Chapter 3 - Composition of Cells1 Composition of Cells Outcome 1 Chapter 3 Pages 51-74

Chapter 3 - Composition of Cells2 Materials to Build & Fuel Cells The main groups of compounds found in cells are: –Carbohydrates –Proteins –Lipids These carbon based compounds are called ‘organic compounds’ and all contain the elements carbon, hydrogen and oxygen.

Chapter 3 - Composition of Cells3 Water – Essential for Life Water is the most abundant compound in our bodies. About 50% of the average female is water, and 60% for males. A newborn consists of about 75% water. The average human contains about litres of water distributed across all body systems.

Chapter 3 - Composition of Cells4 Water – Essential for Life Activity Sheet – Biological Molecules p62

Chapter 3 - Composition of Cells5 Metabolism Goes Well With Water Metabolism includes all the chemical reactions that occur in an organism. It involves catabolism, the breakdown of compounds to release energy. It involves anabolism, the synthesis of new compounds from simpler ones. Water is the predominant solvent for which metabolism occurs.

Chapter 3 - Composition of Cells6 Water is the Major Component of Cells Water is by far the main component of living cells. Quick Check Questions: 1-3 p55

Chapter 3 - Composition of Cells7 Carbohydrates Carbohydrates provide most of the energy in the majority of human diets (16kJ per gram). Most carbohydrates in our diet come from plant material (fruit & veg). The basic unit of carbohydrates is the sugar, or saccharide molecule. Different number of sugar molecules combine to give a variety of carbohydrates called polysaccharides.

Chapter 3 - Composition of Cells8 Carbohydrates One sugar molecule is called a monosaccharide (glucose – C 6 H 12 O 6 ). Two combined sugar molecules are called a disaccharide (maltose). Many combined sugar molecules are called a polysaccharide (starch, glycogen, cellulose). When carbohydrates are broken down into glucose – the glucose is used in respiration and the energy released is utilised by ATP molecules.

Chapter 3 - Composition of Cells9 Carbohydrates

Chapter 3 - Composition of Cells10 Proteins Proteins are large molecules built of subunits called ‘amino-acids’. Amino acids are made up in combination of carbon, hydrogen, oxygen and nitrogen. The structure and function of a protein depends on the number and type of amino acids it contains.

Chapter 3 - Composition of Cells11 Proteins Proteins provide our body with matter by building and regulating. Structural proteins (ie Keratin – hair, Collagen – skin) make up structural components of tissue and organs. Catalytic proteins (Enzymes) speed up chemical reactions in our body. High quantities of proteins are found in foods such as red meat, fish and legumes.

Chapter 3 - Composition of Cells12 Proteins Activity Sheet – Amino Acids p66 Activity Sheet – Proteins p67

Chapter 3 - Composition of Cells13 Lipids Lipid is the general term for fats, oils and waxes. A fat molecule is made of two kinds of molecules, fatty acids and glycerol. Triglycerides are a common form of fats. These have a single glycerol head to which three fatty acid molecules are attached.

Chapter 3 - Composition of Cells14 Lipids Phospholipids, another kind of fat have two fatty acids attached to a single glycerol head. On a weight basis, fat stores twice as much energy as the same weight of polysaccharide. Activity Sheet – Lipids p64 Quick Check Questions 4-7 p60

Chapter 3 - Composition of Cells15 Minerals Minerals are the inorganic ions required by both animal and plant cells. In humans, minerals make up 6% of the body. Common minerals that we need include calcium, potassium, iron and zinc. Minerals play a role in metabolic processes in cells and are also incorporated into cell structure.

Chapter 3 - Composition of Cells16 Minerals

Chapter 3 - Composition of Cells17 Minerals

Chapter 3 - Composition of Cells18 Vitamins Vitamins are a group of organic compounds that occur in minute quantities in food. Animals are unable to produce vitamins so therefore they must be ingested from food. Vitamins are essential for many of the chemical reactions that occur in cells.

Chapter 3 - Composition of Cells19 Vitamins

Chapter 3 - Composition of Cells20 Vitamins

Chapter 3 - Composition of Cells21 Enzymes Most vitamins are co-enzymes which aid the action of enzymes and most chemical reactions in the body. Enzymes are protein molecules that increase the rate of reactions that occur inside the organism. Enzymes control activities such as metabolism, temperature and pH regulation as well as respiration and photosynthesis.

Chapter 3 - Composition of Cells22 Enzymes The compound acted on by an enzyme is called a substrate. The compounds obtained as a result of the enzyme action are called the products. Enzymes are highly specific in their action. Each enzyme acts on a particular substrate. The shape of an enzyme at a region known as its active site fits with part of the substrate molecule.

Chapter 3 - Composition of Cells23 Enzyme Action This complementary fitting of shapes is known as the ‘lock and key’ theory of enzyme action. Quick Check Questions 8-10 p65

Chapter 3 - Composition of Cells24 Producers at Work Using the energy of sunlight, plants can make organic molecules such as sugar, through a process known as photosynthesis. Organisms with this ability are called autotrophic. Photosynthesis is the process in which light energy is transformed into chemical energy stored in sugars.

Chapter 3 - Composition of Cells25 Producers at Work

Chapter 3 - Composition of Cells26 Chloroplasts – Where the action is! Photosynthesis generally occurs in green leaves. Special features of leaves include: Flat shape increases surface area to trap more sunlight. The presence of stomata on one or both sides to allow access to carbon dioxide. The presence of internal air spaces enables rapid diffusion of carbon dioxide. The network of xylem vessels allow transport of water to photosynthetic cells. Each cell contains many chloroplasts to maximise photosynthesis.

Chapter 3 - Composition of Cells27 Chloroplasts – Where the action is!

Chapter 3 - Composition of Cells28 Chloroplasts – Where the action is! In the cytoplasm of leaf cells is where chloroplasts are found. Each chloroplast has an outer membrane and folded inner membranes joined to form stacks of flattened disks, known as ‘grana’. The enzymes needed for the reactions for photosynthesis are located inside the chloroplasts, with some located in the grana membranes and some in solution in the stroma.

Chapter 3 - Composition of Cells29 Light Trapping Pigments Various pigments can trap light energy. The major light trapping pigments are green chlorophylls located on the grana membranes. Other kind of light trapping pigments, known as accessory pigments are also found in the chloroplasts.

Chapter 3 - Composition of Cells30 Light Trapping Pigments The various light trapping pigments that exist include:

Chapter 3 - Composition of Cells31 Light Trapping Pigments

Chapter 3 - Composition of Cells32 Accessing Energy – Cellular Respiration All living organisms require energy to maintain life. The energy required to maintain cellular functions is in the form of Adenosine Triphosphate (ATP). ATP is formed when energy is released during cellular respiration of glucose.

Chapter 3 - Composition of Cells33 Accessing Energy – Cellular Respiration

Chapter 3 - Composition of Cells34 Accessing Energy – Cellular Respiration The transfer of chemical energy from glucose to ATP occurs through a coupling of chemical reactions.

Chapter 3 - Composition of Cells35 Accessing Energy – Cellular Respiration When cellular respiration involves the use of oxygen, the term aerobic respiration is used and the overall equation is: Aerobic respiration yields 36 ATP molecules per molecule of glucose. In some tissues, respiration occurs without the involvement of oxygen and is referred to as anaerobic respiration. Anaerobic respiration is far less efficient than aerobic respiration. Anaerobic respiration yields 2 ATP molecules per molecule of glucose.

Chapter 3 - Composition of Cells36 Chapter Review Bio-Challenge Questions 1-4 p72 Chapter Review –Crossword on CD-Rom –Understand ‘Key Words’ –Questions 1-9