The answer of biochemistry
of 86K English-class and seven-degree class. (A)
2002.07
I. Direction: Each question below contains one correct answer. Choose the most
suitable response to each question. (40 points)
CEECC EBDCC ECCAB DBDCE CDDEE AAEAD CBBCB AEDCB
II. Fill up the blanks. (10 points. 0.5 point each)
1. The sources of heme are__gly__, _succinyl CoA_, Fe2+__.
2. The specificity of enzyme-catalyzed reactions includes __specific__,
__reletive___, and isomeric__.
3. Hormones raising blood sugar level are _epinephrine__ and_glucagon__.
4. The four steps of fatty acid β-oxidatio are _dehydrogenate__, __adding H2O__,
__dehydrogenate_, and _lysis__.
5. The sources of one carbon unit are ___ser__, __gly_, _his__, and __trp__.
6. In eukaryote, when DNA replication, the enzyme that catalyzes the formation
of leading strand is __δ__, the lagging strand is __α___; the enzyme that acts in
mitochondria is ____γ____; the enzyme that takes the role of proofread is
____ε____.
III. Explain the following concepts. (10 points, 2 points each)
1. motif-----In many globular proteins, the secondary structural motifs of -helix
or -pleated sheet from recognizable “super-secondary” motifs.
2. trans-acting factor------ All the protein factors that will bind directly with
cis-acting element or regulate its activity indirectly are called trans-acting
factors.
3. cori cycle-----A metabolic process in which lactate,produced in tissues such as
muscle, is transferred to liver where it becomes a substrate in gluconeogenesis.
4. secondary messenger-----An effector molecule synthesized with a cell in
response to an external signal is the second messenger, which is responsible for
a series of intracellular events.Ca2+,DAG,Cer,IP3,cAMP, cGMP
5. de novo synthesis of nucleotide----- The synthesis of nucleotides begins with their
metabolic precursors: amino acids, ribose-5-phosphate, CO2, and NH3.
IV. Answer the following questions. (20 points, 4 points each)
1. Please describe the NADH respiratory chain.
NADH→FMN→CoQ→cyt b→cyt c1→cyt c→cyt aa3
2. Please describe the sources and outlets of NH3.
Source: intestine: urea hydrolysis
liver: deamination
kidney: Gln deamination
Outlet: formation of Aas
formation of other products
out of the body
3. Please describe the system of protein biosynthesis (translation).
ATP ensure energy
mRNA acts as a template
tRNA acts as an adaptor
20 AAs acts as the substrate
some other enzymes and protein factors
4. Please describe the mechanism of lac operon regulation.
Regulation of the lac operon in E. coli. The repressor of the operon is synthesized from the
i gene. The repressor protein binds to the operator region of the operon and prevents RNA
polymerase from transcribing the operon. In the presence of an inducer (such as the natural
inducer, allolactose) the repressor is inactivated by interaction with the inducer. This allows
RNA polymerase access to the operon and transcription proceeds. The resultant mRNA
encodes the β-galactosidase, permease and transacetylase activities necessary for
utilization of β-galactosides (such as lactose) as an energy source. The lac operon is
additionally regulated through binding of the cAMP-receptor protein, CRP (also termed the
catabolite activator protein, CAP) to sequences near the promoter domain of the operon.
The result is a 50 fold enhancement of polymerase activity.
5. Please describe the types and functions of membrane receptor.
1)ligand-gate ion channels type(cyclic receptor)
2) G protein linked receptor(serpentine R)
H→ R → G protein → AC → cAMP → protein kinase → E or protein
phosphorylation→ effect
3) Single transmembrane α-helix receptor(Tyrosine kinase linked R)
V. 实验题(10 分, 每空 0.5 分)
1
维持亲水胶体稳定的因素（表面电荷），（水化膜）.
2
电泳系统的不连续性是指（缓冲液的不连续性），（PH 值的不连续性），
（凝胶孔
径不连续性）.
3
支持物对电泳结果的影响因素有（吸附作用），
（电渗现象），（分子筛效应）
。
4
检查 NH4 的存在可用（奈氏试剂）。
5
蛋白质的检测用（班氏试剂）
。
6
EDTA 可以防止酶解，是因为它可以除去溶液中的镁离子。
7
DNA 提取实验中，测定 DNA 纯度是通过测定_A260/A280___，然后计算，纯 DNA
＋
该值=___1.8_____.
8
DNA 分子在 PH7.0 溶液中带负电荷,由于 DNA 分子中磷酸根基团的解离引起的.
9
DNA 电泳的支持物为琼脂糖凝胶，电泳方式水平潜水式。
10 测定蛋白质的方法是定氮法，比色法，紫外分光光度法。