topic 2 Flashcards
What are the basic structural components of an amino acid?
An amino acid consists of a carboxyl group (-COOH), an amino group (-NH) and a variable R group that determines its properties.
How are polypeptides formed from amino acids?
Polypeptides are formed through condensation reactions, where a peptide bond is created between amino acids, releasing a molecule of water.
What type of bond holds amino acids together in a polypeptide chain?
Peptide bonds hold amino acids together.
What is the primary structure of a protein?
The primary structure is the sequence of amino acids in a polypeptide chain, held together by peptide bonds.
What determines how a protein folds into its 3D shape?
The amino acid sequence (primary structure) determines which bonds form, which in turn influences how the protein folds into its 3D structure.
What is the secondary structure of a protein?
The secondary structure is the way the polypeptide chain coils or folds due to hydrogen bonds. It can form:
An alpha helix
A beta pleated sheet
What types of bonds are involved in the tertiary structure of a protein?
Ionic bonds
Disulfide bonds
Hydrogen bonds
Hydrophobic and hydrophilic interactions
What is the quaternary structure of a protein?
The quaternary structure is when multiple polypeptide chains are bonded together to form a functional protein, e.g., hemoglobin (4 chains).
What types of bonds hold together the quaternary structure?
The same bonds as the tertiary structure, including hydrogen bonds, ionic bonds, and disulfide bonds.
What is the difference between globular and fibrous proteins?
Globular proteins: Round, compact, soluble proteins, e.g., hemoglobin.
Fibrous proteins: Long, strong, insoluble proteins, e.g., collagen.
How does the structure of hemoglobin relate to its function?
Hemoglobin is globular, soluble, and made of four polypeptide chains, allowing it to bind oxygen efficiently in the blood.
What happens if a protein is heated to a high temperature?
Heating breaks hydrogen bonds, ionic bonds, and hydrophobic interactions, changing the 3D structure and making the protein non-functional (denaturation).
What is a dipeptide?
A molecule formed when two amino acids are linked by a peptide bond.
What does the term polypeptide mean?
A chain of multiple amino acids linked by peptide bonds.
What is the Fluid Mosaic Model?
The Fluid Mosaic Model describes the structure of the cell membrane, showing it as a fluid, flexible bilayer made of phospholipids, proteins, and carbohydrates.
Why is the membrane described as fluid?
The phospholipids are constantly moving, making the membrane flexible and allowing proteins to move within it.
What is the main structural component of the cell membrane?
Phospholipids, which form a bilayer with:
Hydrophilic heads (water-attracting) facing outwards.
Hydrophobic tails (water-repelling) facing inwards.
What is the function of proteins in the cell membrane?
Some proteins are scattered through the bilayer, forming a mosaic pattern.
Some move around to help with transport.
Others are channel or carrier proteins that help large molecules cross the membrane.
What are glycoproteins and glycolipids?
Glycoproteins: Proteins with polysaccharide chains attached.
Glycolipids: Lipids with carbohydrate chains attached.
What is the function of cholesterol in the membrane?
Cholesterol fits between phospholipids, forming bonds with them and making the membrane more rigid and stable.
Why is the membrane partially permeable?
It allows small molecules to diffuse through gaps between phospholipids, while large molecules and ions can only pass through protein channels.
How did electron microscopes change this view?
Early electron microscope (EM) images seemed to show three layers in the membrane.
Later improved EM techniques revealed a bilayer of phospholipids with proteins scattered throughout.
What experiment proved that the membrane is fluid?
Scientists fused a mouse cell and a human cell, and their membrane proteins mixed completely. This could only happen if the membrane was fluid.
What is osmosis?
Osmosis is the diffusion of free water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
What happens if a solute (e.g., sucrose) is present?
A higher solute concentration means there are fewer free water molecules, causing osmosis towards that area.
