METABOLISM, ANABOLISM AND CATABOLISM

metabolism

metabolism is the total sum of chemical reactions within the body of an organism (anabolic + catabolic reactions)

METABOLIC PATHWAYS are essential for producing things that are essential for cells to function

plants : production of glucose, chlorophyll

animals: production of vitamins, haemoglobin

enzymes often play an important role in metabolic pathways

all metabolic pathways together form a network for maintaining life

TYPES OF METABOLIC PATHWAYS

catabolic pathway

anabolic pathway

pathway that releases energy during break down of bonds (from large molecules to smaller molecules)

pathway that requires energy during formation of bonds (from smaller molecules to larger molecules)

exergonic reaction

endergonic reaction

eg: PHOTOSYNTHESIS

CELLULAR RESPIRATION/DIGESTION

CATABOLISM

chemical reaction in which complex substances are broken down into simpler substances

AB = A + B

releases energy

exergonic reaction

food digestion : starch (polysaccharides) --> simple sugars (monosaccharides)

glucose is broken down into carbon dioxide and water during tissue respiration

proteins and amino acid are deaminated in the liver to form urea

ANABOLISM

reaction in which simple substances are built up into more complex substances

A + B = AB

requires energy

important for growth and repair of damaged or worn out tissues

conversion of glucose to glycogen in the liver and muscles

process of photosynthesis in green plants

formation of new proteins from amino acids

example of metabolism

catabolism

the potato gets digested by the animal to make glucose

potato = starch = polysaccharides

glucose are oxidised to make ATP (energy) for the body

starch > glucose [polysaccharides > monosaccharides]

anabolism

excess glucose are made into glycogen or fat for long term storage in the body

glucose > glycogen [monosaccharides > polysaccharides]

complex > more complex

complex > less complex

METABOLISM AND ENERGY FLOW

anabolism + catabolism = metabolism

chemical reaction converts one set of chemical substances, the reactants, into another set, the products

all chemical reactions either release energy (exergonic) or require input of energy (endergonic)

breaking or forming of bonds require energy

in living organisms, potential energy ('stored energy') will often be transformed into kinetic energy ('energy of motion')

energy is defined as the capacity to do work

metabolic pathways and energy flow

exergonic reaction releases energy

the reactants have more energy than the end products

gives off some energy such as heat, light and ATP

occurs during catabolism

example: cellular respiration

glucose + oxygen (reactants) = energy released (ATP) + carbon dioxide + water (products)

glucose is broken down in to carbon dioxide and water

cellular respiration is an important exergonic reaction in humans - provides energy for life

glucose

major breakdown product of carbohydrate digestion

major fuel used for making ATP

oxidised during respiration to release energy for vital activities of the cells

metabolic pathways and energy flow

endergonic reaction requires energy

requires an influx of energy from an outside source

products contain more energy than the reactants

occurs during anabolism

example : photosynthesis

carbon dioxide + water (reactants) + energy (from sunlight) = oxygen + glucose (products)

green plants uses solar energy for sugar (glucose) and oxygen from carbon dioxide and water

most of the biological reactions in an organism are endergonic reactions. they require energy to drive reactions for making molecules and doing work in the cell

energy created by exergonic reactions are used by cells for energy required in endergonic reactions

ENERGY COUPLING

the use of energy released from exergonic reactions (usually in the form of ATP) to drive essential endergonic reactions

in the form of ATP because energy has to be quickly stored somewhere or else it will heat up the cell and you will die

ATP molecules are the key to energy coupling

METABOLIC PATHWAYS OF CARBOHYDRATES : CELLULAR RESPIRATION

in cellular respiration, food molecules are broken down and their energy are captured in ATP molecules

FOUR main carbohydrate metabolic pathways that are involved with cellular respiration

  1. Glycolysis
  1. Acetyl-CoA formation
  1. Krebs Cycle
  1. Electron Transport Chain

occurs in the cytoplasm

occurs in the mitochondria

occurs in the mitochondrial matrix

occurs in the inner membrane of mitochondria