Biology Paper 2 Prep

Explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules in a membrane.

- Cell membrane is hydrophobic inside so hydrophobic molecules will pass through by simple diffusion whereas hydrophilic molecules and charged particles will use facilitated diffusion. - Integral proteins are embedded in the membrane due to hydrophobic properties - Cholesterol is mainly hydrophobic so is located among phospholipids. - Hydrophilic heads of phospholipids face outwards - Hydrophobic tails of phospholipids face inwards - Peripheral proteins are on the membrane surface with phosphate heads due to being hydrophilic.

Outline the control of metabolism by end-product inhibition. (5)

- Metabolism pathways are a chain of enzyme-catalyzed reactions. - End product is the final product of the pathway. - Inhibits the first enzyme in the chain. - End product inhibition binds to an allosteric site away from the active site. - Changes shape of the active site which prevents intermediates from backing up

Outline the functions of rough endoplasmic reticulum and Golgi apparatus. (3)

- Ribosomes on RER synthesize proteins. - Proteins from RER are used for the outside of the cell. - Golgi apparatus modifies and packages proteins. - Prepares them for transport to other parts of the cell.

Outline features of ecosystems that make them sustainable.

-Recycling of nutrients -decomposers break down organic matter and release inorganic nutrients - Unlimited energy from the sun - population regulated by negative feedback

How does natural selection lead to speciation

-Variation is required for natural selection -Mutation is a source of variation - more offspring than the environment can support - Gradual divergence of populations due to differences in the environment - Speciation is a form of a new species - temporal/behavioral isolation of the population can lead to speciation.

Explain production and role of antibodies in defense against bacterial pathogens in humans.

Antibodies are produced in response to the presence of an antigen phagocyte then ingests bacteria/pathogen activated helper T Cell binds to B cell specific to the antigen Stimulate B cell undergoes cell division to form clone of plasma cells which produces specific antibodies antibodies bind to bacteria making them easier to recognize and digest by white blood cells.

Outline how greenhouse gases interact with radiation and contribute to global warming.

CO2 is a greenhouse gas Sunlight radiation passes through the atmosphere Co2 in the atmosphere traps some of the radiation It allows short wave radiation to pass but absorbs long waves thus warming the crust.

Explain Calvin's experiment and what was discovered about photosynthesis.

Calvin Cycle is a independent cycle Algae placed in thin glass container Given plenty of light and CO2 Start of experiment algae supplied with radioactive carbon Showed the RuBP was phosphorylated Showed that a wide range of Carbon compounds was quickly made.

Outline active transport, including the benefits of the process

Can be defined as the movement of molecules against a concentration gradient through a protein pump with the use of ATP Allows for nearly all of the calcium to be absorbed whereas diffusion can only even out concentrations

Explain the stages of aerobic respiration that occur in the mitochondria of eukaryotes.

Cellular respiration is the controlled release of energy from organic compounds to produce ATP. Cell respiration involves the oxidation and reduction of electron carriers. The electrons are deposited to carriers which enable proton pumping to occur, protons accumulate in the inter-membrane space and generate potential energy. Through diffusion the protons now pass through the ATP synthase enzyme embedded into the membrane and using their kinetic energy creates ATP by combining an ADP molecule with an extra inorganic phosphate, this process is known as chemiosmosis. Finally, as the electrons travel from carrier to carrier they reach the final terminal acceptor oxygen.

Outline how plants make use of different wavelengths of light.

Chlorophyll absorbs red and blue light but doesn't absorb green light This can be seen in the absorption spectrum.

Describe the role of oxygen in aerobic cell respiration

During aerobic cellular resperation glucose reacts with O2 forming ATP that can be used by the cell CO2 + H20 ad created as by products. Oxygen is the final electron acceptor at the end of the electron Avoids anaerobic respiration and buildup of lactic acid.

Outline energy flow through a food chain.

Energy from sun converted to chemical energy by photosynthesis Energy is released from carbon compounds by respiration. Heat is lost from food chains Energy losses between trophic leads limits the length of food chains

Outline the rolls of Helicase and Ligase.

Helicase -unwinds DNA -breaks hydrogen bonds between bases Ligase - forms the continuous sugar-phosphate backbone strands - helps to join Okazaki fragments

Explain the importance of hydrogen bonding

In plants hydrogen bonds help cohesion in water. This cohesion helps transport under tension of the water Adhesion helps water to rise in plants and helps keep leaf walls moist. High heat capacity so water temperature changes less.

Outline how neurons generate a resting potential

Neurons pump sodium and potassium ions across their membranes to generate a resting potential by active transport There is higher concentration of sodium outside and potassium higher inside. Resting potential is -70mv

Explain how organic compounds are transported within plants.

Plants transport organic compounds from sources to sinks Active transport is used to load organic compounds into phloem sieve tubes at the source. High concentrations of solutes in the Phloem at the source lead to water uptake by Osmosis.

Draw structure of dipeptide

R O H R O | | | | // H2N -C C N C - C | | \ OH H H

Explain how gas exchange is maintained in the human respiratory system.

Respiration involves three main processes in order to effectively transport oxygen to cells where energy production takes place. Gas exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them Ventilation brings air w/ high O2 concentration into the lungs Cellular respiration: Release of ATP from organic molecules is greatly enhanced by the presence of oxygen. Because gas exchange is a passive, processes like ventilation are needed to maintaining a concentration gradient within the alveoli. Oxygen is needed by cells to make ATP via aerobic respiration while CO2 is a waste product and must be removed Ventilation system maintains this concentration gradient by continually cycling the air in the lungs with the atmosphere.

Outline four types of membrane transport, including their use of energy

Simple Diffusion passive movement of molecules along concentration gradient Osmosis Passage of water through a membrane from a lower solute concentration to a higher Active Transport Movement of molecules against a concentration gradient through a protein channel requires energy Facilitated Diffusion Passive movement of molecules along a concentration gradient through a protein channel.

Outline how ventilation in humans ensures a supply of oxygen.

Ventilation is the exchange of gases between lungs and air During inhalation the diaphragm contracts and lowers. External intercostal muscles contract which results in an increase in volume and decrease in pressure within the thoracic cavity. air drawn into alveoli brings fresh supply of oxygen oxygen concentration gradient causes oxygen to diffuse out of the alevoli into red blood cells.