Proteins, Cell Signalling and Transcription Flashcards
What is transcription?
The process by which sequences of deoxyribonucleic acid (DNA) produce specific messenger ribonucleic acid (mRNA) sequences.
What is translation?
The process by which mRNA determines the final amino acid sequence via transfer ribonucleic acid (tRNA) within a ribosome.
What is the start codon sequence?
AUG (also codes for methionine)
What are the stop codons?
UAA, UAG or UGA
What kind of bonds cause the primary structure of polypeptides to form?
Peptide, through a condensation reaction
What kind of bonds cause the secondary structure of polypeptides to form?
Hydrogen bonds (alpha helices and beta pleated sheets)
How is a polypeptide’s tertiary structure formed?
The helices or sheets fold forming a unique 3D structure. This is caused by various bonding arrangements
How is a protein’s quaternary structure formed?
More than one polypeptide/protein chain joined together. Fibrous or globular proteins result. An example of a globular protein is haemoglobin
What is the amino acid substitution in sickle cell?
Valine is coded instead of glutamic acid
Proteins consist of a primary structure of bases linked via peptide bonds T/F
False. Proteins or polypeptides possess a primary structure of amino acids linked via peptide bonds.
Proteins are folded into helices stabilized by hydrogen bonds T/F
The polypeptide chains are arranged into secondary alpha helices and beta-pleated sheets stabilized by hydrogen bonds.
Proteins rarely have tertiary or quaternary structure T/F
False. The helices or sheets fold, forming a unique tertiary 3D structure. When more than one polypeptide chain is joined together, e.g. the alpha and beta chains in haemoglobin, a quaternary structure results.
Haemoglobin is an example of a protein with a quaternary structure T/F
True
During transcription uracil in mRNA pairs to the adenine on DNA T/F
True
Transcription requires DNA polymerase T/F
False. Transcription requires RNA polymerase.
The cytoplasm is the key site of transcription T/F
False. Transcription occurs in the nucleus.
Amino acids with corresponding bases attach to RNA in the ribosome T/F
False. This statement describes translation not transcription. Transcription is the formation of mRNA from DNA.
Translation requires tRNA to bring amino acids to the ribosome T/F
True
Translation occurs in the nucleus T/F
False. Translation occurs in the cytoplasm.
Translation pairs mRNA adenine with tRNA thymine T/F
False. Translation pairs mRNA adenine with tRNA uracil; RNA does not contain thymine.
Translation requires the anti-codon sequence of tRNA to complement the codon sequence of mRNA T/F
True. Translation requires the anti-codon sequence of tRNA to complement the codon sequence of mRNA.
Translation needs the action of aminoacyl tRNA polymerase to attach amino acids to tRNA T/F
False. Translation requires the action of aminoacetyl tRNA synthetase.
Oestrogen enters its target cell via diffusion T/F
True. Oestrogen is fat soluble and diffuses into target cells.
Oestrogen is not classed as a steroid hormone T/F
False. Oestrogen is classed as a steroid hormone.
Thyroid hormone binds to a cytosol receptor to form a hormone/receptor complex T/F
False. Thyroid hormone binds to a nuclear receptor; oestrogen binds to its cytosol receptor, then the complex enters the nucleus.
Thyroid hormone receptor binds to DNA and affects transcription without the presence of thyroid hormone T/F
True. Thyroid hormone receptor binds to DNA and represses transcription when thyroid hormone is not present.
Hormones can affect genetic transcription in the cell nucleus T/F
True
Hormones act exclusively via cell membrane receptors T/F
False. Thyroid and steroid hormones affect DNA transcription via intracellular nuclear or cytoplasm receptors. Their actions tend to be slower in onset than those of hormones affecting cell membrane receptors.
