Tuesday, 30 August 2022

Biochemistry : Aldehydes and ketones

 Aldehydes and ketones possess the strongly reducing carbonyl group C=O

Aldehydes have one and ketones have two alkyl groups attached to the carbon bearing the crbonyl group.

The sugars in addition to being polyhydric alcohols are also either aldehydes or ketones.



Aldehyde

Organic compounds containing a functional group with the structure −CHO, consisting of a carbonyl

 center (a carbon double-bonded to oxygen) with the carbon atom also bonded to hydrogen and to an R

 group, which is any generic alkyl or side chain




What are aldehydes in chemistry?

Aldehydes are organic compounds, in which a carbon atom shares a double bond with an oxygen atom, a single bond with a hydrogen atom, and a single bond with another atom or group of atoms (designated R in general chemical formulas and structure diagrams). These compounds help create fragrances for products like perfume, laundry detergent and soap.



Industrial Applications. 

Aldehydes are versatile compounds that can help make resins, dyes and organic acids, as well as perfumes , for cologne, detergents and soaps. Of all aldehydes, formaldehyde is produced industrially on the largest  scale.


Perfumes

Aldehydes are present in many organic materials, everything from rose, citronella, vanilla and orange

 rind. Scientists also can create these compounds synthetically to use as ingredients for sweet-smelling

 perfumes and colognes. 


What are the names of these aldehydes?


1 carbon atom: form -


2 carbon atoms: acet -


3 carbon atoms: propion -


4 carbon atoms: butyr -


Methods of preparation of Aldehydes :


There are several methods for preparing aldehydes,[2] but the dominant technology is hydroformylation

Other Methods include :

Oxidative routes 

Specialty Methods


Reaction name

Ozonolysis

Organic reduction

Rosenmund reaction

Wittig reaction

Formylation reactions

Nef reaction

Kornblum oxidation

Zincke reaction

Stephen aldehyde synthesis

Meyers synthesis

Geminal halide hydrolysis

Hofmann rearrangement

McFadyen-Stevens reaction

Biotransformation

Tuesday, 9 August 2022

Biochemistry Basics : Cis trans isomerism

 Cis trans isomerism


Cis–trans isomerism, also known as geometric isomerism or configurational isomerism, is a term used in chemistry that concerns the spatial arrangement of atoms within molecules. The prefixes "cis" and "trans" are from Latin: "this side of" and "the other side of", respectively.

This occurs in compounds with double bonds.

Since the double bond is rigid , the atoms attached to it are not free to rotate as are those attached to a single bond.

Maleic acid cis

Fumaric acis trans 

These 2 structures are not equivalent and have different chemical and physiological properties.

Fumaric acid but not maleic acid is physiologically active.

The cis isomer / maleic acid has 2 more bulky groups ( COOH) on the same side of the double bond.

If they are on the opposite side of the double bond , a trans isomer is produced.

Introduction of trans double bonds in an otherwise saturated hydrocarbon chain deforms the shape of the molecule relatively little.

A cis double bond by contrast entirely changes its shape.

It can this be appreciated why cis and trans isomers of a compound are not interchangeable in cells.

Membranes  composed  of trans and cis isomers would have entirely different shapes.

Enzymes acting on one isomer would be expected to be entirely inert with the other.

The usual formulas fail to represent the actual shape of the molecules.

Portions of the hydrocarbon backbone of a saturated fatty acid and of the cis and trans isomers of an 18 carbon unsaturated fatty acid are represented in Fig 1-7

Cis-trans isomers exhibit a type of stereoisomerism where the atoms have different spatial arrangements in three-dimensional space. In the field of organic chemistry, cis isomers contain functional groups on the same side of the carbon chain whereas the functional groups are on opposite sides in trans isomers.

Why trans isomers are more stable?

Trans isomer is more stable than cis isomer because in cis isomer, the bulky groups are on the same side of the double bond. The steric repulsion of the groups makes the cis isomer less stable than the trans isomer in which the bulky groups are far apart ( They are on the opposite side of the double bond).







Monday, 8 August 2022

Soil Texture : Inter particle forces

 Soil Texture : Inter particle forces

The interaction of soil particles with other particles is influenced by the following forces :

Weight of the particle Fg

Particle surface forces Fs

Weight is the result of gravitational forces and is function of the volume of the particle.

For equidimensional particles such as spherers of diameyter D , the weight Fg is directly proportional to D3.

Particle surface forces are of an electric nature.

They are caused by un satisfied electrical charges in the particles crystalline structure.

Surface forces F3 are directly proportional to the surface areaand hence for equideimensional particles to D 2

The ratio of weight of a particle to the particle surface forces Fg/Fs is directly proportional to D

Thus for large particle sizes which include soil particles in the coarse fraction > 0.075 mm ,the weight of the particle is predominant over the surface forces.

As the particle diameter decreases , the ratio Fg/Fs decreases thus for very small values of D , the surface forces predominate.

This accounts for cohesive nature of most fine grained soils.











Sunday, 7 August 2022

Biochemistry Made Simple : Enantiomers

 Enantiomers are a pair of molecules that exist in two forms that are mirror images of one another but cannot be superimposed one upon the other. Enantiomers are in every other respect chemically identical.


In chemistry, an enantiomer – also called optical isomer, antipode, or optical antipode – is one of two stereoisomers that are mirror images of each other that are non-superposable, much as one's left and right hands are mirror images of each other that cannot appear identical simply by reorientation.


these types of stereoisomers can be considered as mirror images of each other. A common example of a pair of enantiomers is dextro lactic acid and laevo lactic acid, whose chemical structures are illustrated below. Another important example of an enantiomer pair is provided below.











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Saturday, 6 August 2022

Soil Texture

 Soil texture 

The solid phase of soil mass consists of particles of mineral and organic matter in various sizes and amounts.

The texture of soil is its appearance or feel and depends on the relative sizes and shapes of the particles as well as the range or distribution of those sizes.

Soils with respect to texture can be divided into two groups :

Coarse textured soils :

Coarse grained soils or light textured soils include gravels , sands and their mixtures.

Fine textured soils :

Fine grained or heavy textured soils contain grains of a very fine texture which are invisible to naked eye ( size less than 0.05 mm )

Slits and clays are fine textured soils.

For coarse textured soils , engineering behaviour is controlled by soil texture these soils are in general classified into various groups based on basis of grain sizes.

For fine grained soil , the presence of water greatly affects the engineering response.

Water affects the interaction between the mineral grains and this may affect their plasticity / consistency and their cohesiveness.

Fine grain soil are there fore classified on basis of their consistency.

Soil texture (such as loam, sandy loam or clay) refers to the proportion of sand, silt and clay sized particles that make up the mineral fraction of the soil. For example, light soil refers to a soil high in sand relative to clay, while heavy soils are made up largely of clay

What are the 3 soil textures?


Soil texture is usually a complex size distribution represented by the relative proportions of the three particle-size fractions (Staff, 1987): sand, silt, and clay.




Monday, 1 August 2022

A 45 year old man presents to your OPD with 1 month history of difficulty in breathing and cough.

 A 45 year old man presents to your OPD with 1 month history of difficulty in breathing and cough.


On history taking you find out he had a pneumonia 2 months ago in his left lung which required intravenous antibiotics and hospital admission for 1 week.


There is no history of smoking and no blood in sputum.


On examination , he appears weak and distressed.


His Temperature is 37 C and respiratory rate is 22 / minute.

BP is 130 / 80 mmHg.


There is reduced chest expansion on left side.


On auscultation , air entry on left side of lung is reduced and a wheeze in expiration is audible.


Percussion reveals dull percussion notes.


Oxygen saturation is 87 percent.


You decide to organize a chest X ray which is given below :


1. What is the most likely Diagnosis ?


2. How will you mange this patient ?


Copyright reserved with Author.


Answers given in comments section.







1. What is the most likely Diagnosis ?


The chest x ray shows collapse of left lung . And there is a history of recent pneumonia as well.


This is highly suggestive of left sided atelectasis secondary to pneumonia or even a para pneumonic lung effusion.


An ultrasound of chest will better help determine the cause of lung collapse / atelectasis.


Atelectasis is a complete or partial collapse of the entire lung or area (lobe) of the lung. It occurs when the tiny air sacs (alveoli) within the lung become deflated or possibly filled with alveolar fluid.


Atelectasis may be caused by many things, including: Mucus plug, Foreign body,


Tumor inside the airway,Injury, Chest trauma ,Pleural effusion ,Pneumonia ,Pneumothorax and Scarring of lung tissue.


2. How will you mange this patient ?


Treatment of atelectasis depends on the cause. Mild atelectasis may go away without treatment. Sometimes, medications are used to loosen and thin mucus. If the condition is due to a blockage, surgery or other treatments may be needed.


Chest physiotherapy


Techniques that help patient breathe deeply to re-expand collapsed lung tissue are very important. .


They include:

Performing deep-breathing exercises (incentive spirometry) and using a device to assist with deep coughing may help remove secretions and increase lung volume.


Positioning the body so that your head is lower than the chest (postural drainage).


This allows mucus to drain better from the bottom of lungs.

Tapping on chest over the collapsed area to loosen mucus.


This technique is called percussion. Also mechanical mucus-clearance devices, such as an air-pulse vibrator vest or a hand-held instrument may be used.


Surgery



Removal of airway obstructions may be done by suctioning mucus or by bronchoscopy.



If a tumor is causing the atelectasis, treatment may involve removal or shrinkage of the tumor with surgery, with or without other cancer therapies (chemotherapy or radiation).



Continuous positive airway pressure (CPAP) may be helpful in some people who are too weak to cough and have low oxygen levels (hypoxemia).


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Adrenal incidentalomas :

 Adrenal incidentalomas :

Adrenal Adenoma

Clinical Features

ACTH independent Cushings Syndrome :

Hypertension

Adrenal Adenoma

Impaired Glucose tolerance

Hirsutism

Amenorrhea

Elevated urine 24 hours cortisol / creatinine ratio

NORMAL RANGE IS 0 – 25

Undetectable levels of serum ACTH : less than 1 milli units / L ( Normal range : 2 – 20 )

Lack of cortisol suppression with dexamethasone administration ( serum cortisol of  561 nmol / l after 2 days of dexamethasone 0.5 mg)

Good effect with laprascopic resection

Ct Abdomen : adrenal adenoma / lesion with density of 40 HU : Hounsfield Units

Adrenal mass / incidentaloma

Main aim is to determine if its benign or malignant

Size is one clue : 90 % of adrenal carcinomas are more than 4 cm in size / diameter .

However 70 % of incidentalomas more than 4 cm in diameter were fund to be benign

Hence other features should also be taken into account

The most important diagnostic clue is density of the lesion on a non contrast CT scan in Hounsfield Units

If the adrenal incidentalma has a density of less than 10 HU on non-contrast scan , it is certainly a benign lesion.