Topic 1: Cell Biology
What is the function of the golgi body?
Processes and packages proteins, which are ultimately released in Golgi vesicles
What is a condensation reaction?
Condensation reaction refers to the reaction in which two smaller organic molecules combine to form a larger molecule and a molecule of water or some other simple molecule. The reaction opposite to condensation is called hydrolysis. This is a chemical reaction in which water is used to break down the bonds of big compounds.
Define genome, gene and allele.
Species: A group of organisms that can potentially interbreed and produce fertile offspring.
Population: A group of organisms of the same species that live in a particular area at the same time.
Community: A group of populations living and interacting in a particular area.
Define selective breeding.
A form of artificial selection in which organisms with certain characteristics are chosen by humans because they are of some benefit. These organisms are bred to produce offspring that have the same genes and, therefore, the same characteristics.
What type of transport uses ATP?
What are the action and absorption spectrums?
The action spectrum shows the efficiency of photosynthesis or rate of photosynthesis achieved over the various wavelengths of light from the visible spectrum.
The absorption spectrum shows which wavelength of visible light is absorbed by a particular photosynthetic pigment such as chlorophyll a or b measured by a spectrometer.
What are the causes of gene mutation?
- errors made in DNA replication
- exposure to radiation and some hazardous chemicals
Define heterotroph vs autotroph.
Autotrophs: Organisms that make their own complex organic molecules from carbon dioxide and other simple compounds. Almost all plants and some other organisms, for example, Cyanobacteria, Dinoflagellata and Euglenida, are capable of autotrophic nutrition.
Heterotrophs: Organisms that obtain their organic compounds through feeding on other organisms
Discuss the pentadactyl limb and its presence in the process of evolution.
The pentadactyl limb is a homologous structure that is an example of divergent evolution. It is seen in mammals, birds, amphibians and reptiles.
State three differences between eukaryotic and prokaryotic cells.
DNA: prokaryotic has naked DNA, circular. eukaryotic DNA is linear and histone proteins.
Organelles: prokaryotic has no nucleus and 70s ribosomes. eukaryotic has nucleus and 80s ribosomes.
Reproduction:prokaryotes use binary fission, have single chromosome. eukaryotes use mitosis/meiosis, chromosomes paired
Describe the properties of water and their benefits to living organisms.
Water has intramolecular covalent bonds, and intermolecular hydrogen bonds, as it is polar
Water is cohesive due to its polarity and strong hydrogen bonds
Water is adhesive to other polar surfaces due to its polarity
Cohesion and Adhesion helps transpiration in plants as it allows for unbroken columns of water in the xylem
Water has high thermal capacity as it takes more energy to break the strong hydrogen bonds
A high heat capacity allows for a better habitat, and a high point of vaporization makes water an effective coolant like sweat
Water is a good solvent for polar solutes due to its polarity
Water is the medium for metabolic reactions where substances are dissolved
What is the Human Genome Project?
A project that began in 1990 with the aim of determining the complete sequence of the human genome and identifying every gene that it contains. It was a multinational and multidisciplinary initiative involving laboratories around the world. Technological advances sped up the sequencing and, in 2003, two years ahead of schedule, the first complete human genome was published.
Outline the relationship between carbon dioxide and coral reefs.
Marine animals such as coral reefs absorb calcium carbonate ions for their exoskeletons.
The concentration of carbonate ions is already low due to its low solubility.
When CO2 reacts with water, it forms carbonic acid, which dissociates into hydrogen carbonate ions, and hydrogen ions.
The limited carbonate ions then react with excess H+ ions, reducing carbonate ions (and thus calcium carbonate levels), and preventing marine animals from absorbing CaCO3.
This process is happening more due to rising CO2 concentrations. Since the industrial revolution, the ocean has experienced a 30% acidification. Therefore, due to climate change, coral reefs and other marine animals are at risk.
Outline antibiotic resistance as an example of natural selection in action.
This means that resistance to antibiotics will happen regardless of the presence of antibiotics.
However, the use of antibiotics increases the percentage of resistant bacteria. When antibiotics are administered, bacteria without the mutation die.
Bacteria with the mutation are much more likely to flourish as there is less competition.
This occurs as less competition leads to more resources shared among the remaining bacteria.
Resistant bacteria are then able to reproduce and form a colony.
Explain the surface area to volume ratio and its relation to cell size.
Surface area relates to the rate of exchange
Volume relates to the metabolic rate of the cell
A cell’s size is limited by its SA:V Ratio
As a cell’s size increases, its SA:V ratio decreases
As a cell’s size increases, its need for nutrition along with its waste produced also increases
If the cell’s metabolic rate exceeds its rate of exchange it dies
In order to prevent this cells divide through binary fission (prokaryotes) or mitosis / meiosis (eukaryotes)
Describe the production of lactose-free milk and some of its advantages.
Lactose free milk can be produced through the immobilization of lactase on the surface or through porous materials
It allows for more people to enjoy dairy products as many people are lactose intolerant
It allows for dairy products to be sweeter as glucose and galactose are sweeter than lactose
It allows for better textures as lactose crystallizes while glucose and galactose do not
It allows for faster production as glucose and galactose ferment faster than lactose
Describe non-disjunction and methods for sampling for karyotyping an unborn child.
Non-disjunction occurs when chromosomes / chromatids are pulled to the same pole instead of separating in meiosis I or meiosis II, resulting in gametes with too many or not enough chromosomes
Gametes with not enough chromosomes usually die, but gametes with too many can survive. This is called Trisomy. An example of Trisomy is Trisomy-21, where there is an extra 21st chromosome. This is also known as Downs Syndrome.
Gametes can be karyotyped (chromosome testing) with 2 methods. Both use a hypodermic needle that is inserted through the mother’s abdomen and uterus.
Amniocentesis is the extraction of amniotic fluids from the amniotic sac with a hypodermic needle. This has a 1% chance of causing miscarriage.
Chorionic Villus Sampling is the extraction of chorionic villi from fetal tissue with a hypodermic needle. This has a 2% chance of miscarriage.
Outline the organization of ecosystems.
Species is the first level, which shows the different types of organisms.
Population is all the organisms of a species.
Community is all the populations of all the species in a given area.
An ecosystem is the system in which biotic factors of communities and abiotic factors interact.
Abiotic factors are factors that can play a role in the lives of organisms in a community, such as water supply, wind, or humidity.
Outline industrial melanism as an example of natural selection in action
When there is little pollution, the moths are white and camouflage well against the lichen on trees.
When it gets polluted, sulphur dioxide kills the lichen, and soot also blackens the trees.
Melanic (dark) moths have an advantage as they are better camouflaged against the black trees.
Birds and other predators then eat the white, peppered moths.
In industrial areas with more pollution, melanic peppered moths are mostly eaten while melanic moths survive and reproduce, causing the species to evolve from being peppered to being melanic.
Describe the cell cycle, including interphase and the role of cyclins.
The majority of a cell’s life is spent in the 3 parts of interphase. In the G1 phase, there is an increase in the amount of organelles.
In the S phase, the DNA of a cell is replicated in preparation for cellular division.
In the G2 phase, the cell prepares for division, and checks the replication for errors.
After interphase, the cell undergoes cellular division, and the daughter cells start the cycle all over again.
The progression through the cell cycle is controlled by proteins called Cyclins, as well as genes called oncogenes.
There are 4 main types of Cyclins that are produced throughout a cell cycle. Once the 4 Cyclins all reach a certain threshold concentration, the cell is able to progress onto its next stage of the cycle.
Explain the process of DNA replication.
First, the enzyme DNA Gyrase relieves the strain on the double helix of DNA molecules as it is uncoiled.
Helicase uncoils the DNA, splitting it into 2 template strands.
Single-stranded Binding Proteins attached to the strands keep the strands apart, allowing them to be copied.
DNA Primase goes along the 2 strands, adding RNA primers to assist DNA Polymerase.
DNA Polymerase 3 follows the RNA Primers, adding complementary nucleotides to the template strands, in a 5’ to 3’ direction.
DNA Polymerase 1 then replaces RNA on RNA Primers with DNA.
DNA Replication on the lagging strand leaves short lengths of DNA called Okazaki Fragments.
Last, DNA Ligase seals nicks in sugar-phosphate backbones between Okazaki Fragments.
Explain the process of meiosis.
In Prophase I, homologous chromosomes cross over, exchanging genetic material. The nuclear membrane breaks down, and spindle microtubules appear.
In Metaphase I, homologous chromosomes align randomly at the equator of the sell, and spindle fibres attach to centromeres.
In Anaphase I, homologous chromosomes are pulled to each pole.
In Telophase and Cytokinesis I, the cell divides into 2, with half the amount of chromosomes in each cell.
Prophase II is similar to Prophase I, except crossing over does not occur.
Metaphase II is similar to Metaphase I, except with only 1 line of chromosomes, rather than 2.
Anaphase II is similar to Anaphase I, except with sister chromatids being pulled to the poles, rather than homologous chromosomes.
After Telophase and Cytokinesis II, 4 haploid cells are formed, with the same amount of chromatids (now chromosomes) as in the 2 cells after Meiosis I.
Describe the greenhouse effect and discuss whether recent global warming is due to human activity.
The greenhouse effect is a phenomenon where gases in the atmosphere trap long wave radiation in the form of heat emitted from the earth from escaping.
The significance of a given gas depends on its ability to absorb / trap long wave radiation, as well as its concentration in the atmosphere.
Currently, CO2 and Water Vapour are the most significant GHGs, though there are other gases that also play a role in the greenhouse effect.
Therefore, due to the greenhouse effect, heat emitted from the earth is trapped, and thus global temperatures have risen.
Without CO2 in the atmosphere, the planet would be 30º colder.
Global temperatures and CO2 concentrations have risen significantly since the industrial revolution in the 1800s.
This is likely due to the combustion of fossil fuels such as coal, which releases significant amounts of carbon into the atmosphere.
Therefore, human activity is likely the cause behind recent global warming.
Define evolution and discuss related evidence.
Evolution is the process where heritable characteristics of a species change over time.
One example is continuous variation where populations naturally diverge from one another and become different species.
Artificial selection occurs when individual organisms with desirable traits are chosen for and breeded.
Divergence and Speciation happens when populations diverge and become unable to reproduce with one another.
Adaptive radiation cause homologous structures, which are physical traits with similar structures but different functions.4
An example of this is the pentadactyl limb of animals. The 5 fingered limb has evolved from a common ancestor to its current form, serving different purposes. For examples, the pentadactyl limb in birds are used for flying, while in humans, it is used for grasping.
Lastly, the Fossil Record is also evidence for evolution. Fossils of extinct species can be studied, and suggest that changes occur over time. These fossils are also dated through radioactive isotopes.