HL Paper 2
Outline the roles of helicase and ligase in DNA replication.
Explain how natural selection can lead to speciation.
Outline the features of ecosystems that make them sustainable.
Identify the following processes as either anabolism or catabolism by placing a tick (√) in the correct box.
Outline the importance of enzymes to metabolic processes.
Mutagens can be removed from the body by converting them to readily excreted metabolites. NNK is converted to a metabolite, NNAL-Gluc, which can be used as a biomarker for the uptake of NNK. Cotinine, a metabolite of nicotine, is an indicator of tobacco smoke uptake. The graph shows the relationship between these two metabolites in the urine of 233 smokers.
State the highest concentration of cotinine in the urine, giving the units.
Deduce, with a reason, whether the concentrations of cotinine and NNAL-Gluc would be higher in the urine or in the blood plasma of a smoker.
Suggest one advantage of using the urine concentration of cotinine rather than NNAL-Gluc to give a measure of the amount of tobacco smoke inhaled by a person.
Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world’s forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.
Identify the dominant plant phylum in the boreal forest.
In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to accumulate. Suggest reasons for this.
An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.
Suggest one advantage for the evergreen trees of the boreal forest being pollinated by wind.
Discuss the advantages of the production of seeds enclosed in fruit.
The boreal forests are situated close to the north pole and even in summer the intensity of sunlight is lower than at the equator. Sketch a graph showing the effect of light on the rate of photosynthesis, labelling the axes.
In some boreal species, Rubisco is down-regulated during the winter months. Describe the role of Rubisco in photosynthesis.
The image shows a cell in a section of an onion root tip seen under a light microscope.
Identify the structure labelled X.
State the stage of mitosis of this cell.
Compare and contrast the location of ATP synthase and the movement of protons during aerobic cell respiration and photosynthesis.
Using the table, distinguish between the production of ATP, use of oxygen and release of CO2 in aerobic cell respiration between the cytoplasm and the mitochondrion.
The graph shows energy levels throughout an uncatalysed reaction. Draw a curve to show how the action of an enzyme would affect this reaction.
The enzyme ATP synthase has an essential role in aerobic cell respiration.
The sketch shows the relationship between the reaction rate and substrate concentration in the presence and the absence of a competitive inhibitor.
Explain the effect of the competitive inhibitor on the reaction rate.
Describe its location.
Describe its function.
Outline how greenhouse gases interact with radiation and contribute to global warming.
Outline how plants make use of the different wavelengths of light.
Explain how organic compounds are transported within plants.
Calcium is absorbed from food in the human gut by both active and passive processes. Outline active transport, including the benefits of the process.
Describe the role of oxygen in aerobic cell respiration.
Adult humans may absorb more than five hundred litres of oxygen per day. Explain how gas exchange is maintained in the human respiratory system.
Outline reasons for the therapeutic use of stem cells.
Describe how monoclonal antibodies are produced.
Explain the role of the electron transport chain in the generation of ATP by cell respiration.
Cellular processes at the molecular level are regulated by enzymes.
Outline the process of DNA profiling.
Outline the role of DNA polymerase III in DNA replication.
Explain the factors that affect the rate of enzyme-controlled reactions in cells.
Plants have developed efficient methods for transport and for synthesis of foods.
Outline how the properties of water make it an ideal transport medium in plants.
Distinguish between the xylem and phloem of plants.
Explain how the light-independent reactions of photosynthesis rely on the light-dependent reactions.
The image shows part of a plant cell with a chloroplast in close proximity to mitochondria.
[Source: Photo © E. Newcomb.]
State two structural similarities between mitochondria and chloroplasts.
1.
2.
Compare and contrast mitochondria and chloroplasts in terms of the substrates they use and the products they produce.
Outline how the compounds produced by chloroplasts are distributed throughout the plant.
Proteins carry out many important functions in cells and in organisms.
Outline the process of protein denaturation.
Explain the production of antibodies in humans.
Distinguish between competitive and non-competitive enzyme inhibition.
All living organisms depend on a continuous supply of energy.
Explain the stages of aerobic respiration that occur in the mitochondria of eukaryotes.
Outline how ventilation in humans ensures a supply of oxygen.
Describe the reasons for the shape of a pyramid of energy.
Explain the role of hydrogen ions used in photosynthesis.
Describe how the structure of the chloroplast is adapted to its function in photosynthesis.
The enzyme Rubisco is used in carbon fixation during photosynthesis. Identify four other examples of proteins that illustrate the wide range of functions of this group of biochemicals in living organisms.
Oxygen is needed to complete aerobic cell respiration.
Explain how chemical energy for use in the cell is generated by electron transport and chemiosmosis.
Outline four different functions of membrane proteins.
Distinguish between anabolism, catabolism and metabolism.
Outline the functions of rough endoplasmic reticulum and Golgi apparatus.
Outline the control of metabolism by end-product inhibition.
Explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules in a membrane.
In ecosystems, energy is used to convert inorganic compounds into organic matter. Energy enters ecosystems through producers.
Explain the processes by which light energy is converted into chemical energy.
Describe how energy flows through and is used by organisms in ecosystems.
Outline energy flow through a food chain.
Draw a fully labelled graph of the action spectrum for photosynthesis.
Explain Calvin’s experiment and what was discovered about photosynthesis through his work.
Describe the process of photolysis in photosynthesis.
The electron micrograph shows part of a cell including a mitochondrion.
[Source: Used with permission of McGraw-Hill Education, from Harrison’s Principles of Internal Medicine,
J L Jameson et al., 16th edition, 2004; permission conveyed through Copyright Clearance Center, Inc.]
Outline how the structures labelled X and Y are adapted to carry out the function of the mitochondrion.
X:
Y:
Explain how ATP is generated in mitochondria by chemiosmosis.