- 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)
- Group of diseases that involve out-of-control cell division which may spread throughout the body
-`Tumour`: Uncontrolled lump of cells that do not perform normal cellular functions
-`Benign`: Cells that do not metastasise or interfere with normal cell function (harmless)
-`Malignant`: Cells that interefere with normal cell activity and metastasise
-`Carcinoma`: Cancerous/cancer
-`Metastasis`: Primary (original) tumour spreading throughout the body to create secondary tumours
-`Carcinogens`: Anything that can cause cancer, e.g., chemicals, radiation/energy, some viruses
-`Neoplasm`: A solid or fluid-filled sac that the body forms to isolate defective from healthy cells (e.g., cysts)
- Random mutations can also lead to a cancer cell due to irregular DNA replication
- Generally, multiple mutations in several key genes are required for a cell to become cancerous
- Cancer is *not* contagious, neither can it be inherited
- A genetic predisposition to cancer *can* be inherited
- By the time cancer is detected, it can contain millions of cells that have been growing for years
### Cancer screening
- PAP smear for cervical cancer
- Mammogram for breast cancer
- Colonoscopy for colorectal cancer
- PSA blood test for prostate cancer
### Cancer diagnosis
- Endoscopy (using a flexible camera with tissue extractor to search for cancers of the respiratory and/or digestive systems)
- X-rays
- Ultrasounds for soft tissues
- CAT/CT scan (more x-rays)
- MRI scan (uses radio waves and magnetic fields)
### Cancer treatments
- Surgery
- Physically removing tumour with stabby things
- Ineffective if cancer has metastasised
- If even one cell escapes the stabby cancer can regrow
- Radiation therapy
- Blasting radiation at tumours so that their DNA becomes so damaged that DNA replication, and, as a result, cell division is impossible
- Can harm neighbouring cells
- Ineffective if cancer has metastasised
- Chemotherapy
- Blasting drugs that kill dividing cells
- Does not feel very good for the patient
- Fast-growing cells may die off (e.g., hair, skin cells)
- Biophonics
- Using light beams to detect and treat cancer
## Organ systems
**Business model for organ/organ systems**
| 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
- Duodenum digests food chemically even more
- 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
### Respiratory system
- 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
- Diaphragm relaxes to return everything to its normal position
- Air is warmed and moisted while passing through nasal cavity blood vessels
- Trachea and bronchi are made of rigid cartilage rings
- Prevents airways from closing, similar to a vacuum hose
- Respiratory epithelium
- Contains goblet and ciliated cells
-`Cilia`: Singular "cilius", sweep mucous out of the lungs and throat
- Nose hairs and mucous trap debris which is swept out by cilia
- Alveoli (singular "alveolus") epithelial tissue is one cell thick
- Surrounded with capillaries which exchange gases via diffusion
