Enzyme & metabolism
Enzymes bind with substrates at a specific point on the structure of the enzyme. TRUE or FALSE?
True.
Enzyme substrate binding occurs at the active site.
Which of the following occurs when ATP is converted into ADP?
I Energy is stored
II Energy is released
III Condensation reactions
IV Hydrolysis reactions
A I only
B I and II
C II and IV
D I and IV
C II and IV
Which of the following is a limiting factor that affects the rate of photosynthesis?
I Temperature
II Oxygen concentration
III Carbon dioxide concentration
A. I and II
B. I, II and III
C. I and III
D. II and III
B. I, II and III
Which of the following are involved in the creation of a resting potential across a neuron membrane?
I. Diffusion of ions across the membrane.
II. Active transport of ions.
III. ATP from respiration.
IV. Concentration gradients of sodium and potassium ions.
A. I only
B. I and IV only
C. All of the above
D. II, III and IV only
D. II, III and IV only
Which of the following are conditions required for coral reef formation in an ocean?
I. Appropriate salinity of the water.
II. The presence of coral grazing species.
III. The annual mean temperature of the ocean between 22 and 27°C.
IV. The depth of the water allows sunlight to reach the reef.
A. All of the above
B. I and IV only
C. I, II and IV only
D. I, III and IV only
D. I, III and IV only
A change of pH away from the optimum pH will slow the reaction between the enzyme and the substrate. TRUE or FALSE?
True.
A change of pH to a pH above or below an enzyme's optimum pH may damage (or change) enzyme structure.
This will slow the rate of reaction. If the pH change is very large the enzyme may be denatured.
Which of the following processes require ATP?
I Active transport across membranes
II Anabolism
III Catabolism
IV Movement of chromosomes
A I and II
B I, II and III
C I, II and IV
D I and IV
C I, II and IV
Which technique can be used to separate and identify photosynthetic pigments?
A. Centrifugation
B. Gel electrophoresis
C. Spectrophotometry
D. Chromatography
D. Chromatography
Which of the following occur when an action potential arrives at the presynaptic membrane of a synapse?
I. Movement of mitochondria to the membrane.
II. Uptake of calcium ions.
III. Movement of vesicles containing neurotransmitter to the presynaptic membrane.
IV. An action potential occurs in the synapse.
A. All of the above
B. IV only
C. II and III only
D. II, III and IV only
C. II and III only
Which one of the following is a correct feature of a tundra biome but not for a taiga biome?
1. Long cold, dak winters.
2. Frozen soil water during the winter.
3. Thin nutrient-poor soil.
4. There are no trees.
4. There are no trees.
Which of the following statements does anabolic reactions include?
A. Hydrolysis of macromolecules into monomers in digestion
B. The formation of lactic acid in anaerobic respiration
C. Oxidation of substrates in respiration
D. Formation of macromolecules from monomers by condensation
D. Formation of macromolecules from monomers by condensation
What is the difference between anaerobic and aerobic cell respiration in humans?
A. Anaerobic respiration releases more energy
B. Aerobic respiration requires oxygen but anaerobic does not
C. Aerobic respiration occurs in the cytoplasm and anaerobic respiration in mitochondria
D. Aerobic respiration uses glucose as a substrate and anaerobic respiration uses fatty acids
B. Aerobic respiration requires oxygen but anaerobic does not
Describe how photosynthetic pigments can be separated using chromatography and how this is used to calculate Rf values.
Cut a strip of chromatography paper so that it fits into a gas jar;
rule a pencil line across the strip of paper 3 cm from one end;
pour some solvent (acetone and petroleum ether) into the gas jar and seal it, so the atmosphere is saturated with solvent vapour; using a mortar and pestle, grind up fresh leaves (e.g. spinach) in pure acetone (propanone may also be used), producing as concentrated a pigment solution as possible and then filter the solution;
using a very thin capillary tube or the head of a pin, place a drop of
the pigment solution at the centre of the pencil line;
allow the pigment spots to dry (place near a heat source, e.g. a lamp, or use a fan);
place a second drop on the first and repeat for at least 15 minutes so
that a small but concentrated spot of pigment has built up;
pour further solvent into the gas jar to a depth of approximately 1.5 to 2 cm and place a lid over the gas jar so that the atmosphere inside remains saturated with vapour;
place the bottom edge of the chromatography paper into the solvent so that it is just touching, ensuring the pigment spot is not immersed: the chromatography sheet should be placed so that the origin is just above the level of solvent;
Rf value is a constant distance that a particular substance moves up a chromatogram relative to its solvent front;
Rf value is calculated using the distance travelled by the solvent front and the distance from the origin to the centre of each spot.
Outline three reasons why an action potential can only pass in one direction across a synapse.
The neurotransmitter is only synthesised in the pre-synaptic neurone endings. Vesicles of transmitter substance are only released from the pre-synaptic membrane. Receptor sites are only present in the post-synaptic membrane. The entry of ions (occurs at both sides of a synapse) but has a different effect at the pre-synaptic neurone than the post-synaptic membrane.
What is the best description of the limits of tolerance of a species?
A. The predator population that is sustainable.
B. The range of abiotic factors that are survivable by a species.
C. The range of a specific soil factor in which a population is found.
D. The geographical range where a species is found.
B. The range of abiotic factors that are survivable by a species.
Explain the decrease in activity of the enzyme on either side of the optimum temperature.
Outline the role of ATP in cells.
Adenosine triphosphate (ATP) is a nucleotide, present in every living cell, formed in photosynthesis and respiration from ADP and Pi;
ATP functions in metabolism as a common intermediate between energy-requiring and energy-yielding reactions;
ATP provides a direct source of energy for many life processes within cells;
ATP is used in active transport of molecules and ions across membranes by membrane pumps;
synthesis of macromolecules (anabolism); movement of the whole cell;
movement of cell components, e.g. chromosomes.
Explain how increasing levels of atmospheric carbon dioxide can impact plant growth, with reference to carbon dioxide enrichment experiments.
Increased levels of atmospheric carbon dioxide can enhance plant growth due to increased rates of photosynthesis, as carbon dioxide is a key reactant in the photosynthesis process.
Carbon dioxide enrichment experiments have shown that higher concentrations of CO2 can lead to increased biomass production and improved water-use efficiency in plants.
However, the response can vary depending on the plant species, availability of other nutrients, and environmental conditions.
Some experiments also indicate that there may be a saturation point beyond which additional CO2 does not further enhance growth.
Additionally, increased CO2 levels can lead to changes in plant structure and function, such as altered leaf morphology and reduced stomatal density.
Define membrane potential and resting potential.
Membrane potential is the voltage difference across a cell's plasma membrane.
Resting potential is the membrane potential of a neuron when it is not transmitting a signal, typically around −70 mV.
Contrast the fundamental niche with the realized niche of a species.
The fundamental niche is the full range of environmental conditions in which an organism can exist.
The extremes of the fundamental niche include the limits of tolerance of the organism.
The realized niche is the actual range of conditions the organism occupies.
The realized niche is smaller than the fundamental niche
The realised niche is limited by competition with other organisms.
Some enzymes function optimally in acidic conditions, while other enzymes function optimally in alkaline or neutral conditions. Explain why different enzymes have different optimal pH values, relating your answer to the structure of the active site.
Each enzyme is a globular protein with a structurally and chemically specific active site; the specific shape is due to the specific sequence of amino acids in the primary structure, which determines the types
of bonds and location of R-groups (variable side chains) present on the amino acids in the protein;
the conformation (shape) of the active site of each enzyme will change when pH changes;
when the pH increases beyond the optimal pH, positively charged R-groups at active sites can be neutralized by the hydroxide ions (OH−) in the solution; as the pH decreases to a low pH (high H+), negatively charged R-groups at the active sites can be neutralized by the hydrogen ions (H+) in the solution;
both lead to disruption of ionic bonds and hydrogen bonds, which in turn disrupt the secondary and three-dimensional conformation (tertiary) and (if relevant) quarternary structures of the enzyme; the conformation of the active site can no longer be maintained and the substrate no longer fits into the active site as the enzyme is denatured.
Explain how cell respiration affects each level of biological organization.
At the molecular level, energy released by respiration is used in the synthesis of macromolecules (anabolism), e.g. protein synthesis/synthesis of nucleic acid;
at the cellular level, energy/ATP is used in the active transport of molecules and ions across membranes by membrane pumps; pumping of sodium and potassium ions in opposite directions across the plasma
membrane of neurons; movement of cell components such as chromosomes/contraction of spindle fibres; cell division e.g. mitosis and meiosis; movement of whole cells e.g. sperm;
at the organism level, energy is used in movement/muscle contraction; energy used in cardiac muscle contraction/heart contraction, which pumps blood around the body, maintaining concentration gradient of e.g. oxygen between blood and air in alveoli; respiration releases energy which maintains body temperature/homeostasis;energy is needed for reproduction;
at the ecosystem level, energy is transferred from one organism to another in a food chain; only some of the energy transferred becomes available to the next organism in the food chain; energy is lost between trophic levels in a food chain; energy is lost due to inefficient transfer of energy in respiration/heat loss; only about 10% of what is eaten by a consumer is converted into new biomass; energy loss results in short food chains/limited to four or five trophic levels; as a result, feeding relationships of a food chain may be structured like a pyramid/pyramids of energy.
State the chemical equation for photosynthesis.
6CO2+6H2O→C6H12O6+6O2
Outline three mechanisms that create the resting potential in a neuron.
1. Sodium-potassium pump: actively transports 3 Na+ ions out of the neuron and 2 K+ ions into the neuron, using ATP, creating a negative charge inside.
2. Differential permeability of the membrane: the membrane is more permeable to K+ ions than Na+ ions, allowing more K+ to diffuse out than Na+ to diffuse in.
3. Presence of negatively charged proteins inside the neuron that cannot cross the membrane, contributing to the negative charge inside.
Discuss the outcomes you might expect if two species have very similar niches, and they are in direct competition for resources in the habitat.
Competitive exclusion might happen.
This happens if both organisms compete for identical resources.
One organism is better adapted and over time will exclude the other from the habiat.
If the species only compete for some resources, they will coexist in the same habitat.
The two species will have different realized niches.
Organisms may adapt their behaviour to avoid competition/exclusion from habitats.
An example of behavioural adaptation would be to feed at a different time of the day.