INTRODUCTION TO CELLS Topic 1.1 IB Biology Miss Werba

ULTRASTRUCTURE OF CELLS TOPIC 1 – CELL BIOLOGY 1.1 INTRODUCTION TO CELLS 1.2 ULTRASTRUCTURE OF CELLS 1.3 MEMBRANE STRUCTURE 1.4 MEMBRANE TRANSPORT 1.5 THE ORIGIN OF CELLS 1.6 CELL DIVISION J WERBA – IB BIOLOGY 2

THINGS TO COVER U.1 U.2 U.3 U.4 U.5 U.6 U.7 A.1 A.2 A.3 Statement Guidance U.1 Cell theory U.2 Characteristics of living things Name and explain nutrition, metabolism, growth, response, excretion, homeostasis and reproduction. U.3 SA:Vol ratio and cell size U.4 Emergent properties in multicellular organisms U.5 Cell differentiation U.6 Selective gene expression U.7 Stem cells A.1 Questioning cell theory using atypical examples - eg. Striated muscle, giant algae, aseptate fungal hyphae A.2 Investigating unicellular organisms - eg. Paramecium and Chlorella A.3 Stem cell therapy - eg. Stargardt’s disease, burn treatment, leukaemia J WERBA – IB BIOLOGY 3

THINGS TO COVER A.4 S.1 IM.1 NOS 3.1 4.5 Statement Guidance Ethics of stem cell therapy S.1 Practical 1 - Using a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculations of magnification of images and actual size of cells. Use scale bars to indicate actual size in drawings. IM.1 Stem cell research collaboration NOS 3.1 Looking for trends & discrepancies 4.5 Ethical implications of research J WERBA – IB BIOLOGY 4

CELL THEORY

CELL THEORY All living organisms are made of cells U.1 CELL THEORY All living organisms are made of cells Cells are the smallest units of life All cells come from pre-existing cells J WERBA – IB BIOLOGY 6

U.1 U.5 U.7 CELL THEORY J WERBA – IB BIOLOGY Source: fastbleep.com 7

U.1 U.5 U.7 CELL THEORY Evidence: With the invention of microscopes (Janssen) scientists could see cells (Hooke, Leeuwenhoek) Louis Pasteur demonstrated that cells couldn’t grow in sterile conditions (disproved abiogenesis) Organelles (structures within cells) and viruses cannot carry out all of the characteristics of other living things Cell division is visible under a microscope J WERBA – IB BIOLOGY 8

NOS.3.1 CELL THEORY J WERBA – IB BIOLOGY 9

Looking for trends and discrepancies NOS.3.1 CELL THEORY Looking for trends and discrepancies Although most organisms conform to cell theory, there are exceptions. J WERBA – IB BIOLOGY 10

CELL THEORY Exceptions to the cell theory: Striated muscle Erythrocytes (red blood cells) Giant algae Aseptate fungal hyphae J WERBA – IB BIOLOGY 11

CELL THEORY Striated muscle: Skeletal muscle is composed of muscle fibres that are larger than a single cell. The muscle fibres are multinucleated, containing several hundred nuclei. J WERBA – IB BIOLOGY 12

CELL THEORY Erythrocytes (red blood cells): U.1 A.1 CELL THEORY Erythrocytes (red blood cells): Once they have matured, they lose their nucleus. This prevents them from carrying out many cell functions from this point of their life cycle. J WERBA – IB BIOLOGY 13

CELL THEORY Giant algae: U.1 A.1 CELL THEORY Giant algae: The single cells of some large algae are undifferentiated, remaining in a “stem cell”-like state. They form chains so that they can form larger structures. J WERBA – IB BIOLOGY 14

CELL THEORY Aseptate fungal hyphae: Hyphae are long threads. In aseptate or nonseptate hyphae, these threads have multiple nuclei, but the cells are not separated by cell walls. J WERBA – IB BIOLOGY 15

FUNCTIONS OF LIFE

FUNCTIONS OF LIFE MRS C GREN Unicellular organisms carry out all the functions of life: Movement Respiration Sensitivity or stimulus response Composed of cells Growth Reproduction Excretion Nutrition MRS C GREN J WERBA – IB BIOLOGY 17

FUNCTIONS OF LIFE MR H GREN Unicellular organisms carry out all the functions of life: Metabolism Response Homeostasis Growth Reproduction Excretion Nutrition MR H GREN J WERBA – IB BIOLOGY 18

U.2 FUNCTIONS OF LIFE Unicellular organisms carry out all the functions of life: Metabolism – carry out reactions to generate organic molecules Response – monitor stimuli and are capable of reacting Homeostasis – maintain internal environment within narrow limits Growth Reproduction – can produce viable offspring Excretion – waste products of metabolism are disposed of Nutrition – obtains food either through photosynthesis or ingestion J WERBA – IB BIOLOGY 19

FUNCTIONS OF LIFE Examples to learn: Paramecium Chlorella U.2 A.2 J WERBA – IB BIOLOGY 20

FUNCTIONS OF LIFE Paramecium: Unicellular organisms in the kingdom of Protista Small but visible with the naked eye (~200-300μm) They are ciliates, meaning that they are surrounded by tiny hair-like structures Cilia are used to waft food particles towards their oral groove Use contractile vacuoles to respond to changing salinity in their environment J WERBA – IB BIOLOGY 21

FUNCTIONS OF LIFE Chlorella: Unicellular plant Spherical in shape, ~2-10 μm in diameter Come together in large numbers to form algae. Contains chloroplasts, allowing it to photosynthesise. Photosynthesis provides the energy and minerals to multiply rapidly. It reproduces asexually, producing 4 organisms each time. J WERBA – IB BIOLOGY 22

Cell size

CELL SIZE Use your logic to put these in the correct order! Bacteria Cell membrane thickness Cells Molecules Organelles Virus J WERBA – IB BIOLOGY 24

CELL SIZE Relative sizes U.3 S.1 CELL SIZE Relative sizes Cells (<100 μm) - generally plant cells are larger than animal cells Organelles (<10 μm) Bacteria (1μm) Virus (100nm) Cell membrane thickness (10nm) Molecules (1nm) J WERBA – IB BIOLOGY 25

CELL SIZE Relative sizes 2.1.4 CELL SIZE Relative sizes Watch this! http://learn.genetics.utah.edu/content/cells/scale/ J WERBA – IB BIOLOGY 26

CELL SIZE Magnification 2.1.5 CELL SIZE Magnification Measurements need to be in the same units! 1mm =1000μm J WERBA – IB BIOLOGY 27

U.2 A.2 CELL SIZE Paramecium: Use the MIA formula triangle to calculate the magnification of the paramecium shown in this image: 9.4cm J WERBA – IB BIOLOGY 28

U.2 A.2 CELL SIZE Paramecium: Use the MIA formula triangle to calculate the magnification of the paramecium shown in this image: M = ? I = 94mm A = 162μm = 0.162mm M = I ÷ A = 580x J WERBA – IB BIOLOGY 29

U.2 A.2 CELL SIZE Chlorella: Use the MIA formula triangle to calculate the magnification of the Chlorella shown in this image: 1.0cm J WERBA – IB BIOLOGY 30

U.2 A.2 CELL SIZE Chlorella: Use the MIA formula triangle to calculate the magnification of the chlorella shown in this image: M = ? I = 10mm A = 4μm = 0.004mm M = I ÷ A = 2500x J WERBA – IB BIOLOGY 31

CELL SIZE Chlorella: Bonus Q: Could this organism have been viewed under a light microscope? Answer: No. Maximum resolution of light microscopes is usually 1000- 2000x. It would have needed to have been an electron microscope. J WERBA – IB BIOLOGY 32

CELL SIZE Erythrocyte: U.2 A.2 CELL SIZE Erythrocyte: Use the scale bar provided to determine the size of this red blood cell. Then calculate the magnification of this image. HINT: use equivalent fractions first, and then the formula triangle 6.6cm 1.0cm 1.0μm J WERBA – IB BIOLOGY 33

CELL SIZE M = ? I = 66000μm, A = 6.6μm M = I ÷ A = 10000x Erythrocyte: U.2 A.2 CELL SIZE Erythrocyte: M = ? I = 66000μm, A = 6.6μm M = I ÷ A = 10000x 6.6cm 1.0μm J WERBA – IB BIOLOGY 34

CELL SIZE Magnification – sample questions A red blood cell is 8μm in diameter. If drawn 100 times larger than its actual size, what diameter will the drawing be in mm? If a mitochondrion has a length of 5µm and a student’s drawing of the mitochondrion is 10mm, what is the magnification of the drawing? If a Sequoia sempervirens tree is 100m tall and a drawing of it is 100mm tall, what is the magnification of the drawing? J WERBA – IB BIOLOGY 35

CELL SIZE Magnification – sample answers U.2 A.2 CELL SIZE Magnification – sample answers 0.8 mm ×2000 ×0.001 J WERBA – IB BIOLOGY 36

CELL SIZE Limitations Cells cannot grow indefinitely. U.3 CELL SIZE Limitations Cells cannot grow indefinitely. They reach a maximum size and then they may divide. If a cell becomes too large, it would develop problems. These problems may include….? J WERBA – IB BIOLOGY 37

U.3 CELL SIZE Limitations The rate of metabolism varies with a cell’s volume The rate of molecular exchange varies with a cell’s surface area When a cell grows, volume grows quicker than surface area and the cell must divide or die Many cells contains structures to increase the ratio of their surface area to their volume (SA:Vol ratio) eg. microvilli J WERBA – IB BIOLOGY 38

BECOMING MULTICELLULAR

BECOMING MULTICELLULAR Unicellular organisms are in the Kingdom Protoctista (Protists) They evolved 3-4 billion years ago. They remained the dominant life form until 600 million years ago. Unicellular organisms are able to carry out all of the typical cellular processes within their single cell! J WERBA – IB BIOLOGY 40

BECOMING MULTICELLULAR Kingdom Plantae, Animalia and Fungi are all composed of eukaryotic cells They are multicellular organisms – made up of many cells together. These cells specialise (differentiate) so that all energy in the cell is not taken up by performing all cellular functions. These cells group into tissues, organs and systems making us far more capable than a single bacterial cell. J WERBA – IB BIOLOGY 41

CELL DIFFERENTIATION Differentiation: U.4 U.5 U.6 CELL DIFFERENTIATION Differentiation: process by which newly-formed cells specialize as they mature Cells in multicellular organisms share the same genetic info (cf. cell division, reproduction, formation of blastocyst) What is different between cells is gene expression Chemical signals lead to differential gene expression and thus specialization of cells J WERBA – IB BIOLOGY 42

U.4 U.5 U.6 CELL DIFFERENTIATION J WERBA – IB BIOLOGY 43

U.4 U.5 U.6 EMERGENT PROPERTIES The combination of different cell types can give rise to emergent properties in multicellular organisms Means that the whole organism is greater than the sum of its parts: because of the varied gene expression because of the complex interactions between cells J WERBA – IB BIOLOGY 44

STEM CELLS

STEM CELLS Stem cells retain the capacity to divide U.7 STEM CELLS Stem cells retain the capacity to divide They are undifferentiated They have the ability to differentiate along different pathways J WERBA – IB BIOLOGY 46

THERAPEUTIC USE OF STEM CELLS Stem cells have the potential for tissue repair and can theoretically treat a variety of degenerative conditions In 1968, doctors performed the first successful bone marrow transplant. Bone marrow contains somatic stem cells. It is transplanted routinely to treat a variety of blood and bone marrow diseases, blood cancers, and immune disorders. More recently, peripheral blood stem cells (from the blood stream) and umbilical cord stem cells have been used to treat some of the same blood-based diseases. J WERBA – IB BIOLOGY 47

THERAPEUTIC USE OF STEM CELLS eg. Stargardt’s disease a genetic eye disorder it is a type of macular degeneration affecting the retina at the back of the eye causes progressive loss of central vision in both eyes Macula J WERBA – IB BIOLOGY 48

THERAPEUTIC USE OF STEM CELLS eg. Stargardt’s disease recent stem cell research has involved using retinal pigment epithelium (RPE) can use embryonic stem cells to generate RPE first human therapeutic trials were conducted in 2012, improving vision in the patients receiving the treatment Australian researchers are now focusing on the use of IPSCs for the treatment of similar disorders J WERBA – IB BIOLOGY 49

THERAPEUTIC USE OF STEM CELLS eg. Stargardt’s disease Click to read the related article J WERBA – IB BIOLOGY 50

THERAPEUTIC USE OF STEM CELLS eg. Parkinson’s Disease, MS, strokes all involve loss of neurons or other cells in the nervous system could potentially use stem cells to replace them J WERBA – IB BIOLOGY 51

THERAPEUTIC USE OF STEM CELLS eg. Leukaemia a cancer of white blood cells or leukocytes chemotherapy is normally used to kill the abnormal cells; however, a bone marrow transplant is needed if it doesn't work. The patient's existing bone marrow and abnormal leukocytes are first killed using chemotherapy and radiation. A sample of donor bone marrow containing healthy, matched stem cells is introduced into the patient's bloodstream. If the transplant is successful, the stem cells will migrate into the patient's bone marrow and begin producing new, healthy leukocytes to replace the abnormal cells. J WERBA – IB BIOLOGY 52

THERAPEUTIC USE OF STEM CELLS eg. Burn treatment Therapeutic cloning can be used to regenerate skin cells in burns victims Use the nucleus from the required cell to generate new cells with the correct genetic information – eg. skin cells See Topic 3.5 for detailed process J WERBA – IB BIOLOGY 53

STEM CELLS J WERBA – IB BIOLOGY 54

STEM CELLS Stem cell research has depended on the work of teams of scientists in many countries who share results thereby speeding up the rate of progress. However, national governments are influenced by local, cultural and religious traditions that impact on the work of scientists and the use of stem cells in therapy. J WERBA – IB BIOLOGY 55

U.7 A.4 ETHICS OF STEM CELL USE There is enormous potential in the therapeutic use of these cells. The source of these cells is no longer limited to embryos, reducing some of the associated ethical concerns – eg. adult SC, umbilical cord SC, IPSC. Some religious groups support SC research if embryos are not involved. Some groups still oppose SC research, regardless of where the SC are sourced from, as it goes against the laws of nature. J WERBA – IB BIOLOGY 56

INTRODUCTION TO CELLS Q8. Which functions of life are carried out by all unicellular organisms? Response, homeostasis, growth and photosynthesis Metabolism, ventilation, reproduction and nutrition Response, homeostasis, metabolism and growth Reproduction, ventilation, response and nutrition J WERBA – IB BIOLOGY 59

INTRODUCTION TO CELLS Q9. A botanist measures a leaf and finds it is 24 cm long and 8 cm wide. His drawing of the leaf is 4 cm wide. Which was the magnification and length of his drawing, assuming that the proportions of the drawing were correct? Scale Length / cm A. x2 48 B. 12 C. x0.5 D. J WERBA – IB BIOLOGY 60

INTRODUCTION TO CELLS Q10. a. Outline the cell theory [2] b. Calculate the magnification of the electron micrograph. [1] J WERBA – IB BIOLOGY 61