Crash Course Biology: Episode 20 - Carbon & Biological Molecules

The acronym “CHNOPS” helps us remember the six elements that make up most living things. What elements do the letters stand for?

• calcium, hydrogen, nitrogen, oxygen, phosphorous, sulfur

• calcium, hydrogen, nitrogen, oxygen, potassium, sulfur

• carbon, helium, nitrogen, oxygen, phosphorus, sulfur

• carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur

Answer explanation

CHNOPS stands for carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.

Carbon atoms can form four covalent bonds. What are covalent bonds?

• bonds made specifically by carbon and hydrogen atoms

• bonds between atoms that cannot be broken

• bonds made when two atoms share a pair of electrons

Answer explanation

Covalent bonds are formed when an atom contributes a single electron to pair up with the single electron of

another atom. Both atoms share the new pair of electrons, which binds them together.

This image shows a model of a methane molecule. Is this statement about methane true or false?
It has the chemical formula CH₄.

• True

• False

Answer explanation

Methane is made up of a carbon atom bonded to four

hydrogen atoms, so its formula is CH4.

Tags

NGSS.MS-PS1-1

This image shows a model of a methane molecule. Is this statement about methane true or false?
It is an organic molecule. 

• True

• False

Answer explanation

Organic molecules contain carbon and hydrogen. Methane is the simplest organic molecule.

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NGSS.HS-LS1-6

This image shows a model of a methane molecule. Is this statement about methane true or false?
It contains five types of atoms. 

• True

• False

Answer explanation

It contains two types of atoms: one carbon (C) and four hydrogens (H).

Tags

NGSS.MS-PS1-1

This image shows a model of a methane molecule. Is this statement about methane true or false?
It is an isomer of carbon dioxide. (CO₂)
Hint: Isomers are molecules that have the same chemical formula but different arrangement of atoms.

• True

• False

Answer explanation

Isomers have the same chemical formula, but carbon dioxide (CO₂) has a different chemical formula than methane (CH₄).

Tags

NGSS.MS-PS1-1

This image shows a model of a methane molecule. Is this statement about methane true or false?
It has four covalent bonds. 

• True

• False

Answer explanation

Methane has four bonds, each between the carbon atom and a hydrogen atom.

Tags

NGSS.MS-PS1-1

Match this molecule with the larger biological molecule it is used to build.

• carbohydrate

• lipid

• protein

• nucleic acid

Answer explanation

Amino acids have the general structure shown here, but each has a unique “variable group.” They are building blocks for proteins.

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NGSS.HS-LS1-6

Match this molecule with the larger biological molecule it is used to build.

• carbohydrate

• lipid

• protein

• nucleic acid

Answer explanation

Nucleotides have a phosphate group, simple carbohydrate (“sugar”), and nitrogen base. They are building blocks for nucleic acids, such as DNA and RNA.

Match this molecule (a monosaccharide) with the larger biological molecule it is used to build.

• carbohydrate

• lipid

• protein

• nucleic acid

Answer explanation

Monosaccharides, such as the glucose molecule shown here, often take the form of carbon rings. They are building blocks for carbohydrates.

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NGSS.HS-LS1-6