1.1 Introduction to Cells Understanding: According to the cell theory, living organisms are composed of cells Organisms consisting of only one cell carry out all functions of life in that cell Surface area to volume ratio is important in the limitation of size Multicellular organisms have properties that emerge from the interaction of their cellular components Specialized tissues can develop by cell differentiation in multicellular organisms Differentiation involves the expression of some genes and not others in a cells genome The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development. It also makes stem cells suitable for therapeutic uses Applications: Questioning the cell theory using atypical examples Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism Use of stem cells to treat Stargardt’s disease and one other named condition Ethics of the therapeutic use of stem cells Nature of science: Looking for trends and discrepancies: although most organisms conform to cell theory, there are exceptions Ethical implication of research: research involving stem cells is growing in importance and raises ethical issues Skills: Use of a light microscope to investigate the structure of cells and tissues Drawing cell structures as seen with the light microscope Calculation of the magnification of drawings and the actual size of structures shown in drawings and micrographs

Cell theory principles All organisms are made of one or more cells Cells are the smallest units of life One cell can perform all functions of life Cells vary in shape and size but have some common features… Unicellular = made of one cell Multicellular = made of more than one cell https://www.youtube.com/watch?v=4OpBylwH9DU Understanding: According to the cell theory, living organisms are composed of cells Organisms consisting of only one cell carry out all functions of life in that cell

Collaboration between scientists Robert Hooke Zacharius Jansen All played a role in the development of ‘Cell Theory’ Date of birth Date of death Where were they from? What did they do? How has their work contributed to science today? Isaac Newton Zacharius Jansen Antonie Van Leeuwenhoek Theodore Schwann Matthias Schleiden Robert Remak Rudolf Virchow Skills: Use of a light microscope to investigate the structure of cells and tissues

Robert Hooke Isaac Newton Antonie Leeuwenhoek

Matthias Schleidon Theodore Schwann Rudolf Virchow

Robert Remak Robert Remak Robert Remak

Zacharius Jansen

Common cell features Every living cell is surrounded by a membrane, separating the cell contents from everything else Cells contain genetic material – storing all instructions for cell activities Enzymes inside cells catalyze reactions Cells create their own energy Nothing smaller than a cell can survive on it’s own Understanding: According to the cell theory, living organisms are composed of cells Organisms consisting of only one cell carry out all functions of life in that cell

More Cell Theory Principles 4. Cells come from pre-existing cells 5. Energy flow within cells 6. DNA passed from cell to cell 7. All cells have the same basic chemical composition All cell theory principles lay the foundation for the study of life. Understanding: According to the cell theory, living organisms are composed of cells Organisms consisting of only one cell carry out all functions of life in that cell

Draw a simple animal cell (like you would in Year 6) Skills: Drawing cell structures as seen with the light microscope

Correct or annotate onto your diagram: Rules: Drawing Correct or annotate onto your diagram: Sharp pencil Draw single lines not sketches No shading Label each structure with a straight line Include a title Include the magnification or scale 1635-1703 Studied microorganisms Microscope ‘invented in 1590s’ still disputed Monks cells = cells Skills: Drawing cell structures as seen with the light microscope

Nutrition Irreversible increase in size Metabolism Ability to react to changes in the environment Growth Chemical reactions that happen inside the cell Response Obtain food to provide energy and materials needed for growth Excretion Keep conditions inside the organism within tolerable limits Homeostasis Produce offspring (sexually or asexually) Reproduction Get rid of waste products

Unicellular Organisms Draw and label into your books. How do they carry out the functions of life? Paramecium Chlorella Applications: Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism

Function of life Paramecium Chlorella Reproduction Divides transversely Metabolism Metabolic pathways happen in cytoplasm Homeostasis Manages water content using vacuole Growth Ingests food, grows and divides Response Cilia moves in waves = movement Nutrition Cilia sweep food into cell ‘mouth’ Photosynthesis in cytoplasm provides food Also ingests Excretion Expel water containing metabolic waste controlled by membrane Oxygen waste controlled by plasma membrane Also metabolic waste

Longitudinal division Transverse division

Light Microscope

Microscope’s ability to separate objects that are close together so more detail can be seen How clear an image is Resolution Low Magnification Good Resolution High Magnification Poor Resolution

Magnification Quantified by a calculated number Magnification is the process of enlarging something only in appearance, not in physical size. Quantified by a calculated number The ratio of the size of an image to the size of the object

What is the equation for the following? Magnification What is the equation for the following? Image size Actual size Magnification um x um Skills: Calculation of the magnification of drawings and the actual size of structures shown in drawings and micrographs

Measurements are expressed in micrometers (um) Magnification Either: Magnification = Apparent size of image Real size of image Or: Calculated by multiplying the viewing lens magnification by that of the objective lens E.g. you have a x10 eyepiece and x40 objective, the total magnification is x400 Measurements are expressed in micrometers (um) 1mm = 1000 um 1635-1703 Studied microorganisms Microscope ‘invented in 1590s’ still disputed Monks cells = cells Skills: Calculation of the magnification of drawings and the actual size of structures shown in drawings and micrographs

Magnification 30mm Green blobs always measure 0.01 mm Magnification = Apparent size of image Real size of image 30mm Green blobs always measure 0.01 mm Remember to convert into um first 1mm = 1000 um Skills: Calculation of the magnification of drawings and the actual size of structures shown in drawings and micrographs

Magnification 30mm Green blobs always measure 0.01 mm Now work your way through the calculation sheet 30mm 0.01 mm x 1000 = 10 um 30 mm x 1000 = 30,000 um Magnification = 30,000/10 Magnification = x3000

How are giant algae, fungi and striated muscle ‘misfits’? Nutrition: Obtain food to provide energy and materials needed for growth Metabolism: Chemical reactions inside the cell Growth: Irreversible increase in size Response: Ability to react to changes in the environment Excretion: Getting rid of the waste products in the environment Homeostasis: Keeping conditions inside the organism within tolerable limits Reproduction: Producing offspring either sexually or asexually Giant Algae: huge structure with only one nucleus (technically one cells) Striated muscle and hyphae: Large structures with no divisions – many nuclei Applications: Questioning the cell theory using atypical examples Nature of science: Looking for trends and discrepancies: although most organisms conform to cell theory, there are exceptions

Prescribed Practical Calculation of the magnification of drawings and the actual size of structures shown in drawings or micrographs Use your practical books to complete the investigation: Prepare onion cell slide View under microscope Draw onion cell (following drawing rules!) Look at other specimens if time Skills: Drawing cell structures as seen with the light microscope Use of a light microscope to investigate the structure of cells and tissues

Rules: Drawing Remember your rules Sharp pencil Draw single lines not sketches No shading Label each structure with a straight line Include a title 1635-1703 Studied microorganisms Microscope ‘invented in 1590s’ still disputed Monks cells = cells Skills: Drawing cell structures as seen with the light microscope

Smaller cells have a larger surface area compared to their volume. Surface Area: Volume Smaller cells have a larger surface area compared to their volume. Whereas larger cells have smaller surface area compared to their volume Understanding: Surface area to volume ratio is important in the limitation of size

Who would freeze first? Husky Chihuahua Understanding: Surface area to volume ratio is important in the limitation of size

Surface Area: Volume Larger cells have less surface area to bring in the materials that the cell needs, and to get rid of waste. Smaller cells have lots of surface area compared to their volume to do this. This limits the size of cells Reactions inside the cytoplasm would not work well otherwise Understanding: Surface area to volume ratio is important in the limitation of size

Cell Size Larger animals do not just have just a few large cells in them, they have many small cells. Understanding: Surface area to volume ratio is important in the limitation of size

How do we get from… This… (A simple animal cell) To this… (A human)

Cells Many multicellular organisms start as a single cell, made from sexual reproduction. This cell can reproduce at a rapid rate. But then we are just a pile of the same cells… Understanding: Multicellular organisms have properties that emerge from the interaction of their cellular components

The possibilities are endless…

Differentiation Every cell has - An entire set of genes Instructions to develop into any type of cell Cells just use the genes they need for their pathway Once on a pathway they are committed Understanding: Specialized tissues can develop by cell differentiation in multicellular organisms Differentiation involves the expression of some genes and not others in a cells genome

Differentiation Some cells have greatly reduced ability to reproduce after specializing Nerve cells & muscle cells However some can reproduce throughout their life Skin cells Understanding: Specialized tissues can develop by cell differentiation in multicellular organisms Differentiation involves the expression of some genes and not others in a cells genome

How does surface area to volume ratio limit the size of cells? Practical How does surface area to volume ratio limit the size of cells? Use your practical books to complete the investigation Understanding: Surface area to volume ratio is important in the limitation of size

Retain their ability to divide and differentiate into various cell types. What are stem cells Give examples of how stem cells can be used (Stargardt’s disease and leukemia) Describe the sources of stem cells (Embryonic, cord blood or adult) Described how stem cell research has progressed – how may local, cultural and religious traditions impact stem cell research in different countries Arguments for and against stem cell research Your own thoughts/opinions on the matter Stem Cells Nature of science: Ethical implication of research: research involving stem cells is growing in importance and raises ethical issues Understanding: The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development. It also makes stem cells suitable for therapeutic uses Applications: Use of stem cells to treat Stargardt’s disease and one other named condition Ethics of the therapeutic use of stem cells