Identify and describe What is Metabolism?, Building and Breaking Down Molecules and Metabolic Waste Products in the context of metabolism.
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GCSE Biology Revision
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GCSE Biology revision
Metabolism
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Explain the relationships between What is Metabolism?, Building and Breaking Down Molecules and Metabolic Waste Products and how they contribute to metabolism.
Apply and analyse knowledge of What is Metabolism?, Building and Breaking Down Molecules and Metabolic Waste Products to interpret unfamiliar information about metabolism.
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What is Metabolism?
- Metabolism is the sum of all chemical reactions occurring in an organism's body.
- All metabolic reactions are controlled by enzymes and involve either making or breaking down molecules.
- Both photosynthesis (making glucose) and respiration (breaking down glucose) are examples of metabolic reactions.
Building and Breaking Down Molecules
- Anabolic reactions involve building large molecules from smaller ones, such as glucose being converted into starch.
- Catabolic reactions involve breaking large molecules down into smaller ones, releasing energy in the process.
- Nitrate ions from the soil are combined with glucose (from photosynthesis) in plants to make amino acids, which can then be joined together to form proteins.
Metabolic Waste Products
- Metabolic waste products are potentially toxic substances produced as by-products of metabolic reactions that must be removed from the body.
- Carbon dioxide is a metabolic waste product produced by all cells during respiration.
- Lactic acid is a metabolic waste product produced during anaerobic respiration in muscle cells.
- Urea is a metabolic waste product formed in the liver from the breakdown of excess amino acids.
Metabolic Rate
- Metabolic rate is the speed at which chemical reactions occur in the body.
- It can be measured as the amount of energy (calories) the body uses to maintain all living processes whilst at rest, known as the basal metabolic rate (BMR).
- A higher number of energy-requiring reactions, such as building new molecules, leads to a higher metabolic rate.
Removal of Carbon Dioxide and Lactic Acid
- Carbon dioxide produced during respiration is transported in the blood plasma to the lungs, where it diffuses into the alveoli and is exhaled.
- Lactic acid produced during anaerobic respiration is transported in the blood to the liver, where it can be reacted with oxygen to be fully broken down.
- The liver can also convert excess lactic acid back into glucose, which may then be stored as glycogen if energy is not immediately needed.
Removal of Urea
- Amino acids are broken down in the liver, and the nitrogen-containing part is combined with carbon dioxide to form urea.
- Urea is toxic if it builds up, so it is transported in the blood to the kidneys where it is filtered out.
- Urea is dissolved in water and leaves the body as urine.
Factors Affecting Metabolic Rate
- Sex, age, and growth rate can all influence an individual's metabolic rate.
- Body mass affects metabolic rate, as a larger body generally requires more energy to maintain its living processes.
- Genetics can also play a role, as inherited genes from parents may influence how quickly chemical reactions occur in the body.
Growth and Metabolic Rate
- Children tend to have a higher metabolic rate than adults because they are constantly building new molecules and cells through mitosis to support growth.
- Pregnant women also have a higher metabolic rate due to the energy demands of growing new cells and tissues for the developing baby.
- Whenever the body is actively building new molecules, more respiration occurs to release the energy needed, raising the overall metabolic rate.