- Substances enter and exit the nucleus via `nuclear pores`. `Nuclear pores` are holes in the membrane that allow `proteins` and `nucleic acids` into the `cytoplasm`
- Produce "large" and "small" subunits of `ribosomes`, which either form complete `ribosomes` in `cytosol` or mix with `endoplasmic reticulum`, forming `rough endoplasmic reticulum` (RER)
- The endoplasmic reticulum is a network of `tubules` and **flattened sacs** with a <b>*rough*</b> appearance because of the presence of `ribosomes` on the surface
- Cells have maximum size before transportation of substances within cell becomes **inefficient**, due to **larger cells** decreasing efficiency of `diffusion`
- Cells transport chemicals (e.g., nutrients) via `diffusion`, this **limits cell size**
- The only way to maintain proper function and get bigger is to **add more cells**
### 3. Repair
- **Organisms need to repair cells to stay alive and maintain proper health**
| Prophase | <imgsrc="http://www.edupic.net/Images/Mitosis/prophase_3D.png"width="250"> | - Chromatin condenses into two identical `sister chromatids` which condense into `chromosomes`<br> - Happens to 23 pairs of chromosomes <br> - Nuclear membrane dissolves <br> - Centrosomes move to opposite ends (`poles`) of cell, creating `spindle fibres` that begin to attach to `centromeres` in animal cells |
| Metaphase | <imgsrc="http://www.edupic.net/Images/Mitosis/metaphase_3D.png"width="250"> | - Chromosomes line up in centre of cell to ensure they divide evenly <br> - Everything in prophase has completed (e.g., nuclear membrane has dissolved completely) |
| Anaphase | <imgsrc="http://www.edupic.net/Images/Mitosis/anaphase_3D.png"width="250"> | - Centromeres split, separating sister chromatids <br> - Sister chromatids are pulled towards opposite sides of cell via shortening spindle fibres <br> - Sister chromatids are now called `daughter chromomsomes` |
| Telophase | <imgsrc="http://www.edupic.net/Images/Mitosis/telophase_3D.png"width="250"> | - Effectively opposite of prophase <br> - Nuclear membranes form across each of the two new nuclei <br> - Daughter chromosomes unwind into chromatin and are no longer visible <br> - Nucleolus forms in each nucleus <br> - Spindle fibres break apart <br> - **Cytokinesis** usually begins in telophase <br> - 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
| Type of Stem Cell | Obtaining | Potential | Pros | Cons |
| :--- | :--- | :--- |:--- | :--- |
| Totipotent | Morula (16-cell ball) 3-4 days after lab-fertilised zygote | Unlimited | Unlimited potential, does not initiate immune response | Ethical concerns of destroying fertilized embryos |
| Pluripotent | Blastocyst (200-300 cell ball) 4-7 days after fertilisation | Nearly unlimited | Nearly unlimited potential, no need to create new embryo as most are taken from discarded in vitro fertilisation | Ethical concerns of destroying embryos, greater chance of initiating immune response |
| Multipotent | Adult stem cells | Limited to cells of their group/organ/location (e.g., blood stem cells to red blood cells, white blood cells, etc.) | Easy to harvest, easy to find | Immune response, limited potential |
| Induced pluripotent | Multipotent stem cells | Reprogramming multipotent stem cells using embryonic genes using a virus | Same as pluripotent | Does not require new embryos, immune response not expected, high potential | Technology not there yet to make this possible |
### Potential uses of stem cells
- Studying cell growth and function
- Testing drugs on specific target cells
- Lab-grown meat for vegetarian purposes
- Regenerative medicine to replace tissues (e.g., blindness, bone marrow transplant, cancers, limb regrowth)
| Business thing | Corresponding organ/organ system |
| :--- | :--- |
| Management | Central nervous system (brain) |
| Messaging | Endocrine + peripheral nervous systems |
| Workplace | Body |
| Transport | Circulatory, digestive, urinary systems (internal, import, export, respectively) |
| Storage | Fats |
| Cash flow | Digestive + respiratory systems |
| Security | Immune + integumentary (skin) systems |
| Workers | Cells + muscular system |
## Tissues
-`Tissues`: Different cell types grouped together performing the same task
- Organisms have a hierarchical organisation
- Basic tissues: Connective, muscle, nervous, and epithelial tissues
- Epithelial tissue
- Tightly packed cells that line body surfaces, e.g., skin
- Connective tissue
- Produces collagen fibres that support organ structures and bone, e.g., ligaments (bone -> bone), tendons (muscle -> bone)
- Muscle tissue
- Fibrous tissue that can be subdivided into cardiac (heart), smooth (digestive), and skeletal (voluntary) muscle tissues
- They contract
- Nervous tissue
- Responds to external/internal stimuli, e.g., brain, nerves
## Digestive system
- Two types of digestive systems
- Bag digestive system
- One way in, same way out (e.g., coral, jellyfish)
- Tube digestive system
- One way in, another way out (e.g., worms, humans)
- Mouth -> esophagus -> stomach -> small intestine -> large intestine -> rectum -> anus all part of the tube
- Gallbladder, liver, salivary glands, and pancreas produce digestive enzymes/juices in humans
- Process of eating food: **Ingestion** (eat) -> **digestion** (physical and chemical breakdown) -> **absorption** (of nutrients to bloodstream) -> **egestion** (poo)
- Flies digest before ingesting
-`Jujunum`: Centre of small intestine
-`Duodenum`: Beginning of small intestine
-`Ileum`: End of small intestine
-`Rectum`: Holds waste to be excreted voluntarily
-`Anus`: Controls waste to be defecated voluntarily
-`Appendix`: Used to be used to digest plant matter, now virtually useless in humans
-`Gallbladder`: Stores and secretes bile as buffer between liver and small intestine that helps break down fats (lipids)
-`Ruminants`: Herbivores that digest food using a chambered tube
- Chew -> Reticulum and rumen (first and second stomachs) -> regurgitate and rechew -> Omasum (third stomach) -> Abomasum (fourth stomach) -> small intestine -> large intestine -> waste
-`Eoprophagy`: Consumption of feces
### Human digestive system
- Mouth ingests food
- Teeth, tongue, and salivary glands work to begin digestion
- Esophagus squeezes food down in waves (peristalsis) down its smooth muscle tube
- Stomach
- Mixes hydrochloric acid with digestive enzymes to break down food
- Hydrochloric acid is diluted and does not break down the food itself much, enzymes are more effective at a lower pH
- Liquifies food and kills bacteria
- **Goblet cells** produce **mucous**, which lubricates the stomach and intestines, protecting the stomach
- Made of smooth muscle to churn food, somewhat like cooking with enzymes or a washing machine
- Intestines
- Pancreas makes most digestive enzymes and pumps them in the duodenum
- Absorbs nutrients and water to bloodstream
- Forms and excretes feces
- Contains smooth muscle to continue peristalsis
- Contains plenty of blood vessels for faster nutrient absorption
- Intestinal epithelium
- Optimised for surface area
- Folds contain `villi` (singular, "villus")
- Villi contain capillaries and absorbing and goblet cells
- Absorbing cells caintain microvilli, which absorb nutrients via diffusion
- Exchanges oxygen gas and carbon dioxide gas between red blood cells and the surrounding air, which is required for cellular respiration
- Diaphragm contracts to lower itself, causing the rib cage to rise, which increases lung volume, which subsequently causes pressure to decrease and air to rush in to the lungs
- Carries oxygen and nutrients to cells, carries carbon dioxide and waste away
### Components
- Composed of heart, arteries, veins, and capillaries
-`Arteries` flow **away** from the heart
- Made of **thick** muscle layers and elastic connective tissue
- Muscle layers must withstand and **maintain** higher blood pressure throughout body due to proximity to heart
- May `vasoconstrict` or `vasodilate` to increase or restrict blood flow, for example, to blush or to pale, respectively
-`Veins` flow **to** the heart
- Made of **thin** muscle layers and elastic connective tissue
- Carries low pressure blood with valves to ensure one-way flow
- Blood moves by movement of skeletal muscles pushing blood
-`Capillaries` are one cell thick
- They transition between arteries and veins
- Blood cells are forced to go in single file
- Present, amongst other places, in alveoli and villi
- The `heart` pumps blood throughout the body
- Has one-way valves
- Has four chambers, two `atria` (sing. `atrium`) and two `ventricles`
- Blood is returned to atria which push them to ventricles which push them out of the heart
- **Right** side of heart receives and sends **deoxygenated** blood **to** lungs
- **Left** side of heart receives and sends **oxygenated** blood **from** lungs
- Invertebrate circulatory systems are either **open** or **closed** (douse everything with blood then collect or use vessels like we do, respectively)
- Most invertebrates have an open circulatory system
- When `atherosclerosis` occurs in `coronary arteries` (when fatty plaque deposits build up in arteries feeding the heart)
- If clots break open a larger clot forms over it
- This repeats until the artery is completely blocked, leading to death of cardiac muscle cells
- Caused by lifestyle choices, although predisposition can be increased due to genes
### Blood
- Composed of red blood cells, white blood cells, platelets, and plasma
-`Red blood cells`: Biconcave discs carrying oxygen and carbon dioxide to and from cells, respectively, using `hemoglobin`
- Denucleated, instead packing as much hemoglobin as possible inside
- Hemoglobin and oxygen give them their colour
-`White blood cells`: Part of the immune system, they neutralise and remove foreign threats
- Can make antibodies
- Can engulf and kill pathogens
- 700:1 ratio of red blood cells to white blood cells
-`Plasma`: Clear fluid made of 90% water filled with proteins and dissolved nutrients
-`Platelets`: Irregular colourless "bodies" that form **fibrous** clots
## Immune system
-`Pathogens`: any**thing** that cause disease
- Pathogen waste can be toxic which cause symptoms of disease
- Passive defense
- Skin - physical barrier
- Sweat/tears - `lysozymes` kill bacteria
- Stomach acid - it's acid dangit acid kills things
- Beneficial bacteria overpopulate surfaces to prevent harmful bacteria from settling
- Adaptive defense
-`White blood cells`: For the sake of G10, divided into two subtypes:
- Cells that engulf and consume bodies (`phagocytes`, e.g., macrophages)
- Cells that produce antibodies (`plasma B cells`, i.e., plasma B cells)
-`Antibodies`: Secreted proteins that stick to a specific molecule found on pathogens
- Clumps pathogens together for simple cleanup and prevents them from spreading
- Covers and prevents toxins from reacting
- Acts as a flag for phagocytes to destroy marked pathogen or toxin
- Acquired immunity
- After initial immune response, antibodies are still produced for that type of pathogen
- Once pathogen is detected again, "memory cells" reactivate and kill things faster
- Much faster than initial response, typically resulting in no symptoms
- This is why you generally can never be sick from the same pathogen twice
- Pathogens mutate (e.g., influenza) so that they are no longer recognisable by antibodies
-`Vaccination`: Injecting a small amount of a **dead/weakened** version of pathogen giving acquired immunity without actually getting disease
- There may be mild side effects
-`Boosters` are required for some vaccines as "memory" fades over time (e.g., tetanus)
-`Herd immunity`: When enough of the population (90% in general) is immune to a disease, drastically reducing rate of disease even amongst those not immune
- Those who cannot be vaccinated for whatever reason are protected due to a far lower chance of encountering the disease itself
- Prevention (vaccine) > cure (treatment)
- Chance of disease from the vaccine are far lower than chance of death or serious infection from a pathogen
- Vaccines do not cause autism or seizures, but may act as a trigger for the latter due to genetics
