edexcel bio b

• Why is it important that water is a good solvent? -Can be used to transport substances around the body or up xylem -Water containing dissolved oxygen making it a habitat
• What is the difference between polar and ionic substances? Ionic have an overall charge but polar do not because they have slight negative areas and slight positive areas
• Why is it important that water is cohesive? -Causes surface tension giving rise to new habitats -Allows long collumns of water to travel up the xylem
• Why is it important that water has a high specific heat capacity? -So the seas won't freeze -Maintains a stable environment for organisms to inhabit
• What is the role of hydrogencarbonate ions in animals? Buffers the blood to prevent it from becoming too acidic
• What role do magnesium ions play in plants? Used in the production of chlorophyll
• How does hydrogencarbonate act as a buffer in the blood? If their are too many H+ ions in the blood, hydrogencarbonate will react with them to create a new acid that is weaker (carbonic acid), balancing the PH of the blood.
• Why is it important that ice is less dense than water? -Ice floats above water as it is less dense providing insulation for the water below preventing it from freezing so organisms can still inhabit it -The ice is another habitat for animals
• Why is it important that water is transparent? To allow light to travel through so plants can photosynthesise
• Why is water a good solvent? It is a polar molecule so water can surround other polar molecules allowing them to dissolve
• How are hydrogen bonds formed between water molecules and what effect does this have on the properties of water? -Water is a polar molecule -The partially negative oxygen will attract the partially positive hydrogen in a weak electrostatic hydrogen bond -This makes water molecules cohesive
• What role do phosphate ions play in organisms? Formation of ATP, ADP, RNA and DNA
• Why does water have a high specific heat capacity? The energy goes into breaking the weaker hydrogen bonds between water molecules and not the covalent bonds within the molecules
• What role does hydrogen play in organisms -Cellular respiration and photosynthesis -PH balance
• What do sodium and chloride ions do in organisms? Used in nerve impulses and many secretory systems
• What role do nitrate ions play in plants? -Formation of amino acids and proteins -Formation of DNA
• Why is ice less dense than water? It has less thermal energy than water meaning molecules in ice are more stagnant
• Why is it important that water has a high latent heat of vapourisation? Allows organisms to cool themselves without losing a lot of water
• What are the properties of water? -High specific heat capacity -Solid form less dense -Good solvent -Cohesive -Adhesive -Polar -High latent heat of vapourisation
• What role do calcium ions play in organisms? -Formation of calcium pectate for lamella -Bone formation -Muscle contractions
• What do peroxisomes do in animal cells? Protects cells from harmful hydrogen peroxide
• What do peroxisomes do in plant cells? Breaks down long chains of fatty acids into sugar -Assists chloroplasts in photosynthesis and respiration
• Why is it important that water is incompressible? -Provides turgidity in plant cells -Provides hydrostatic skeleton to some soft tissued organisms e.g. earthworms
• Why are unsaturated fatty acids a liquid at room temperature? The carbon double bond causes the fatty acid tail to bend which pushes each triglyceride further away from each other which weakens the intermolecular forces so they form a liquid
• What reaction is undergone to produce a triglyceride and what is the name of the bonds made? -Condensation reaction -Ester bond
• What is the difference between a saturated and unsaturated fatty acid? -SATURATED have a carbon chain with only single bonds -UNSATURATED have at least one double bond within the carbon chain
• How does the structure and function of phospholipids relate to their function in the cell membrane? -They create a bilayer as there is water on both sides -The hydrophilic heads stay on the outside of the bilayer -The hydrophobic tails stay on the inside of the bilayer to be protected from water
• Why is the head of a phospholipid hydrophylic? -The phosphoric acid gives off hydrogen atoms in water creating a negatively charged head -Water molecules are polar meaning the negative head will be attracted to the positive hydrogen atoms in water
• What are the functions of lipids? -Insulation -Protection of organs -Waterproofing -Forms myelin sheath -Component in cell membrane
• What is the test for lipids? Add ethanol to tube and shake. Look for cloudiness
• Draw a phospholipid H | H-C--PO4- | O | || H-C--O--C--R | O | || H-C--O--C--R | H
• What is the structural difference between a phospholipid and a triglyceride? PHOSPHOLIPID has 2 fatty acid chains and a phosphate group TRIGLYCERIDE has 3 fatty acid chains and no phosphate group
• What is the quaternary structure of a protein? More than one peptide chain in a protein e.g. haemoglobin
• What is the tertiary structure of a protein? The 3D shape of the polypeptide chain after further folding due to the different charges on the R groups
• What breaks: -Ionic bonds -Hydrogen bonds -Disulphide bonds/bridges HYDROGEN- high temperature or PH IONIC- PH DISULPHIDE- chemicals
• What are the properties of globular proteins? -Has a tertiary and sometimes quaternary structure -Folds into spherical shapes -Soluble in water
• How is the structure of Collagen related to its function? -Has a high tensile strength because of covalent bonds between adjacent collagen molecules
• What bond holds together the secondary structure of a protein? Hydrogen bonds
• What is the name given to proteins with a prosthetic group? Conjugated proteins
• How does hydrogen bonding hold secondary structure of a protein together? -Oxygen in the carboxyl group has a negative charge -Hydrogen in amine group has a positive charge -So hydrogen bonds form