iGCSE Biology Section 2 lesson 1

The iGCSE Biology course Content The iGCSE Biology course Section 1: The nature and variety of living organisms Section 2: Structures and functions in living organisms Section 3: Reproduction and inheritance Section 4: Ecology and the environment Section 5: Use of biological resources

The iGCSE Biology course Content The iGCSE Biology course Section 1: The nature and variety of living organisms Section 2: Structures and functions in living organisms Section 3: Reproduction and inheritance Section 4: Ecology and the environment Section 5: Use of biological resources

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

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

a) Levels of organisation Content Lesson 1 a) Levels of organisation 2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.

Lesson 1 b) Cell structure Content 2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole 2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole 2.4 compare the structures of plant and animal cells.

Levels of Organisation

Levels of Organisation A. Cells

Levels of Organisation A. Cells

Levels of Organisation A. Cells Animal Cell membrane Cytoplasm Nucleus

Levels of Organisation A. Cells Animal Cell membrane Controls the passage of substances into and out of the cell. Cytoplasm Nucleus

Levels of Organisation A. Cells Animal Cell membrane Controls the passage of substances into and out of the cell. Cytoplasm Most chemical reactions occur here Nucleus

Levels of Organisation A. Cells Animal Cell membrane Controls the passage of substances into and out of the cell. Cytoplasm Most chemical reactions occur here Nucleus Controls the activities of the cell

Levels of Organisation A. Cells

Levels of Organisation A. Cells Plant Cell membrane Cytoplasm Nucleus

Levels of Organisation A. Cells Plant Cell membrane Cytoplasm Cellulose cell wall Strengthens the cell Nucleus

Levels of Organisation A. Cells Plant Cell membrane Cytoplasm Cellulose cell wall Strengthens the cell Permanent vacuole Contains cell sap Nucleus

Levels of Organisation A. Cells Plant Cell membrane Cytoplasm Cellulose cell wall Strengthens the cell Permanent vacuole Contains cell sap Chloroplast Absorbs light energy to make food through photosynthesis Nucleus

Comparing plant and animal cells Found in both plant and animal cells Found in plant cells only

Nucleus Cytoplasm Cell membrane Comparing plant and animal cells Found in both plant and animal cells Found in plant cells only Nucleus Cytoplasm Cell membrane

Nucleus Chloroplasts Cytoplasm Cell walls Cell membrane Comparing plant and animal cells Found in both plant and animal cells Found in plant cells only Nucleus Chloroplasts Cytoplasm Cell walls Cell membrane Permanent vacuoles

Specialised cells The egg cell , or ovum, is much larger than other cells so that it can carry food reserves for the developing embryo if fertilisation takes place.

Specialised cells Sperms cells have elongated tails that enable them to swim towards the egg (ovum) following ejaculation into the vagina.

Specialised cells Red blood cells do not have a nucleus, so they are able to pack in more haemoglobin molecules, and so carry even more oxygen.

Specialised cells Nerve cells are very elongated, and some may be over a metre in length. They carry electrical signals around the body.

Levels of Organisation B Tissues Tissues are groups of similar cells that are able to work together to carry out a specific function.

Levels of Organisation B Tissues eg. Muscle tissue Muscle tissue is very specialised, and has the ability to contract and also to conduct electrical impulses. There are three types of muscle: smooth, skeletal and cardiac.

Levels of Organisation C Organs Organs consist of groups of tissues working together to perform specific functions.

Levels of Organisation C Organs eg. the Heart The heart is a muscular organ found in all animals with a circulatory system. It is composed mostly of cardiac muscle and connective tissue, but also nervous tissue and blood.

Levels of Organisation D Organ system An organ system is a group of organs that work together to perform a certain task.

Levels of Organisation D Organ system eg. the Digestive system The digestive system consists of numerous organs, including the stomach and liver. It digests food and enables it to be absorbed into the blood stream.

Levels of Organisation A. Cells B. Tissues C. Organs D Organ system

c) Biological molecules 2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils) 2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol 2.7 describe the tests for glucose and starch 2.8 understand the role of enzymes as biological catalysts in metabolic reactions 2.9 understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site 2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH 2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature. Lesson 1 c) Biological molecules

Biological molecules To maintain a healthy body we need to eat the right amount of food and also the right types of food.

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

Biological molecules carbohydrates

Biological molecules carbohydrates Carbon C

Biological molecules carbohydrates Carbon C Hydrogen H

Biological molecules carbohydrates Carbon C Hydrogen H Oxygen O

Biological molecules carbohydrates Carbon C H Oxygen O Hydrogen H Oxygen O Eg. glucose, C6H12O6

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

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 Starch is found particularly in bread, potatoes and cereals. Starch is a storage molecule, but it does provide us with energy. Cellulose

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 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.

Biological molecules

Biological molecules Simple sugars Starch / glycogen

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

Biological molecules Amino acids Proteins

Food tests Glucose Benedict’s Test

Food tests Glucose Positive result: Benedict’s Test BLUE GREEN YELLOW ORANGE BRICK RED

Food tests Starch IodineTest

Food tests Starch IodineTest

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 ACTION Binding site

ENZYME ACTION

ENZYME ACTION

Enzymes and Temperature Time (minutes) Temperature (oC) 10 20 30 40 50 60 An experiment was carried out to investigate how temperature affects the rate at which an enzyme converts starch into sugar.

Enzymes and Temperature Time (minutes) Temperature (oC) 10 20 30 40 50 60 The results are shown in this table. A black circle means that there is still starch present. An orange dot means that there is no starch present.

Enzymes and Temperature Temperature (oC) 10 20 30 40 50 60 Time taken for starch to disappear (min.) Plot a graph with temperature along the x-axis (across) and time up the y-axis. What can you conclude about this investigation? How does temperature affect the action of enzymes. Find out what ‘denatured’ means. How does it apply to this investigation?

Lesson 1 d) Movement of substances into and out of cells 2.12 understand definitions of diffusion, osmosis and active transport 2.13 understand that movement of substances into and out of cells can be by diffusion, osmosis and active transport 2.14 understand the importance in plants of turgid cells as a means of support 2.15 understand the factors that affect the rate of movement of substances into and out of cells, to include the effects of surface area to volume ratio, temperature and concentration gradient 2.16 describe experiments to investigate diffusion and osmosis using living and non-living systems.

Movement of substances into and out of cells.

Movement of substances into and out of cells. Diffusion Osmosis Active transport

What is diffusion? Spray air freshener in the corner of a room

What is diffusion? Particles spread out in all directions

What is diffusion? Eventually the particles occupy the whole room

What is diffusion? Other examples of diffusion include: Smell of frying bacon from a kitchen Leaking of air from inside a balloon Sugar dissolving in a cup of tea

What is diffusion? Diffusion is the movement of particles from areas of high concentration to areas of low concentration until they are evenly spread. Diffusion depends upon the random movement of particles.

What is diffusion? Diffusion is the movement of particles from areas of high concentration to areas of low concentration until they are evenly spread. Diffusion depends upon the random movement of particles. Diffusion is slower in liquids than in gases because liquid particles are not as free to move as gas particles.

Diffusion in living organisms

Diffusion in living organisms Food oxygen

Diffusion in living organisms Food oxygen Out: Carbon dioxide Waste products

Diffusion in living organisms Eg. movement of oxygen in Amoeba

Diffusion in living organisms Eg. movement of oxygen in Amoeba High oxygen concentration Low oxygen concentration

Diffusion in living organisms Eg. movement of oxygen in Amoeba High oxygen concentration Low oxygen concentration Oxygen will move from a high concentration outside the cell to a lower concentration inside the cell. It is moving from high to low – i.e. down a concentration gradient.

Diffusion in living organisms Where diffusion occurs in living organisms, the surfaces across which gases are exchanged are often specialised by having LARGE SURFACE AREAS to increase the rate at which diffusion can occur. Eg. alveoli in the lungs provide a huge surface area for the exchange of oxygen and carbon dioxide.

What is osmosis?

What is osmosis? Osmosis is: a special type of diffusion it is the diffusion on water molecules from an area of high water concentration to an area of lower water concentration through a partially permeable membrane.

What is osmosis? A partially permeable what ……… ?

What is osmosis? A partially permeable what ……… ? Membrane!

What is osmosis? A partially permeable what ……… ? Membrane!

A partially permeable what ……… ? Membrane! What is osmosis? A partially permeable what ……… ? Membrane! Higher water concentration (fewer solute particles) Lower water concentration (more solute particles)

A partially permeable what ……… ? Membrane! What is osmosis? A partially permeable what ……… ? Membrane! Higher water concentration (fewer solute particles) Lower water concentration (more solute particles)

What is osmosis? Water particles will continue to move until there are equal numbers of water molecules on both sides of the membrane. Higher water concentration (fewer solute particles) Lower water concentration (more solute particles)

What is osmosis? More concentrated solution inside WATER WATER Less concentrated solution outside (more DILUTE) WATER WATER In root hair cells water moves from the surrounding soil into the cell by osmosis, along a concentration gradient

Dialysis tubing containing sugar solution Osmosis experiments Dialysis tubing containing sugar solution

Osmosis experiments Dialysis tubing containing sugar solution Placed in pure water Dialysis tubing containing sugar solution Water enters by osmosis, tubing swells up

Osmosis experiments Dialysis tubing containing sugar solution Placed in pure water Dialysis tubing containing sugar solution Placed in concentrated sugar solution Water enters by osmosis, tubing swells up Water leaves by osmosis, tubing shrivels up

Osmosis experiments Weighed potato chip

Water enters by osmosis, potato chip weighs more Osmosis experiments Placed in pure water Weighed potato chip Water enters by osmosis, potato chip weighs more

Osmosis experiments Weighed potato chip Placed in pure water Placed in concentrated sugar solution Water enters by osmosis, potato chip weighs more Water leaves by osmosis, potato chip weighs less

What is Active Transport?

What is Active Transport? Active transport is moving substances against a concentration gradient.

What is Active Transport? Active transport is moving substances against a concentration gradient. Imagine trying to push a trolley up a hill

What is Active Transport? Active transport is moving substances against a concentration gradient. Imagine trying to push a trolley up a hill It will require ENERGY!

What is Active Transport? Similarly, when substances are moved into a cell where there is already a higher concentration, then ENERGY from respiration will be required.

What is Active Transport? Similarly, when substances are moved into a cell where there is already a higher concentration, then ENERGY from respiration will be required. Root hair cell with a high concentration of nitrate ions. Soil with a lower concentration of nitrate ions.

What is Active Transport? Similarly, when substances are moved into a cell where there is already a higher concentration, then ENERGY from respiration will be required. Root hair cell with a high concentration of nitrate ions. Energy will be used to ‘pull’ nitrate ions from the surrounding soil into the cell Soil with a lower concentration of nitrate ions.

What is Active Transport? Active transport also occurs in the human body. For example, in the kidneys, sugar is recovered back into the blood by transporting it against a concentration gradient.

Factors affecting the movement of substances

Factors affecting the movement of substances Surface area to volume ratio Temperature Concentration gradient

Factors affecting the movement of substances Surface area to volume ratio The bigger the surface area compared to the volume, the faster the rate of movement of substances – eg. the lungs Temperature Concentration gradient

Factors affecting the movement of substances Surface area to volume ratio The bigger the surface area compared to the volume, the faster the rate of movement of substances – eg. the lungs Temperature As temperature increases, particles gain kinetic energy. They therefore move faster, and so diffusion, osmosis and active transport all occur at a faster rate. Concentration gradient

Factors affecting the movement of substances Surface area to volume ratio The bigger the surface area compared to the volume, the faster the rate of movement of substances – eg. the lungs Temperature As temperature increases, particles gain kinetic energy. They therefore move faster, and so diffusion, osmosis and active transport all occur at a faster rate. Concentration gradient The bigger the concentration difference, for example inside and outside of the cell, the faster substances will move – think about a steeper hill?

End of Section 2 Lesson 1 In this lesson we have covered: Levels of organisation Cell structure Biological molecules Movement of substances into and out of cells