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As biology paper1 Jan2021 第一次圣诞大考
Terms in this set (24)
Raffinose is a trisaccharide of three monosaccharides: galactose, glucose fructose. The chemical formulae of these monosaccharides are: galactose = C6H12O12 glucose = C6H12O12 fructose = C6H12O12 Give the number of carbon atoms, hydrogen atoms and oxygen atoms in a molecule of raffinose.
Number of carbon atoms 18
Number of hydrogen atoms 32
Number of oxygen atoms 16
因为要减去两个water molecules H2O
A biochemical test for reducing sugar produces a negative result with raffinose solution. Describe a biochemical test to show that raffinose solution contains a non-reducing sugar.
1. Heat with acid & neutralise 2.Heat with Beredict's solution. 3. Red peapitate
0 2 .1 Explain the arrangement of phospholipids in a cell-surface membrane.
1.The hydrophobic tail of phospohlipid repel water so face inside, The hydrophilic head face outside attract water.
2. Makes phospholipid outomaticaly form bilayer with hydrophobic region inside
Describe how an ester bond is formed in a phospholipid molecule.
1. A condensation reaction remove water molecules
2. Between the glycerol CH2OH's H. and fatty acidCOOH's OH
State and explain the property of water that helps to prevent temperature increase in a cell.
Property ： high heat capacity
Explanation: so lots of energy required to increase the temperature
Describe how a phagocyte destroys a pathogen present in the blood.
1. Engulf the pathogen
2. Form vesicle( phagosome), fuse with lysosome
3. Enzyme hydrolysis
Give two types of cell, other than pathogens, that can stimulate an immune response.
1. Cell from transplant orgam
2. Tumour cell
Figure 2 shows the structure of an antibody. Which letter shows where an antigen- antibody complex forms?
What is the role of the disulfide bridge in forming the quaternary structure of an antibody?
Hold & join the polypeptide
Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells. Do not include details of transcription and translation in your answer.4mark
1. Ribosome produce protein
2. ATP produce ATP release energy
3. Golgi appratus package and modify protein
4. And sent them via Vesicle
Suggest why a nucleus is not visible in Figure 3.
Describe how MRNA is produced from an exposed template strand of DNA. Do not include DNA helicase or splicing in your answer. [3 marks]
1. Free nucleotide come and do complementary base pairing with exposes template strand of DNA
2. RNA polymerase join bases together through condensation form phosphodiester bond, pre- mRNA prosuced
3. Introns removed exons spliced together form mature mRNA
Define the term exon.
Base sequence coding for sequence of polypeptide
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.
1. The bobd formed between phosphate of 1 nucleotide to another nuclleotide's Deoxyribose(DNA)
2. Through condensation
The two DNA strands of a particular gene contain 168 guanine bases between them. The relationship between the numbers of guanine bases (G), adenine bases (A). thymine bases (T) and cytosine bases (C) in these two strands of DNA is shown in the following equation.
G = 4(A + T) - C
Use this information and your understanding of DNA structure to calculate the maximum number of amino acids coded by this gene.
168 = 4 (A+T)- 168
A+T = 42x2 =84
(336+ 184)/3 =140
Describe how the separation of strands occurs. (2 marks]
1. DNA Helicase unwind the double strand
2. Through break the Hydrogenbond Between the bases , form replication fork
outsde A student investigated the effect of ethanol, hydrochloric acid and temperature on the loss of red pigment from beetroot cells. Give one way in which the student could ensure the first three beetroot cylinders were kept at 25 °C throughout her experiment. (1mark)
1. Measure the temperature in interval use therometer
2. Add hot or cold water as appropriate, try to keep the temperature close to 25c
Give two variables that the student did not control in her procedure.
1. Cylimder beetroot Surface area
2. Time in solution
A different student used the same procedure and she controlled all variables appropriately. Her results are shown in Figure 3. Using Figure 3, what can you conclude about the damage water, ethanol, hydrochloric acid and different temperatures? caused to beetroot cells by Provide explanations for your conclusions. (4 marks)
1. Beetroot Cell Membrane damage seriously by 70c water
2. No damage cause by water
3. Which means High temperature will denature the transport protein in membrane ,akes them can not function properly-can't control substace in or out( membrane permeability increased)
4. At same temperature, ethanol and hydrochloric acid have similar littile damage to membrne
Which piece of laboratory equipment would he use to take a quantitative measure of the colour of solution?
A competitive inhibitor decreases the rate of an enzyme-controlled reaction. Explain how.
1. Competitle inhibitor has similar chemical structre/ Shape as substrate.
2. it will directly bind to that enyme's active site block the way, makes the origimal substrate no Longer bind to the active site.
3.So that reduce the number af Enzyme - Substrate compex
Suktate When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch.
Scientists have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine.
Assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain.
1.less enyme - substrate complex.(amylase and starch)
2. less hydrolyis of Starch into Mattose
3. so less absorption of glucose
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. [5 marks]
1. Micelles contain salts and fatty acid/ monoglycerides
2. Bring them to epithelial cell of the ileum and makes fatty acid more soluble ( in water)
3. Fatty acids/ monoglycerides being absorbed by diffusion
4. Triglycerides reformed
5. Vesicle move to cell membrane
Describe how the structure of a protein depends on the amino acids it contains. [5 marks]
1. Structure is determined by position of amino acid
2. Primary structure is sequence of amino acid
3. Secondary structure formed by hydrogen bond between amino acid
4. Tertiary structure formed by interaction between R groups
5. Quaternary structure formed by bonds between polypeptide
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