生物讨论专区

Jec

原帖由 morphv02c01 于 8-9-2007 11:18 AM 发表



2006 past year right?
1. Because the enzyme that catalyses the forward rxn is done by enzymephosphatase, whereas the backward rxn is catalysed by enzymephosphorylase?(not sure)
2. (The ...

谢谢。我不是很sure第三的答案对不对。我猜是：glycogen phosphorylase

Jec

原帖由 lipterstar 于 5-9-2007 10:01 AM 发表


我没有refer书。。。。不知道有没有记错。。。。。
1。 explain using group translocation
2. phosphokinase, 没错的话。。。。
3。 忘记了。。。

谢谢你的努力解答。

我新来的,想与大家分享一些题目,请大家多多指教.
(为了节省时间,我将问题与答案一起贴)

(a)State mendel's first law and second laws . Explain the conditions under which these law are applicable .

Mendels first law or law of segregation state that each individual characteristic of an organism is determined by a pair of alleles . Each pair of alleles seperated during meosis and only one of the member of each pair of alleles can be present in a single gamete .

Mendel's second law or law of independent assortment state that each member of a pair of alleles can conbine randomly with the member of another pair of alleles during gametogenesis .

The conditions are :
-the characteristics studied show discontinuous variation .
-the genes are not linked on the same chromosome .
-there is no codominance or incomplete dominant .
-no multiple alleles .

Jec

原帖由 庄Ch'ng 于 8-9-2007 03:53 PM 发表
我新来的,想与大家分享一些题目,请大家多多指教.
(为了节省时间,我将问题与答案一起贴)

(a)State mendel's first law and second laws . Explain the conditions under which these law are applicable .
...

［拍手鼓励鼓励］欢迎！你inspire我来support你了。我也把Biology习题贴上来吧。

The theory that chloroplast and mitochondria had their evolutionary beginnings in eukaryotic cells as endosymbionts is supported by the following statement:

A. chloroplast and mitochondria are completely autonomous within eukaryotic cells.
B. chloroplast and mitochondria have DNA.
C. chloroplast and mitochondria have small ribosomes for protein synthesis.
D. chloroplast and mitochondria are approximately the same size as prokaryotic cells.
E. chloroplast and mitochondria have the same shape as prokaryotic cells.















答案: A

原帖由 Jec 于 9-9-2007 01:01 PM 发表


［拍手鼓励鼓励］欢迎！你inspire我来support你了。我也把Biology习题贴上来吧。

The theory that chloroplast and mitochondria had their evolutionary beginnings in eukaryotic cells as endosymbio ...

谢谢..其实我也想透过这里来获得更多题目.

By refering to an example , describe how sexual reproduction takes place in the
(a)Phylum Bryophyta      [8]
(b)Coniferophyta         [7]




(a)-the example of phylum Bryophyta is marchantia .
    -marchantia is a dioecious plant .
    -the antheridium produces antherozoid by mitosis and archegonium contains oospheres .
    -after antheridium absorbs water , it breaks and release antherozoids .
    -antherozoids swim to the archegonium and fuse with the oospheres to form a zygote.
    -zygote developed in archegonium to form diploid sporophyte .
    -the sporophyte , that is the sporangium , is devided into 3 parts ,which is ,foot, seta
     and capsule .      
    -in the capsule , the spore mother cell produce spore by meiosis .
    -the spore then germinate to form a new marchantia thallus .

(b)-the example of Coniferophyta is Pinus .
    -the pinus is a monoecious plant .
    -megasporangium develope in female cone . In megasporangium , megaspore mother cell
     produce megaspore by meiosis . The megaspore then developed into megagametophyte
     by mitosis .The megagametophyte then develope an archegonium with oosphere in it.      
    -microsporangium developed in the male cone . In microsporangium , microspore mother
     cell produce microspore by meiosis .
    -The microspore then developed into pollens grains .
    -the pollen grains transfered by winds to the opening of ovule .Then,the pollen grains
     digest its way to archegonium and sperm nucleus is migrated into the archegonium to
     fertilize with the oosphere inside to form a zygote .

[ 本帖最后由 庄Ch'ng 于 10-9-2007 10:02 PM 编辑 ]

(a)State the external factors which influence the germination of seed .   [3]

-temperature
-water
-oxygen


(b)The germination of dormant seeds involves the metabolisation of food reserve which is stimulated by gibberellin . Describe this process in detail .  [12]

-insoluble food reserve in seed included carbohydrate , lipid and insoluble protein .
-after the seed absorb water , the insoluble food have to be hydrolysed to form soluble food .
-so , at the early stage of germination , the embryo start to synthesize gibberellin which   triggers the secretion of hydrolase enzyme .
-in some plant , hydrolase enzyme present in the seed .
-the hydrolysed food are utilized later .
-the carbohydrate is hydrolased into simple sugars such as sucrose and  glucose .
-the simple sugars then are used in the formation of cellulose and other cell wall substances.
-the lipid is hydrolased into fatty acid and glycerol .
-the fatty acid and glycerol are involved in cell respiration and formation of cell membrane .
-the insoluble protein are hydrolased into amino acids .
-the amino acids are involved in the formation of cell membrane and synthesis of enzyme needed

muse

我浏览了很多次的stpm专区
不过觉得看了有点晕。。因为它们的课跳来跳去
考试将近，时间不多了
我们把问题归类
我将会开25个bab的问题区
你们post问题后
我会把它们编辑上去
方便阅读。。
objective+structure+essay questions...
希望大家支持，大家加油！

[ 本帖最后由 muse 于 13-9-2007 11:14 PM 编辑 ]

muse

1.An example of a process that involves active transport is
A.An influx of sodium ions into a nerve axon during the conduction of a nerve impulse
B.The movement of sodium ions from glomerular filtrate into blood plasma during reabsorption in the nephron tubule
C.The movement of potassium ions from blood plasma into the lumen of a Bowman's capsule during ultrafiltration
D.A shift of chloride ions across the membrane of a red blood cell during transport of carbon dioxide

Answer:B

[ 本帖最后由 muse 于 13-9-2007 11:14 PM 编辑 ]

muse

1.The absence of nucleoli causes the cell to die because they do not process
A.chloroplast and are unable to undergo photosynthesis
B.Golgi bodies and are unable to obtain energy
C.mitochondria and are unable to obtain energy
D.ribosomes and are unable to manufacture proteins

Answer: D

[ 本帖最后由 muse 于 13-9-2007 09:49 PM 编辑 ]

muse

1.Enzymes play an important role in cell metabolism.Which of the following statements is not an effect of enzymes on biochemical reactions?
I   It lowers the activation energy of reactions
II  It shifts the equilibrium point of reversible reactions
III It increases the rate of reaction
IV  It breaks the chemical bonds of reactants

A I and IV
B II and III
C II and IV
D III and IV

Answer: C

[ 本帖最后由 muse 于 13-9-2007 09:50 PM 编辑 ]

muse

1.In what aspect are the photosynthetic adaptation of C4 and CAM plants similar?

A.In both cases,the stomata normally close during days
B.Both types of plants make their sugar without Calvin cycle
C.In both cases, an enzyme other than Rubisco carries out the first strp in carbon fixation
D.Neither C4 plants nor CAM plants have grana in their chlorophyll

Answer: C

muse

1.The function of molecular oxygen in cellular respiration is
A.to cause the breakdown of citric acid
B.to combine with glucose to produce carbon dioxide
C.to combine with carbon to produce carbon dioxide
D.to combine with hydrogen to produce water

Answer: D
-by muse-

2.
答案是:
(a) Acetyl CoA
(b) Coenzyme A + oxidised NAD + pyruvate ---> Acetylcoenzyme A + reduced NAD + CO2
(c) Matrix of mitochondrion
(d) NAD & FAD
(e) 18 NAD & 4 FAD
(f) Between the C-D and D-succinate
(g) 4 carbon atoms

-by jec-

3.Describe the main stages of glycolysis.


Glycolysis can be divided into three main stages as follows:

·
Phosphorylation of glucose
Glucose is phosphorylated with a phosphate molecule, using up 2 ATP molecules and producing fructose phosphate.

·
Splitting sugar biphosphate
Further phosphorylation produces fructose biphosphate, which splits into 2 molecules of C3 sugar phosphate, called glyceraldehydes-3-phosphate (PGAL).

Both sugar phosphate molecules are isomers of each other and one of the molecules will then convert to become identical to each other.

·
Oxidation by dehydrogenation
Each PGAL molecule is further phosphorylated with inorganic phosphate and undergoes dehydrogenation to produce 1 molecule of glycerate-1,3-biphosphate and a pair of hydrogen atoms.

Each glycerate-1,3-biphosphate loses a phosphate molecule and produces 1 molecule of glycerate-3-phosphate.

Each dehydrogenation produces 2 ATP molecules, synthesized using the phosphate molecules that were released and 1 reduced NAD molecule carrying the removed hydrogen. It is then converted to another C3 compound called pyruvate.

As both C3 sugar phosphate molecules are converted to pyruvate, thus a total of 4 ATP molecules and 2 reduced NAD molecules are produced.

Since 2 ATP molecules are used during the first stage, the net gain of ATP is actually only 2 ATP molecules at the end of glycolysis

-by jec-

3.With the aid of a diagram, explain the light independent reaction or Calvin cycle.
The Calvin cycle takes place in the stroma of the chloroplast. ATP provides the energy and NADPH provides the reducing power needed for biosynthesis using carbon dioxide. Calvin cycle can be divided into three phases:

Carbon fixation
Catalysed by ribulose biphosphate (RuBP carboxylase), a C5 sugar named ribulose biphosphate (RuBP) takes up carbon dioxide to form the unstable C6 compound. RuBP is the carbon dioxide (CO2) acceptor. The C6 compound breaks down immediately to form 2 molecules of a C3 compound, glycerate-3-phosphate (GP) as the first product in photosynthesis.

Reduction
NADPH will then reduce 1,3-biphosphate (GP) by removing the oxygen from it and converting it to a C3 sugar, glyceraldehydes-3-phosphate (G3P), using ATP energy from the light dependent reaction.

For every three molecules of CO2, 6 molecules of 3GP are yielded. However, only 1 molecule of this C3 sugar can be counted as a net gain of carbohydrate. This molecule can be converted to glucose, sucrose, starch, amino acids and other products.

Regeneration of the CO2 acceptor (RuBP)
The other five molecules of G3P are converted into 3 molecules of RuBP to keep the cycle going. This process requires energy from ATP.



-by jec-

[ 本帖最后由 muse 于 16-9-2007 05:15 PM 编辑 ]

muse

1.Which of the following organisms uses hydrogen as a source of hydrogen in the synthesis of organic molecules?
A.Chromatium
B.Ababaena
C.Leptothrix
D.Thiobacillus

Answer: A

muse

1.The release of oxygen from oxyhaemoglobin will be easier in
A.low concentration of H+ ions
B.low blood pH
C.low concentration of carbon dioxide
D.high oxygen content

Answer: B

muse

1.During ventricular systole in a mammalian heart the
A.bicuspid valve open
B.semilunar valve closes
C.ventricular pressure increases
D.ventricular volume increases

Answer: C

muse

1.Which of the following metabolic processes listed below are functions of the liver?
I   synthesis of plasma protein
II  regulation of fat metabolism
III Storage of vitamin A
IV  Manufacture of digestive enzymes

A. I,II and III
B. I,II and IV
C. I,III and IV
D. II,III and IV

Answers: A

muse

1.The drug curare causes paralysis by preventing a specific neurotransmitter from binding with receptor protien.Which neurotransmitter is affected so?
A.Serotonin
B.Dopamine
C.Glutamic acid
D.Acetylcholine

Answer: D

2.
(a) 答案是:
A: mitochondrion
B: Synaptic vesicles
C: presynaptic membrane
D: postsynaptic membrane
E: synaptic cleft


(b)答案是:
- When an action potential reaches the synapse, calcium channels open up, causing Ca2+ ions to flow into the cells (synaptic knob).

- Ca2+ ions cause the synaptic vesicles to fuse with the presynaptic membrane, thus releasing their contents (neurotransmitter chemicals) by exocytosis.

- The neurotransmitter diffuses across the synaptic celft. It binds to the neuroreceptors in the postsynaptic membrane, causing the sodium channels to open, so Na+ ions flow in.

- A depolarisation takes place in the postsynaptic membrane, which initiate the action potential.

The neurotransmitter is broken down by a specific enzyme (acetylcholinesterase) in the synaptic cleft.

- It breaks down the neurotransmitter acetylcholine. The products are absorbed by the presynaptic neuron by endocytosis and used to resynthesise more neurotransmitter. Energy is acquired from the mitochondria for this process.

-by jec-

[ 本帖最后由 muse 于 16-9-2007 04:33 PM 编辑 ]

muse

An intact dwarf pea plant treated with compound X showed considerable elongation of the internode distance.Compound X is
A. Gibberellic acid
B. Indoleacetic acid
C. Ethene
D. Abscisic acid

Answer: A

muse

1.Which of the following statements are true of B-lymphocytes?
I   derived from bone marrow
II  mature in thymus gland
III form plasma cells
IV involve in the humoral response

A.I,II and III
B.I,II and IV
C.I,III and IV
D.II,III and IV

Answer: C

muse

1.Which of the following reproduction processes are not sexual reproduction?
I   Paedogenesis
II  Polyembryony
III Conjugation
IV  Parthenogenesis

A.I and II
B.III and IV
C.I,II and IV
D.II,III and IV

Answer: C