Chapter 5- Biochemistry (1) Flashcards
Give some functions of proteins:
1- Proteins come in the form of enzymes
2- Can be used for transport and storage, i.e, haemoglobin
3- Mechanical support
4- Signalling and receptors
What do amino acids contain?
1- A central C that forms 4 single covalent bonds to
2- Amino group (NH2)
3- Carboxyl group (COOH)
4- H atom
5- R group- variable unit and determines what type of amino acid and determines the chemical nature of that amino acid
How many standard amino acids are there?
20
The different chemical properties are:
1- Acidic
2- Basic
3- Non- polar
4- Polar
What is the formation of proline?
The R group covalently binds to the NH2 group of the central carbon which folds back the amino acid.
What makes proline different to other amino acids?
It has more rigidity compared to other amino acids
What does the rigidity of proline help stabalise?
Folded proteins
Where is proline often found?
Often found in very tight turns in protein structures, where the polypeptide chain must change direction.
How are amino acids held together?
Amino acids are held together by peptide bonds.
What is a dipeptide?
Two amino acids joined together
What is a polypeptide?
Two or more amino acids joined together
When amino acids join together, what reaction takes place?
Condensation reaction
What is a condensation reaction?
When two molecules join together and release water.
How is the protein shape dictated?
By the amino acid sequence
What bonds never form between R groups?
Covalent bonds
What is a disulphide bond?
Disulphide bond- covalent links between the sulphur atoms of two cysteine amino acids.
Secondary protein structures include:
Alpha- helix- rod like structure or coil that has a single polypeptide chain
Beta- pleated sheet- extended polypeptide chains that fold back over each other
How is the alpha helix held together?
By hydrogen bonds
How is the beta pleated sheet formed?
Formed by linking two or more beta- strands.
In a beta pleated sheet, why is the polypeptide chain fully extended?
Because it allows for more hydrogen bonding
What are the levels of organisation of protein structure?
1- Primary structure- sequence of amino acids
2- Secondary structure- alpha- helix and beta sheet formation with folding as a result of hydrogen bonding between peptides.
3- Tertiary structure- folding of the polypeptide chain. Disulphide bonds form between the R groups of the alpha- helixes and beta sheets.
4- Quaternary structure- complex of several polypeptide chains, e.g, haemoglobin
Carbohydrates are what type of polymers?
Sugar polymers
What do carbohydrates contain?
Carbon, hydrogen, and oxygen
What is the role of polysaccharides?
Polysaccharides serve as compact energy storage molecules (glycogen or starch) or structural elements in plant cell walls (cellulose)
What do phosphorylated sugars form?
The structural framework of DNA and RNA (ribose).
