AP bio unit 1 explanation

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Hydrogen Bonds

Weak bonds between a partially positive hydrogen (-NH or -OH group) and a partially negative atom (like O or N).

Role of Hydrogen Bonds

Stabilize secondary structure (α-helices and β-sheets) and help maintain tertiary structure.

Disulfide Bonds (Covalent Bonds)

Strong covalent bond between two sulfur atoms from cysteine side chains.

Role of Disulfide Bonds

Provide extra stability in tertiary and quaternary structure by locking parts of the protein together.

Ionic Bonds (Salt Bridges)

Attraction between positively charged (basic) and negatively charged (acidic) side chains.

Role of Ionic Bonds

Help stabilize tertiary and quaternary protein structure.

Phospholipids

Amphipathic molecules with a hydrophilic phosphate head and two hydrophobic fatty acid tails.

Function of Phospholipids

Form the cell membrane (phospholipid bilayer), controlling what enters and exits cells, and providing a semi-permeable barrier.

Cellulose

A polymer of glucose linked by β-1,4 glycosidic bonds. Chains are straight and pack tightly, stabilized by hydrogen bonds between chains.

Function of Cellulose

Provides structural support in plant cell walls, making them rigid and strong. Humans can't digest cellulose because we lack the enzyme cellulase.

DNA

A polymer of nucleotides. Each nucleotide has a deoxyribose sugar, phosphate group, and nitrogenous base (A, T, C, G). DNA forms a double helix with complementary base pairing (A-T, C-G) held together by hydrogen bonds.

Function of DNA

Stores genetic information that determines protein sequences and passes hereditary information from one generation to the next.