S6 4p - Chapter 1,2 & 3

The peptide bond is...

• The bond in between 2 amino acids

• The bond in between 2 carbohydrates

• The bond in between in lipids

• The bond in between 2 nucleic acids

Answer explanation

The peptide bond is specifically the covalent bond that forms between two amino acids during protein synthesis, linking them together in a polypeptide chain. This distinguishes it from bonds in carbohydrates, lipids, or nucleic acids.

Among the following statements, which one is wrong?

• Cellular membranes are made of proteins

• Nucleic acids can form a molecule of only 1 chain

• Lipids are are made of a chain of C and H

• Carbs are ring-like structures

Answer explanation

The statement "Cellular membranes are made of proteins" is wrong. Cellular membranes are primarily composed of a phospholipid bilayer with embedded proteins, not made solely of proteins.

The tertiary structure of a protein is...

• The way the entire chain is folded

• The amino acids sequence

• The presence of alpha helices and beta sheets

• The assembly of different chains

Answer explanation

The tertiary structure of a protein refers to the overall three-dimensional shape formed by the entire chain of amino acids folding. This is distinct from the amino acid sequence, secondary structures, or assembly of chains.

On what point is RNA similar to DNA

• The nucleotide structure (sugar+phosphate+nitrogenous base)

• The function is has in the cell

• the nucleic acids it is composed of

• It's 3D structure

Answer explanation

RNA and DNA are similar in their nucleotide structure, which consists of a sugar, phosphate group, and nitrogenous base. This fundamental similarity underlies their roles in genetic information storage and transfer.

This molecule is ...

• A carbohydrate

• A nucleic acid

• A protein

• A lipid

Answer explanation

This molecule is classified as a carbohydrate because it consists of carbon, hydrogen, and oxygen in a specific ratio, typically in the form of sugars or starches, which are key energy sources for living organisms.

This molecule is made of...

• Nucleic acids

• DNA

• Amino acids

• Sugars

Answer explanation

This molecule is made of nucleic acids, which are the building blocks of DNA and RNA. While DNA is a type of nucleic acid, the broader category encompasses all nucleic acids, making 'nucleic acids' the correct answer.

The presentation in α-helices is defined as the...

• secondary structure

• quaternary structure

• primary structure

• primary structure

Answer explanation

The presentation of α-helices refers to the arrangement of polypeptide chains in a specific way, which is classified as the secondary structure of proteins. This distinguishes it from primary and quaternary structures.

Looking at those 3 molecules, we can say that...

• 2 has no quaternary structure

• They all have the same function

• They have the same primary structure

• They are complex carbs

Answer explanation

Molecule 2 lacks a quaternary structure, which is a specific arrangement of multiple polypeptide chains. The other options are incorrect as they imply similarities in function, primary structure, or complexity that may not exist.

Among the following, which one is Wrong?

• The nucleus of eukaryotes is bigger than the one of prokaryotes

• All cells possess a membrane

• Organelles are what allows a cell to perform a certain function

• All cells are different depending on the organism and tissue

Answer explanation

The statement is wrong because prokaryotes do not have a true nucleus; they have a nucleoid region. Eukaryotic nuclei are indeed larger and more complex than the nucleoid in prokaryotes.

What statement is right about cell membranes?

• They are composed of phospholipids, carbohydrates and proteins

• They act as an impermeable barrier

• There are nucleic acids that cross it completely

• The membrane has the same chemical property no matter the layer

Answer explanation

Cell membranes are primarily composed of phospholipids, proteins, and carbohydrates, which contribute to their structure and function. The other statements are incorrect as membranes are selectively permeable, not impermeable.