Metabolism, Exercise and Health GCSE Biology Revision PDF

**Cancer** **Tumours** are formed when [**cells divide**](https://mmerevise.co.uk/gcse-biology-revision/cell-division/) uncontrollably and can be **benign** or **malignant**. **Cancers **are **malignant** tumours and can be fatal. The chances of developing certain types of cancer can be increased b...

**Cancer** **Tumours** are formed when [**cells divide**](https://mmerevise.co.uk/gcse-biology-revision/cell-division/) uncontrollably and can be **benign** or **malignant**. **Cancers **are **malignant** tumours and can be fatal. The chances of developing certain types of cancer can be increased by various **risk factors**. **Growth of Tumours** A diagram of a cell Description automatically generated [**Cell division**](https://mmerevise.co.uk/gcse-biology-revision/cell-division/) by **mitosis **is controlled by many different **genes **to produce the correct amount of cells needed by the body. Changes to the [**DNA **](https://mmerevise.co.uk/gcse-biology-revision/dna/)of cells may mean that **genes **can no longer regulate **mitosis **and therefore cells grow and divide **uncontrollably**, forming **tumours**. **Tumours **can be **benign** or **malignant **(**cancerous**): - **Benign** tumours usually stay in one place in the body, within a **membrane**. They therefore do not invade other **tissues **and are most often harmless. - **Malignant** tumours are **cancerous**. They can spread to neighbouring healthy tissues or break off and travel in the **[blood](https://mmerevise.co.uk/gcse-biology-revision/components-of-the-blood/) **and **lymphatic system** to other parts of the body. The spreading of the cancerous cells cause **secondary tumours** to form in different places. Cancers disrupt the functioning of healthy organs and therefore can be fatal.  **Respiration Revision** **Respiration** **Respiration** is an essential process by which all **living organisms** release **energy**. Organisms respire **aerobically **when oxygen is available and **anaerobically** when it is lacking.  **What is Respiration?** **Respiration** is the process by which all **living cells** continuously release **energy **from **glucose**. Animals get their **glucose** from [**digested food**](https://mmerevise.co.uk/gcse-biology-revision/digestive-system/), plants make their own **glucose **in [**photosynthesis**](https://mmerevise.co.uk/gcse-biology-revision/photosynthesis/).  **Respiration** is an **exothermic** reaction because it **releases energy**.  **Energy** is required for many **living processes**: - To **build large molecules** from smaller ones, e.g. proteins from amino acids, starch and cellulose from glucose. - To provide **movement** by contracting their muscles. - To maintain a warm **body temperature** that is suitable for enzymes to work efficiently.  The type of respiration a cell does is dependent on the **amount of oxygen** it receives.  **Aerobic Respiration** When cells receive **sufficient oxygen**, they will respire **aerobically**.  **Glucose **and **oxygen** are converted into **carbon dioxide** and **water**, which releases **energy**. Word equation: **Glucose   +   Oxygen  ------------\>  Carbon dioxide   +   Water   (+ energy)** Chemical equation: **C~6~H~12~O~6~   +   6O~2 \   ~------------\>  6CO~2 \  ~+   6H~2~O   (+ energy)**   **Aerobic respiration** is the most **efficient** way of releasing **energy **and takes place in the [**mitochondria**](https://mmerevise.co.uk/gcse-biology-revision/cell-structure/). **Anaerobic Respiration** When cells do not receive enough **oxygen**, they **respire anaerobically** (**without oxygen**).  The **glucose** is not fully **oxidised** so it is much **less efficient **than aerobic respiration and makes different **products**.    **Animals ** In animals, **glucose** is broken down into **lactic acid** if there is **no oxygen**. **Glucose   ------------\>  Lactic acid   (+ energy)** This often occurs in **muscle cells** during vigorous [**exercise**](https://mmerevise.co.uk/gcse-biology-revision/respiration-and-exercise/) as the body cannot supply them with enough **oxygen**.   **Plants and Yeast** In plants and yeast cells, **glucose **is broken down into **ethanol **and **carbon dioxide**.  **Glucose   ------------\>  Ethanol   +   Carbon dioxide  (+ energy)** Anaerobic respiration in **yeast cells **is called **fermentation **and is a very important process in the production of food and drinks: - **Ethanol** produced from fermentation is a type of **alcohol **which is used to make beers, wines and other alcoholic drinks. - **Carbon dioxide** produced from fermentation is used to make **bread **rise.  **Metabolism Revision** **Metabolism** In every living cell, **[enzyme](https://mmerevise.co.uk/gcse-biology-revision/enzymes/) **controlled **chemical reactions **take place continuously and are all linked together. The sum of all the reactions of a cell or organism is called its **metabolism**.  **What is Metabolism?** **Metabolism** is the word used to describe all the **chemical reactions** that happen within a cell or organism.  Some reactions join smaller molecules together to make bigger ones: - **Glucose **and **nitrate** ions react to make** amino acids**, that join together to form **proteins**. - **Glucose** molecules join together to make **starch**, **cellulose** or **glycogen**. - **Fatty acids** and **glycerol** molecules react to form **lipids**. Other reactions break down big molecules into smaller ones.  - **Glucose **is broken down to release **energy **in **respiration**.  - Excess **protein** is broken down to produce **urea**, excreted in the **urine**.  **Plant Metabolism** This is a brief summary of some of the **reactions **that take place within **plants**:  - Plants carry out [**respiration**](https://mmerevise.co.uk/gcse-biology-revision/respiration/)-- producing **energy** from the break down of **glucose**. - Plants also create their own **glucose** using** carbon dioxide**, **water **and **light energy** in a process called [**photosynthesis**](https://mmerevise.co.uk/gcse-biology-revision/photosynthesis/). - **Glucose** can be stored as **lipids** or **starch** and converted back to glucose when required. - **Glucose** is used to make **cellulose** which provides strength to [**cell walls**](https://mmerevise.co.uk/gcse-biology-revision/cell-structure/).  - **Glucose** can react with **nitrates** from the soil to form **amino acids** that make up **proteins**.  **Animal Metabolism** This is a brief summary of some of the **reactions **that take place within **animals**: A diagram of a structure Description automatically generated Animals intake large molecules in food which get [**digested**](https://mmerevise.co.uk/gcse-biology-revision/digestive-system/) by [**digestive enzymes**](https://mmerevise.co.uk/gcse-biology-revision/digestive-enzymes/) into smaller molecules that can be **absorbed **into the **blood**. - **Starch ---\> glucose** - **Proteins ---\> amino acids** - **Lipids ---\> fatty acids and glycerol ** **Glucose** is either used for **[respiration](https://mmerevise.co.uk/gcse-biology-revision/respiration/) **(producing **energy**) or stored as **glycogen **in the **liver **and **muscles** until required. **Amino acids** are used to build new **proteins** and any excess are converted into **urea **in the **liver **and excreted via the [**kidneys**](https://mmerevise.co.uk/gcse-biology-revision/maintaining-water-and-nitrogen-balance/).   **Fatty acids** and **glycerol** are converted back into **lipids** that are used to build [**cell membranes**](https://mmerevise.co.uk/gcse-biology-revision/cell-structure/).  If animals do not have sufficient **glucose** in their bloodstream for [**respiration**](https://mmerevise.co.uk/gcse-biology-revision/respiration/), the body will begin to break down its stores of **glycogen** to supply more glucose. If the body runs out of glycogen, it will start break down **fat stores** and then **proteins **as a last resort.  **Photosynthesis Revision** **Photosynthesis** **Photosynthesis** the process by which plants make their own food in the form of **glucose**. Glucose is then either **stored **within the plant, used for [**respiration**](https://mmerevise.co.uk/gcse-biology-revision/respiration/) or used to build **new molecules**. Many **factors **affect the [**rate of photosynthesis**](https://mmerevise.co.uk/gcse-biology-revision/rate-of-photosynthesis/) and being able to control these factors enables farmers and gardeners to efficiently produce lots of healthy plants. **What is Photosynthesis?**  **Photosynthesis** is the process by which **plants **(and some algae) use** light energy** to create their own food, in the form of **glucose**, from **carbon dioxide** and **water**. **Oxygen** is also made which can be released into the atmosphere or used for aerobic [**respiration**](https://mmerevise.co.uk/gcse-biology-revision/respiration/). Word equation: **Carbon dioxide   +   Water    ------Light------\>  Glucose   +   Oxygen** Chemical equation: **6CO~2 \  ~+   6H~2~O   ------Light------\>   C~6~H~12~O~6~   +   6O~2~** **Respiration and Exercise Revision** **Respiration and Exercise** When we **exercise** the body has to adapt to meet the increased demand for **oxygen**. If this need is not properly met, cells start **respiring anaerobically**. [**Anaerobic respiration**](https://mmerevise.co.uk/gcse-biology-revision/respiration/) causes **lactic acid** to build up and disrupt muscle function and creates an **oxygen debt**. Simple investigations can show the effects of exercise on the body. **Increased Demand for Energy** During exercise, **muscle** **cells** **contract **more often to create **movement**. Muscles require **energy** to contract so will need to **[respire](https://mmerevise.co.uk/gcse-biology-revision/respiration/) **more to meet the energy demand. The body must supply the** respiring cells** with more **oxygen **for the increased **respiration **and also remove the **carbon dioxide** that is produced. It does this in three ways: - Increasing **heart rate** -- increases rate of **[blood flow](https://mmerevise.co.uk/gcse-biology-revision/circulatory-system/) **around the body. - Increasing **breathing rate**-- increases the rate of **[gas exchange](https://mmerevise.co.uk/gcse-biology-revision/exchange-surfaces/) **in the [**lungs**](https://mmerevise.co.uk/gcse-biology-revision/the-lungs/). - Increasing **breath volume**-- increases the rate of **[gas exchange](https://mmerevise.co.uk/gcse-biology-revision/exchange-surfaces/) **in the [**lungs**](https://mmerevise.co.uk/gcse-biology-revision/the-lungs/). If the body cannot meet the increased demand for oxygen, the muscle cells must respire [**anaerobically**](https://mmerevise.co.uk/gcse-biology-revision/respiration/).  **Exercise and Anaerobic Respiration** [**Anaerobic respiration**](https://mmerevise.co.uk/gcse-biology-revision/respiration/) happens in the absence of **oxygen **and causes the** incomplete oxidation** of **glucose**, producing **lactic acid**. **Lactic acid** builds up in the muscles, causing them to **contract less efficiently** and become **fatigued**.  An **oxygen debt** is also created. This is the amount of **oxygen **the body needs after exercise to **oxidise **the** lactic acid **into **carbon dioxide** and **water** and remove it from the cells. To help repay the **oxygen debt** and remove any remaining **carbon dioxide**, the **heart rate **and **breathing rate** stay high for some time after exercise. **Note: ** Higher tier students should also know that some** lactic acid** is transported to the **liver **via the **blood**, where it is converted into **glucose** and then stored as **glycogen**.  **Investigating the Effects of Exercise** A graph with blue and white bars Description automatically generated with medium confidence Simple investigations can be carried out to determine the effects of exercise on the body such as comparing** breathing rate** or **heart rate** before and after **exercise**.  **Breathing rate** can be calculated by counting how many **breaths** a person takes in a **minute**. **Heart rate** can be calculated by measuring the **pulse **over a **minute**. The results can then be plotted on a simple **bar chart**.  Monitoring breathing rate and heart rate can help determine the **physical fitness** of an individual.