Metabolism Flashcards
Enzymes
• Enzymes break large molecules of carbohydrates, lipids and proteins into smaller molecules that can be absorbed.
• Catalyst – a substance that speeds up a reaction
• Enzymes – are organic catalysts, that speed up the rate of biochemical reactions in the body, without being used up themselves.
• At normal body temperature our body reactions would occur too slowly.
• Enzymes reduce the amount of energy required for the reaction to get started and take place.
• The energy needed to get a chemical reaction started is called the Activation Energy.
• So, enzymes decrease the activation energy of a reaction.
Enzyme Substrate Complex
• Enzymes will act on a molecule known as a Substrate to produce a Enzyme-Substrate Complex, which then produces the Products of a reaction.
• The part of the enzymes surface that the substrate will bond to is known as the Active Site
• The enzyme itself will not change in the reaction. (It’s presence simply allows the reaction to take place more rapidly).
Lock and Key Model (Enzymes)
Enzymes are Specific:
• This means each enzyme can only combine with one particular type of substrate.
• Therefore, will only be involved in one specific reaction.
• The enzyme and the substrate have a specific shape that allows them to fit together perfectly to form a complex.
• Lock and Key Model: a specific key (the enzyme) is shaped to fit the lock (the substrate), only the correct key will open the lock.
Factors affecting Enzyme Activity
There are a number of factors that affect the activity of an enzyme and the rate at which a chemical reaction will take place:
Concentration
Temperature
ph
Co-factors/Co-enzymes
Enzyme Inhibitors
Concentration (Enzyme Activity)
• The higher the concentration of enzymes the faster the rate of a chemical reaction.
• The body can regulate the rate that reactions take place by regulating the type and number of enzymes available.
• Increasing the substrate concentration also increases the rate of reaction.
• This is because there will be more substrate molecules coming into contact with the enzymes.
• However, beyond a certain concentration, increasing the substrate will have no effect because all the enzyme molecules will be occupied.
• The products of the reaction must be continually removed, otherwise it will be more difficult for the substrates to make contact with the enzymes, causing the reaction rate too slow.
Temperature (Enzyme Activity)
• As temperature increases the rate at which the enzyme will speed up a reaction also increases.
• However, enzymes are proteins so when they reach a temperature of 45-50°C the structure of the enzyme changes and they become Denatured (inactivated) and they do not work.
• The temperature at which the enzyme works best is called the Optimum temperature which is between 30°C and 40°C.
pH (Enzyme Activity)
• Enzymes are very sensitive to pH, each enzyme will have an optimum pH at which it works best.
• If the pH is too high or low in the specific environment the shape of the Enzyme changes and it becomes Denatured
• Stomach – 2
• Mouth – 7
• Intestine - 7-9
Co-factors/Co-enzymes
• Many enzymes require the presence of certain substances called co-factors or co-enzymes before they can catalyse a reaction.
• Co-factors and co-enzymes change the shape of an active site so that the enzyme can combine with the substrate.
• Co-factors – typically metal ions (eg. Iron)
• Co-enzymes – organic molecules (eg. Vitamins)
Enzyme Inhibitors
• Are substances that slow or stop an enzyme’s activity.
• Inhibitors can be used by cells to control reactions so that products are produced in specific amounts.
• Drugs such as penicillin are examples.
Metabolism
• Metabolism - all the chemical reactions that take place in cells.
• These reactions convert the food you eat into the energy and materials needed for all life processes.
There are 2 processes:
Catabolism:
• Breaks large molecules into smaller ones
• Releases energy E.g., Cellular respiration
Anabolism:
• Builds smaller molecules up into larger ones
• Requires energy E.g., Protein synthesis
Cellular Respiration
• Cellular Respiration - process by which organic molecules are broken down in the cells to release energy for the cell’s activities.
• Respiration can be summarised by the equation:
• Glucose + Oxygen = Carbon Dioxide + Water + Energy
• C6 H12 O6 + O2 = CO2 + H20 + Energy
• This summarised reaction is made up of over 20 smaller reactions.
• At each step an intermediate product is formed, and small amounts of energy are released along the way.
• That way the energy release is controlled, rather than all at once.
Energy from Cellular Respiration
• Approx 60% of the energy released from respiration is in the form of heat.
• Useful in maintaining body temperature. Also acts as a catalyst for reactions.
• The remaining 40% of the energy is released as ADENOSINE TRIPHOSPHATE (ATP).
• ATP is formed when a phosphate molecule bonds to ADP (adenosine diphosphate).
• Building molecules (anabolism) requires energy, so energy is stored in the bond between the 2nd and 3rd phosphate molecules.
• When the energy is required, the ATP molecule breaks its bond to form ADP + P which releases that stored energy.
Energy usage by Cells
Our body uses this energy in a number of ways:
• Building complex molecules
• Cell division and growth (mitosis) -> Movement of organelles
• Movement of whole cell
• Maintaining cell organisation
• Active transport
• Transmission of nerve impulses
Cellular Respiration
There are 2 forms of cellular respiration:
• Aerobic Respiration – requires oxygen
• Anaerobic Respiration – occurs in the absence of oxygen
• Both forms begin with the process of glycolysis
• Takes place in the cytoplasm, where the enzymes required are present.
• In a series of ten steps one glucose molecule is broken down to form 2 molecules of pyruvic acid.
• This also forms 2 ATP molecules.
• Does NOT require energy as a larger molecule is being broken down (catabolism).
• Glycolysis is to destroy or break down Glucose.
Aerobic Respiration
Aerobic Respiration - respiration requiring oxygen
• After Glycolysis in the Cytoplasm, there are 2 more stages:
The Krebs Cycle and The Electron Transport System:
• These both occur in the mitochondria.
• They both require oxygen to be available.
• The reactions take place in the inner folds of the mitochondria called the CHRISTAE
• The enzymes required for the reaction are attached to this internal membrane.
• So, 1 glucose molecule has the ability to produce up to 38 ATP molecules:
• 2 in the glycolysis stage,
• 2 in the Krebs cycle stage,
• 34 at the electron transport system phase.
• However, 38 molecules of ATP is the theoretical maximum that can be created, but the actual yield is often less than this.
• C6H1206 + 6O2 = 6H20 + 6CO2 + 38ATP
