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Biology Prelim Notes
Biology- Unit 2
High School - Australia
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Biology
Prelim
Notes
Cells as a Basis of Life
Cell Structure - WHAT Distinguishes One Cell from Another?
Syllabus Dot Point: Notes:
- Investigate different cellular structures including but not limited to; ↳ Examining a variety of prokaryotic and eukaryotic cells ↳ Describe a range of technologies that are used to determine a cell’s structure and function
Cell Theory: - All organisms are made up of cells. - New cells are produced from existing cells. - A cell is the smallest unit within a living thing.
Types of Cells: - Prokaryotic; ↳ They are the simplest cells which do not have a membrane-bound nucleus. ↳ There are two types; ○ Bacteria ○ Archaea ↳ DNA is in a circular loop called a plasmid. ↳ Typically unicellular. - Eukaryotic; ↳ Are larger and more complex than prokaryotic cells. ↳ Possess a membrane-bound nucleus which stores genetic information. ↳ They have membrane-bound organelles which work together to undergo biochemical processes such as respiration and photosynthesis. ↳ Linear DNA is held in the nucleus. ↳ Usually multicellular. ↳ Animal and plant cells are eukaryotic.
but not limited to; ↳ Scaled diagrams of a variety of cells ↳ Comparing and contrasting different cell organelles and arrangements ↳ Modelling the structure and function of the fluid mosaic model of the cell membrane
= 1 000 000 micrometres = 1 000 000 000 nanometres Organelles in Cells:
Organelle Plant/Animal? Function
Cell Membrane Both A thin membrane which surrounds the cell wall and filters what can enter and exit the cell.
Cell Wall Plant It gives the cell its shape which is thicker and more frigid.
Centriole Animal A dense, granular structure that has two centrioles that play an important role in cell division and informing the spindle.
Chloroplast Plant Conducts photosynthesis
Cytoplasm Both A fluid that contains all organelles and supports them.
Cytoskeleton Both Helps maintain shape, move and shift things around and inside the cell.
Golgi Body Both Responsible for directing molecular traffic in the cell; modifies, sorts and transfers molecules.
Lysosomes Animal Contains enzymes that digest waste and “clean up” the cell.
Mitochondria Both Converts chemical energy from food into compounds more convenient for the cells to use.
Nucleus Both Directs the activity of
the cell and stores DNA
Plasma Membrane Both The outer part of the cell which allows things inside and outside of the cell.
Protoplasm The living content of a cell that is surrounded by the cell membrane
Rough Endoplasmic Reticulum (RER)
Both Responsible for synthesis and transport of proteins.
Smooth Endoplasmic Reticulum (SER)
Both Makes sex hormones, lipids and enzymes
Vacuole Plant Stores nutrients and water
The Fluid Mosaic Model: - The cell membrane is selectively permeable and performs the function of controlling the movement of substances into and out of the cell. - The currently accepted model of the structure of the cell membrane is the fluid mosaic model. ↳ It depicts a ‘fluid’ phospholipid bilayer with different types of proteins embedded in it, creating a ‘mosaic’ effect. ↳ Some membrane proteins form pores (temporary or permanent), some form of active carrier systems or channels for transport and others (glycoproteins) have carbohydrates attached for cell recognition.
Active Transport: - It is the movement of molecules from a region of low concentration to an area of high concentration. - It moves against the concentration gradient and requires the input of energy.
Endocytosis: - It moves large molecules that cannot cross the cell membrane into a cell. - Requires the expenditure of energy. - The cell membrane changes shape and surrounds and engulfs the particle so that it enters the cell. → - Phagocytosis; ↳ Process whereby solid particles are engulfed by the cell membrane - Pinocytosis; ↳ The engulfing of fluid substances by the cell membrane.
Exocytosis: - Involves a membrane-bound vesicle moving to the cell membrane, fusing with it and then releasing its contents to the exterior of the cell.
Factors Affecting the Exchange of Materials Across Membranes: - Chemical factors; ↳ The chemical properties of a substance affect its transport across cell membranes, uncharged molecules can easily penetrate the cell membrane as they can dissolve through the phospholipid bilayer. - Physical factors; ↳ The size and shape of the molecule affects its ability to move across the cell membrane. Small molecules are able to easily diffuse between the phospholipids, however, very large molecules need to be transported via endocytosis or exocytosis. - Concentration gradient; ↳ The relative concentration of the substance on either side of the membrane affects the rate of diffusion of that substance. ↳ If the concentration gradient is high, the substance will diffuse rapidly. ↳ If the concentration gradient decreases, the rate of diffusion will be slower. ↳ When the concentration gradient reaches equilibrium, there will be no net movement across the cell membrane.
Surface-Area-to-Volume Ratio: - It is calculated by finding the total area of the surface of the shape. - Volume is the total space that a shape takes up. - SA: V is calculated by dividing the surface area of an object by its volume. - The SA: V ratio of a cell will determine how efficiently substances move into and out of a cell. - A high SA: V allows the most efficient movement of substances into
and out of the cell.
Large cells have a low SA: V, small cells have a large SA: V.
Long, flat cells have a higher SA: V than a spherical cell with the same volume.
Investigate cell requirements, including but not limited to: ↳ Suitable forms of energy, including light energy and chemical energy in complex molecules ↳ Matter, including gases, simple nutrients, and ions. ↳ Removal of wastes
Cell Requirements: - Cells require organic and inorganic nutrients. - They are utilised in the following ways; ↳ Essential building blocks from which cells and living tissues are made. ↳ As a source of stored energy for the cell.
The four main groups of biomacromolecules are carbohydrates, proteins, lipids and nucleic acid.
They are made up of carbon, hydrogen and oxygen atoms, but they are in different proportions.
Autotrophic organisms can build their own organic compounds, whereas consumer organisms must make their own organic compounds from their food.
Carbohydrates can be used as a source of energy, for storage of energy and sometimes as a structural component of the cell.
Lipids are used for energy storage, structural parts of membranes and components of hormones.
Proteins have structural roles in cells and tissues. Proteins such as enzymes also have a functional role.
The two types of nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
DNA contains chemical information that controls the cell activities and the production of proteins, RNA assists in the manufacture of the proteins.
Investigate the biochemical processes of photosynthesis, cell respiration and the removal of cellular products and wastes in eukaryotic cells
The energy in cells is transported within cells by small and mobile ATP molecules.
ATP stores energy in a high-energy bond that attaches the third phosphate group to the ADP molecule.
When energy is required, the high-energy bond is broken, releasing energy, a phosphate group and ADP.
Photosynthesis: - It is the process where plants use light energy, trapped by chlorophyll, to break down water and carbon dioxide molecules, and build them up into oxygen, glucose and water molecules.
Light energy Carbon dioxide + water ------------------- → glucose + oxygen Chlorophyll
- It is a series of smaller reactions occurring across two stages.
- The light-dependent stage occurs in the grana where light splits the
efficiently.
- Substrate Concentration; ↳ As the substrate concentration increases, the activity of the enzyme increases until all the enzymes are saturated. After this, further increases in substrate concentration will not lead to increases in enzyme activity.
Organisation of Living Things
Organisation of Cells-How are Cells Arranged in a Multicellular Organism?
Syllabus Dot Point: Notes:
Compare the differences between unicellular, colonial and multicellular organisms by: ↳ Investigating structures at the level of the cell and organelle ↳ Relating structure of cells and cell specialisation to function
Organisms can exist as a single cell (unicellular), single cells working together (colonial) or as an organism made up of many cells (multicellular), however, they all have similarities; ↳ They are all composed of cells ↳ These cells all possess cell membranes, cytosol, ribosomes and some sort of genetic material.
Unicellular Organisms: - They contain only one cell which can either be prokaryotic or eukaryotic. - A single cell is responsible for all of its own life processes. - Prokaryotic cells have no membrane-bound nucleus or organelles, however, their simple structures limit the number of reactions that they can carry out. - Cells of unicellular organisms have a highSA: V, which allows efficient movement of substances into and out of the cell.
Colonial Organisms: - They are thought the be the evolutionary link between unicellular and multicellular organisms. - They are composed of individual cells living together in a colony. - All cells in the colony are capable of carrying out all of the metabolic functions necessary for life, however, simple specialised cells can be present in the colony to improve the efficient functioning of the organism.
Multicellular Organisms:
- They are composed of many different types of specialised cells. Similar specialised cells are grouped together and perform specific functions that combine for the efficient functioning of the organism.
- Individual cells cannot live independently of each other.
Specialised Cells: - Stem cells are undifferentiated cells with no specialised structure or function. - Specialised cells are formed when differentiation of the stem cells occurs and they develop suitable structural features that allow them to carry out their specific functions. - They type of cell that is formed is determined by the location of the undifferentiated cells in the organism and the particular genes that are switched on. - Stem cells can either be embryonic or adult stem cells. - In plants, specialised cells are formed by the differentiation of meristematic tissue.
Relationships between Cell Structure and Function: - The cells of those parts of the body involved in exchanging substances with the environment have special structural features to increase their SA: V, allowing them to exchange the required materials more efficiently. - The cell structure is related to the particular function of the specialised cell. - Some cells may flatten and become longer to increase the SA: V or have many folds to increase surface area. E. root hair cells - Another example is the red blood cells that are very small and have a particular shape to increase SA: V for the exchange of oxygen. They lack a nucleus and organelles, enabling more haemoglobin to be carried in the cell.
- Investigate the structure and function of tissues, organs and systems and relate those functions to cell differentiation and specialisation
Animal Tissues: - Epithelial Tissue; ↳ It is a tissue that covers body surfaces, protects organs and forms glands. ↳ The cells are densely packed and can occur in either single sheets or layers. ↳ Does not contain blood vessels and relies on the underlying connective tissue for nutrients. ↳ Skin, the surface of organs of the digestive system, respiratory system and other organs. ↳ The cells are organised very close to each other, aiding their role as barriers to injury and infection. ↳ They may also be specialised for absorption or secretion. - Connective Tissue; ↳ It varies greatly in the form it takes and its function. ↳ They all share the common characteristic of an extracellular matrix with cells scattered through it. ↳ This matrix is made up of protein fibres collagen (strength) and
soil for the use of the rest of the plant. ○ Roots, including the root hairs, are the organs involved. ↳ Vascular system; ○ Responsible for transport. ○ Made up of xylem and phloem.
Meristematic Tissue; ↳ Found at the tips of the roots and shoots. ↳ Can also be found in the buds and in a ring around the stem of woody plants. ↳ Cells divide to produce new growth
Dermal Tissue; ↳ Protects the plant tissues from damage and controls interactions with the plant’s surroundings. ↳ Found on the outer layers of the stem, roots and leaves. ↳ The epidermal layer (outermost) secretes a waxy layer called the cuticle which is vital to reduce water loss/ ↳ Epidermal cells generally lack chloroplasts but produce fine hairs in the surfaces of leaves and stems. ↳ The hairs trap a layer of air to prevent the flow of air and decrease the evaporation of water. Some hairs contain harmful substances to prevent insects from eating them. ↳ Some cells have root hairs which increase surface area for the movement of water into the root thus increasing water and mineral uptake.
Vascular Tissue; ↳ It is responsible for the transport of substances around the plant. ↳ Found in the roots, stems and leaves. ↳ Xylem; ○ Transports water and mineral salts from the roots to the leaves. ↳ Phloem; ○ Transports the products of photosynthesis around the plant.
Ground Tissue; ↳ It is all of the internal cells of a plant. ↳ It is the bulk of the plant tissue which consists of different types of cells that are specialised for food storage, support and photosynthesis.
Justify the hierarchical structural organisation of organelles, cells, tissues, organs, systems and organisms.
Organelles (membrane-bound structures that have specific roles in the cell) ↓ Cells (basic structural and functional unit of living organisms) ↓ Tissues (cells that perform similar functions) ↓ Organs (different tissues grouped together to carry out a particular function) ↓ Organ System (organs grouped together to carry out a particular function) ↓ Organism (a living thing made up of many interrelated components that work
together)
Nutrient and Gas Requirements - WHat is the Difference in Nutrient and Gas
Requirements between Autotrophs and Heterotrophs?
Syllabus Dot Point: Notes:
- Investigate the structure of autotrophs through the examination of a variety of materials; ↳ Dissected plant materials ↳ Microscopic structures ↳ Imaging technologies to determine plant structure
Autotroph Structure and Function: - Non-vascular plants (mosses) do not possess specialised structures for support and transport. - Most plants are vascular plants and possess a transport system to move substances around the plant and provide support. - Vascular plants contain a number of body systems - the root, shoot and vascular system. - Each system has specialised organs to carry out specific functions. - these organs allow the plan to obtain the required nutrients and gases and carry out all functions and efficiently and effectively. - The two types of vascular tissue are xylem and phloem. ↳ Xylem; transports water and mineral ions ↳ Phloem; transports dissolved sucrose and other plant products around the plant.
The Root System: - The main functions of the root system are to anchor the plant in the soil and absorb water and mineral ions. - A large surface area is required for efficient absorption of water and mineral ions. - The large surface area is achieved with flattened epidermal cells that possess fine extensions called root hairs. - Branching root systems increase the surface area for absorption. - Water moves from the soil into the root by osmosis. - Mineral ions usually move into the route by diffusion but if the concentration gradient is to learn they moved him by facilitated diffusion or active transport. - Root cells do not contain chloroplasts and do not photosynthesise but if the concentration gradient is too low they carrier aerobic cellular respiration. - Oxygen gas diffuses into the root cells and carbon dioxide gas diffusers out.
The Shoot System: - Stems; ↳ The stem provides structural support and a transport pathway
- Investigate gas exchange structures in animals and plants; ↳ Microscopic structures: alveoli in mammals and leaf structure in plants ↳ Macroscopic structures: respiratory systems in a range of animals
Gas Exchange in Plants: - Gas exchange in plants occurs through the stomata and lenticels. - When guard cells fill with water, they bend outwards and open the stomata, allowing for gas exchange. - When water is lost from the guard cells they straighten and close, preventing both gas exchange and water loss. - Plants have to balance their requirement for gas exchange and the necessity for water conservation. - Stomata opens in light and closes in the dark. - Lenticels are pores through which gaseous exchange occurs in the woody parts of plants such as the trunks and branches of trees and woody shrubs.
Gas Exchange in Animals: - The movement of gases between the external environment (alveolar air) and internal environment (bloodstream) is known as gaseous exchange. - Different animals possess different specialised structures to exchange gases with their environment. - Common characteristics of all respiratory surface as our that they have: ↳ A large surface area ↳ Thin, moist surface ↳ A close proximity to the transport system ↳ The concentration gradient maintained for continued diffusion - Terrestrial animals have internal respiratory system to reduce water loss. - Alveoli, located in the lungs, are the gaseous exchange surfaces in mammals. - Millions of alveoli in the lungs create a very large surface area for the exchange of gases. - The surface of the alveoli is very thin and moist. Many capillaries surround each alveolus. - oxygen diffuses from where it is more concentrated in the alveoli into the capillaries where it is less concentrated. - Carbon dioxide is more concentrated in the capillary and diffuses out into the alveolar space.
Respiratory Systems in Other Animals: - Fish have specialised structures called gills to absorb the small amount of oxygen that is dissolved in water. Gills are well supplied with blood capillaries. - Insects exchange gases by pores called spiracles, which lead to tracheal tubes, which then branch into smaller tubes called tracheoles. - The tracheoles bring air directly to and from the cells of the insects. Blood is not involved in the transport of gases in an insect.
Investigate the exchange of gases between the internal and external environments of plants and animals
Trace the digestion of foods in a mammalian digestive system including; ↳ Physical digestion ↳ Chemical digestion ↳ Absorption of nutrients, minerals and water ↳ Elimination of solid waste
The Process of Digestion: - Digestion is the breakdown of food into particles small enough to be absorbed into the bloodstream. - Mechanical digestion is the physical breakdown of food into small pieces to increase surface area for the action of enzymes. - The teeth and the churning motion of the stomach are the main ways in which mechanical digestion occurs. - Digestive enzymes enable the chemical breakdown of large, complex molecules into small molecules that can then be absorbed into the transport systems of the body. - Complex molecules and their simple products formed after digestion are listed below; ↳ Proteins are broken down into amino acids. ↳ Carbohydrates are broken down into simple sugars, such as glucose. ↳ Lipids are broken down into glycerol and fatty acids.
Pathway through the Digestive System: - Mechanical digestion occurs in the mouth by the use of teeth and the tongue. - Chemical digestion begins in the mouth with the enzyme salivary amylase breaking the complex carbohydrate starch down into simpler sugars. - Mechanical digestion is continued in the stomach. - Pepsin begins the chemical digestion of proteins into the chyme to form shorter peptide chains and the digestion of nucleic acids into nucleotides.
The small intestine is very long and folded and has three regions; the duodenum, jejunum and ileum.
Most digestion is completed in the duodenum.
The pancreas releases many different digestive enzymes and bicarbonate ions.
Bicarbonate ions neutralize the acidic chyme as it enters the small intestine.
Bile produced by the liver and stored in the gallbladder emulsifies fat molecules to increase surface area for breakdown by lipases.
Other enzymes complete the chemical breakdown of larger molecules.
Most absorption of the products of digestion occurs in the jejunum.
Villi microscopic projections on the wall of the jejunum that are one-cell thick. There are blood capillaries and lymph vessels in close contact with these cells. Small molecules diffuse or are actively transported through the walls of the villi into the capillary or lymph vessels to be distributed throughout the body.
Water and mineral salts are absorbed from the large intestine into the bloodstream.
The remaining undigested material is called faeces and is stored in the rectum before being eliminated from the body.
Digestive products absorbed into the body are used in many different
Plasma is a pale yellow liquid that carries the blood cells and many other dissolved substances that are required by the cells.
Blood Vessels: - The three types of blood vessels are arteries, capillaries and veins. - Arteries carry blood away from the heart and have thick, elastic walls to cope with the pressure of pulsing blood. These walls expand and return to their original diameter, helping to propel the blood. - Veins carry blood back to the heart and have thinner walls because they do not have to cope with blood under pressure. - Veins contain valves to ensure that the blood moves only in one direction. - The movement of blood in veins is caused by the contraction of the surrounding muscles. - Capillaries form networks so that all cells can be supplied with nutrients and gases, and wastes can be removed. - Capillary walls are one cell thick to allow easy exchange between blood and cells. - Only one cell at a time can move through capillaries; this increases their exposed surface area for exchange of gases, nutrients and wastes.
The Heart: - Mammals have a four-chambered heart with two chambers on each side. The top chamber on each side is called the atrium and the bottom chamber on each side is called the ventricle. - The septum separates the two sides. - The left ventricle has a thicker muscular wall because it has to pump blood all around the body while the right ventricle only has to pump the blood to the lungs. - Deoxygenated blood enters the right atrium and then moves to the right ventricle from which it is pumped to the lungs to gain oxygen. - Oxygenated blood flows back into the left atrium and then to the left ventricle from which it is pumped to the rest of the body before it once again returns to the right atrium.
- Compare the structures and functions of the transport systems in animals and plants; ↳ Vascular systems in plants ↳ Open and closed transport systems in animals
Transport Systems in Animals: - Open and closed circulatory systems: ↳ Open circulatory systems contain a heart that contracts and pushes haemolymph through vessels to to bathe the organs. ↳ When the heart muscle relaxes, the heart expands and the fluid is drawn back into the heart. ↳ Haemolymph transports only nutrients and wastes; gases are exchanged in a different system. ↳ Closed circulatory systems contain blood that is totally enclosed in vessels, with a heart providing the driving force to push the blood around the body. ↳ The pathway of blood in blood vessels from the heart, around the body and back to the heart: Arteries → arterioles → capillaries → venules → veins → heart
↳ Interpret a range of secondary-sourced information to evaluate processes, claims and conclusions that have lead scientist to develop hypotheses, theories and models about the structure and function of plants; - Photosynthesis - Transpiration- cohesion- tension Theory
Our scientific understanding of the structure and functioning of plants has been developed by scientists over many years.
Hypotheses, theories and models are modified when required if new information and results indicate that they are no longer correct.
Many scientists have contributed to our understanding of photosynthesis and the transpiration-cohesion-tension theory.
Compare the changes in the composition of the transport medium as it moved around and organism
Change in Composition of the Transport Medium: - The composition of blood changes as it moves around the body and it depends on the organ it is moving through. - In all organs and tissues except the lungs, blood loses oxygen and gains carbon dioxide. In the lungs, it gains oxygen and loses carbon dioxide. - In all organs except the small intestine, blood loses nutrients, such as the products of digestion, and gains waste. Blood gains products of digestion in the small intestine. - In the kidneys, blood has less urea when it leaves, and the concentration of water and salts will have changed according to the needs of the body
Biology Prelim Notes
Subject: Biology- Unit 2
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