Mojza-Biology-Notes.pdf

MOJZA O Levels & IGCSE BIOLOGY NOTES 5090 & 0610 BY TEAM MOJZA  MOJZA` CONTENTS Pg 02 Unit 1 Cells Pg 58 Unit 13 Excretion Pg 06 Unit 2 Classification Pg 60 Unit 14 Coordination Pg 14 Unit 3 Movement In and Co...

MOJZA O Levels & IGCSE BIOLOGY NOTES 5090 & 0610 BY TEAM MOJZA  MOJZA` CONTENTS Pg 02 Unit 1 Cells Pg 58 Unit 13 Excretion Pg 06 Unit 2 Classification Pg 60 Unit 14 Coordination Pg 14 Unit 3 Movement In and Control in Humans and Out of Cells Pg 68 Unit 15 Coordination Pg 16 Unit 4 Biological and Control in Plants Molecules Pg 70 Unit 16 Development of Pg 17 Unit 5 Enzyme organisms and continuity of Pg 19 Unit 6 Plant Nutrition life Pg 22 Unit 7 Transport in Pg 85 Unit 17 Inheritance Flowering Plants Pg 89 Unit 18 Biotechnology Pg 28 Unit 8 Human Nutrition and Genetic Modification Pg 38 Unit 9 Human Gas Pg 92 Unit 19 Relationships of Exchange organisms with one another Pg 40 Unit 10 Respiration and with the environment Pg 42 Unit 11 Transport in (Ecology) Humans Pg 97 Practical Work Pg 49 Unit 12 Disease and Immunity 1  MOJZA` Unit 1: Cells Cell Structure and Function - Staining ➔ Cells are soaked in chemicals/dyes before being examined under a microscope, so that certain organelles take up the dye, making the cells more visible. ➔ Common stains are: ↳ Methylene blue for animal cells ↳ Iodine solution for plant cells - Functions of different structures cells: Structure Description Location Function Cell Surface Partially permeable layer Surrounding the ➔ Prevents cell’s contents from Membrane enclosing the cell made cytoplasm escaping of lipids and proteins ➔ Controls the movement of substances into and and out of the Not found in Virus cell cell Cytoplasm Jelly-like substance Surrounded by the cell ➔ Most chemical reactions take place containing organelles membrane and fills the here and food granules entire cell ➔ Contains the organelles, which are embedded in it ➔ Contain enzymes, salts and food reserves such as lipids Nucleus Circular or oval, double Present in the cytoplasm ➔ Nucleus controls: membrane-bounded ↳ Cell activities structure ↳ Cell division (contains hereditary material) ↳ Cell development Mitochondria Small spherical or Present in cytoplasm ➔ Site of cellular/aerobic respiration rod-shaped structure ➔ Release energy to sustain metabolic reactions and cellular activities Ribosomes Small circular structures; Present in the ➔ Proteins’ synthesis membraneless cytoplasm, either attached to membranes or lying free 2  MOJZA` Cell wall Fully permeable, rigid, First outer layer, ➔ Lets water, salts and other non-living layer made of enclosing the cell substances move through it freely cellulose in plants. membrane ➔ Gives cells rigidity and structure, while protecting them from bursting Extra: Made up of peptidoglycan in bacteria, chitin in fungi and cellulose in plant cells Vacuole Large, permanent Inside the cytoplasm ➔ Provides turgidity to plant cells membrane-bound ➔ Contains water, salts and sugar structure in plant cells, ➔ Used as a disposal site for while temporary in by-products animal cells Chloroplast Round, oval or Inside the cytoplasm ➔ Site of photosynthesis disk-shaped structure, ➔ Traps light energy for containing pigment photosynthesis called chlorophyll Circular DNA Single, coiled, circular Inside the cytoplasm ➔ Controls: chromosome ↳ Cell division ↳ Cell growth ↳ Cell activities Plasmids Circular pieces of DNA Inside the cytoplasm ➔ Contain extra genes than those in the circular DNA to aid in the processes of reproduction and survival KEY: Only plant cells Only animal cells Only bacterial cells Both plant and animal cells Both plant and bacterial cells All three cells - Specialised Cells ➔ Specialised cells have specific functions ➔ Their structures are specialised and specific, to help them in their function. ➔ Examples: ↳ ciliated cells – movement of mucus in the trachea and bronchi away from lungs ↳ root hair cells – absorption of ions and water ↳ palisade mesophyll cells – photosynthesis ↳ neurones – conduction of electrical impulses ↳ red blood cells – transport of oxygen ↳ sperm and egg cells (gametes) – fertilisation and hence reproduction 3  MOJZA` - Examples of specialised cells according to 2023-2025 syllabus: - Red Blood Cell Function: ➔ Contains a red pigment - haemoglobin - which enables the cell to transport oxygen from the lungs to all parts of the body. Adaptive Features: ➔ Bi concave → Increases surface area to volume ratio; as a result, O2 can diffuse in and out of the cell quicker ➔ Flexible and elastic → So they can squeeze into the capillaries - Root Hair Cells Function: ➔ Absorb water through osmosis and uptake mineral salts from the soil through active transport Adaptive Features: ➔ Long and narrow root hair/cytoplasmic extension → Increases surface area to volume ratio of the cell for more efficient absorption ➔ Mitochondria: Many mitochondria are present to provide energy for active transport ➔ Concentrated sap vacuole: Creates a water potential gradient for entry of water into the cell Definitions: - Cells: ➔ All organisms are made of cells. ➔ Cells are fundamental units of life which can survive independently and carry out necessary functions for survival. ➔ All cells originate from pre-existing cells. ➔ Examples: root hair cell, palisade mesophyll cell, ciliated cell, red blood cell, sperm cell, egg cell, etc. - Tissue: ➔ A group of cells with similar structures working together to perform a shared, specialised function. ➔ Examples: blood - group of blood cells; mesophyll layer - group of spongy and palisade mesophyll cells, etc. 4  MOJZA` - Organ: ➔ Structure made up of a group of tissues working together to perform a specific function. ➔ Examples: Heart - group of muscle tissues; Leaf - group of mesophyll tissues, vascular tissues, etc. - Organ systems: ➔ Group of organs with related functions working together to perform a bodily function. ➔ Examples: Cardiovascular system - group of organs such as blood vessels and heart, etc; Shoot system - group of organs such as stem, leaves, etc. - Organism: ➔ An individual animal or plant, formed by all the organs and systems working together to produce an independent living thing. Size of Specimens: ➔ Magnification = image size/actual size ➔ Conversion of units: ↳ 1000000 micrometres = 1 metre ↳ 10000 micrometres = 1 centimetre ↳ 1000 micrometres = 1 millimetre 5  MOJZA` Unit 2: Classification ➔ Classification means arranging the organisms in groups and sub-groups based on their similarities and differences ➔ Species are the group of closely related organisms that can reproduce fertile offspring freely in nature ➔ Dichotomous key is a commonly used tool for classification, which helps in identifying unknown organisms (Mostly MCQs will be related to this) Used to: ↳ Identify unfamiliar organisms ↳ Simplify the process of identification ↳ Separating species by contrasting features System of Classification ➔ All the living organisms are classified into domains; the two domains are Domain Prokaryotes and Domain Eukaryotes ➔ Living organisms are then divided according to the Kingdom ➔ Examples: Kingdom Animalia, Kingdom Plantae; we have 5 major kingdoms which are included in our syllabus. ➔ Viruses are at the boundary of living and nonliving organisms and hence, aren't a part of the 5 kingdoms ➔ Within each kingdom, the organisms are further divided into several phyla (Singular: Phylum); this is equivalent to division, which we use in the case of plants ➔ Each phylum consists of organisms which differentiate them with other kingdoms. The organisms of one phyla share similar characteristics, but they might not be obvious, forming one of the main categories in biological classification that ranks above the class and below the kingdom ➔ The phylum is made up of classes; organisms of a class further share more common attributes ➔ Class ranks below the phylum and above the order ➔ Classes are divided into orders; the orders further divide organisms into more specialised groups which have more qualities in common. Order ranks above family and below class ➔ Within each order are the families. In the family, the name suggests the species' resemblance is fairly close ➔ For animals, the family usually ends with idae; meanwhile, in plants it ends with aceae. Family ranks below order and above genus ➔ Each family consists of a varying number of genera (Singular: Genus). Each genera divides species into having similar structural characteristics, but the species are not as closely related ➔ Lastly, genera divides into species; each genus has several species ➔ Binomial nomenclature means ‘two-term naming system’; it comprises of genus and species and is often written in italics E.g. Canis (Genus) familiaris (specie) 6  MOJZA` Modes of nutrition ➔ There are 2 modes of nutrition, and they are: ↳ Autotrophic nutrition: In which organisms make their own food; such organisms are called autotrophs, which includes Plants and some bacteria ↳ Heterotrophic nutrition: In which the organisms feed on readily available food materials; such organisms are called heterotrophs - Animals and their kingdoms ➔ There are further two types in the animal kingdom: ↳ Vertebrates: animals with a backbone ↳ Invertebrates: animals without a backbone Invertebrate Groups - Arthropods ➔ Arthropods are invertebrate animals that have an exoskeleton, a segmented body and jointed appendages as their main features ➔ The "Phylum" arthropoda is subdivided into 4 classes: ↳ Insects ↳ Arachnids ↳ Myriapods ↳ Crustaceans ➔ Characteristics of all arthropods: ↳ Exoskeletons made of chitin ↳ Highly developed sense organs ↳ Jointed limbs ↳ Segmented bodies ↳ Ventral nervous system ↳ Bilateral symmetry, which is the same externally and internally Key terms: ➔ Appendages : refer to any of the homologous body parts that may extend from a body segment, including antennae,wings etc. ➔ Ventral : Underside; along the stomach 7  MOJZA` Insecta ➔ 3 pairs of legs (Total 6) ➔ Have compound eyes which ➔ Examples: ➔ 3 segments of the body (Head, produce several images on Ants, Wasps, Butterflies thorax and abdomen) the retinula cells ➔ 1 pair of antennae ➔ This forms a complex image, ➔ Usually have 2 pairs of wings due to which the insects are able to detect even the slightest of movements Arachnida ➔ 4 pairs of legs and have 2 ➔ Mostly carnivorous and feed ➔ Examples: pairs of appendages near the on insects and other small Spiders, Scorpions mouth: Chelicerae and animals Pedipalps(Total 10 ➔ Some arachnids are appendages). venomous, who inject venom ➔ 2 segments of the body, which in their prey to paralyse it are the cephalothorax (head ➔ Arachnids usually lay eggs, and thorax fused together) and which hatch into immature abdomen arachnids that are similar to ➔ No antennae or wings adults. Scorpions, however, ➔ Several pairs of simple eyes give birth to live young ➔ Chelicerae are tipped with fangs for feeding ,while pedipalps are sensing or mating. Myriapoda ➔ Many joined limbs ➔ Breath through series of ➔ Examples: ➔ They have a head and the small openings known as Centipedes, Millipedes body is elongated with spiracles numerous segments, ➔ Most abundant and diverse in tropical and temperate therefore, it does not divide forests into a thorax or abdomen ➔ There is at least 1 pair of legs on each segment ➔ Simple eyes ➔ They have a pair of antennae Crustaceans ➔ 2 pairs of antennae ➔ Exclusively aquatic ➔ Examples: ➔ The head is fused with the ➔ Gills for breathing Crabs, Lobsters, thorax region to form a ➔ Front limbs are modified into Shrimps cephalothorax, and an chelipeds, which help in abdomen is also present holding and biting, as well as Therefore, it has two segments catching the prey of the body ➔ Hard covering of the ➔ Compound eyes exoskeleton ➔ 5 or more pairs of limbs 8  MOJZA` Phylum Cordata/Vertebrates ➔ The "Phylum" Cordata is sub-divided into 5 classes: ↳ Fishes ↳ Amphibians ↳ Reptiles ↳ Birds ↳ Mammals ➔ Common features of Phylum Cordata animals: ↳ All the animals except tunicates are vertebrates ↳ They have separate openings for the mouth and the anus ↳ Vertebrates do not have an exoskeleton, but they have an internal skeleton ↳ Animals are heterotrophs (Feed on other organisms for nutrition Features Fishes Amphibians Reptiles Mammals Birds Skin ➔Scally, lose ➔ Thin, moist ➔ Dry, hard and ➔ Hair/fur on their ➔ Scales on legs, wet scales and slimy scaly body and body covered with feathers Reproduction ➔ External ➔ External ➔ Eggs are ➔ Sexual ➔ Internal Fertilisation fertilisation takes internally Reproduction fertilisation, when takes places place, when fertilised, when between male and birds mate when male male amphibians the reptiles mate. female shed sperm on shed sperm on Females can lay ➔ Sexual the eggs laid eggs the eggs, or keep reproduction by females it until the time for ➔ Sexual hatching ➔ Sexual reproduction reproduction ➔ Sexual as two parents reproduction involves Eggs ➔ Soft ➔ Do not have a ➔Thick, leathery ➔ Sperm and ➔ Hard, jelly-like shell soft skin, not a or rubbery shells, Ovum fertilised calcareous shells in water hard shell which are together to make waterproof embryo ➔ Laid on land, in ➔Laid on land the nests, where ➔ Embryo turns mother will into foetus and incubate them then a baby (Pregnancy) Sensitivity ➔ Lateral lines ➔ Sensory ➔ Eyes and ears ➔ Sense organs ➔ Eyes and ears along their organs such as to sense such as eyes, present body to detect eyes and ears ears and nose are and respond to are present ➔ Do not have a present ➔ Pinna is absent vibrations pinna ➔ Do not have a ➔External flap of 9  MOJZA` pinna ear known as pinna is also present Have ears with 3 bones: Malleus, incus and stapes Locomotion / ➔Fins ➔Some ➔4 limbs, which ➔4 limbs are ➔2 Wings and 2 Mobility ➔Stream-line amphibians such each having 5 present Feet body as frogs and toes toads have 4 ➔Helps to limbs ➔Snakes don’t swim have any limbs underwater, ➔Their hind feet while have webbed maintaining toes, which balance provides a large surface area for efficient swimming Breathing ➔Use gills ➔They can live ➔Lungs ➔Lungs ➔Lungs on land and water both, hence may have lungs and gills both; however, diaphragm is absent ➔Amphibians perform gas exchange through their skin, which is thin, most and has good supply of blood Blood Temp. Cold-Blooded Cold-Blooded Cold-Blooded Warm-Blooded Warm-Blooded Food ➔ Diet consist ➔ Adults ➔ Mostly ➔ Carnivores, ➔ Omnivores of eggs, algae, amphibians are carnivores Herbivores or plants, carnivores which Omnivores ➔ Have beak to crustaceans, feed on insects ➔ Feed on feed on variety of worms, insects, ➔ Have 4 types of things mollusks, ➔ Young ones, amphibians and teeth: incisors, insects, insect such as, can feed on other canines, larvae, tadpoles, are reptiles premolars and amphibians, herbivores and molars to chew and plankton feed on algae the food Other ➔ Transparent ➔ Nictitating ➔ Have nictitating ➔ Have special ➔ Have 10  MOJZA` features eyelids to membrane to membrane, to mammary glands lightweight bones, prevent water protect the eyes protect the eyes to breastfeed their which help in entering and young ones flying allowing focus ➔Wings also help in flying Examples Shark, Tuna, Frogs, Toads, Snakes, lizards Humans, cats and Chicken, Rahu, Trout Newts, and crocodiles bears hummingbird Salamanders Plants ➔ Kingdom Plantae plants are the multicellular organisms which belong to the Domain Eukaryote; therefore, they have a nucleus and membrane bound organelles ↳ Plants are the organisms that use chlorophyll to carry out photosynthesis ↳ There are two main divisions of plants: ferns and flowering plants ↳ Flowering plants have further two types: monocots and dicots - Ferns: ➔ Ferns, also known as filicinophytes are the plants that do not have flowers; therefore, they do not reproduce by pollination. Ferns do not produce: ↳ Flowers ↳ Fruits ↳ Seeds ↳ Ovules (female gamete) ↳ Pollen (male gamete) Cambium tissue is also absent in ferns ➔ Flowering plants reproduce sexually by pollination, (which we will study in a later Unit) while ferns reproduce in a way similar to fungi ➔ This asexual way of reproduction is known as spore formation. The leaves of ferns are known as fronds. At the underside of fronds, sporangia can be found ➔ When sporangia are mature, they burst and the spores are released; they are carried by the wind and rain to far away areas. The spores find moist soil, germinate and then grow. - Flowering plants: ➔ Also known as angiospermophytes can be classified into: ↳ Dicotyledons ↳ Monocotyledons ➔ In flowering plants, roots, stems, and leaves are present ➔ Cambium tissue is also present 11  MOJZA` - Reproduction in flowering plants/angiospermophytes: ➔ Flowering plants reproduce by pollination ➔ This process of sexual reproduction involves two gametes: pollen and ovule ➔ The pollen is released from the anthers of flowers, and is carried by the wind or insects to the stigma of the flower ➔ The pollen grains secrete special hydrolysis enzymes on the stigma and digest its wall to make its way to the ovary ➔ The male nucleus from the pollen then travels through this pollen tube and enters the ovary through the microphile. The male nucleus will fuse with the ovule (female nucleus), and fertilisation will occur ➔ After fertilisation, the ovule develops into a seed and the ovary develops into a fruit The dispersal of seeds by wind/water/animals will allow the seeds to find a place for germination and grow into a plant Dicotyledons and Monocotyledons Dicots Monocots Two cotyledons present in their seeds One cotyledon present in their seeds Broad leaves, with network a of veins Elongated leaves, with parallel veins Petals in multiples of 4 or 5 Petals in multiples of 3 Tap roots Fibrous roots Ringed vascular bundle Scattered vascular bundle Viruses ➔ They are at the boundary of living and non-living things ➔ Viruses have the following characteristics: ↳ Live as parasites in the hosts’ body ↳ Strictly parasitic ↳ Take food and shelter in the hosts’ body, and give diseases in return ↳ Have no organelles, cytoplasm, etc. ↳ Acellular ↳ Reproduce inside the hosts’ body ↳ Cannot survive outside (die outside) ↳ Crystallise outside hosts ↳ Different shapes ➔ Viruses are made up of: ↳ A nucleic acid (Either RNA or DNA) 12  MOJZA` ↳ Protein coat, known as capsid ↳ No protoplasm and, therefore, are non-cellular ➔ Viruses are made up of a nucleic acid, which can be RNA or DNA (genetic material), which is surrounded by a protein coat known as a capsid ➔ In cellular cells, DNA is always double strand, and RNA is single strand. Since viruses are not cellular structures, they can have single strand DNA and double strand RNA as well; therefore, viruses can have 4 types of nucleic acids 1. Single strand DNA 2. Double strand DNA 3. Single strand RNA 4. Double strand RNA ➔ Viruses cause various diseases such as: ↳ AIDS (Acquired Immunodeficiency Syndrome) ↳ Ebola ↳ Influenza ↳ SARS (Severe Acute Respiratory Syndrome) ↳ Smallpox ↳ Chicken Pox ↳ Herpes ➔ Antibiotics cannot be used to treat viral infections, and viruses can only be destroyed by antibodies produced by white blood cells. However, doctors might prescribe antibiotics when you have a viral infection as a precautionary/deterrent measure. ➔ This protects your body from acquiring a possible bacterial infection which it would normally be able to fight against, but not currently, as your resistance is very low during this time. 13  MOJZA` Unit 3: Movement In And Out Of The Cell Roles of Water: ➔ Digestion: water is required for the hydrolysis of food molecules, alongside being a major component of digestive juices ➔ Excretion: water is the solvent for the removal and dilution of toxic excretory substances ➔ Transport: water is the main solvent, acting as the transport medium by being an essential constituent of blood plasma Diffusion: ➔ The net movement of molecules or ions from a region of their higher concentration to a region of their lower concentration (i.e. down the concentration gradient), as a result of their random movement. ➔ Both solute and solvent move. ➔ The energy for diffusion comes from the kinetic energy of random movement of molecules or ions. - Factors affecting the rate of diffusion: Surface Area The greater the surface area between the areas of the different concentrations, the greater the rate of diffusion, as more particles can diffuse across the surface in the same time period when compared to a lesser surface area. Temperature The greater the temperature of the molecules, the greater the rate of diffusion, as the particles have more kinetic energy and hence a greater speed. Concentratio Concentration gradient is the difference in concentrations of a substance n Gradient between two areas. The steeper the concentration gradient between the areas of different concentrations, the greater the rate of diffusion Distance The greater the distance between the areas of different concentrations, the lesser the rate of diffusion, as the particles have to travel more distance in the same time period as compared to a lesser distance. 14  MOJZA` Osmosis: ➔ The net movement of water molecules from a region of higher water potential to a region of lower water potential (i.e. down the water potential gradient), through a partially permeable membrane ➔ Only solvent moves ➔ Water potential: the potential energy of water to move from one place to another ➔ A water potential gradient is required for the uptake and loss of water via osmosis ➔ Placing an animal cell in a high water potential solution will lead to the osmosis of water into it, causing the cell to increase in size and burst, as it does not have a rigid cell wall to withstand the pressure. ➔ Placing a plant cell in a high water potential solution will lead to the osmosis of water into it, causing the cell to become turgid; it won’t burst ,as the cell wall exerts an opposing pressure to further entry of water. ➔ Placing an animal cell in a low water potential solution will lead to the osmosis of water out of it, causing the cell to undergo crenation i.e. shrinkage and formation of ruffled and crescent-shaped edges. As water is lost from it and can lead to the dehydration and cell’s death ➔ Placing a plant in a low water potential solution will lead to the osmosis of water out of it, causing it to undergo plasmolysis ➔ Turgid: the state of a cell being swollen and hard due to high turgor pressure ➔ Turgor pressure: the force caused by water within a cell that presses the cell membrane outwards against the cell wall - this is what supports plant cells and keeps them erect and upright ➔ Plasmolysis: the process of shrinkage of the protoplasm of a plant cell away from the cell wall due to the loss of water in a cell ➔ Flaccid: the state of a cell lacking turgidity and being soft and floppy Active Transport: ➔ the movement of molecules or ions into or out of a cell through the cell membrane, from a region of their lower concentration to a region of their higher concentration (i.e. against the concentration gradient), using energy released during respiration. ➔ Active transport requires energy because molecules or ions move against the direction they would naturally move towards ➔ Importance of active transport in root hair cells: Active transport takes place in root hair cells where it enables ions to be taken up by the root hair cells even if the ions’ concentration in the soil falls below the ions concentration in the root hair cells, in which case the ions would have moved out of the root hair cells by diffusion. 15  MOJZA` Unit 4: Biological Molecules Molecules: Molecule Elements Monomers Examples Key Carbohydrates C, H, O Glucose Starch C = Carbon Cellulose H = Hydrogen Glycogen O = Oxygen N = Nitrogen Lipids (fats C, H, O Fatty acids + Glycerol Oils and Fats: P = Phosphorus and oils) Olive oil (S) = Sometimes Butter Sulfur Cod liver oil Proteins C, H, O, N, (S) Amino acids Enzymes Hormones Carrier Proteins Cell Membranes DNA C, H, O, N, P, (S) Nucleotides —---- Food Tests: Sample Test Method Positive Negative Result Result Starch Iodine Add a few drops of reagent Turns Remains orange- solution to sample, on a white tile. blue-black brown Reducing Benedict’s Add equal volumes of the Turns cloudy Remains blue sugar solution sample and reagent in a green, yellow, boiling tube. orange, or brick-red Heat it in a water bath to (Order of anywhere between increasing 60-100oC. positivity) Protein Biuret Add a few drops of the Turns lilac Remains blue solution reagent to the sample in a boiling tube. Lipids Ethanol Dissolve a few drops of the Milky-white Remains a clear emulsion sample in 5 cm3 of ethanol. emulsion solution formed Pour this solution into a boiling tube of water. 16  MOJZA` Unit 5: Enzymes Definitions - Catalyst: a substance that increases the rate of a chemical reaction and is not chemically changed by the reaction - Enzymes: proteins that function as biological catalysts and are involved in all chemical reactions - Substrate: the substance on which an enzyme acts - Active site: a groove on the surface of the enzyme, where the substrate binds and chemical reactions take place - Enzyme-substrate complex: a temporary molecule formed when a substrate binds with the enzyme - Product: the molecule formed at the end of the reaction that separates from the enzyme Enzyme action: ➔ Substrate binds with the enzyme at the active site to form an enzyme-substrate complex. ➔ Reactions take place at the active site to form the product, which separates from the enzyme, letting it catalyse another reaction. - Enzyme specificity: ➔ Enzymes are specific in nature, which catalyse only specific types of chemical reactions. ➔ Every enzyme represents a lock which has a specific substrate complementary to it, which is its key. ➔ The active site has a specific 3D structure, complementary to a specific substrate; only that specific substrate can bind with the active site to form an enzyme-substrate complex. ➔ So, the enzyme can only catalyse that reaction. This is known as “Lock and key hypothesis” 17  MOJZA` - Effect of temperature and pH changes on enzyme activity ➔ Rate of reaction can be found out by measuring the concentrations of substrates and products; the rate of decrease of substrate or rate of increase of products ➔ Enzymes, being proteins, are sensitive to temperature and pH changes - Temperature ➔ Increasing the temperature increases the rate of reaction, up to a certain point ➔ Increasing the temperature increases the kinetic energy of the molecules ➔ More collisions occur between the enzyme and the substrate ➔ The frequency of effective collisions increases ➔ The optimum temperature of an enzyme is the temperature at which the enzyme shows the maximum rate of activity ➔ Beyond the optimum temperature, the enzyme starts to get denatured ➔ Denaturation is the destruction of the 3-dimensional structure of an enzyme ➔ The active site is permanently destroyed; thus, no enzyme-substrate complex can be formed ➔ The enzyme can no longer catalyse a reaction, and enzyme activity drops - pH ➔ The optimum pH of an enzyme is the pH level at which the enzyme shows maximum activity ➔ Extreme pH changes decrease enzyme activity, exactly like temperature changes described above 18  MOJZA` Unit 6: Plant Nutrition: Photosynthesis: ➔ Photo means light; synthesis means to produce; therefore, photosynthesis is a process by which green plants make their own food, i.e. carbohydrates in the form of glucose from raw materials, which are carbon dioxide and water, by converting light energy into chemical energy. ➔ Photosynthesis is photoautotrophic nutrition. - Chlorophyll: ➔ Photosynthesis is a reaction which requires light energy. ➔ Chlorophyll absorbs light energy and ensures that photosynthesis takes place (Since photosynthesis is a photoautotrophic nutrition, light energy along raw materials is important for the reaction to take place) ➔ Chlorophyll is present in the chloroplasts of the photosynthesising cells ➔ Chlorophyll is a green pigment, responsible for the green colour of plants ➔ The light energy absorbed by chlorophyll is transferred to chemical energy (glucose) - Balanced Equation ➔ 6 moles of carbon dioxide react with 6 moles of water in the presence of light energy absorbed by chlorophyll. It converts the light energy into chemical energy in the form of glucose, and 6 moles of oxygen are the byproduct ➔ 6CO 2 + 6H2O → C6H12O6 + 6O2 - Use And Storage Of Glucose Produced From Photosynthesis ➔ Glucose is a monosaccharide and when many molecules of glucose combined together, they form long-chain polysaccharides ➔ Glucose is converted into starch which is stored in cells as an energy store; this means that when needed, starch molecules break down into glucose to provide chemical energy for cellular respiration ➔ Glucose is also converted into cellulose, which is used to make the cell wall of the plant cell ➔ Glucose is also used in the process of cellular respiration to release energy (ATP) ➔ Glucose is converted into sucrose for transport around the plant known as Translocation ➔ Glucose is also used to secrete nectar in insect-pollinated flowers to attract insects for pollination ➔ Glucose combines with other minerals absorbed from roots to form lipids and amino acids 19  MOJZA` - Variegated Leaf ➔ A variegated leaf is a leaf whose lamina has some green parts which contain chlorophyll, therefore, they can photosynthesise ➔ Some parts of a variegated leaf’s lamina do not contain the green pigment, due to which they do not photosynthesise ➔ As no photosynthesis occurs, they give negative results for the starch test (Iodine test), because no glucose is produced to be converted into starch ➔ Chlorophyll containing areas will turn blue-black while areas with no chlorophyll will be brown or changed. Limiting Factors ➔ Limiting factor is the factor that directly affects the rate of the reaction if its quantity is changed ➔ Photosynthesis is a reaction which results in a series of enzymes. We can say that photosynthesis is an enzyme-controlled reaction; therefore, enzymes need the optimum temperature to work at their full potential. (A higher temperature means more kinetic energy, and the frequency of effective collisions increases) ➔ If the temperature is altered, the rate of reaction may be affected ➔ We also know that carbon dioxide is necessary for photosynthesis. ➔ 6 moles of CO2 react with 6 moles of H2O to produce one mole of glucose (C6H12O6) ➔ If the concentration of CO2 is altered, the rate of reaction may be affected ➔ Light intensity is also important for photosynthesis ➔ If light intensity is increased or decreased, the rate of reaction may be affected Limiting factor Effect Varying temperature ➔Photosynthesis is an enzyme-controlled reaction, where enzymes such as rubisco are involved in a series of chemical reactions that enable photosynthesis to take place ➔ Enzymes are proteins in nature and their rate of reaction increases as the temperature increases, until the optimum temperature is reached, after which the enzyme denatures ➔ Optimum temperature is the temperature at which enzymatic activity is at its highest Varying light intensity ➔ Light energy is transferred into chemical energy in the form of glucose during the process of photosynthesis ➔ Increasing light intensity will increase the rate of reaction, until another factor like the concentration of CO2 or temperature becomes limiting ➔ Light is also important to start the process of photosynthesis, as it accounts for opening of stomata for gas exchange. 20  MOJZA` Varying carbon ➔ Carbon dioxide is reduced by hydrogen to form glucose during dioxide concentration photosynthesis ➔ Increasing the concentration of carbon dioxide will increase the rate of reaction, until another factor like the temperature or intensity of light becomes limiting. Mineral Nutrition Mineral Importance Deficiency - Reacts with glucose molecules - Stunted and weak growth Magnesium ions Mg⁺² to synthesise amino acids for - Reduced yield production of proteins - Also required for synthesis of chlorophyll - Chlorosis - Synthesis of chlorophyll, - Chlorosis: leaves become Nitrate ions NO3- needed for photosynthesis pale and yellow; yellowing between the veins of leaves 21  MOJZA` Unit 7: Transport In Flowering Plants ➔ The hypothesis that explains the mechanisms which control the opening and closing of the guard cells ➔ During the daytime, the energy from the sunlight is used by the guard cells to transfer the light energy into chemical energy via photosynthesis ➔ This chemical energy is then used to pump the sodium - potassium ions from the neighbouring epidermal cells inside the guard cells ➔ This reduces the water potential inside the guard cells ➔ The reduced water potential inside the guard cell causes them to become more turgid ➔ The increased turgidity of the guard cells causes them to stretch towards the outside, and hence causes the opening of the stomata ➔ During the night time, the accumulated potassium ions that were inside the guard cells now diffuse out of them ➔ This increases the water potential on the inside of the guard cell ➔ Water then leaves the guard cells through osmosis ➔ This causes the guard cells to become flaccid and thus, the opening of the stomata closes - Diagram of stomata in the day and night Note: To be added - The movement of carbon dioxide into via the stomata ➔ During the day, carbon dioxide is consumed inside leaves, leading to a lower concentration of carbon dioxide within them ➔ A concentration gradient is created, with a higher concentration of carbon dioxide outside the leaf ➔ Carbon dioxide moves into the leaf through the stomata via diffusion and dissolves in the moist surface of the mesophyll cells to facilitate efficient diffusion - The functions of xylem in the leaf ➔ The xylem is responsible for the transportation of water and dissolved mineral ions to the leaves from the roots ➔ Veins in a leaf form a network and contain xylem and phloem to create a vascular bundle, which extends to the mesophylls. The contents of the vascular bundle exit the vein when necessary, and then move from cell to cell towards mesophyll cells where photosynthesis occurs 22  MOJZA` - The structure of the transport system in flowering plants ➔ Plants have a series of vessels present that are responsible for the movement of water and other dissolved substances. These vessels are called transport / vascular tissues, which is composed of two types of tissues: ↳ Xylem ↳ Phloem Xylem ➔ It is responsible for the transport of the water and other dissolved minerals from the roots to the stem and the leaves ➔ It is also responsible for providing mechanical support for the plant. ➔ Xylem is mainly composed of xylem vessels ➔ The xylem vessels are long, hollow tubes that stretch from the roots till the leaves ➔ The xylem vessels are composed of many dead cells ➔ The inner walls of the xylem vessels are further strengthened by deposits of a waterproof substance called lignin - Adaptations of xylem vessels ➔ The lumen is empty, as there is no protoplasm present; furthermore, the cells are joined end-to-end with no cross walls, forming a continuous pathway for water. This helps in providing a smoother flow of water and dissolved ions with little resistance ➔ The presence of lignin helps thicken the walls of the xylem vessels and provides mechanical support to the vessel, allowing conduction of water without it collapsing Phloem ➔ The phloem is responsible for transporting manufactured substances such as sucrose and amino acids from the leaves to the other parts of the plants ➔ This transportation of prepared food is known as translocation, which is from source to the sink ➔ During summers, when abundant photosynthesis is taking place, excess carbohydrates and amino acids are translocated from leaves to storage organs such as roots. Here leaves become source of food and roots are sink where food is stored ➔ During winters, when photosynthesis rate is lower, stored food from roots is translocated to other parts of plants; hence roots become source now ➔ Translocation can occur in both directions, unlike xylem where water is conducted in one direction only. 23  MOJZA` - Adaptations of a phloem ➔ Phloem is composed of companion cells, too, that are responsible for providing energy to sieve tubes to load photosynthesis from the mesophyll cells by active transport. ➔ There are holes present in sieve plates which allow for rapid movement of the food substances into the sieve tube cells The arrangement of the Vascular system - In the stem ➔ In the dicotyledonous stem, the xylem and the phloem are grouped together to form a vascular bundle ➔ The vascular bundles are arranged in a ring around the central region called the pith ➔ The phloem always faces towards the outside, while the xylem faces towards the inside ➔ Present between the xylem and the phloem is tissue called cambium ➔ The region between the pith and the epidermis is called the cortex ➔ The outermost region of the stem is covered by the epidermis. This epidermis is composed of a waxy, waterproof region called the cuticle - In the roots ➔ In the dicotyledonous root, the xylem and the phloem are not bundled; instead, they are in an alternating arrangement The cortex of the root is also a storage tissue ➔ Present on the epidermis of the root are root hair cells, which together are the outermost layer of the cells. This layer is also called piliferous layer Entry of water into the plant ➔ Each root hair cell is a tubular extension of the epidermal cell and is elongated enough to come into close contact with the solution that is surrounding the soil ➔ The solution that is present in the soil in close contact with the root hair cell is a dilute solution of mineral salts ➔ There is a sap of high concentration present inside the root hair cell, and this causes water potential inside the root hair cell to become low ➔ The water then moves into the root hair cell from the soil through osmosis ➔ This causes the water potential inside the root hair cell to decrease and is then passed on to the cell next to it until the water reaches up the plant 24  MOJZA` - The absorption of ions and minerals by root hair cells ➔ The absorption of ions and minerals by the root hair cells can vary accordingly, depending on the condition of the concentration of the soil ➔ If the concentration of mineral ions is high in the sap of the root hair cell, active transport would take place to move the ions and minerals from the soil. The energy for this active transport comes from the cellular respiration taking place in the root hair cell ➔ If the concentration of mineral ions is higher in the soil than the root hair cell, then diffusion would take place - Adaptations of the root hair cells ➔ The root hair cell is thin and long, which increases the surface area to volume ratio of the cell, making it more efficient at water absorption: uptake of mineral ions ➔ The root hair cell has a sap that is surrounded by the cell surface membrane, which helps to prevent its contents from leaking. The cell sap serves an important role in maintaining the osmotic potential ➔ The root hair cell has many mitochondria present to provide energy for the active transport Root pressure ➔ The living cells that surround the xylem vessel actively pump ions into the vessels ➔ This reduces the water potential inside the vessels ➔ Water then moves into the vessels from the living cells that surround the vessels by osmosis ➔ This process is called root pressure ➔ However, it's worth noting that this process alone is not sufficient to move water up into leaves in case of tall trees Capillary action ➔ When in very narrow tubes, water tends to move up due to the interactions between water molecules ➔ This effect is called capillary action ➔ This is made possible in the case of xylem vessels because the vessels are considered as narrow tubes too - Cohesion ➔ The force of attraction between water molecules is called cohesion - Adhesion ➔ The force of attraction between water molecules and the inner surface of the xylem vessels is called adhesion 25  MOJZA` Transpiration ➔ The loss of water from the plant in the form of water vapour. ➔ Water evaporates from the surfaces of mesophyll cells into the air spaces, and then diffuses out of the leaves through stomata in the form of water vapours. - The role of transpiration in the plant ➔ Transpiration is a major factor that contributes to the movement of water ➔ When water is lost due to transpiration, it causes the generation of a suction force, leading to the water moving up the plant ➔ This suction force is called the transpirational pull ➔ The stream of water that can be seen moving up towards the plant due to this effect is called a transpiration stream - The importance of transpiration ➔ Helps move the water from the roots all the way to the leaves ➔ Helps reduce the latent heat as the water evaporates from the leaf, which in turn helps in cooling down the plant ➔ Provide water to cells to be used in photosynthesis, and for maintaining the turgidity of the cells - Factors affecting rate of transpiration ➔ Temperature, wind speed and light intensity have direct relation with transpiration, while humidity has inverse relation, Temperature ➔ As temperature increases, the rate of transpiration also increases ➔ Increase in temperature means increase in average kinetic energy of water vapour particles; higher kinetic energy means faster rate of evaporation and diffusion, which results in faster loss of water Humidity ➔ Humidity is a measure of water vapours present in air. ➔ More humidity means less concentration gradient; slower rate of diffusion of water vapours out of plant into air; hence increase in humidity decreases the rate of transpiration Wind Speed ➔ Humidity is a measure of water vapours present in air. ➔ More humidity means less concentration gradient; slower rate of diffusion of water vapours out of plant into air; hence increase in humidity decreases the rate of transpiration Light Intensity ➔ Increase in light intensity increases the rate of transpiration ➔ As mentioned above, light causes increase in potassium ions concentration in guard cells, which results in water entering them making them turgid ➔ As the guard cells become turgid, stomata opens and transpiration surface area increases 26  MOJZA` How wilting occurs: ➔ Wilting occurs when the rate of transpiration is higher than rate of water uptake, resulting in loss of turgor pressure of cells ➔ Turgidity of cells keep the plant firm and leaves erect ➔ When cells lose their turgor pressure, due to excessive water loss, they become flaccid or plasmolysed causing them to appear floppy. ➔ As a result of wilting, the guard cells also lose their turgor pressure and stomata closes; consequently, rate of transpiration will decrease 27  MOJZA` Unit 8: Nutrition in Human - What is nutrition? ➔ It is the intake of nutrients for metabolic activities, such as growth, repair and maintenance. Monosaccharides ➔ General formula of monosaccharides: C6H12O6 ➔ Some examples of the important monosaccharides are: ↳ Glucose (The form in which carbohydrates are transferred around in animals’ body) ↳ Galactose ↳ Fructose ➔ Sources where we can obtain these monosaccharides from: ↳ Glucose: Fruits, products of starch digestion ↳ Galactose: Through the hydrolysis of lactose ↳ Fructose: Through the hydrolysis of sucrose Disaccharides ➔ General formula of disaccharides: C12H22O11 ➔ Some examples of important disaccharides: ↳ Sucrose (the form in which carbohydrates are transferred in plants) ↳ Lactose ↳ Maltose - Condensation and Hydrolysis of Disaccharides: ➔ Condensation: When small molecules join to form a large molecule with the removal of water ↳ C6H12O6 + C6H12O6 → C12H22O11 + H2O ➔ Hydrolysis: When large molecules break up into smaller molecules with the addition of water ↳ C12H22O11 + H2O → C6H12O6 + C6H12O6 28  MOJZA` Disaccharides Condensation Hydrolysis Glucose + Fructose → Sucrose + Sucrose + Water → Glucose + Sucrose Water Fructose Glucose + Galactose → Lactose + Lactose + Water → Glucose + Lactose Water Galactose Glucose + Glucose → Maltose + Maltose + Water → Glucose + Maltose Water Glucose Polysaccharides ➔ They are of two types: ↳ Storage polysaccharides = Glycogen, Starch ↳ Structural polysaccharides = Cellulose Polymerisation ➔ When many small units (monomers) combine to form a very large unit (polymer) ➔ General formula: (C6H10O5)n Dietary Importance and Principal Sources Principal Sources Dietary Importance ➔ Grains: wheat bread, pasta, rice and ➔ Aerobic respiration for energy Carbohydrates cereal. ➔ Formation of cell wall from cellulose ➔ Starchy vegetables: Potato and corn ➔ Formation of nucleic acids ➔ Dairy products: milk and yoghurt ➔ Synthesis of mucus ➔ Synthesis of nectar in flowering plants ➔ White meat: chicken, turkey and fish ➔ Growth and repair Proteins ➔ Eggs ➔ Synthesis of muscles, bones, skin, ➔ Legumes: lentils, chickpeas, kidney hair and cell membranes beans, etc. ➔ Formation of antibodies, enzymes ➔ Dairy products and certain hormones ➔ Nuts and seeds: almond, peanuts, ➔ Formation of blood proteins such as pumpkin seeds, etc. fibrinogen ➔ Grains: quinoa, oats and rice 29  MOJZA` ➔ Red meat: beef and mutton ➔ Source of energy ➔ Vegetable oils: canola, olive and ➔ Storage compound stored in Lipids sunflower oil adipose tissue ➔ Fats: butter, margarine and lard ➔ Synthesis of cell membrane ➔ Nuts and seeds ➔ Solvent for fat-soluble vitamins ➔ Dairy products, especially cheese ➔ Insulation to prevent heat loss ➔ Egg yolk ➔ Vegetables and fruits ➔ Promotes digestive health: adds Fibre ➔ Seeds and nuts bulk to faeces, making it easier to (Roughage) pass through the alimentary canal ➔ Prevents constipation: softens the faeces by absorbing water in the intestines ➔ Drinking water ➔ Solvent for inorganic salts and Water ➔ Fruits and vegetables organic compounds ➔ Juices and milk ➔ Main constituent of protoplasm, mucus, saliva, blood plasma and digestive juices ➔ Sweating helps to cool down the body ➔ Site for many important chemical reactions ➔ Transportation agent for blood cells, proteins, hormones and excretory products ➔ Hydrolysis of large compounds ➔ Activation of enzymes ➔ Photosynthesis Vitamins and Minerals ➔ Vitamins are substances needed in small, fixed amounts to healthy development and functioning of the body. There are two types of vitamins: ↳ Fat-soluble vitamins, which can be stored in body ↳ Water-soluble vitamins, which cannot be stored in body ➔ Minerals are inorganic nutrients needed in small amounts for healthy body Principal Sources Dietary Importance Deficiency Symptoms ➔ Citrus fruits: ➔ Formation of ➔ Scurvy ➔ Swelling and Vitamin C oranges, lemon and collagen protein, bleeding gums lime which is a major ➔ Painful and swollen (Water ➔ Fruits: strawberry, structural unit for joints Soluble) papayas and tomatoes skin, bones and ➔ Slow healing of ➔ Raw green connective tissues wounds vegetables: spinach, ➔ Maintenance of ➔ Tooth loss kale and broccoli healthy epithelial ➔ Muscle pain tissue 30  MOJZA` ➔ Fish liver oil e.g. ➔ Essential for ➔ Rickets ➔ Poor bone and Vitamin D cod liver oil and absorption and (in children) teeth development seafood assimilation of ➔ Pliable bones (Fat Soluble) ➔ Egg yolk calcium and (softening and ➔ Dairy products phosphorus for weakening of bones; ➔ Exposure to healthy bones and can easily be bent) sunlight teeth ➔ Pain in pelvis, spine and muscles ➔ Deformities, such as bowed legs or knock knee ➔ Dairy products ➔ Building and ➔ Rickets ➔ As mentioned Calcium ➔ Eggs maintenance of above ➔ Green vegetables strong healthy teeth and bones ➔ Blood clotting ➔ Transmission of nerve impulses ➔ Animal liver ➔ Synthesis of ➔ Anaemia ➔ Fatigue, weakness Iron ➔ Red meat haemoglobin and shortness of ➔ Egg yolk ➔ Synthesis and breath ➔ Green vegetables proper functioning of ➔ Dizziness and ➔ Kidney beans certain enzymes such headache as catalase ➔ Cold hands and feets ➔ Low haemoglobin levels Digestive System ➔ The digestive system consists of two parts: ↳ Alimentary canal or the gut, which is the passage along which the food moves through the digestive tract ↳ Accessory digestive structures, which are the glands associated with digestion. Accessory organs of digestion are organs that secrete substances needed for the digestion of food, but through which food does not actually pass as ‘digested’. The accessory digestive structures include salivary gland, liver, gallbladder and pancreas. ➔ Gland: A gland is a cell, tissue or an organ which secretes chemicals e.g. salivary gland, pancreas, pituitary gland, etc. - Key Terminologies: ➔ Ingestion is taking in food/drink into the body through the mouth ➔ Mechanical/Physical digestion is the breakdown of food into smaller pieces without any chemical change to the food molecules 31  MOJZA` ➔ Chemical digestion is the breakdown of large insoluble molecules into small soluble molecules ➔ Absorption is the movement of small food molecules and ions through the wall of the intestine into the blood ➔ Assimilation is the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells ➔ Egestion is the passing out of food that has not been digested or absorbed, as faeces, through the anus - Reason for digestion before absoption: ➔ Digestion is a process in which large, insoluble and complex biological molecules are broken down into small, soluble and simple molecules, as a result of enzyme catalysed hydrolytic reactions ➔ The molecules have to be digested in order to be absorbed in the bloodstream, and transported to tissues; diffused across the cell membrane into the cells for assimilation - Physical/Mechanical digestion: ➔ The breakdown of food into smaller pieces without any chemical change to the food molecules, hence increasing the surface area to volume ratio for enzymes to effectively act. ➔ Takes place in various parts of alimentary canal: ↳ Chewing by teeth ↳ Churning of food by the stomach ↳ Emulsification of fats by bile Mouth/Buccal Cavity - Structure: ➔ There are 2 jaws present in the mouth cavity: upper jaw and lower jaw ➔ The upper jaw is fixed at its position, while the lower jaw is movable ➔ Along the teeth, the mouth contains a tongue and salivary glands ➔ Physical/mechanical digestion takes place in the mouth with the help of the teeth ➔ Chemical digestion takes place in the teeth with the help of the enzyme, amylase, secreted by the salivary gland ➔ The mouth has a pH that ranges from 6-7, which is optimum for amylase - Function: ➔ Ingestion takes place in mouth i.e. food enters into the body through the mouth ➔ The mouth does physical digestion by breaking down large food pieces into smaller pieces; this helps in increasing the surface area to volume ratio of food for enzymes to act on during chemical digestion 32  MOJZA` ➔ Salivary glands (accessory digestive structures) open into the mouth through the ducts, which secrete saliva (spit) into the mouth. Saliva contains salivary amylase, which is an enzyme that chemically digests starch into maltose. ➔ The tongue has taste receptors, which allow us to taste the food. The food is rolled up by the tongue into small, slippery, spherical masses known as boli. - Types of Teeth ➔ There are two jaws present in the mouth: upper jaw and lower jaw ➔ Each jaw contains equal number of teeth i.e. 16 each and 32 total, which are : Teeth Location Structure Function Incisors Present on the front side Chisel-shaped Biting and holding the food Canines Present next to the incisors Sharp-pointed Tearing the food Premolars Present behind the Large and flat Grinding of food canines Chewing the food Usually have 2 Crushing the food cusps Molars Present behind, in the back of Large and flat Same as pre-molars the mouth Usually have 4-5 cusps - Tooth Structure ➔ Crown is the visible part of the tooth ➔ Root is the part of the tooth under the gums Tooth structure Function Gums Teeth are embedded in the gums Enamel The outer part of the tooth is known as enamel, which is mainly composed of hydroxyapatite, which is a mineral form of calcium phosphate Dentine The layer under the enamel is known as dentine, which is made up of hard tissue and is calcified. Dentine contains microscopic tubules; if the protective layer over dentine i.e. enamel is damaged then the tubules allow heat, cold, acidic or sticky foods to stimulate the nerves and cells inside the tooth, causing sensitivity. Pulp Pulp is the inner structure of the tooth, which is soft; contains blood Vessels and nerve endings Cementum A layer of connective tissue that binds the roots of the teeth firmly to the gums and jawbone. 33  MOJZA` Oesophagus ➔ Oesophagus, the gullet, is a part of the alimentary canal which is a narrow, muscular tube ➔ Bolus from the mouth goes down into stomach through oesophagus, through the process of peristalsis ➔ Oesophagus has a pair of antagonistic muscles, known as longitudinal and circular muscles. These muscles work together, but in opposite directions to each other. - Peristalsis ➔ Peristalsis is the rhythmic wave-like movement of an antagonistic pair of muscles i.e. circular muscles and the longitudinal muscles ➔ When the food moves down the alimentary canal, the circular muscle behind it contracts and longitudinal muscles relax; this constricts the lumen. Constriction of lumen makes it narrower and longer from behind, exerting a force that pushes the food forward ➔ Simultaneously, the circular muscles ahead of the food relax and the longitudinal muscle contracts, dilating the lumen. Dilation of the lumen makes it wider and short, helping the food to enter forward. ➔ Mucus helps to reduce friction between the food and wall of alimentary canal, making peristalsis easier Stomach - Functions of stomach: ➔ Temporary stores food until it passes to the small intestine through pyloric sphincter muscle ➔ Churning ➔ Chemical digestion of proteins ➔ HCl (hydrochloric acid) kills pathogens, acting as a chemical barrier against diseases - Physical digestion in stomach ➔ Churning is a type of physical digestion, where walls of the stomach rhythmically contract and relax ➔ This allows mixing of bolus with the digestive juices and HCl present; squeezing the food increases the surface area to volume ratio for enzymes to act on ➔ The liquid formed after churning is known as chyme, which moves into the duodenum - Chemical digestion in stomach ➔ The gastric juice is secreted by the gastric glands present on the walls of stomach, which is a dilute solution of HCl along digestive enzymes; has a pH of around 2 34  MOJZA` ➔ HCl inhibits the action of salivary amylase by denaturing it, while proving acidic medium optimum for activity of protease enzymes in stomach ➔ Main enzyme secreted in the stomach is pepsin, which breaks down proteins into polypeptides Small Intestine ➔ As chyme enters the duodenum it stimulates the following functions to take place: ↳ Gallbladder to release bile ↳ Pancreas to secrete pancreatic juice ↳ Intestinal glands to secrete intestinal juice - Bile ➔ Bile is a greenish-yellow liquid which contains bile salts and bile pigment, giving it its colour. It is alkaline in nature. ➔ Produced by the liver, and temporarily stored in gallbladder (attached to the liver), and it is released into the duodenum through the bile duct ➔ Bile does not contain any enzymes, therefore, it does not chemically digest chyme ➔ It neutralises the chyme which comes from the stomach, making pH optimum for enzymes acting in duodenum ➔ Bile emulsifies fats: emulsification is a form of mechanical digestion, where it breaks large fat globules into minute fat droplets, increase surface area for lipase enzymes to act on it ➔ Bile salts also reduce the surface tension of lipids, assisting in emulsification of fats - Pancreatic Juice ➔ Pancreas is connected to duodenum with pancreatic duct through which pancreatic juice travels into duodenum ➔ Pancreatic juice contains digestive enzymes which are: ↳ Pancreatic amylase, which breaks down remaining starch into maltose ↳ Pancreatic lipase, which breaks down fats into fatty acids and glycerol ↳ Trypsin, which breaks down proteins into polypeptides - Intestinal Juice ➔ Intestinal juice is secreted by the lining of the walls of the small intestines which bear glands. ➔ Intestinal juice contains digestive enzymes which are: ↳ Erepsin/peptidase, which breaks down polypeptides into amino acids ↳ Intestinal lipase, which breaks down fats into fatty acids and glycerol ↳ Maltase, which breaks down maltose into glucose ↳ Lactase, which breaks down lactose into glucose and galactose ↳ Sucrase/invertase, which breaks down sucrose into glucose and fructose - End products of digestion ➔ Carbohydrates: glucose, galactose and fructose 35  MOJZA` ➔ Proteins: amino acids ➔ Lipids: fatty acids and glycerol ➔ Vitamins and minerals: not digested as they are already soluble and diffusible ➔ Cellulose: not digested by our gut, as we don’t have the enzyme cellulase Absorption and Assimilation ➔ Absorption of digested nutrients mainly takes place in the ileum of the small intestines, which is adapted to carry out this in the following ways: ↳ Large diameter, increases the surface area for absorption ↳ Numerous transverse folds, which increases the surface area to volume ratio for maximum absorption ↳ Millions of minute like projections known as villi, which further increases the surface area ↳ Epithelial cells of villi bear many microvilli, to increase surface area ↳ The wall of villus is one-cell thick, decrease distance and resulting in faster rate of diffusion ↳ The intestinal wall is richly supplied with blood vessels and lacteals, for faster and efficient absorption ➔ Absorption is the process by which digested nutrients are taken up by the cells lining the small intestine, and then transported into the bloodstream or lymphatic vessels for distribution throughout the body. ➔ Assimilation is the process by which the absorbed nutrients are taken up by the bloodstream or lacteals, and used up by the body's cells for various functions End products Absorption Assimilation Glucose, Galactose ➔ Move from the intestines into the ➔ Excess glucose is and Fructose cell linings and then into the blood converted into glycogen and stored in liver ➔ Initially by diffusion, then active transport, depending upon the ➔ Uses discussed under diet concentration gradient Amino Acids ➔ Excess amino acids are ➔ Capillaries of villi will unite to deaminated in the liver form hepatic portal vein, which carry these nutrients to the liver from - Uses discussed under diet small intestine once absorbed ➔ Fat- soluble vitamins such Vitamins and Minerals as vitamin D is stored in liver ➔ Uses discussed under diet Fatty acids and ➔ Move from the intestines into the ➔ Excess stored in adipose glycerol cell linings and then the lacteals, tissue into the lymphatic system 36  MOJZA` ➔ Uses discussed under diet ➔ Initially by diffusion, then active transport, depending upon the concentration gradient Water ➔ About 80-90% of water is ➔ Discussed under diet absorbed in the small intestine, while remaining in the large intestine - Egestion/Defecation ➔ The undigested and unabsorbed passes into the large intestine and the faeces moves through the colon ➔ Cellulose adds bulk to the faeces and also helps in absorption of water to make faeces soft; hence, helping in bowel movement ➔ Faeces are stored temporarily in the rectum, before being discharged through the anus ➔ Egestion is different from excretion, as the faeces have not actually entered the body cells before removed from body 37  MOJZA` Unit 9: Human Gas Exchange - Features of Gas Exchange Surfaces (Alveoli) in Humans: ➔ Large surface area ➔ Thin surface ➔ Good blood supply ➔ Good air supply - Differences between composition of exhaled and inhaled air: Gas Inspired Air (%) Expired Air (%) Explanation Nitrogen 79 79 Not used/ produced by bodily processes Oxygen 21 16 Used up in respiration Carbon dioxide 0.04 4 Produced in respiration Water vapour Variable Saturated Due to the lining of moisture inside alveoli Pathway of air in the body - Nose ➔ The nose has two nasal passages that have hair ➔ Nasal hair traps dust and other pathogens, acting as a physical barrier against diseases - Larynx ➔ The air from the nose travels to pharynx, and then passed to the larynx - Trachea and Bronchi ➔ Trachea is supported by c-shaped cartilages that prevents it from collapsing under pressure, and further divided into two tubes known as bronchi ➔ These are the two tubes that connect with each of the lungs ➔ Each bronchus is further divided to form bronchioles, and eventually ends into an alveoli ➔ The epithelium lining present on the walls of the trachea and the bronchi have the following cells: 38  MOJZA` ↳ Goblet cells, which secrete mucus. The mucus traps foreign particles. ↳ Epithelial ciliated cells have cilia, that flick in continuous fashion to move mucus, trapped with foreign particles, away from lungs. - Alveoli ➔ These are the clusters or air sacs ➔ Are extremely thin, have a moist wall and are well supplied with blood capillaries - Adaptations of Lungs: ➔ The lungs are elastic, which helps them in contracting and relaxing easily when needed ➔ The number of alveoli that are present help provide a large surface area ➔ Lungs lie in the pleural cavity, which gets completely filled when the lungs are expanded - Diaphragm ➔ Separates the thorax from the abdomen ➔ It flattens when it contracts, which increases the volume of pleural cavity ➔ It arches upwards when it is relaxed, which decreases the volume of pleural cavity - The breathing system Note: Diagram to be Added - Volume & Pressure Changes in the Lungs ➔ The diaphragm and intercostal muscles control the movement of air in and out of the lungs. Diaphragm Volume in Thorax Intercostal Rib Cage Pressure in Lungs Muscles Inhaling / Contracts Volume Increases External Contract Upwards and Inspiration Flattens Pressure Decreases Internal Relax Outwards Exhaling / Relaxes Volume Decreases External Relax Downwards Expiration Goes upward Pressure Increases Internal Contracts and Inwards 39  MOJZA` Unit 10: Respiration What is respiration? ➔ Respiration is a series of chemical reactions controlled by enzymes to release energy from glucose in all living organisms ➔ This energy is used to bring about various life processes described below in the table: : Muscle Contraction ➔ Peristalsis ➔ Pupil constriction ➔ Intercostal muscles ➔ Sphincter muscle ➔ Vasodilation ➔ Vasoconstriction Protein synthesis ➔ Proteases ➔ Haemoglobin ➔ Carbohydrases ➔ Insulin ➔ Lipases ➔ Antibodies Cell division ➔ E.g. New RBCs formed to replace dead cells Growth ➔ Permanent increase in dry mass Active Transport ➔ Root hair cells to intake ions ➔ Absorption in Intestine ➔ Selective reabsorption in nephrons Nerve Impulse ➔ Reflex action ➔ Muscles and glands Body Temperature ➔ Maintaining constant body temperature Aerobic and Anaerobic respiration ➔ Aerobic respiration is the oxidation of glucose in order to release large amounts of energy, with carbon dioxide and water as the waste products. ➔ Anaerobic respiration is the breakdown of glucose in the absence of oxygen, to release a relatively small amount of energy. 40  MOJZA` Aerobic Respiration Anaerobic Anaerobic Respiration Respiration (Yeast) (Humans) Reactants Glucose and oxygen Only glucose Only glucose Products Carbon dioxide and water Only lactic acid Ethanol and carbon dioxide Energy yield High Low Low Word Glucose + Oxygen → Carbon Glucose → Lactic Glucose → Ethanol + Carbon Equation dioxide + Water acid dioxide Chemical C6H12O6 + 6O2 → 6CO2 + 6H2O ------------------------ C6H12O6 → 2C2H5OH + 2CO2 Equation ➔ Anaerobic respiration in yeast is also termed as alcoholic fermentation, as this process results in the formation of alcohol ➔ During anaerobic respiration glucose is partially broken down into alcohol or lactic acid, which is why there is a small amount of release of energy. Energy is still stored in bonds of these products. - Physical activity and its effect on breathing: ➔ Increase in energy requirements, due to strenuous exercising, leads to more aerobic respiration taking place, for which more oxygen needs to be provided, while simultaneously, more carbon dioxide has to be removed from the body cells ➔ This increases the breathing rate, for rapid gas exchange, and heart rate, for quicker transport to meet the body’s increased oxygen demand ➔ If vigorous exercise continues, and the energy requirement is not met, then the body starts to respire anaerobically alongside, producing lactic acid ➔ A high build-up in the amount of lactic acid can cause muscle soreness, as it lowers the pH, which is not optimum for enzymes. Muscles in this state are said to be in a state of fatigue, leading to ‘oxygen debt’ ➔ Oxygen debt refers to the temporary shortage of oxygen supply to the body’s tissues during physical activity - After Physical Activity: ➔ Breathing rate and heart rate continue to remain high after exercise to repay the oxygen debt i.e. restoring the body's normal oxygen levels ➔ This is done by transporting excess lactic acid to the liver, where it gets broken down by reacting it with oxygen 41  MOJZA` Unit 11: Transport in Humans - Blood vascular system ➔ It has two constituents: ↳ Blood ↳ Heart and the blood vessels - Blood ➔ The composition of blood is as follows: ↳ 55 % blood plasma ↳ 45 % blood corpuscles (Blood Cells) - Plasma ➔ It is a non-cellular, non-living, transparent, liquid part of the blood that mainly acts as a medium of transportation for all substances in the body, except for oxygen ➔ Transport of nutrients, for e.g. glucose, amino acids and vitamins to all cells of body in need ➔ Transport of ions to maintain proper functioning of body processes, and to maintain the osmotic pressure of body ➔ Transport of CO2 , usually in the form of bicarbonate ions before exhalation ➔ Transport of different metabolic wastes, such as urea and uric acid to the site of excretory organs like kidney ➔ It carries fibrinogen to the site of injury for clotting ➔ Transports antibodies from lymphocytes to the site of infection Blood corpuscles ➔ The three types of blood corpuscles are: ↳ Red blood cells ↳ White blood cells ↳ Platelets - Red blood cells (erythrocytes) ➔ The following are the features and adaptations of the red blood cells: ↳ Biconcave: increases surface area to volume ratio, for faster rate of absorption of oxygen ↳ Absence of nucleus and other organelles: allows for more space to be available for haemoglobin ↳ Flexible: so they can pass squeeze through capillaries in the body ↳ Haemoglobin: shows a high affinity for oxygen; binds with it reversibly to form oxyhemoglobin, for transport ↳ RBCs are made in the bone marrow and have a life span of 3-4 months 42  MOJZA` - White blood cells (leucocytes) ➔ The following are the features of the white blood cells: ↳ Usually larger ↳ Roughly spherical ↳ Nucleated ↳ Produced in the bone marrow ↳ Life span is variable ↳ They play an important role in providing immunity to the body against pathogens ↳ Fewer in number as compared to RBC’s - Types of white blood cells ➔ There are two types of white blood cells: ↳ Phagocytes ↳ Lymphocytes - Phagocytes ➔ Lobed and irregular nucleus ➔ More flexible (can even move out of the ca