It is the controlled stability of the internal environment of cells and tissues.
Some examples include:
- Water regulation (osmoregulation)
- Temperature regulation (thermoregulation)
- Glucose regulation
Why is there a need for homeostasis?
It is so that a state of dynamic equilibrium can be achieved. A dynamic equilibrium means a state of balance achieved within an environment as a the result of internal control mechanisms that continuously oppose outside forces that tend to change that environment.
Cell Structure
| Component | Organelle Name | Function |
|---|---|---|
A
|
Nuclear Membrane | - Controls entry and exit of substances |
B
|
Nuclear Pore | - Allows transport of water-soluble substances |
C
|
Nucleolus | - Contains chromatin that controls cell activity; DNA, genetic material - Compartmentalized to increase efficiency of processes and protection |
D
|
Lysosome | - Breaks down worn out organelles - Digests materials |
E
|
Rough Endoplasmic Reticulum | - Isolate and transport proteins synthesized by attached ribosomes - Proteins may undergo further folding |
F
|
Smooth Endoplasmic Reticulum | - Synthesis and transport lipids |
G
|
Cytoplasm | - Contains the cell organelles - Site of cellular reactions - Means of transport for substances in cell |
H
|
Golgi Apparatus | - Process and package complex molecules - Transports proteins and fat molecules to cytoplasm for secretion |
I
|
Cell plasma membrane | - Compartmentalize - Controls entry and exit - Increase surface area - Cell recognition - Cell communication - Site of chemical reactions |
J
|
Vesicle/Vacuole | - Sacs for storage (plant cell), digestion and waste removal (animal cell) |
K
|
Mitochondria | - Produce adenosine triphosphate (ATP) from cellular respiration - Energy currency of cell |
L
|
Ribosome | - Sites of protein synthesis |
Cell Plasma Membrane
| Organelle | Function |
|---|---|
| Phospholipid | - Major component of the membrane - When they come into contact with water, they tend to line up heads in water and hydrophobic tails away from the water |
| Proteins | - Extrinsic - Loosely attach at hydrophilic surface of phospholipid bilayer - Intrinsic (partially or completely) - Contain both hydrophilic and hydrophobic regions |
| Glycoproteins | - Interspersed among phospholipids - Consists of carbohydrate chains bound to peripheral proteins and hydrophilic regions of internal proteins that occur on surface of outer membrane - Cell recognition or cell adhesion for immune response |
| Glycolipids | - Interspersed among phospholipids - Consists of carbohydrate chains bound to the head of phospholipid - Involved in cell recognition or cell signalling pathways |
| Cholesterol | - Interspersed among phospholipids - Essential in maintaining membrane fluidity - Allow protein movement within cell membrane |
Cell Transport
| Transport Mechanism | Type of substances | Energy input | Examples of substances | Importance of mechanism | |
|---|---|---|---|---|---|
| Simple Diffusion | Across the phospholipid bilayer directly, following a concentration gradient. | Small, lipid soluble and hydrophobic in order to be able to interact with the hydrophobic tails of the bilayer | Passive transport, ATP input not required | Oxygen gas, carbon dioxide, minerals in soil (in high concentration) | To allow for the absorption of small, lipid soluble substances into living cells for essential processes like respiration |
| Facilitated Diffusion - Ion Channel | Across the phospholipid bilayer through a water, filled pore, following a concentration gradient | Water and water-soluble substances and small lipids | Passive Transport, ATP input not required | Urea, glycerol | To allow for the absorption of water, water-soluble substances and small lipids into living cells for essential processes |
| Facilitated Diffusion - Carrier Protein | Across the phospholipid bilayer through a carrier protein that has a specific binding site, following a concentration gradient | Too large and too hydrophilic substances | Passive transport, ATP input not required | Amino acids, glucose, fructose | To allow for absorption of too large and too hydrophilic substances into living cells for essential processes |
| Osmosis | Across a partially permeable membrane, following a concentration gradient | Water | Passive Transport, ATP input not required | Water molecules | To allow for absorption of water into living cells for essential processes such as hydrolysis and condensation and a medium for transport within the cell |
| Active Transport | Across the phospholipid bilayer through a specific protein pump, against the concentration gradient | Particles | Active Transport, ATP input is required as substances go against the concentration gradient | Amino acids and glucose (in low concentration) | To allow for absorption of large particles against the concentration gradient into living cells for essential processes. |
| Bulk Transport - Endocytosis | Ingestion of fluids/solids from outside the cell into the cell | Fluid, solids | Active Transport, ATP input is required as substances go against the concentration gradient | Bacteria, food | To allow for the ingestion of fluids and/or solids into living cells for essential processes such as processing food and digestion |
| Bulk Transport - Exocytosis | Expelling contents from inside of the cell to outside the cell | Waste materials, excess materials | Active Transport, ATP input is required as substances go against the concentration gradient | Enzymes, hormones and antibodies | To allow for the expelling of waste and excess materials from the cell into the outside of the cell |
| Pinocytosis | Encloses fluid and pinches off to form vesicle | Fluid or suspensions | Active Transport, ATP input is required as substances go against the concentration gradient |
-
|
To allow ingestion of fluid or suspension into the cell |
| Phagocytosis | Encloses particles and buds off to form vacuole | Bio-organisms | Active Transport, ATP input is required as substances go against the concentration gradient | Food molecules | To allow ingestion of solids from outside the cell |
Feedback Loop
It is a self-regulated system in which feedback to the input a part of a system's output so as to reverse or enhance the direction of change.
Positive Feedback Loop (Rare)
- Increases the output of a system, further enhancing deviation from internal equilibrium
eg. Giving birth, rashes, blood clotting
Negative Feedback Loop (Common)
- Reduces the output of a system in order to stabilize or re-establish internal equilibrium
eg. Body temperature, osmoregulation, glucose level
Keywords:
Increase in ____ is detected by the receptors and insulin is released into the blood.
