Salters Nuffield Advanced Biology AS Student Book (Edexcel A Level Sciences) 1st Edition
Topic 2 summary question bank
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1. High SA, short diffusion distance, steep diffusion gradient
2.
3. - Large SA due to many alveoli
- Steep conc. Gradient maintained due to fast blood circulation
- Short diffusion distance due to one cell thick alveoli walls
4. A partially permeable membrane
5. Phospholipids and proteins
6. Transport proteins, receptor proteins, enzymes, structural and
recognition proteins
7. Controlling movement of substances in/out of the cell and allowing
adjacent cells to stick together
8. The fluidity of the membrane and the mosaic arrangement of the
proteins
9. passive movement of small, non-polar, lipid-soluble molecules (eg.
carbon dioxide and oxygen) from an area of high to low concentration
10. requires a channel protein in cell membrane to transport polar,
charged and water-soluble molecules across membrane
11. movement of water molecules from an area of low to high
solute concentration through a partially permeable membrane
12. Transport of all types of molecules through carrier proteins from
an area of low to high concentration.
13. ATP energy
14. Adenine-thymine, cytosine-guanine
15. Deoxyribose sugar (pentose sugar)
16. - Phosphodiester bonds between phosphate and sugar
- Hydrogen bonds between bases
17. Double-stranded, alpha double helix with a sugar-phosphate
backbone on each strand
18. Adenine-uracil, cytosine-guanine
19. Ribose sugar (pentose sugar)
20. Yes
, 21. single-stranded, not usually folded, carries codons which attach
to tRNA via hydrogen bonds
22. single-strand folded into specific pattern held together by
hydrogen bonds, carries anticodons which attach to mRNA via
hydrogen bonds
23. - RNA polymerase breaks hydrogen bonds between the
complementary bases and DNA uncoils
- One of the DNA strands is used as a template (antisense) to make
the mRNA molecule
- Free RNA nucleotides line up by complementary base pairing
- Adenine and uracil (instead of thymine), cytosine and guanine
- Adjacent nucleotides are joined by phosphodiester bonds, forming
mRNA
- mRNA moves out of the nucleus through a pore and attaches to a
ribosome in the cytoplasm
24. - mRNA start codon ‘AUG’ is exposed
- tRNA binds to a specific amino acid from the cytoplasm depending
on its anti-codon
- Complementary anticodons of tRNA bind to mRNA codons and is
held in place by hydrogen bonds.
- Amino acids attached to two adjacent tRNA molecules join by
peptide bond due to condensation reaction
- tRNA detaches from amino acids.
- ribosome moves along mRNA molecule and exposes new codon
- Process is repeated, leading to the formation of polypeptide chain
until stop codon is reached on mRNA.
25. Series of bases on a DNA molecule which code for a series of
amino acids in a polypeptide chain
26. Triplet of bases that codes for a specific amino acid
27. Introns
28. Exons (expressed)
29. - non-overlapping; each triplet is only read once and triplets
don’t share any bases.
- degenerate; more than one triplet codes for the same amino acid.
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