Introduction to Cells 1.1 Flashcards
Essential Idea (Introduction to Cells 1.1)
- The evolution of multicellular organisms allowed cell specialization and cell replacement
- Multicellular organisms have properties that emerge from the interaction of their cellular components
Cell Theory Creators & Date
- Created in 1838
- Theodor Schwann
- Matthias Schleiden
- Rudolph Virchow
Rules of Cell Theory
- Living organisms are composed of cells
- Cells are the smallest units of life
- Cells come from pre existing cells
- All cells contain hereditary information (DNA) which is passed on during cell division
Exceptions of Cell Theory
- Striated muscle fibres
- Aseptate fungal hyphae
- Giant Algae
Living vs Non Living Organisms
All living organism can do the functions of life (MRHGREN) while non living cannot (viruses)
Striated Muscle Cell
- Multiple nucleus per cell
- Composed of sarcomeres which show a stripped pattern under a microscope
- Average length is 30mm
Giant Algae
- Single cell of gigantic size that challenges the idea that cells are the smallest unit of life
- Size can vary from 5-100mm
- Three anatomical parts: rhizoid, long stalk, top umbrella branches that fuse into a cap
Aseptate Fungal Hyphae
- Doesn’t have cell walls resulting in shared cytoplasm and multiple nuclei
- Tubular system of hyphae from dense networks called mycelium
- Outer cell wall composed of chitin
Light Microscope
- Uses lenses to bend light and magnify images
- Used to study dead or living cells in colour
- Cell movement can be studied
- Larger field of view
- Magnified up to 2000x and resolve objects 200nm apart
Electron Microscope
- Uses electron beams focused by electromagnets to magnify and resolve
- Requires cell to be killed and chemically treated before viewing
- No movement can be seen, no colour without stain or dye
- Smaller field of view
- Magnified up to 250000x and can resolve objects 0.2nm apart
Magnification Equation
- Magnification = size of image / actual size
- Calculations must be done in the same units
Functions of Life (7)
Metabolism, response, homeostasis, growth, reproduction, excretion, nutrition
Paramecium
- Widespread in aquatic environments
- Protists (any eukaryotic organism that is not an animal, plant or fungus)
- Heterotrophs (cannot produce its own food)
Chlamydomonas
- Green algae found in water (stagnant water, damp soil, freshwater, seawater and snow)
- Autotrophs (can produce its own food, photosynthesis)
Reason for Cell Division (SA:V)
Once a cell grows to a certain size they divide due to the volume growing larger than the surface area, if the volume is greater not enough molecules can get in and not enough waste (including heat) can get out
Surface Area to Volume Ratio
Volume increases by the power of 3 (cubed), surface area increases by the power of 2 (squared)
Better Efficiency, Small or Large Cells?
More energy is necessary for diffusion (membrane to location in cell, high to low concentration) if the distance between the organelle and plasma membrane is larger therefore small is more efficient
Increasing the Surface Area
Cells and tissues specialized for gas or material exchange will increase the surface area to optimize the transfer of material
Alveoli
Tiny air sacs in the lungs that store oxygen and they maximize the surface area for gas exchange
Villi
Small folds in the small intestine that increase surface area allowing for a higher nutrients absorption efficiency
Volume Formula
Length x width x height
Surface Area Formula
Length x width x number of sides
Surface Area to Volume Ratio Formula
SA/V, simplify and find the ratio (SA:V)
Evolutionary Steps of the Organisms
Organisms were originally one cell however through differentiation cells became specialized. This allowed multicellular organisms to display emergent properties
Emergent Properties
An emergent property is a property which a collection or complex system has, but which the individual members do not have.
Cell Differentiation
- Differentiation is the process during development whereby newly formed cells become more specialized and distinct from one another as they mature
- The process involves the expression of some genes and not others in the cells genome
Stem Cell
- Stem cell is an undifferenced cell of a multicellular organism
- They can divide indefinitely and give rise to various specialized cells
- Once a cell is specialized it is very difficult to change back
- Stem cells ability to divide and differentiate along different pathways is necessary in embryonic development and makes them suitable for therapeutic use
Types of Stem Cells
- Totipotent
- Pluripotent
- Multipotent
- Unipotent
Totipotent
Can differentiate into any type of cell and can give rise to a complete organism
Pluripotent
Can differentiate into any type of cell but cannot give rise to a complete organism
Multipotent
Can differentiate into a few types of body cells
Unipotent
Can only associate with their own type of cell
Stargardt’s Disease (Stem Cell)
- Disease of the eye caused by a recessive gene mutation in the gene ABCA4
- Causes active transport proteins on photoreceptor cells to malfunction leading to vision loss
- Production of dysfunctional proteins cannot perform transports
- Degenerated photoreceptor cells can be replaced with retinal cells from a steam cell
- Retinal cells are injected into the retina and central vision is improved
- Affects 1 in 10000 children
Leukaemia (Stem Cell)
- High levels of abnormal white blood cells causes leukaemia which is cancer of the blood or bone marrow
- Hematopoietic stem cells (multipotent) are harvested from bone marrow, peripheral blood or umbilical cord blood
- Abnormal white blood cells removed from chemotherapy and radiotherapy
- Healthy white blood cells are transplanted
Ways to Obtain Stem Cells
- Embryo
- Cord blood
- Adult stem cells
Embryo Stem Cells
- Can be obtained from excess embryos generated by IVF (in vitro fertilization) programs
- Almost unlimited growth potential
- High risk of tumour development
Cord Blood Stem Cells
- Umbilical cord is removed at birth and the stem cells can be harvested
- Reduced potential of growth
- Low risk of tumour development
Adult Stem Cells
- Difficult to obtain as there are very few buried deep in tissues
- Adult patients can give permission for cells to be extracted
Supporting Arguments for Stem Cells
- Used in therapy to replace bad cells eliminating a serious disease or disability
- Donating organs not needed and doesn’t put pressure on someones body
- Stem cells harvested when the embryo is at an early stage and when it hasn’t developed a nervous system
- Stem cell research beneficial for future discoveries and some technology would not have occurred if they were banned
Arguments Against Therapeutic Cloning
- Involved creation and destruction of human embryo
- Embryonic stem cells are capable of continued division leading to cancerous cells and tumours
- More embryos are produced than needed, extra death
- Not cost efficient other technology may fulfil similar roles
- Religious moral objects
- Cloning humans is illegal, there is potential to clone
Reproduction (Paramecium & Chlamydomonas)
Both reproduce asexually using mitosis or sexually using meiosis and gametes
Homeostasis (Paramecium & Chlamydomonas)
Both regulate and keep internal conditions, contractile vacuoles expel excess water
Metabolism (Paramecium & Chlamydomonas)
Both produce enzymes which catalyze different chemical reactions in the cytoplasm
Excretion (Paramecium)
Expels waste products of metabolism, CO2 from respiration diffuses out of the cell
Excretion (Chlamydomonas)
Expels waste products of metabolism, oxygen from photosynthesis diffuses out of the cell
Response (Paramecium)
Reacts to stimuli, reverses if direction of movement when it touches a solid object
Response (Chlamydomonas)
Reacts to stimuli, senses where the brightest light is with its eyespot and swims towards it
Growth (Paramecium)
Increases in size and dry mass by accumulating organic matter and minerals from its food
Growth (Chlamydomonas)
Increase in size and dry mass due to photosynthesis and absorption of minerals
Nutrition (Paramecium)
Feeds on smaller organisms by ingesting and digesting them in vesicles (endocytosis)
Nutrition (Chlamydomonas)
Produced its own food by photosynthesis using a chloroplast that occupies much of the cell
Tissues
A groups of cells that do the same kind of work are called tissues
Metabolic Rate vs Exchange of Material
If the metabolic rate is greater than the rate of exchange of vital materials and wastes, the cell will eventually die
Rate of metabolism
Chemical reactions in the cell
Rate of material exchange
Movement of material in a cell
Cristae Mitochondria
Increases the surface area
