diff --git a/Grade 10/Science/SNC2DZ/Unit 2: Biology.md b/Grade 10/Science/SNC2DZ/Unit 2: Biology.md index e6a1acf..d795523 100644 --- a/Grade 10/Science/SNC2DZ/Unit 2: Biology.md +++ b/Grade 10/Science/SNC2DZ/Unit 2: Biology.md @@ -45,13 +45,13 @@ A person contains roughly 100 trillion cells - Allows **waste products** to leave (removal of waste) - Surrounds and holds other organelles in cell - Interact with outside chemicals (e.g., hormones) -- Must transport food (ATP), nutrients into the cell +- Transports food and nutrients into the cell ### Nucleus - Is the control center of the cell - Holds deoxyribonucleic acid (DNA) in form of `chromatin` - DNA is a double helix containing genes - - `Genes` are a full set of instructions in DNA to make either RNA or a protein, they are **found** in the DNA + - `Genes`: any section of DNA that contains a full set of instructions to make either RNA or a protein, **found** in nucleus - `Chromatin`: is DNA **wrapped tightly** in protein - `Chromosomes`: are even more tightly wrapped `chromatin` used in cell division only, formed when `DNA` **condenses** in `mitosis` - Surrounded by a double membrane @@ -61,8 +61,8 @@ A person contains roughly 100 trillion cells ### Nucleolus - - Dense region of DNA located in the nucleus (codes `ribosomes`; enzyemes that make protein) - - This area of DNA is specially for ribosomal DNA (rDNA), or DNA used to make ribosomes + - Dense region of DNA located in the nucleus + - This area of DNA is specially for ribosomal DNA (rDNA), or DNA used to code `ribosomes`, enzymes that assemble proteins - Produce "large" and "small" subunits of `ribosomes`, which either form complete `ribosomes` in `cytosol` or mix with `endoplasmic reticulum`, forming `rough endoplasmic reticulum` (RER) ### Cytoplasm & Cytosol @@ -122,10 +122,10 @@ A person contains roughly 100 trillion cells 1. Centrioles and centrosomes 2. Lysosomes -### Centrioles and centrosomes +### Centrosomes - Made of same protein as `cytoskeleton` - - Important to cell division in animal cells - - Create cilia and flagella (e.g., small hair-like things that swipe dirt out of lungs and tails of sperm, respectively) + - Crucial to mitosis in animal cells + - **Create and manipulate spindle fibres** during mitosis in animal cells ### Lysosomes - Explained before. @@ -140,7 +140,7 @@ A person contains roughly 100 trillion cells - A more stronger, thicker, rigit version of the `cell membrane` - Made of **cellulose** (type of sugar) - Also present in most bacteria, fungi, and protists -- The antibotic **Penicillin** works by destroying the cell walls of bacteria, thereby killing the bateria +- The antibotic **penicillin** works by destroying the cell walls of bacteria, killing it ### Chloroplast - The **solar panel** of the plant cell @@ -158,7 +158,7 @@ A person contains roughly 100 trillion cells ## Cell Division -## Purpose +### Purpose ### 1. Reproduction - Single-cellular organisms reproduce via division **asexually** @@ -177,32 +177,59 @@ A person contains roughly 100 trillion cells - Cells naturally die and need to be replaced - e.g., red blood cells, hair cells, skin, injuries, broken bones -## Cell cycle +### Cell cycle + + + - **Interphase** - - **G1** (normal groth and function), + - Large majority of a cell's time is spent in interphase + - **G1**: (normal growth and function), - Prepare for cell divison - - Duplication of DNA **S**, - - Duplication of organelles **G2** + - **S**: Replication of DNA + - **G2**: Replication of organelles + - Checkpoints + - Cells check various things before progressing through various stages in interphase + - Causes of stopping via checkpoints include damaged DNA, not replicated DNA, lack of nutrients for cell growth, and/or signals from other cells - **Mitosis** - Occurs only in eukaryotic cells - - P-MAT: Prophase Prometaphase, Metaphase, Anaphase, Telophase Cytokinesis - - nuclear divison + - P-MAT: Prophase, Metaphase, Anaphase, Telophase + - Division of the nucleus - **Cytokinesis** - **cell division** + - The parent cell splits into two daughter cells - **G0** - - Cell no longer divides - - Outisde of cell cycle + - Cell no longer divides ("cell cycle arrest") + - Outside of cell cycle ### Mitosis +- `Chromatid`: Supercoiled DNA, only visible during mitosis, cannot be read without unwinding, similar to compressed zip file +- `Chromosome`: Two identical "sister chromatids" held together in centre by `centromere`, or one sister chromatid after anaphase +- `Centromere`: Proteins sticking sister chromatids - PMAT (prophase, metaphase, anaphase, telophase) +- Division of the nucleus +| Phase | Diagram | Description | +| :--- | :--- | :--- | +| Prophase | | - Chromatin condenses into two identical `sister chromatids` which condense into `chromosomes`
- Happens to 23 pairs of chromosomes
- Nuclear membrane dissolves
- Centrosomes move to opposite ends (`poles`) of cell, creating `spindle fibres` that begin to attach to `centromeres` in animal cells | +| Metaphase | | - Chromosomes line up in centre of cell to ensure they divide evenly
- Everything in prophase has completed (e.g., nuclear membrane has dissolved completely) | +| Anaphase | | - Centromeres split, separating sister chromatids
- Sister chromatids are pulled towards opposite sides of cell via shortening spindle fibres
- Sister chromatids are now called `daughter chromomsomes` | +| Telophase | | - Effectively opposite of prophase
- Nuclear membranes form across each of the two new nuclei
- Daughter chromosomes unwind into chromatin and are no longer visible
- Nucleolus forms in each nucleus
- Spindle fibres break apart
- **Cytokinesis** usually begins in telophase
- Cells starts to **cleave** (cell centre starts to pinch itself) | + +### Cytokinesis + - Cell division + - Cell splits completely to two daughter cells + - In **animal cells**: Cell membrane pulled inward by cytoskeleton + - **"Pinches in"** along equator of cell, forming **"cleavage furrow"** + - In **plant cells**: Golgi apparatus produces and sends vesicles to centre of plant cell **"cell plate"** to make new cell wall and membrane between daughter cells ## Cell Specialization -- `Zygote`: A one-celled organism formed from the fertilization of an egg by a sperm cell +- `Zygote`: A single-celled organism formed from the fertilization of an egg by a sperm cell, is a totipotent stem cell - A cell's position in the `gastrula` (outer, middle, inner layer) will determine the fate of the cell, or its potiental. +- Chemical signals from other cells will also determine activated genes that lead to specialisation - (LOCATION LOCATION LOCAION!) +- Specialisation is determined by reading only certain genes ### Stem Cells - They are an **unspecialized** cell that has the potential to become one of several types of cells. -- After cell division, either both can become stem cells or one stays as a stem cell and the other becomes a specialized cell -- \ No newline at end of file +- Can either divide to two stem cells or one stem cell and one specialised cell +- Specialised cells generally do not divide \ No newline at end of file