Biology: Edexcel Ial Unit 1 - Past Paper Questions |120 Questions| With Correct Answers.

The sequence of events in the cardiac cycle is.. {Ans: atrial systole --> ventricular systole --> atrial diastole --> ventricular diastole.}Explain why each codon for the DNA genetic code must contain at least three bases. {Ans: º enough codons needed for 20 different amino acids (1) º four bases are used in the genetic code (1) º triplet code provides enough / 43 / 64 possible codons (1)}How is temperature controlled in an investigation? {Ans: heat shield.}Triglycerides can combine with protein to form a lipoprotein. Explain the effect that having large quantities of this lipoprotein would have on blood cholesterol levels. {Ans: 1) increased (blood) cholesterol. 2) (because) the triglyceride is saturated. 3) The lipoprotein is an LDL. 4) lipoproteins / LDLs transport cholesterol. 5) LDL binds to receptors (on cell surface membranes) / LDL accumulates in blood if receptors overloaded.}Explain why people with CF can have breathing difficulties. {Ans: 1) produces {thicker / stickier / more viscous / eq} mucus. 2) blocking { trachea / bronchi / bronchioles / airway / eq} / eq. 3) cilia are unable to move mucus out of lungs / eq. 4) idea of reduced flow of {air /