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54 lines
2.2 KiB
Markdown
54 lines
2.2 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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### 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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- 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 |