IB Cell Biology Test

Simple diffusion and Facilitated Diffusion

Simple diffusion- involves the diffusion of molecules through the phospholipid bilayer, while facilitated diffusion involves the use of channel proteins embedded in the membrane. Both are passive movement (no external energy source needed) Hydrophobic molecules pass through by simple diffusion, and hydrophilic molecules pass through by facilitated diffusion. In both cases, the molecules are moving from regions of high concentrations to regions of low concentration.

Osmolarity

Solute concentration

Development of Cell Theory (Scientists)

*People who contributed to the discovery of cells Robert Hooke-1665-first described cells by looking at cork cells with a microscope which he constructed. Antonie van Leeuwenhoek- observed the first living cells Louis Pasteur- Found that living organisms can only come from other living organisms (curved neck and chicken broth experiment)

Cell Theory

-All living organisms are composed of cells -Cells are the smallest unit of structure and function (if you were to take apart a cell, the separate pieces could not function alone) -All cells come from pre-existing cells -Although most organisms conform to cell theory, there are exceptions

Multicellular Organisms

-Each type of cell in a multicellular organism has the same genes, but certain ones are turned on and off in the cells genome.(differentiation). Not all genes are on for each cell. (Can create specialized tissues)

Functions of Life

-Growth: irreversible increase in size -Reproduction: producing offspring either sexually or asexually -Response to stimulus (responding to environmental changes) -Homeostasis (ability to maintain internal conditions) -Nutrition (ability to somehow obtain nutrients) -Metabolism (ability to use and obtain energy) -Excretion (expelling waster matter)

Stem Cell Research

-Has depended upon the work of teams of scientists in many countries -They share their results to speed up the progress. -However, governments are influenced by local, cultural and religious beliefs, which impact scientists work and stem cell use for therapy.

How Louis Pasteur disproved spontaneous generation

-He put chicken broth in a curved neck flask and boiled it to kill the bacteria. -He left the flask on a table for a year and yet the broth remained free of micro-organisms -A year later he broke the neck (took off the curved neck) -Within a few days micro-organisms began to grow in the broth *No micro-organisms could grow with the curved neck because they could not travel all the way into the flask. *Proves that living things cannot come from non-living things

Prokaryotes

-No nucleus -No organelles -Carry out all functions of life including metabolism, response, homeostasis, growth, reproduction and nutrition.

Eukaryotes

-Organelles -Have a nucleus

Atypical examples of cell theory

-aseptate fungal hyphae -Giant algae -striated muscle * all are long and multinucleated

Be able to draw prokaryotic and Eukaryotic cells

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Be able to draw the fluid mosaic model

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Conversion of micrometers to millimeters

1000 micrometers=1 mm 1000 nanometers= 1 micrometer

Actual size

Actual size=drawing size/magnification

Multipotent

Adult stem cells. Can become few types of cells.

Membrane proteins

Are diverse in terms of structure, position in the membrane and function

Identification on Electron Micrographs

Be able to identify the parts of a cell on an electron micrograph

Animal Cell membranes

Cholesterol is a component in animal cell membranes. It reduces membrane fluidity and permeability to some solutes.

Membrane protein functions

Enzymes-used in cell surface reactions Channels- passive transport across the membrane Pumps- active transport across the membrane receptor proteins-hormone binding and recognition adhestion proteins-binding cells together neurotransmitter receptors-communication between cells. Integral proteins-sites for chemical reactions peripheral proteins-act as receptors and recognize other cells

Ethical Implications of Stem Cell Research

Ethical issues are raised due to the destruction of human embryos to harvest stem cells. Depending on the culture/beliefs of a country, the acceptability of stem cell research varies. Also harvesting adult (non-embryonic) stem cells can have ethical implications. Ex. Having a kid in order to save another child with their stem cells. -Taking stem cells from umbilical cord blood of newborns is not unethical because the stem cells harvested can be very useful, and would have been removed regardless.

Exocytosis and Endocytosis

Exocytosis-moving large molecules out of the cell Endocytosis- moving large molecules into the cell.

Electron Microscopes

Have a much higher resolution than light microscopes. This helps us to see structures better, although living things cannot be viewed under electron microscopes.

Hypertonic, hypotonic and isotonic

Hypertonic=more solute, less water Hypotonic=less solute, more water isotonic=equal parts solute and water

Magnification

Magnification=drawing size/actual size

Microscope Invention

Microscopes were invented simultaneously in different parts of the world, during a time when communication was limited, so there is no way of knowing who was the first creator. Modern communications have allowed for better collaboration on scientific experiments.

Emergent Properties

Multicellular organisms have emergent properties. Emergent Properties are properties which emerge from the interaction of their cellular components. Cell --> tissue --> organ --> organ system --> multicellular organism

Eukaryotic Cell Functions

Nucleus-contains chromosomes and hereditary material. Controls the cell. Nucleolus-Where ribsomes are made Plasma membrane- SAME AS ABOVE Rough Endoplasmic reticulum-site of protein synthesis Smooth Endoplasmic reticulum-carries out metabolic reactions Golgi apparatus- stores and packages proteins Mitochondria-organelles that carry out respiration lysosome-contains digestive enzymes for breaking down nutrient molecules and dead cell parts for recycling. Centriole- produces spindle fibers which are used to pull apart chromosomes in mitosis and meiosis.

How do Chlorella carry out the functions of life?

Nutrition-Consumed food is stored in food vacuoles Growth-consumes and digests biomass, gets larger until reproduction Metabolism-enzymes needed to make glucose. Activity occurs in cytoplasm Excretion-diffusion of waste products through membrane Response-response towards light (phototrophism) Homeostasis-have a cell wall which protects them from too much water build up. Reproduction-cells divide by mitosis.Supported by nucleus being able to divide (asexual).

Unicellular Organisms

Organisms consisting of only one type of cell carry out all the functions of life in each cell

Osmosis and Active Transport

Osmosis is the passive movement of water molecules, across a semi-permeable membrane, from a region of low concentration to a region of high concentration. Active transport-involves the movement of substances through the membrane using energy from ATP. Moves substances against the concentration gradient (from low to high). It uses protein pumps which are embedded in the membrane to move substances in and out.

Use of Stem cells to treat Osteoperosis

Osteoporosis is a disease which causes bones to become weak and easily breakable. The disease causes people to lose bone density. -This can be treated with MSC's (mesenchymal stem cells). These are stem cells which come from bone marrow and umbilical cord blood tissues. The treatment is drugs which bring the stem cells to areas of the body affected by osteoporosis, making these areas increase their speed of healing.

How do Paramecium carry out the functions of life?

Paramecium: Nutrition-Gains nutrition through movement (cilia propels paramecium so it can find food) Metabolism-Metabolic pathways in the cytoplasm Growth-After consuming and obtaining biomass from food, paramecium grow until they divide Excretion-Anal pore. Plasma membrane controls exit/entry of substances Response-Cilia moves paramecium in response to changes in environment Homeostasis-Contractile vacuole fills with water and expels through plasma membrane to manage water content Reproduction-paramecium splits into two by copying its genetic information and giving one set of genes to each daughter cell.

Amphipathic

Phospholipids are amphipathic which means that they have both hydrophobic and hydrophilic regions. This allows the phospholipid bilayer to be formed.

Prokaryotic Cell functions

Pili- helps bacteria adhere to each other for exchange of genetic material Flagella-Helps bacteria move around by the use of motor proteins which spin the flagellum Cell Wall- maintains support and structure of the cell Plasma Membrane-Outer limit of the cell, controls exit and entry of nutrients and waste. Contains integral and peripheral proteins. Cytoplasm-contains many enzymes and solutes needed for metabolic reactions within the cell, as well as dissolving minerals, ions, nutrients and waste Ribosomes- site of protein synthesis Nucleoid- Region containing naked DNA, which stores genetic information that will be passed on to daughter cells. Chloroplast-receive energy from sun light and use it to perform photosynthesis, producing food for the plant.

Prokaryotic vs. Eukaryotic

Prokaryotes- naked DNA (floats free around cytoplasm), DNA located in cytoplasm, no mitochondria, 70S ribosomes, no internal membrane bound organelles, organisms reproduced by binary fission (replicate DNA and divide it into two), no nucleus Eukaryotes-DNA associated with histone proteins, DNA enclosed in nuclear envelope, has mitochondria, 80S ribosome (slightly bigger), has internal membranes that compartmentalize their functions, organism reproduces by production of gametes during meiosis which then come together to make a new organism, has nucleus

How vesicles transport materials

Ribosomes synthesize proteins, transport them to rough endoplasmic reticulum to be modified, then vesicles carry it to golgi apparatus to be more modified, then vesicles carry it to plasma membrane. Vesicles fuse into membrane, protein is pushed out of cell through exocytosis.

Pluripotent

Source is embryo. They can become most kinds of cells

Totipotent

Source is zygote. Can become any kind of cell

Use of Stem Cells to treat Stargardts disease

Stargardts disease is the depletion of the RPE layer in the eye, which causes a loss of nourishment for photo receptors. -This can be treated with pluripotent embryonic stem cells, which are injected into the retina, which repairs the RPE layer.

Stem Cells

Stem Cells retain the ability to divide and differentiate along different pathways. This is necessary for embyronic development and makes stem cells suitable for therapeutic treatments.

Davson Danielli Model-Led to singer nicolson model

The Davson Danielli model came about in 1935 to try to explain the surface tension that was seen through the electron microscope. However, in 1972 the singer nicolson model added transmembrane proteins and stated that the phospholipid bilayer was enough to explain the surface tension. This model falsified the previous model because the previous one did not the hydrophobic and hydrophilic nature of membrane proteins.