1. Cell Theory
1.1. classical cell theory
1.1.1. all living organisms are made of cells
1.1.1.1. unicellular and multicellular organisms
1.1.1.1.1. colonies of unicellular organisms
1.1.1.1.2. multicellular organisms
1.1.1.2. viruses depend on a host cell for replication
1.1.1.3. in 1663 Robert Hooke discovers cells
1.1.1.3.1. in a piece of cork, which he examined under his primitive microscope
1.1.1.4. in 1674 Anton von Leeuwenhoek discovers unicellural organisms ("animalcules")
1.1.1.4.1. father of microbiology
1.1.1.4.2. while examining pond water
1.1.1.5. in 1831 Robert Brown discoveres the nucleus in orchids for the first time
1.1.1.5.1. nucleus is Latin for little nut
1.1.1.6. in 1838 Matthias Schleiden realizes all plants are made of cells
1.1.1.6.1. they worked together and cofounded the cell theory
1.1.1.7. in 1839 Theodore Schwann realizes all animals are made of cells
1.1.2. the cell is the smallest unit of life
1.1.2.1. structural and functional units
1.1.2.2. cells vary considerably in size and shape
1.1.2.3. every living cell is surrounded by a membrane
1.1.2.3.1. the membrane seperates the cell contents from its external environment
1.1.3. cells only arise from pre-existing cells that have multiplied
1.1.3.1. in 1855 Rudolf Virchow proposed that all cells come from other cells (Omnis Cellula e Cellula)
1.1.3.2. in 1859 Louis Pasteur disproved the theory of spontaneous generation
1.1.3.2.1. an experiment with meat broth in a "goose-like" flask
1.2. modern cell theory
1.2.1. DNA is passed between cells during cell division
1.2.1.1. cells contain genetic material
1.2.1.1.1. it stores all of the instructions needed for the cell's activities
1.2.2. the cells of all organisms within a similar species are mostly the same, both structually and chemically
1.2.3. energy flow occurs within cells
1.2.3.1. cells have their own energy release system that powers all of the cell's activities
1.2.3.2. many of these activities are chemical reactions, catalyzed by enzymes produced inside the cell
1.3. caveats to the cell theory
1.3.1. striated muscle fibres
1.3.1.1. muscle cells fuse together to form fibres
1.3.1.1.1. each fibre has multiple nuclei (from hundreds to thousands nuclei)
1.3.2. giant algae
1.3.2.1. unicellular organisms that are very large in size (~7 cm)
1.3.2.1.1. cells may not always be microscopic
1.3.2.1.2. acetabularia can grow up to 10 cm
1.3.3. hyphae of fungi
1.3.3.1. they are separated into cells by septa (internal walls) - septate hyphae
1.3.3.1.1. some hyphae lack separation (aseptate) - aseptate hyphae
1.4. functions of life
1.4.1. organisms consisting of only one cell carry out all the life functions in that single cell
1.4.1.1. metabolism
1.4.1.1.1. all chemical reactions including cell respiration to release energy
1.4.1.2. reproduction
1.4.1.2.1. sexual or asexual
1.4.1.3. sensitivity
1.4.1.3.1. response to external stimuli
1.4.1.4. homeostasis
1.4.1.4.1. stable internal environment
1.4.1.4.2. the maintenance and regulation of internal cell conditions
1.4.1.5. excretion
1.4.1.5.1. removal of metabolic waste
1.4.1.6. nutrition
1.4.1.6.1. energy and materials for growth
1.4.1.7. growth
1.4.1.7.1. living things can grow/change
1.4.2. the structure of unicellular organisms is more complex than most cells in multicellural organisms
1.4.3. in Paramecium
1.4.3.1. metabolism: cytoplasm
1.4.3.2. reproduction: nucleus, asexual via mitosis
1.4.3.3. sensitivity: can travel towards food particle
1.4.3.4. homeostasis: contractile vacuole, regulates gas and water levels
1.4.3.5. excretion: plasma membrane
1.4.3.6. nutrition: food vacuoles, oral groove, cilia
1.4.3.7. growth: prior to cell division, move via cilia
1.5. SA to volume ratio
1.5.1. cells need to produce energy to survive and this requires material exchange
1.5.1.1. matebolic rate is a function of its volume
1.5.1.2. rate of material exchange is a function of its surface area
1.5.1.3. cells specialized for material exchange will increase their SA to ptimise material transfer
1.5.1.3.1. specialized structures: e.g. folds and microvilli
1.5.2. as a cell grows, its volume increases faster than its surface area
1.5.2.1. this leads to a decreased SA:Vol ratio
1.5.2.2. if material exchange is insufficient to maintain metabolism, the cell will die
1.5.2.2.1. hence cells must stay small by dividing
1.5.3. most of the metabolic reactions take place in cytoplasm
1.5.4. substances are carried into and out through the plasma membrane
1.6. cell differentation
1.6.1. cell differentation in multicellular organisms
1.6.1.1. different cells - different functions
1.6.1.2. tissue
1.6.1.2.1. a group of cells specialized in the same way and performing the same function
1.6.1.3. cells and tissues can carry out their roles more efficiently - ideal structure, specialized enzymes
1.6.1.4. there are 240 different cell types in humans
1.6.2. gene expression
1.6.2.1. all cells have the same set of genes
1.6.2.1.1. the activation of different genes will cause cells to differentiate from one another
1.6.2.2. there are about 25,000 genes in a human cell
1.6.3. differentiation is the process by which new cells become more specialized and distinct from each other
1.7. stem cells
1.7.1. unspecialized cells with two key qualities
1.7.1.1. self renewal
1.7.1.1.1. can divide and replicate
1.7.1.2. potency
1.7.1.2.1. capable of differentiation
1.7.2. they can be defined by their level of potency
1.7.2.1. totipotent cells
1.7.2.1.1. can form new organisms
1.7.2.2. pluripotent cells
1.7.2.2.1. can form most cell types
1.7.2.3. multipotent cells
1.7.2.3.1. form limited cell types
1.7.2.4. unipotent cells
1.7.2.4.1. cannot differentiate
1.7.3. the body's raw materials
1.7.3.1. cells from which all other cells with specialized functions are generated
1.7.3.1.1. they have the potential to repair, restore, replace, and regenerate cells
1.7.3.2. in bone marrow, skin, liver
1.8. stem cell therapy
1.8.1. stem cells are used to replace damaged or diseased tissue with healthy tissue
1.8.2. examples of therapeutic uses
1.8.2.1. Stargardt's disease
1.8.2.1.1. replacing dead retinal cells to treat macula dystrophy
1.8.2.2. grafting new skin cells in burns victims
1.8.2.3. replacing nerve cells in spinal injuries
1.8.2.4. bone marrow transplants for patients on chemotherapy
1.8.2.5. healing diseases such as type I diabetes
1.8.2.6. growing whole replacement organs
1.8.3. embryonic stem cells
1.8.3.1. embryos can be deliberately created in the lab (4-16 cells)
1.8.3.2. almost unlimited growth potential
1.8.3.3. can differentiate into any type of body cell
1.8.3.4. more risk of becoming tumour cells than with adult cells
1.8.3.5. less chance of genetic demage due to the accumulation of mutations
1.8.3.6. likely genetically different than the patient
1.8.3.7. it kills the embryo
1.8.4. cord blood stem cells
1.8.4.1. stem cells from blood from the umbilicalcord of a new-born baby
1.8.4.1.1. can be frozen and stored for possible use later in the baby's life
1.8.4.1.2. easily obtained and stored
1.8.4.1.3. fully compatible, no rejection problems
1.8.5. adult stem cells
1.8.5.1. difficult to obtain
1.8.5.1.1. very few of them, buried deep in tissues
1.8.5.2. less growth potential than embryonic stem cells
1.8.5.3. smaller chance of malignant tumours developing than from embryonic stem cells
1.8.5.4. limited capacity to differentiate
2. Ultrastructure of Cells
2.1. plant vs animal cells
2.1.1. plastids
2.1.1.1. PC may have chloroplasts
2.1.1.2. AC do not have plastids
2.1.2. cell wall
2.1.2.1. PC have a cellulose cell wall
2.1.2.2. AC do not have a cell wall
2.1.3. vacuole
2.1.3.1. PC have a large, central vacuole
2.1.3.2. AC may have temporary vacuoles
2.1.4. glucose storage
2.1.4.1. PC store excess glucose as starch
2.1.4.2. AC store glucose as glycogen
2.1.5. other differences
2.1.5.1. only PC may have plasmodesmata
2.1.5.2. PC do not possess centrioles
2.1.5.3. there is no cholesterol in PC membranes
2.2. nucleus
2.2.1. in animal and plant cells
2.2.2. stores genetic material (DNA)
2.2.3. nuclear membrane
2.2.3.1. double, pores
2.2.4. chromatin
2.2.4.1. DNA associated with high histone proteins
2.2.4.2. more loosely condensed, high rate of transcription
2.2.5. chromosomes
2.2.5.1. highly condensed chromatin fibers during cell division
2.2.6. nucleolus
2.2.6.1. producing and assembling ribosomes
2.3. endoplasmic reticulum
2.3.1. in animal and plant cells
2.3.2. internal transport network
2.3.3. rough ER = proteins
2.3.4. smooth ER = lipids
2.4. golgi apparatus
2.4.1. in animal and plant cells
2.4.2. export secretory products
2.4.3. cisternae
2.4.3.1. not as long as rER, often curved
2.4.3.2. no attached ribosomes
2.4.4. many vesicles nearby
2.4.5. processes proteins from rER
2.4.5.1. glycosylation, phosporylation
2.5. lysosome
2.5.1. animal cells only
2.5.1.1. presence in plants is subject to debate
2.5.2. digests macromolecules
2.5.3. formed from Golgi vesicles
2.5.4. aproximagelly spherical, single membrane
2.5.5. contains digestive enzymes in high concentrations (densely straining)
2.5.6. breaks down digested food, organelles, even the whole cell
2.6. mitochondtion
2.6.1. in animal and plant cells
2.6.2. double membrane
2.6.3. cristae - inner membrane invaginated
2.6.4. matrix - fluid inside
2.6.5. aerobic cell respiration - production of ATP
2.6.6. powerhouse of the cell
2.6.7. has its own genome
2.7. free ribosomes
2.7.1. in prokaryotic and eukaryotic cells
2.7.2. dark granules in cytoplasm, no membrane
2.7.3. synthesization of proteins released into the cytoplasm
2.8. chloroplast
2.8.1. plant cells only
2.8.2. site of photosynthesis
2.8.3. double membrane
2.8.4. has its own genome
2.9. vacuoles and vesicles
2.9.1. plant cells only
2.9.1.1. animal cells may have temporary vacuoles
2.9.2. single membrane, fluid inside
2.9.3. plant cells have large vacuoles (more than half of the cell)
2.9.4. vesicles are small vacuoles for transportation
2.10. microtubules and centrioles
2.10.1. microtubules are small cylindrical fibres in cytoplasm
2.10.2. centrioles - animal cells
2.11. cilia and flagella
2.11.1. whip-like structures projecting from the cell surface
2.11.2. cilia - smaller, more of them
2.11.2.1. is also used to create a current in the fluid next to the cell
2.11.3. flagella - larger, usually only one
2.11.4. used for locomotion
3. Membranes
3.1. two key properties
3.1.1. semi-permeability
3.1.1.1. only some materials can cross unaided
3.1.1.1.1. small, lipophilic molecules can freely cross
3.1.1.1.2. large or charged material cannot cross unaided
3.1.2. selectivity
3.1.2.1. the passage of material is regulated
3.1.2.1.1. membrane proteins assist material movement
3.2. structure
3.2.1. fluid, flexible and dynamic
3.2.2. any changes in the membrane structure are likely to affect the exchange of substances
3.2.2.1. the membrane plays a key role in cellular homeostasis
3.3. the fluid mosaic model
3.3.1. proposed by Singer and Nicolson in 1972
3.3.2. is accepted as one of the best models of the cell membrane
3.3.3. according to this model, biological membranes consist of phospholipid bilayers with proteins embedded in the bilayer, making the membrane look like a mosaic
3.4. phospholipid bilayer
3.4.1. has two layers of phospholipids that are arranged according to their properties
3.4.1.1. the phosphate heads are hydrophilic because of their charge
3.4.1.2. fatty acids, which are non-polar, are hydrophobic
3.4.1.3. a molecule that has both a hydrophilic and hydrophobic part is called an amphipathic molecule
4. Cell Division
4.1. prokaryotes
4.1.1. cells divide by binary fission
4.1.1.1. =asexual reproduction by a separation of the body into two new bodies
4.2. eukaryotes
4.2.1. somatic cells (body) divide by mitosis
4.2.1.1. the cell nucleus splits in two
4.2.1.1.1. next, the parent cell divides into two daughter cells
4.2.2. gametes (sex cells) divide by meiosos
4.2.2.1. it reduces the number of chromosomes to half the normal number
4.2.2.2. it creates egg and sperm cells
5. Transport
5.1. passive transport
5.1.1. movement along concentration gradient
5.1.1.1. from region of high concentration to low
5.1.2. simple diffusion
5.1.2.1. for materials that can freely cross the plasma membrane
5.1.2.2. small molecules may freely move via the gaps between phospholipid molecules
5.1.2.2.1. e.g. water, oxygen, carbon dioxide
5.1.2.3. lipophilic molecules (lipid soluble) can dissolve across the membrane
5.1.2.3.1. e.g. alcohol, steroids, chloroform
5.1.3. facilitated diffusion
5.1.3.1. for materials that cannot freely cross the plasma membrane
5.1.4. osmosis
5.1.4.1. for free water molecules
5.2. active transport
5.2.1. movement against the concentration gradient
5.2.1.1. from region of low concentration to high
6. Origin of Cells
6.1. Louis Pasteur (1822-1895)
6.1.1. gave crucial evidence to support the hypothesis that cells must come from pre-existing cells
6.1.2. his experiment disproved the theory of spontaneous generation
6.1.2.1. which stated that life could appear from a combination of dust, air and other factors
6.1.2.2. Pasteur boiled nutrient broth in three swan-neck flask
6.1.2.2.1. he then broke the neck of one flask to allow air to enter, but left the other flask unbroken
6.2. the first cells
6.2.1. life, in the form of cells, was transported to Earth from elsewhere in the universe
6.2.1.1. evidence supporting this hypothesis has not been found
6.2.2. must have come from non-living material
6.2.2.1. Miller-Urey experiment
6.2.2.1.1. they recreated the conditions of early Earth in a closed system by including a reducing atmosphere, high temperatures and electrical storms
6.2.2.1.2. this experiment proved that non-living synthesis of simple organic molecules was possible
6.2.2.1.3. conditions for emergence of life
6.3. the endosymbiotic theory
6.3.1. supports the idea that mitochondria and chloroplasts were prokaryotes that were taken in by larger by larger prokaryotes by endocytosis
6.3.1.1. instead of being digested and broken down, these cells remained inside the host cells
6.3.2. both mitochondria and chloroplasts
6.3.2.1. the following evidence supports the endosymbiotic theory
6.3.2.2. have double membranes, as expected for cells taken in by endocytosis
6.3.2.3. have circular naked DNA, as in prokaryotes
6.3.2.4. DNA is formed as single chromosomes
6.3.2.5. have 70S ribosomes, as in prokaryotes
6.3.2.6. divide by binary fission like prokaryotic cells
6.3.2.7. are susceptible to some antibiotics