Review - Essay Questions Flashcards
Outline the action of enzymes
They catalyze reactions. They have specific substrates. They lower the activation energy of chemical reactions. Substrates collide with the active site of the enzymes. An enzyme-substrate complex is formed.
Explain the roles of specific enzymes in prokaryote DNA replication
DNA gyrase prepares for uncoiling strains in the double helix. Helicase uncoils the double helix by breaking the hydrogen bonds between the two strands of DNA. DNA primasse adds an RNA primer. DNA polymerase 3 adds DNA nucleotides at the primer in a 5’ to 3’ direction. DNA polymerase 1 removes the primer, replacing RNA with DNA. DNA ligase links sections of replicated DNA.
Outline the effects of putting plant tissue in a hypertonic solution
Hypertonic solution has a higher solute concentration than the tissue. Water moves out of the tissue by osmosis into the hypertonic solution - from lower solute concentration to higher solute concentration. The cell becomes flaccid. The cell becomes plasmolysed.
Explain how the structure of the nephron and its associated blood vessels enable the kidney to carry out its functions
Osmoregulation of urea is a function of the kidney. Ultrafiltration in the glomerulus filter out small molecules. The basement membrane prevents loss of blood cells and large proteins. Selective reabsorption of glucose occurs in the proximal convoluted tubule. Water is reabsorbed in the descending limb of the loop of Henle. Active pumping of sodium ions out of the ascending limb from filtrate to medulla. The distal convoluted tubule adjusts concentration of sodium, potassium and hydrogen. Water is reabsorbed in the collecting duct.
Outline how the energy flow through food chains limits their length.
Only a small proportion of energy is passed from one trophic level to the next. Energy is released by respiration and lost as heat. Energy gets lost due to uneaten parts. More energy is available in the early stages of a food chain.
In hot, dry conditions plants lose water rapidly due to transpiration. Explain how the structures and processes of the plant allow this water to be replaced.
Evaporation of water in the leaf creates a transpiration pull. Water is drawn through cell walls by capillary action to cellulose due to low pressure in the xylem. Hydrogen bonds make water cohesive, allowing the transpiration pull to move water. Water travels from the roots to the leaves in the xylem. Water is absorbed in the roots by osmosis. Active transport of ions into roots enables osmosis. Leaves have thick waxy cuticles to reduce water loss. Plants in dry conditions have less surface area (less leaves) and fewer stomata which open at night. They have hairs on the leaf surface to reflect sunlight.
Explain how circulation of the blood to the lungs and to other systems is separated in humans and what the advantages of this separation are.
Humans have a double circulatory system. The left and right sides of the heart are separated. Each side of the heart has an atrium and a ventricle. The left ventricle pumps blood to the body, the right ventricle pumps blood to the lungs. Deoxygenated blood is pumped to the lungs and oxygenated blood is pumped to the rest of the body. The left atrium receives blood from the lungs and the right atrium receives blood from the rest of the body. The left ventricle pumps blood via the aorta and the right ventricle pumps blood via the pulmonary artery. The left atrium receives blood via the pulmonary vein and the right atrium receives blood via the vena cava. Lungs require low blood pressure. High pressure is required to pump blood to the rest of the body.
Describe what happens in the alveoli
Gas exchange occurs in the alveoli. Oxygen diffuses from air to blood and CO2 diffuses from blood to air. Oxygen binds to haemoglobin in RBC. Air enters and exits the alveoli during ventilation. Secretion of surfactant to prevent sides of alveoli from adhering.
Distinguish between the composition of blood in the renal artery and the blood of the renal vein
In the renal vein, there is less urea, less oxygen, more CO2, less glucose.
Describe the transport of organic compounds in vascular plants
The phloem transports organic compounds from the roots. Active transport loads organic compounds out of the phloem. High solute concentrations causes water to enter by osmosis. High pressure cause flow from source to sink. Translocation occurs.
Outline three processes required for successful reproduction of vascular plants
Production of male and female gametes occur. Pollination occurs from anther to stigma. Fertilization happens after pollination. Then seed dispersal.
Growth in living organisms included replication of DNA. Explain DNA replication.
In semi conservative replication, DNA gyrase prepares the double helix to be uncoiled. Helicase unwinds the double helix by breaking hydrogen bonds. DNA primase adds an RNA primer. DNA polymerase 3 adds nucleotides to the primer in a 5’ to 3’ direction. There is complimentary base pairing. DNA polymerase 1 replaces the primers with DNA. Ligase joins the fragments together.
Explain the processes by which light energy is converted into chemical energy
Producers convert light to chemical energy by photosynthesis. Chlorophyll absorbs light. Electrons are raised to a higher energy level and pass along a chain of electron carriers. Energy from the electrons are used to pump proteins into the thylakoid space. Chemiosmosis used to make ATP. ATP synthase generates of ATP. Electrons from photo system 2 flow via the electron chains to photo system 1. Electrons from photo system 1 are used to reduce NADP. ATP and NADP are used in light independent reactions. Carbon compounds produced contain energy.
Producers extract phosphates and nitrates from soil. Outline how these ions are used in the synthesis of organic molecules.
When you are synthesizing something, you need energy, and plants get it from the sunlight through photosynthesis. The phosphates and nitrates are attached to carbon compounds. Phosphates are used to make phospholipids, nucleotides and nucleic acids. Nitrates are used to make amino acids, proteins, nucleotides and nucleic acids. The nutrients are transported from the roots to the leaves via the xylem.
Describe how energy flows through and is used by organisms in ecosystems
Producers obtain energy from light. Energy is passed in the form of food. Consumers obtain energy from previous trophic levels. Energy is released by cell respiration. ATP is produced. Energy is lost through each trophic level.
Explain how chemical energy for use in the cell is generated by electron transport and chemiosmosis
NAD/FAD is reduced by adding two H atoms. Reduced NAD is produced during glycolysis/link reaction/Krebs Cycle. Reduced NAD/FAD delivers electrons in to the ETC which is in the mitochondria’s cristae. Electrons release energy as they flow along the chain. Electrons from the ETC are accepted by photo system 1. Electron carriers act as proton pumps. Energy from electrons used to pump protons into the inter membrane space. ATP synthase in the cristae converts ADP to ATP.
Outline four different functions of membrane proteins
- Cell to cell communication
- Responsible for facilitated diffusion and active transport.
- Binding site for neurotransmitters
- The serve to connect and join two cells together.
Distinguish between anabolism, catabolism and metabolism.
Anabolism is the synthesis of larger molecules from smaller molecules. Catabolism is breaking down complex molecules into smaller molecules. Metabolism is the enzyme-catalyses reactions in a cell or organism.
Describe the functioning of immunoglobulins
Immunoglobulins function as antibodies. They have a variety of binding sites that are specific to antigens on pathogens. The constant region of antibodies aid in the identification and destruction of the pathogen. Macrophages then engulf the pathogens.
Outline how antibiotics offer protection from certain forms of infectious disease.
Antibiotics protect against the growth of bacteria and they block metabolic pathways. Antibiotics block processes that occur in prokaryotic cells, but not eukaryotic cells. They don’t protect against viruses because viruses have no metabolism. Some strains of bacteria have a resistance to antibiotics.
Coughing to clear the airways is accomplished by muscle contraction. Explain muscle contraction.
Myofibrils are cylindrical structures extending the entire length of the muscle fibers. Sacromeres are the repeating units in myofibrils and they shorten during muscle contraction. Actin and myosin overlap and the dark bands become wider and the light bands become narrower. Myosin is a thick filament and actin is a thin filament. Nerve impulses cause depolarization of sarcolemma which is spread through the muscle fibers via T-tubules. This causes the sarcoplasmic reticulum to release calcium ions. Troponin causes tropomyosin to expose the binding sites on actin. Myosin heads form cross bridges with the actin filaments. Myosin filaments pull actin towards the center of the sacromere, causing the Z-lines to move closer. ATP binds to the myosin head, breaking the cross bridge between actin and myosin. Myosin heads swivel towards the next actin binding site. This results in muscle contraction. Intercostal muscles contract to cough.
Discuss the role of genes and chromosomes in determining individual and shared character features of the members of species.
Genes are heritable factors that consist of a length of DNA and influences a specific characteristic. Chromosomes are DNA molecules associated with histone proteins. In genes, mutations change genes. They can have multiple alleles and different alleles of a gene can give different characteristics e.g. eye color. Alleles are dominant or recessive. Certain genes are expressed in all members of a species. Genes are inherited from parents. Each chromosome of a species, has the same sequence of genes. Every member of a species has the same number of chromosomes. Sex chromosomes determine gender of an individual. Meiosis gives new combinations of chromosomes.
Outline the process of speciation
Speciation is the splitting of a species into two species. It occurs when groups in a species become reproductively isolated or geographically isolated. Speciation can occur gradually over thousands of years or there can be a punctuated equilibrium where they change over a short period of time.
Describe, using one example, how homologous structures provide evidence for evolution.
Homologous structures have different functions but similar structures. This can be seen through pentadactyl limbs. They have similar bone structure but different uses e.g. crocodiles use their webbed hind limbs for swimming and penguins use their hind limbs for walking and forelimbs as flippers for swimming. Homologous structures suggest that there was a common ancestor and evolutionary divergence from a process called adaptive radiation.
Outline the roles of the different binding sites for tRNA on ribosomes during translation
A, P and E sites are on the large subunit of the ribosome. The large subunit of the ribosome contains three tRNA binding sites:
A site - where the tRNA molecules carrying an amino acid enter and bind, and the site of peptide bond formation with resulting transfer of the polypeptide chain.
P site - holds the tRNA attached to the growing polypeptide chain.
E site - where the empty tRNA exits the ribosome.
Explain the production of antibodies.
Each antibody corresponds to a specific antigen. Antibodies fight infectious diseases. Macrophages engulf and then digest pathogens. The macrophage then displays antigens from the pathogen on its surface. T-lymphocytes are activated by antigen binding. The T-lymphocytes active B-cells. The B-cells divide by mitosis to form plasma cells which secrete specific antibodies. Some activated B-cells act as memory cells.
Outline how reproductive isolation can occur in an animal population.
Reproductive isolation can be sympatric or allopatric. There can be geographic isolation where populations are separated by rivers/mountains etc. There can be temporal isolation where members of different populations reproduce at different times. Polyploidy can also occur.
Describe the different types of cells in the seminiferous tubules that are involved in the process of spermatogenesis.
Spermatogonia are undifferentiated sperm cells. They mature and divide by mitosis into primary spermatocytes. The primary spermatocytes then divide by meiosis 1 into secondary spermatocytes. The secondary spermatocytes then divide by meiosis 2 into spermatids. The spermatids then differentiate.
Explain the roles of specific hormones in the menstrual cycle, including positive and negative feedback mechanisms.
The anterior pituitary secretes FSH which stimulates the ovary for follicles to develop. Follicles secrete estrogen. Estrogen stimulates more FSH receptors on follicle cells which produces more FSH. Increased estrogen results in positive feedback on the anterior pituitary. Estrogen stimulates LH secretion and promotes development of the uterine lining. LH levels increase and cause ovulation. LH results in negative feedback on follicle cells. LH causes follicle cells to produce more progesterone. Progesterone thickens the uterine lining. High progesterone results in negative feedback on pituitary. Progesterone levels drop and allow FSH secretion and degradation of the uterine lining.
Cells go through a repeating cycle of events in growth regions such as plant root tips and animal embryos. Outline this cell cycle.
The cells under go mitosis. Mitosis is the division of a nucleus into two daughter nuclei. It consists of four phases: prophase, metaphase, anaphase and telophase. Cytokinesis occurs after mitosis. Interphase is the metabolically active phase between cell divisions. Interphase consists of three phases: G1, S phase, and G2. In G1, protein synthesis and cell growth occur. In the S phase, DNA is replicated and each chromosome is doubled. In G2, proteins necessary for cell division are made.
Explain the control of gene expression in eukaryotes.
mRNA convey genetic information from DNA to the ribosomes. Gene expression requires the production of specific mRNA through transcription. Some genes can only be expressed at certain times. Some genes can only be expressed in certain cells. Transcription factors can increase and may prevent or enhance the binding of RNA polymerase. Nucleosomes limit access of transcription factors to DNA. The chemical environment of the cell can affect gene expression.
