you have watched the movie, then click the link that is highlighted blue for "the virtual scope." Follow the tutorial to practice using the microscope.

We looked at our cheek cells under scanning, low, and high powers.  Below is a link to an image of those cheek cells that you should have seen.

Cheek Cell Smear

Tuesday, September 7, 2010

Cell Anatomy and Physiology

Microscopes allowed scientists to view organisms and their subunits.  This new advance in technology allowed us to better understand how organisms are organized on a small scale and see that all organisms at least have one cell.

The first microscopes were simple using one lens and natural light.

Scientists like Antonie van Leeuwenhoek used these simple microscopes to study the small world once unknown.

Robert Hooke used a compound light microscope to study cells and develop his cell theory.  These microscopes use a series of lenses to magnify the image to an even greater degree.  He coined the term "cells" because he thought that the compartments looked likes cells in a monastery.  

Current microscopes used electricity and provide even more detailed images for scientists to study.  

Electron microscope set up in a research lab facility

Modern day compound light microscope

We also discussed cell anatomy and function.  Below are diagrams and charts to help you study!

Below is a link to a table of each organelle and it's function!  

Organelle Function

Check back for more links to help you interact and study!

Tomorrow we look at our own cheek cells and possibly plant tissues.

Out until then,  Bode!

Thursday, September 2, 2010

Bubble Bubble Liver Prevents Trouble

After we discussed the results of our food lab, I did a demonstration about enzymes using liver and peroxide.

Liver tissue contains an enzyme called catalase that acts upon hydrogen peroxide to break it down into oxygen gas and liquid water.  By breaking down the hydrogen peroxide, the liver prevents build up and damage to the organism's tissues.

An enzyme's ability to chemically match its substrate depends on maintaining its shape.  Influences like high heat or altering the pH (too basic or too acidic) can serve to change the chemical shape of the enzyme and thus making it not fit its lock anymore. 

The liver dropped into plain water had no reaction....why??  Because water doesn't chemically fit with the catalase and therefore it isn't chemically altered.

The liver dropped into peroxide gave off heat and bubbles; both are signs that a chemical reaction has occurred.  Catalase has a specific chemical site that fits hydrogen peroxide thus causing it to decompose (break into smaller molecules).  Even when the bubbles ceased, adding more hydrogen peroxide started the process all over again proving that the enzyme wasn't destroyed.

However, the liver boiled in the test tube failed to produce the same chemical reaction when exposed to the hydrogen peroxide.  The high heat denatured or "messed with" the chemical structure of the enzyme.  Just like melted or bending a key will affect its ability to work in a lock, heat can alter a chemical's ability to do a reaction.

Below is a video link that will review today's class demonstration.

Liver and Hydrogen Peroxide

Once at the website, type "enzyme" into the search box at the top right hand corner of the page.  Choose the video that is described as "liver enzyme lab" that is 7 minutes and 33 seconds long.  Click on the picture of the test tubes in their rack and enjoy!

1. Test on Organic Molecules Friday 9/3
2. Notebook Check Friday 9/3
3. Organic Molecule Review Project Due Wednesday 9/8

See you in the a.m.!


Wednesday, September 1, 2010

Say What!!! That's in My Food???

Today we tested common household foods for the biomolecules they contain.  The tests were as follows:


Simple Sugars -- Use Benedict's solution.  If the original blue color changes to blue/green, green, yellow, orange, or red after sitting in a warm water bath, then you had an item that was positive for simple sugars.  The degree of color change indicates the amount/type of simple sugar present.

Starch -- Use iodine.  When iodine was added to cause a change from brown/red to a dark black/brown color, then your food item tested positive for starches.


Drop a small amount of your food item on a piece of newspaper.  When your paper dries, you might be able to see light pass through the paper.  This property is known as translucence. If your paper allows light to pass through, then your food tested positive for lipids. 


Add Biuret reagent to see if protein is present.  If you see a vivid to pink to purple color appear, then you have a food filled with protein. 

What group of organic molecules did we not search for during our lab?

Why would this test be unneeded when it comes to living organisms?

Below is a link to an online version of this food lab.  Once you are at the page, click on the words "Organic Molecules." Review each step and observe the additional test for lipids.

Online Food Lab

Be sure that you are able to determine which test is necessary to find a particular type of molecule as well as read the results of each test.