iGCSE Biology Section 2 lesson 3

iGCSE Biology Section 2 lesson 3

Structures and functions in living organisms
Content Section 2 Structures and functions in living organisms a) Levels of organisation b) Cell structure c) Biological molecules d) Movement of substances into and out of cells e) Nutrition f) Respiration g) Gas exchange h) Transport i) Excretion j) Coordination and response

Lesson 2 e) Nutrition Content Flowering plants
2.15 describe the process of photosynthesis and understand its importance in the conversion of light energy to chemical energy 2.16 write the word equation and the balanced chemical symbol equation for photosynthesis 2.17 understand how varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis 2.18 describe the structure of a leaf and explain how it is adapted for photosynthesis 2.19 understand that plants require mineral ions for growth and that magnesium ions are needed for chlorophyll and nitrate ions are needed for amino acids 2.20 describe experiments to investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll Lesson 2 e) Nutrition

Lesson 3 e) Nutrition Content Humans
2.21 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, the mineral ions calcium and iron, water and dietary fibre as components of the diet 2.22 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas 2.23 understand the processes of ingestion, digestion, absorption, assimilation and egestion 2.24 explain how and why food is moved through the gut by peristalsis 2.25 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases 2.26 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids Lesson 3 e) Nutrition

Types of nutrition AUTOTROPHS –organisms that can produce complex organic compounds from simple inorganic molecules. They are the PRODUCERS in a food chain. HETEROTROPHS – organisms that cannot produce their own food, but acquire complex organic molecules by consuming plants or other animals.

Biological molecules Our diet needs to contain sufficient and balanced quantities of carbohydrates, proteins and lipids.

Biological molecules carbohydrates Sugar Starch Cellulose
Different foods contain different kinds of sugar. Eg fruit contains fructose or glucose. Lactose is in milk. Table sugar is sucrose. Sugar gives us energy, so we call it an energy food. Starch Cellulose

Different foods contain different kinds of sugar. Eg fruit contains fructose or glucose. Lactose is in milk. Table sugar is sucrose. Sugar gives us energy, so we call it an energy food. Starch Starch is found particularly in bread, potatoes and cereals. Starch is a storage molecule, but it does provide us with energy. Cellulose

Different foods contain different kinds of sugar. Eg fruit contains fructose or glucose. Lactose is in milk. Table sugar is sucrose. Sugar gives us energy, so we call it an energy food. Starch Starch is found particularly in bread, potatoes and cereals. Starch is a storage molecule, but it does provide us with energy. Cellulose Cellulose is found in plant cell walls It is a structural molecule, and supports the plant cell.

Biological molecules Fats
Fats also contain C, H and O, but relatively less O. Fats occur in both plant and animal foods. Fats – solid at room temperatures. Oils - liquid at room temperatures.

Biological molecules Fats
Fats also contain C, H and O, but relatively less O. Fats occur in both plant and animal foods. Fats – solid at room temperatures. Oils - liquid at room temperatures. Fats also give us energy. They also provide insulation in humans and other mammals, and are energy stores.

Biological molecules Proteins
Proteins contain C, H and O, and also some nitrogen (N) and a little suplhur (S). Proteins are found in milk, eggs, meat and fish.

Biological molecules Proteins
Proteins contain C, H and O, and also some nitrogen (N) and a little suplhur (S). Proteins are found in milk, eggs, meat and fish. Proteins are needed for growth and body-building (muscles and skin), and they are also used to make enzymes.

Components of our diet Minerals: contain certain elements essential for the proper functioning of our bodies.

Components of our diet Calcium
Minerals: contain certain elements essential for the proper functioning of our bodies. Calcium Needed for hardening our bones and teeth. Occurs in foods such as milk, cheese and fish Deficiency results in rickets

Rickets Rickets is a softening of bones in children due to deficiency or impaired metabolism of vitamin D, magnesium, phosphorus or calcium, potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries.

Components of our diet Calcium Iron
Minerals: contain certain elements essential for the proper functioning of our bodies. Calcium Needed for hardening our bones and teeth. Occurs in foods such as milk, cheese and fish Deficiency results in rickets Iron Present in haemoglobin, the red pigment in blood used to carry oxygen Occurs in a number of foods, especially liver and kidneys Deficiency results in anaemia

Anaemia Anaemia is a decrease in the number of red blood cells in the blood, meaning that less oxygen can be carried by the blood to various organs and tissues,. The main symptoms are tiredness and lethargy.

Components of our diet Vitamins: a collection of organic substances needed in small quantities in the body. Their overall function is to help control the chemical reactions taking place in the body.

Components of our diet Vitamin A
Vitamins: a collection of organic substances needed in small quantities in the body. Their overall function is to help control the chemical reactions taking place in the body. Vitamin A Important for our eyes – helps protect their surfaces Found in fish liver oil, and carrots. Deficiency makes it difficult to see in dim light

Components of our diet Vitamin A Vitamin C
Vitamins: a collection of organic substances needed in small quantities in the body. Their overall function is to help control the chemical reactions taking place in the body. Vitamin A Important for our eyes – helps protect their surfaces Found in fish liver oil, and carrots. Deficiency makes it difficult to see in dim light Vitamin C Needed for strong gums Found in citrus fruits, green vegetables and blackcurrants Deficiency results in scurvy

Scurvy Scurvy can result in swollen gums, severe pain in joints, shortness of breath, and blurred vision.

Components of our diet Vitamin D
Vitamins: a collection of organic substances needed in small quantities in the body. Their overall function is to help control the chemical reactions taking place in the body. Vitamin D Necessary for bones to take up calcium salts Occurs in fish liver oil, and can be made in the skin provided sunlight is present. Deficiency results in rickets.

Components of our diet Fibre is necessary for a healthy balanced diet, but the body can’t absorb it. It helps our digestive system to process food and absorb nutrients. It helps your bowel to pass food by making stools soft and bulky. It helps prevent constipation. Fibre is found in foods such as brown rice, oats, wholegrain breads and cereals.

Components of our diet Water makes up more than two-thirds of the weight of the human body. It serves as a lubricant, helps regulate body temperature, prevents and relieves constipation. Without enough water we can become dehydrated.

From mouth to anus The human digestive system
(also known as the alimentary canal) From mouth to anus

The human digestive system

In digestion, large insoluble molecules are broken down into smaller soluble particles that can be absorbed into the bloodstream.

Mouth – mechanical chewing of the food. Salivary glands produce the enzyme amylase which begins breaking down polysaccharides into simpler sugars.

Oesophagus (also known as the gullet). Passes food down from the mouth to the stomach by a process known as peristalsis.

Peristalsis Rings of muscle around the oesophagus effectively ‘squeeze’ food towards the stomach, as you would with toothpaste in a tube.

Stomach – more mechanical digestion happens here. The stomach produces the enzyme protease, and also hydrochloric acid which kills bacteria, and this acid also provides the ideal conditions for protease.

Pancreas – produces many enzymes, including amylase, protease and lipase.

Small intestine – can be over six metres long. Digested food is absorbed here into the blood stream. The surface area of the small intestine is greatly increased by the presence of small, finger-like projections called villi (villus).

Large intestine – as the fibre and other undigested material passes along the large intestine, water is absorbed from it, so it becomes more solid. This solid matter then passes on to the rectum where it is stored as faeces.

The Liver – produces a substance known as bile, which is stored in the gall bladder before it is released into the small intestine. Bile has 2 functions:

The Liver – produces a substance known as bile, which is stored in the gall bladder before it is released into the small intestine. Bile has 2 functions: 1. It neutralises the acid from the stomach, producing more alkaline conditions.

The Liver – produces a substance known as bile, which is stored in the gall bladder before it is released into the small intestine. Bile has 2 functions: 2. It emulsifies fats – i.e. it breaks large drops of fat into small droplets to increase their surface area, so enzymes can work faster.

Pause time!

definitions

Definitions Ingestion Digestion Absorption Assimilation Egestion

Definitions Ingestion Digestion Absorption Assimilation Egestion
This is the process of taking in food substances through the mouth. Digestion Absorption Assimilation Egestion

This is the process of taking in food substances through the mouth. Digestion This is the mechanical and chemical breakdown of food into smaller, more soluble, components. Absorption Assimilation Egestion

This is the process of taking in food substances through the mouth. Digestion This is the mechanical and chemical breakdown of food into smaller, more soluble, components. Absorption This is the process of taking soluble food through the wall of the small intestine by diffusion into the blood stream. Assimilation Egestion

This is the process of taking in food substances through the mouth. Digestion This is the mechanical and chemical breakdown of food into smaller, more soluble, components. Absorption This is the process of taking soluble food through the wall of the small intestine by diffusion into the blood stream. Assimilation This is the process whereby absorbed food is altered chemically by the liver or chemical substances before being utilised by the cells of the body. Egestion

This is the process of taking in food substances through the mouth. Digestion This is the mechanical and chemical breakdown of food into smaller, more soluble, components. Absorption This is the process of taking soluble food through the wall of the small intestine by diffusion into the blood stream. Assimilation This is the process whereby absorbed food is altered chemically by the liver or chemical substances before being utilised by the cells of the body. Egestion This is the process where solid undigested food material is removed from the digestive system via the anus.

Biological molecules Simple sugars Starch / glycogen

Biological molecules Fatty acids, glycerol Fats, oils (lipids)

Biological molecules Amino acids Proteins

ENZYMES

ENZYMES Enzymes are biological catalysts – they speed up the rate of chemical reactions going on inside living things.

ENZYMES Enzymes are biological catalysts – they speed up the rate of chemical reactions going on inside living things. What are the features of enzymes?

ENZYMES Enzymes are biological catalysts – they speed up the rate of chemical reactions going on inside living things. What are the features of enzymes? Enzymes are globular proteins Every enzyme has an area called its active site Enzymes are specific Enzymes are affected by temperature and pH

ENZYMES Commonly named by adding the ending “-ase” to the substrate molecule being acted upon. Eg. sucrase works on sucrose, lipase works on lipose. A few enzymes are known by common names, eg. pepsin, trypsin

ENZYME ACTION Enzyme e.g. Sucrose Glucose + Fructose Sucrase
Substrate Product Enzyme e.g. Sucrose Glucose + Fructose Sucrase

Enzyme summary Salivary Gland - produces amylase which breaks down carbohydrates (such as starch) into simple sugars (eg. glucose)

Enzyme summary Stomach – produces protease which breaks down proteins into amino acids

Enzyme summary Pancreas – produces amylase (carbohydrates  sugars), protease (proteins  amino acids), lipase (fats  fatty acids + glycerol)

Enzyme summary Small intestine – produces amylase (carbohydrates  sugars), protease (proteins  amino acids), lipase (fats  fatty acids + glycerol)

Enzyme summary One more thing ………….
Maltase, thought to be produced by the walls of the small intestine, converts the disaccharide maltose (formed by the action of amylase on starch) into the simple sugar glucose.

Lesson 1 e) Nutrition Content Humans
2.21 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, the mineral ions calcium and iron, water and dietary fibre as components of the diet 2.22 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas 2.23 understand the processes of ingestion, digestion, absorption, assimilation and egestion 2.24 explain how and why food is moved through the gut by peristalsis 2.25 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases 2.26 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids Lesson 1 e) Nutrition

End of Section 2 Lesson 3 In this lesson we have covered:
Nutrition – human

iGCSE Biology Section 2 lesson 3

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