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106 lines
4.3 KiB
Markdown
106 lines
4.3 KiB
Markdown
# Unit 2: Biology
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## Cellular Biology
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A person contains roughly 100 trillion cells
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- Cells are roughly 20 `μm` (micrometre, 10<sup>-6</sup> m), around 250 cells / cm
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## Cell Theory
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1. All living things are composed of cells
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2. Cells are the basic units of living organisms
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3. All cells came from pre-existing cells
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## Eukaryotic versus Prokaryotic Cells
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`Prokaryotic cell`: Meaning before/lacking nucleus
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`Eukaryotic cell`: Means complete nucleus
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|Factors|Prokaryotic|Eukaryotic|
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|:-----------|:----------|:---------|
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|DNA|In nucleoid region|Usually in membrane-bound nucleus|
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|Size|Usually smaller|Usually larger|
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|Organelles|Not membrane-bound, smaller|Membrane-bound, more complex|
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|Organization|Usually singlecelled|Often form multicellular organisms|
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|Metabolism|May not need oxygen|Usually need oxygen|
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## Cellular Organelles
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### Business Analogy
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| In a business | In a cell |
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| ------------- | --------- |
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| Building | Cytoplasm & Cytoskeleton |
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| Department Head | Organelles |
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| Boss | DNA |
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| Workers | Ribosomes & Enzymes |
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| Waste management | Lysosomes |
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| Storage | Vacuoles |
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| Powerhouse | Chloroplasts & Mitochondria |
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| Security gate | Cell membrane controls entrance and exit from the cell |
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| Transportation Department | IMPORT: Cell membranes and vesicles, INTERNAL: Endoplasmic reticulum & vesicles, EXPORT: Golgi apparatus, vesicles, and cell membrane |
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### Cell Membrane
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- Controls what substances enter/leave the cell selectively via various receptors/osmosis
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- Allows nutrients to enter
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- Allows waste products to leave
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- Surrounds and holds other organelles in cell
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- Interact with outside chemicals (e.g., hormones)
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### Nucleus
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- Holds deoxyribonucleic acid (DNA) in form of chromatin
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- DNA is a double helix that make genes
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- Genes are a complete set of instructions to make a complete product (typically proteins)
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- `Genes`: one of the many sets of instructions, in your DNA, found on a **chromosome**, for making a functional product (mostly proteins)
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- Chromatin is DNA wrapped tightly in protein
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- Chromosomes are even more tightly wrapped chromatin used in cell division only
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- Surrounded by a double membrane
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- Substances enter and exit the nucleus via nuclear pores
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- Messenger RNA (mRNA) is encoded from DNA and sent to ribosomes to produce proteins
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### Nucleolus
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- Dense region of DNA located in the nucleus
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- This area of DNA is specially for ribosomal DNA (rDNA), or DNA used to make ribosomes
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- Produce "large" and "small" subunits of ribosomes, which either form complete ribosomes in cytosol or mix with endoplasmic reticulum, forming rough endoplasmic reticulum (RER)
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- Is *not* surrounded by a membrane, literally is just same as rest of nucleus but denser
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### Cytoplasm & Cytosol
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- Cytosol is the fluid cells contain
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- All organelles are suspended in cytosol
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- Cytoplasm is the cytosol along with everything in a cell, excluding the nucleus
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## Endoplasmic Reticulum
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- Network of tubules and flattened sacs
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- Transport proteins via cytoskeleton in vesicles
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### Rough ER
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- Appears "rough" due to the ribosomes attached to its outer surface
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- Located directly adjacent and attached to nucleus
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- Located next to Golgi apparatus
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- Ribosomes in rough ER synthesize proteins
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- Only specific proteins are synthesized by ribosomes of rough ER
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- Proteins synthesized in ribosomes of rough ER are always sent to either Golgi apparatus via vesicles or stay in rough ER
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- Ribosomes attach to and leave the rough ER regularly
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- About half the cell's proteins are produced here
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- Modify, fold, and fix proteins
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### Smooth ER
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- Does not synthesize proteins
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- Appears "smooth" due to lack of ribosomes
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- Located directly adjacent and attached to nucleus
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- Synthesizes lipids (fats, e.g., cholesterol)
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- Metabolises carbohydrates
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## Lysosome
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- Spherical vesicle that contains enzymes
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- Digests and kills foreign matter which is then excreted
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- Digests and breaks down old and unused material to be recycled
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- Digests and breaks down old or non-functional organelles as needed
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- Only plays a very minor role in cell suicide (apoptosis)
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- If lysosome does rupture (accidentally) everything dies
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## Mitochondrion
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- **Plural is "mitochondria"**
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- Contains an inner and outer membrane
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- Processes glucose + oxygen gas to form carbon dioxide + adenosine triphosphate (ATP) |