How many lessons is it?

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Constance Cunningham
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1 Science Unit Learning Summary Content Eukaryotes and Prokaryotes Cells are the basic unit of all life forms. A eukaryotic cell contains genetic material enclosed within a nucleus. Plant and animal cells are eukaryotic cells and have a cell membrane, cytoplasm and genetic material contained within a nucleus. Prokaryotic cells do not have genetic material enclosed within a nucleus. Bacterial cells are an example of a eukaryotic cell, they have a cytoplasm, a cell membrane surrounded by a cell wall. Bacterial cells are much smaller than plant and animal cells. The genetic material in a bacterial cell is not enclosed in a nucleus, instead it is a single loop of DNA and there may be one or more small rings of DNA known as plasmids. Animal and Plant Cells Most animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. In addition to the parts found in animal cells plant cells also have chloroplasts, and a permanent vacuole filled with cell sap. Plant and algal cells also have a cell wall made of cellulose to strengthen the cell. The nucleus contains the DNA and directs the cells activities. The cell membrane controls what can enter and leave the cell. The mitochondria are the site of respiration. Chloroplasts absorb sunlight to produce glucose in the process of photosynthesis. A microscope can be used to observe, draw and label animal and plant cells. Cell Specialisation and Differentiation There are many different types of plant cells in plants and animals Cells specialise to carry out a particular function. Specialised cells in animals include; sperm cells, nerve cells, muscle cells. Specialised cells in plants include; root hair cells, xylem and phloem. As an organism develops, cells differentiate to form different types of cells. Most types of animal cells differentiate at an early stage. How many lessons is it? Approximately 8/10 lessons How will I be assessed? Completion of homework Completion of SAM learning tasks Milestone tasks A mid-module assessment of keywords and basic scientific skills An end of module test that covers the content of the lessons What homework will be set? Simple tasks at the end of every lesson

2 Many types of plant cells retain the ability to differentiate throughout life. Cell division in animals is mostly for the purpose of repair and replacement. As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function. Once differentiated a cell is a specialised cell. Microscopy Microscopes can be used to observe cells. Microscopes techniques have improved over time. The electron microscope has increase understanding of sub-cellular structures as a result of its higher magnification and resolving power. The electron microscope can be used to study cells in much finer detail. Cell Division and Stem Cells The nucleus of a cell contains chromosomes made of DNA molecules, each chromosome carries a large number of genes. In body cells chromosomes are normally found in pairs. Cells divide in a series of stages called the cell cycle. During the cell cycle the genetic material is doubled and then divided into two identical cells. Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome. Mitosis is a part of the cell cycle. During mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides. After the nucleus divides the cytoplasm and cell membranes divide to form two identical cells. Cell division by mitosis is important in the growth and development of multicellular organisms. Stem Cells A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type and from which certain other cells can arise from differentiation. Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells. Stem cells from adult bone marrow can form many types of cells including blood cells. Meristem tissue in plants can differentiate into any type of plant cell throughout the life of the plant. Treatment with stem cells may be able to help conditions such as diabetes and paralysis. In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient s body so they may be used for medical treatment. The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections. Stem cells from meristems in plants can be used to produce clones of plants quickly and economically. Rare species can be cloned to protect from extinction.

3 Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers. Diffusion Substances may move into and out of cells across the cell membrane via diffusion. Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration. Oxygen, carbon dioxide and urea are transported in and out of cells by diffusion. Factors that affect the rate of diffusion include; the difference in concentration, temperature and surface area of the membrane. Single-celled organisms have a relatively large surface area to volume ratio allowing sufficient transport of molecules in and out of the cell to meet the organism s needs. Multicellular organisms require exchange surfaces and a transport system to meet the organisms need. The small intestine and lungs in mammals are adapted for exchanging materials. Gills in fish are adapted for exchanging materials. Thee roots and leaves of plants are adapted for exchanging materials. In multicellular organisms, surfaces and organ systems are specialised for exchanging materials. The effectiveness of an exchange surface is increase by having a large surface area, a thin membrane, and in animals an efficient blood supply and ventilation. Osmosis Water may move across cell membranes via osmosis. Osmosis is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane. The movement of water by osmosis can affect the mass of plant tissue. Active Transport Active transport moves substances from a more dilute solution to a more concentrated solution against a concentration gradient. Active transport requires energy from respiration. Active transport allows mineral ions to be absorb by plant root hairs from very dilute solutions in the soil. Active transport allows sugar molecules to be absorbed from lower concentrations in the gut into the blood.

4 Know: Science Unit Key Facts - To know the characteristics of eukaryotic and prokaryotic cells. - To know that a specialised cell is a cell which is adapted to carry out a particular function. - To be able to name specialised cells found in plants and animals. - To know the difference between a light microscope and an electron microscope. - To know that cells divide in a series of stages called the cell cycle. - To be able to describe the stages of the cell cycle, including mitosis. - To know what a stem cell is and where they are found. - To be able to describe the process of diffusion. - To be able to describe the process of osmosis. - To be able to describe the process of active transport. Understand: - To be able to explain the difference between a prokaryotic and a eukaryotic cell and give examples. - To be able to explain how the main sub-cellular structures found in animal and plant cells are related to their functions. - To be able to explain how sperm cells, nerve cells, muscle cells, root hair cells, xylem and phloem are specialised to carry out their functions. - To be able to explain the importance of cell differentiation. - To understand how the process of cell differentiation occurs. - To understand how the development of microscopy techniques has changed over time. - To understand how the higher magnification and resolving power of the electron microscope has improved understanding of sub-cellular structures. Keyword Eukaryotic Cell Prokaryotic Cell Nucleus Cell Membrane Cytoplasm Genetic Material Cell Wall Plasmid Chloroplast Ribosome Algae Cellulose Microscope Organ Cell differentiation Cell division Meaning Cells from eukaryotes that have a cell membrane, cytoplasm and genetic material enclosed in a nucleus. Cells from prokaryotes that have a cytoplasm surrounded by a cell membrane, and a cell wall that does not contain cellulose. The genetic material is a DNA loop that is free in the cytoplasm and not enclosed by a nucleus. Sometimes there are one or more small rings called plasmids. An organelle found in many living cells containing the genetic information surrounded by a nuclear membrane. The membrane around the contents of the cell that controls what moves in and out of the cell. The water-based gel in which the organelles of all living cells are suspended and most of the chemical reactions take place. The hereditary material known as DNA found in nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells. The rigid structure around plant and algal cells. It is made of cellulose and strengthens the cell. A genetic structure found in the cells cytoplasm. Plasmids are usually circular. The organelles in which photosynthesis takes place. The site of protein synthesis in a cell. Simple aquatic organisms that make their own food by photosynthesis. The complex carbohydrate that makes up plant and algal cell walls and gives them strength. An optical instrument used for viewing very small objects, such as plant and animal cells magnified several hundred times. An aggregation (collection) of different tissues working together to carry out specific functions. The process where cells become specialised for a particular function. The division of a cell into two daughter cells with the same genetic material.

5 Science Unit Key Facts Understand: - To understand the three overall stages of the cell cycle. - To understand the importance of cell division in multicellular organisms. - To be able to describe and explain the uses of embryonic and adult stem cells. - To understand the uses of meristem tissue found in plants. - To understand the factors that affect the rate of diffusion. - To understand the need for exchange surfaces and transport systems in multicellular organisms. Application/skills: - To be able to undertake order of magnitude calculations including the use of standard form. - To be able to use a light microscope to observe, draw and label a selection of plant and animal cells and include a magnification scale. - To be able to recognise and describe situations in given contexts where mitosis is occurring. - To be able to evaluate the use of stem cells for therapeutic cloning and treatment of disease. - To be able to evaluate the use of meristem tissue to produce plant clones. - To be able to calculate and compare surface area to volume ratios. - To investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue. Keyword Organ System Specialised cell Magnification Resolution Cell cycle Mitosis DNA Chromosome Stem cell Embryo Meristem tissue Cloning Therapeutic cloning Meaning A group of organs that work together to carry out specific functions and form organism. A cell that has differentiated to perform a specific function. Examples include; sperm cells, egg cells, root hair cells, nerve cells, xylem and phloem. The action of magnifying something or the process of being magnified. The ability to distinguish between two separate points that are very close together. The three-stage process of cell division in a body cell that involves mitosis and results in the formation of two identical daughter cells. Part of the cell cycle where one set of new chromosomes is pulled to each end of the cell forming two identical nuclei during cell division. A self-replicating material found in nearly all living things as the main component of chromosomes. A thread-like structure made of DNA carrying genetic information in the form of genes. Undifferentiated cells with the potential to form a wide variety of different cell types. An unborn offspring in the process of development. A tissue found in plants made up of undifferentiated cells found in regions of the plant where growth can take place. The production of identical offspring by asexual reproduction. A process where an embryo is produced that is genetically identical to the patient so the cells can then be used in medical treatment.

Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.

Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and genetic material enclosed in a nucleus. 4.1 Cell biology Cells are the basic unit of all forms of life. In this section we explore how structural differences between types of cells enables them to perform specific functions within the organism.