Cell and developmental biology Part II

a) Communication between the cells of the heart is very important for its functioning in the body of the mouse where it is expected to deliver blood continuously and adapt to changes within the organism. The cardiac muscle cell is found in the cardiac muscle tissues of the heart specifically the myocardium, therefore is surrounded by other cardiac muscle cells (myocardioctes) and other cardiac cells such as cardiomycocytes. Image

      These cells of the myocardium are self contracting and are autonomically regulated they contract in a rhythmic fashion throughout the life of the mouse.  For this to occur the cells in the tissue have special features, between these Y shaped cells there are intercalated disks that contain gap junctions which provide communicating channels between  the cells.


      Gap junctions are a type of communicating junction, they can be described as protienaceous tubes that correct adjacent cells.  They are formed from connexins which in turn form connexins, they allow the passage of inorganic ions and small water soluble molecules to pass from one cell cytoplasm to another also they can couple cells electrically

. Image


            The  intercalated disks allow waves of depolarization to sweep across the cells which synchronize muscle contraction in the heart.  This occurs when ions pass between cells of the cardiac tissue, the ions that does this is Ca2+. When intracellular Ca2+ concentration is low the gap junctions open, when the concentration is high the close. This allows extracellular Ca2+ to enter and create the action potential, it occurs rapidly and can be reversed since the cells can regulate their permeability of their gap junctions.

b   b) http://alienbiochemistry.wordpress.com/  (group part)

Cell and Developmental Biology Blog part I


I am a cardiac muscle cell from a mouse. 




a)      Mouse.

A model organism can be described as a species that is non-human, which is studied extensively in order to understand a certain biological phenomena. It is expected that what is discovered when studying this particular organism would give insight when it comes to the mechanisms of other organisms. These model organisms are living models that are vastly used as to assist research in human disease, because human experimentation brings about many concerns such as ethics. Since all living organisms have some common descent and show some conservation of their metabolic pathways, development pathways, and genetic material over evolution. It would make their study very informative. Model organisms are used to teach because they allow the student to grasp important concepts and have a greater understanding because students can see and observe real life activity. They can be involved with practical activities and be exposed to the methods used to study these organisms.

 b)      I am a muscle cell of the heart found in the cardiac muscle tissue. Image


a)  The cardiac muscle cell originates from a stem cell in the embryo before birth of the organism.  Cardiac muscle cells make up part of the cardiac tissue of the heart of the mouse, and the heart is responsible for the transport of blood throughout the body the organism. A cardiac muscle cell last throughout the life span of the mouse, the cardiac muscle cell does not divide because it is highly specialized and lacks this ability. Once a cardiac muscle has differentiated form a stem cell it remains this way until death. Image

b) A cardiac muscle cell also known as a myocardiocyte, contains myofibrils also known as muscle fibers. These are composed from long proteins such as actin, myosin and titin, and they are organized into filaments. THE cardiac muscle cell contains only one nucleus and a high density of mitochondria. This allows the cell to produce ATP quickly, which explains why cardiac muscle cells are resistant to fatigue.  


The nucleus functions in:

·         The controlling of the cell.

·         Processing various inputs from the cytoplasm.

·         Storing information and retrieving it.

·         Fulfilling the instructions contained in the genetic material.

The nucleus is a two layered organelle, it contains a nuclear envelope, chromosomes and small dark areas called nucleoli. This organelle basically contains the DNA that codes for proteins which are vital for the cell, such as in cell repair.


The mitochondrion is another cell organelle that contains two membrane layers. The outer membrane has large aqueous channels which are permeable to most small molecules. The inner membrane is impermeable to ions and small molecules, unless they are specific its transport proteins. The inner membrane is folded continuously and it is referred to as cristae, the purpose of this is to increase the surface area. This membrane encloses a space called the matrix which contains the different components that aid in ATP (adenosine triphosphate) production. The inter membrane space is found between the outer and the inner membrane, its purpose is to maintain a hydrogen ion diffusion gradient. Overall the function of the mitochondria is to generate ATP from different precursors during cellular respiration.



Nucleic acids video review

Nucleic acids video review

Most well known is DNA and RNA.


·         Make proteins

·         Make up genes

Nucleic acids are made up of nucleotides, these are composed of three parts:

·         Phosphate group

·         Pentose sugar

·         Nitrogenous base

DNA and RNA both have four nitrogenous bases:

DNA: adenine (A), cytosine(C), guanine (G), thymine (T)

RNA: adenine (A), cytosine(C), guanine (G), uracil(U)



A and G

C,T and U


The nucleotides bond to each other by condensation reactions by where water is removed.

Adenine and thymine bond to each other by two hydrogen bonds.(same occurs with uracil)

Guanine and cytosine bond to each other with three hydrogen bonds.

Differences between DNA and RNA



Contains Uracil

Contains Thymine

Single strand structure

Double helix structure

Found throughout the cell

Found in nucleus

Breif veiw of Nucleic acids.

Nucleic acids are biological molecules that are made up of different components. They are very large (macromolecules) and can be found in all living organisms where they usually play a role in encoding, transmitting and expressing genetic information in the organisms. These interesting molecules were discovered by Friedrich Miescher in 1869. Nucleic acids resemble proteins in terms on the atomic make up but they lack sulphur, analysis of nucleic acids showed the presence of phosphorus and C, H, N & O atoms.

The most well known nucleic acid is DNA (Deoxyribonucleic acid) is composed of deoxyribose sugar, phosphate and 4 heterocyclic bases.  The deoxyribose and phosphate are usually described as the sugar phosphate back bone while the 4 heterocyclic bases can be classified into 2 groups called the : pyrimidines, purines.Image

The bonding between these bases gives the characteristic double helix structure of DNA which was proposed by James D. Watson and Francis Crick, the two scientists who discovered the structure of DNA in 1953. The bases adenine and thymine form two hydrogen bonds while the bases cytosine and guanine form three hydrogen bonds.




 RNA only differs to DNA is three ways:

·         The base thymine is replaced by uracil.

·         The sugar deoxyribose is replaced by ribose sugar

·         RNA is single stranded and not double stranded like DNA.



The central dogma.

“The original postulate that genetic information can be transferred only from nucleic acid to nucleic acid and from nucleic acid to protein, that is from DNA to DNA from DNA to RNA and from RNA to protein (although information transfer from RNA to DNA was not excluded and is now known to occur [reverse transcription]). Transfer of genetic information from protein to nucleic acid never occurs”.






Lipids are a diverse group of organic compounds. Although this group is large they all share similar properties such as solubility in non polar solvents, and insolubility in water. Lipids have varying structures and can be classified as saturated or unsaturated.

·         Saturated fats are usually solid and have no double bonds between the carbons in its structure, also they have high melting points.

·         Unsaturated fats are usually liquid and contain at least one double bond between the carbons in its structure, also they have lower melting points compared to saturated fats.

Fat in the body has many functions such as:

·         Source of energy

·         Energy storage

·         Insulation



A common question asked is “why fat have more energy than carbohydrates?”

Fat is a more reduced organic molecule than carbohydrates, hence fats contain more hydrogen. This means there are more hydrogen atoms to be oxidized, so it consumes more oxygen when combusted therefore more energy is released.

The higher melting points of the saturated fatty acids reflect the uniform rod-like shape of their molecules. The cis-double bond in the unsaturated fatty acids introduces a kink in their shape, which makes it more difficult to pack their molecules together in a stable repeating array or crystalline lattice.


One thing that may be expected when learning lipids is the give the ∆ designation of the fatty acid, this may seem difficult but just following some simple methods that you will be able to do this with ease. For example:

CH3-CH2– CH2– CH2– CH= CH- CH2– CO2H


Trans fats are fats with a trans configuration around the carbon to carbon double bond also called an E configuration. These are more stable than the cis fats and tend to stay in the body for longer periods due to its stability it is harder to break down.  This is why trans fats are made out to be a bad fat.



Lipids are very important to organisms as they are an essential part of the membranes that bound the contents of cells. These cell membrane components called phospholipids and are formed from different components.



The phospholipids have different groups which have different properties, they have a hydrophobic tail and a hydrophilic head. The way in which these groups act can be observed when they are mixed with water which leads to different configurations.


 A cell can be considered as a very complex liposome. The phospholipid  bilayer membrane that separates the interior of a cell from the surrounding fluids is largely composed of phospholipids, but it incorporates many other components, such as cholesterol, that contribute to its structural integrity, and proteins which act as pumps and channels.

Lipids are an important part of steroids, they are actually metabolic derivatives of terpenes and consist of a tetracyclic skeleton, consisting of three fused six-membered and one five-membered ring. These rings can have different R groups attached to them to form different steroids. These steroids are important to animals for different physiological processes.


Electron tansport chain (ETC)

The electron transport chain was not a new topic it had been covered before but not in depth, it gave me trouble to understand at first but with a little reading it proved to be a fairly good topic.


The electron transport chain (ETC) can be found on the inner membrane of the mitochondria in eukaryotic cells. Most catabolic processes produce high energy byproducts such as NADH and FADH2. In metabolic processes NADH and FADH2 are used to transport elections in the form of hydride ions (H). In the electron transport chain these electrons are passed on form NADH or FADH2 , and they go to the membrane bound electron carriers. These electron carriers in turn pass the electrons on to other electron carriers which lead to the formation of water when electrons combine with oxygen. It is seen as the electrons are passed on from each electron carrier to another that H+ ions are pumped into the intermembrane compartment. This movement of H+ ions results in the formation of a greater concentration of H+ ions in the intermembrane compartment than that found in the matrix of the mitochondrion. This is now utilized by ATP synthase to produce ATP molecules. Image

The force that drives the electron transport chain is that each of the electron carriers has a higher reduction potential than the electron carrier that it gets its electrons from. This reduction potential is the ability to accept or donate electrons. A closer look at the ETC reveals that oxygen is found at the end since it has the highest standard reduction potential it accepts electrons more readily.

The proton motive force (PMF) refers to the energy gained from the H+ ion gradient formed by the electron carriers. Of the four complexes I, II, III, and IV only complexes I , III and IV are able to transport H+ ions into the intermembrane space from the matrix. This H+ ion gradient is what causes the production of ATP when ADP and Pi are joined. This is done by ATP synthase using the energy transferred from the H+ ions, note that is a phosphorylation reaction.

As we can clearly see that with a little understanding and investigation we have observed that certain chemicals such as cyanide and 2,4-DNP are able to disturb the ETC, and we can explain these by looking at the components of the ETC. Again this can be used to benefit us by using it to control pests and harmful organisms, or to predict what kind of chemicals or compounds that can affect the electron transport chain.