USMLE Exam 2024/25

In patients with orthostatic hypotension, which of the following red flag findings suggests a more serious etiology?

A.
Bloody stool

B.
Heat intolerance

C.
Incontinence

D.
Urinary retention

Foreign accent syndrome: Symptoms, causes, treatment, and more
https://www.medicalnewstoday.com/articles/foreign-accent-syndrome

Florida boy Jesse Brown dies after injured ankle leads to flesh eating bacteria
https://nypost.com/2023/02/16/fl-boy-jesse-brown-dies-after-injured-ankle-leads-to-flesh-eating-bacteria/

🟠🟠Types of Chemical Bonds🟠🟠

☑️ Ionic Bond
As the name suggests, ionic bonds are a result of the attraction between ions. Ions are formed when an atom loses or gains an electron. These types of bonds are commonly formed between a metal and a nonmetal [1-5].

Examples
✅ Magnesium (Mg) and oxygen (O) combine to form magnesium oxide (MgO).
✅ Potassium (K) and chlorine (Cl) combine to form potassium chloride (KCl)


☑️ Covalent Bond
In the case of a covalent bond, an atom shares one or more pairs of electrons with another atom and forms a bond. This sharing of electrons happens because the atoms must satisfy the octet (noble gas configuration) rule while bonding. Such a type of bonding is common between two nonmetals. The covalent bond is the strongest and most common form of chemical bond in living organisms. Together with the ionic bond, they form the two most important chemical bonds [1-7].

A covalent bond can be divided into a nonpolar covalent bond and a polar covalent bond. In the case of a nonpolar covalent bond, the electrons are equally shared between the two atoms. On the contrary, in polar covalent bonds, the electrons are unequally distributed between the atoms.

Examples
✅ Two atoms of iodine (I) combine to form iodine (I2) gas.
✅ Two atoms of hydrogen (H) combine with one atom of oxygen (O) to form a polar molecule of water (H2O).
 

☑️ Hydrogen Bond
A hydrogen bond is a chemical bond between a hydrogen atom and an electronegative atom. However, it is not an ionic or covalent bond but is a particular type of dipole-dipole attraction between molecules. First, the hydrogen atom is covalently bonded to a very electronegative atom resulting in a positive charge, which is then attracted towards an electronegative atom resulting in a hydrogen bond [1,4-6].

Examples
✅ Hydrogen atom from one molecule of water bonds with the oxygen atom from another molecule. This bonding is quite significant in ice.
✅ Nitrogen bases present in DNA are held together by a hydrogen bond. 
                                                            
☑️ Metallic Bonds
A metallic bond is a force that holds atoms together in a metallic substance. Such solid consists of tightly packed atoms, where the outermost electron shell of each metal atom overlaps with a large number of neighboring atoms. As a consequence, the valence electrons move freely from one atom to another. They are not associated with any specific pair of atoms. This behavior is called non-localization [1,2,4].
Examples
✅ Sodium metal
✅ Aluminum foil
✅ Copper wire

📌Other Types of Chemical Bonds

☑️ Van der Waals Bond
☑️ Peptide Bond

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🟣5 Minutes Reading

Types of Chemical Bonds

✅✅Chemical Bonding ✅✅

➡️(5 min reading)

Definition: What is a Chemical Bond?


When atoms are attracted to each other and join together to form a molecule, we call the connection between each atom a chemical bond. The bond “holds together” the atoms in the molecule, ion, or crystal. The bonds can often last indefinitely, until they are broken apart by an external force or energy.

Chemical bonding is the attraction between two or more atoms that allows them to be able to form a stable chemical compound. The specific nature of a chemical bond can vary, but the most commonly known are covalent and ionic bonds. With these bonds, it provides sufficient energy between atoms when one has less. It’s the force of attraction that holds atoms, allowing the electrons to form a bond together.

https://youtu.be/8B5jMbJZM-k

20 minutes reading

Memory & Recollect

Biochemistry.

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