cells

Cell theory, specialization and replacement There are 3 main principles to cell theory, (3) Can we look at a section of onion (Allium) and come up with the 3 main principles? Similar to Robert hook looking at a section of cork in 1665? Get 2 small sections of onion fibre, place them on clean slides, put a small drop of iodine one and a small drop of water on the other, put a cover slip on them and draw what you see under the microscope in a 5cm radius circle on your page.

There are 3 main principles to cell theory, 3 Can we look at a section of onion (Allium) and come up with the 3 main principles? Similar to Robert hook looking at a section of cork in 1665? 1. all organisms are composed of one or more cells 2. cells are the smallest units of life 3. all cells come from pre-existing cells

All cells are capable of carrying out the functions of life in order to produce a viable living unit. What are the 7 functions of life?

All cells are capable of carrying out the functions of life in order to produce a viable living unit. What are the 7 functions of life? metabolism growth reproduction response homeostasis nutrition exctrtion

https://www.youtube.com/watch?v=gN42ggEgO8g Single cell Paramecium The 7 functions

How big are they? Recall: 1 millimeter (mm) = 10-3 meter 1 micrometer (μm) = 10-6 meter  1 nanometer (nm) = 10-9 meter A molecule = 1 nm Thickness of cell membrane = 10 nm Viruses = 100 nm Bacteria = 1μm Organelles = up to 10 μm Eukaryotic cells = up to 100 μm

What is limiting their size? Why make so many cells? Why not just make less but bigger? Go outside

What is limiting their size? Why make so many cells? Why not just make less but bigger? Surface area to volume ratio Functions like rate of heat and waste production, resource consumption depend on the cell volume. A cell with more SA per unit Volume is able to move more materials in and out of the cell, for each unit of volume i.e the more SA you have to volume the more access you have to the outside of the cell, more efficient transfer

Sa to v https://www.youtube.com/watch?v=xuG4ZZ1GbzI

What is limiting their size? Eg. If the metabolic rate is greater than the rate of exchange of vital materials and wastes, the cell will eventually die

It takes around 3.72 × 10(13) cells to make up an adult human (how do they know what to be?)

It takes around 3.72 × 10(13) cells to make up an adult human Growth and complexity of an organism is accomplished through: Cell differentiation: the process where a cell changes from one cell type to another by expressing some of their genes and not others. Most commonly this is a less specialized type becoming a more specialized type. i.e muscle or nerve cells (nonrepro) or epithelial (skin cells) (repro) https://sangerinstitute.wordpress.com/2014/04/28/single-cell-genomics-thinking-small/

Home work/class work What is meant by the term emergent properties? Read Stem Cells page 10-11, make notes including the TOK section Answer exercise questions 1-4

Emergent properties

Emergent properties The function of each part of the cell is less than the overall function of the whole cell. Cells to tissue Tissue to organ Organ to organ systems Organ systems to multicellular or 

What is meant by emergent properties Multicellular organisms show emergent properties. For example: cells form tissues, tissues form organs, organs form organ systems and organ systems form multicellular organisms. The idea is that the whole is greater than the composition of its parts. For example your lungs are made of many cells. However, the cells by themselves aren’t much use. It is the many cells working as a unit that allow the lungs to perform their function.

How is the excretion of metabolic wastes from cells related to the concept of the surface area to volume ratio?

How is the excretion of metabolic wastes from cells related to the concept of the surface area to volume ratio? As the surface area to volume ratio decreases, there is relatively less membrane surface to allow the exchange of wastes between the inside and outside of the cell. The surface area increases much more slowly than the volume when the diameter of a cell increases. Thus, the relative amount of membrane available for exchange is less. If a cell grows too large, the result is cell death because of waste accumulation.

Explain how the function of life known as nutrition differs in paramecium and chlorella

Explain how the function of life known as nutrition differs in paramecium and chlorella Paramecia are heterotrophs and must gain their nutrition by ingestion of nutrients from their surroundings. Chlorella are autotrophs and are able to capture sunlight to carry out photosynthesis, thus they can make their own nutrition.

How does specialization in muscle and nerve cells affect their ability to reproduce?

How does specialization in muscle and nerve cells affect their ability to reproduce? These cells have very specific roles in the organism. Nerve cells conduct impulses, and to do this they require adaptations that allow depolarization and repolarization or rapid electrical changes within them. Muscle cells produce movement; they possess certain proteins and specific arrangements of these proteins to bring about movement. The result is that nerve and muscle cells carry out their functions without expending valuable time and energy in a reproductive stage.

What would prevent stem cells from other species being successful in humans?

What would prevent stem cells from other species being successful in humans? Even though stem cells are capable of great variation in what they differentiate into, they still have nuclear DNA as their controlling factor. The DNA of one animal is potentially quite different from the DNA of another.

Stem cell summary

Stem cell summary Stem cells retain the ability to divide and differentiate Cannot be distinguished by appearance but only behaviour In Plants: stem cells can be found in the meristematic tissue around the root and stem tips.

Specific stem cell use Besides general stem cells that differentiate to become any type if cell, there are ‘tissue specific stem cells’ . These cells are found in specific tissues and retain only the ability to form cells of that tissue Blood stem cells: replace damaged bone marrow cells in leukemia patients Stargardts disease (look at the stars). Affects ability to produce vitamin A resulting in vision loss. Currently using embroyonic stem cells

General stem cell us In the 1980’s the first stem cells were found in the embryonic cells of mice. They found that the cells retained the ability to differentiate to form any cell in an organism or even form a complete organism When stem cells divide and differentiate they also produce some daughter cells that stay as stem cells. (replacement source) Use of stem cells in injury or disease is know as therapeutic cloning Parkinsons and Alzheimers: replace lost or defective brain cells Diabetes: replace depleated pancreas cells

Prokaryotic v eukaryotic