Studied by 3 peopleState three points of cell theory (3)
living organisms are made of cells
cells are the smallest units of life
cells come from pre-existing cells
Outline Robert Hooke’s contribution to cell theory
He developed a microscope, observed samples of cork, named ‘cells’
Outline Antoni Van Leewuwhenok’s contribution to cell theory
developed a microscope, observed many microorganisms
Outline Louise Pasteur’s contribution to cell theory
Louis Pastuer 1862 who disproved sponteanous generation- all cells must come from pre existing cells.
Outline Robert Remak’s contribution to cell theory
Robert Remak 1855 discovered cell division by making cell membranes visible under a microscope and observing cells during cell division.
Discuss the work of scientists and how they contribute to cell theory.
Hooke Leeuwhenhoek's microscopes allowed observation of celluary structure- > living things are made of cells.
Microscope allowed observation of cell's carrying out life processes, showing they were the smallest unit of life.
Remak was able to observe a single cell during cell division dividing to form two indicical cells, showing that new cells come from pre-exisiting cells.
Microscopes allowed observation of organelles, which showed they did not carry out all the life processes, which meant cells were the smallest unit of life.
Name Three Exceptions to Cell Theory
Skeletal muscle fibres- large with many nuclei, no need for a microscope.
Fungal Hyphae- often not divided up into individual cells, instead one very large cell with many nuclei.
Vitreous humour of eye in trees- large extracelluar material that support them and required for their function of life.
Explain Function of Life (Nutrition) in Paramecium
Feed on organisms such as algae/ bacteria (heterotroph). Sweeps it into oral cavity w cilia. Food surrounded by vacuole (phagocyotosis) that contains enzymes to digest it.
Explain Function of Life (Metabolism) in Paramecium
Food contained in vacuoles is broken down by enzymes in those vacuoles and absorbed into the cytoplasm where the nutrients from it are used by the cell for energy and replace cell parts.
Explain Function of Life (Metabolism) in
Chlamydomonas
Produces enzymes which catalyze many different chem reactions in the cytoplasm.
Explain Function of Life (Growth) in
Paramecium
The paramecium divides into much smaller paramecium, so must increase in size. Nutrients are also used to replace/grow cell parts.
Explain Function of Life (Growth) in
Chlamydomonas
Increase in size and dry mass due to photosynthesis and absorption of minerals.
Def: Nutrition
Obtaining nutrients for energy/materials needed for growth.
Def: Metabolism
Chemical reactions inside the cell where the compounds are broken down, synthesized and converted from one form to another.
Def: Growth
Irreversible increase in size (or
increase in size and dry mass due to photosynthesis and absorption of minerals)
Def: Response
reacting to external stimuli
Explain Function of Life (Response) in
Paramecium
Can perceive/respond to movement, move towards moving prey in it's environment. Can sense/respond to chemicals dissolved.
Explain Function of Life (Response) in
Chlamydomonas
Reacts to stimuli, eye spot where it senses light.
Explain Function of Life (Homeostasis) in
Chlamydomonas
Keeps internal conditions within limits, expels excess water using contractile vacuoles
Explain Function of Life (Homeostasis) in
Paramecium
Undigested wastes are removed through the anal pore. The contractile vacuole pumps out liquid waste, excess water from the cell. They also move towards and away from chemicals in their environment.
Explain Function of Life (Paramecium) in
Paramecium
Usually reproduce asexually, where one paramecium grows and replicates its genetic information, then divides equally to form two new paramecium. Can also reproduce sexually through conjugation.
Explain Function of Life (Excretion) in
Paramecium
Their contractile vacuole pumps liquid waste and excess waste from the cell.
Def: Homeostasis
Maintaining a constant internal environment.
Def: Reproduction
Producing offspring either sexually or asexually
Def: Excretion
Removing the toxic waste products of metabolism.
Explain Function of Life (Reproduction) in
Chlamydomonas
Usually reproduces asexually, where one Chlamydomonas grown and forms two new Chlamydomonas. can reproduce sexually using meiosis and gametes.
Explain Function of Life (Excretion) in
Chlamydomonas
Expels waste produces of metabolism- oxygen from photosynthesis diffuses out of cell.
State the effect of surface area to volume ratio of a cell as it increases in size.
Cell size increases, sa: v ratio decreases
Explain the importance of sa: v ratio as a limitng factor of cell size. (4)
-rate of demand for raw materials and production of waste product is a function of volume.
-ability to exchange waste products and raw materials as a function of surface area
-growth in size, volume increases faster than surface area
-as cell size increases, sa: v ratio decreases
- larger cell, less of the cell volume/cytoplasm has access to the cell membrane for exchange
- rate of diffusion remains the same
Outline what is meant be emergent properties
properties seen in multicellular organisms that arise from the interactions between cellular components of the organism
Def: Differentiation
The development of unspecialized cells in different ways to perform different functions
Describe how differentiation is controlled
The cell expresses some of it's genes in it's genome but not others:
only genes which are expressed will influence development of that cell and therefore define structure/function.
the gene is switched on by chem signals, only the information in it is used to make a product, such as a protein.
specialized cells only use the genes that they need to follow their particular pathway of development, all others remain switched off.
List two examples of differentiated cells from the human body.
red blood cells, white blood cells, nerve cells, muscle cells and skin cells.
Why are stem cells special?
Unspecialized, retain capacity to divide, can differentiate along different pathways.
What are the two main types of stem cells?
Adult and embryonic.
How can stem cells treat severe burns? (5)
Emrboynic stem cells can be triggered to divide and differentiate to form nueral cells. Nueral cells are transplated into paralyzed mice. They divide and eventually attach to damaged tissue, allowing mice to regain some movement. Skin cells placed on artificial scaffold and grow to form a layer of skin.
Grafted onto mice and further develop into human skin.
Arguments against Stem Cell Therapy (3)
Harvesting of Stem Cells from embryos require it to be destroyed when it could've developed into a person if left alive= abortion/murder. Lack of knowledge about long-term side effects, including features that stem cells can divide uncontrollably and result in tumors. Destroying one life (embryos) to save another is not justifiable.
Arguments for Stem Cell Therapy (3)
Emrbroys are balls of cells that were created in a lab and not developed any human features and cannot feel pain.
Never been implanted, therefore never had a chance of life and better served to treat disease and save lives. Potential to save lives and reduce suffering > potential and unproven negative long-term side effects.
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