Organelles of a Cell

The nucleus is an organelle enclosed by the nuclear membrane (double membrane), found in eukaryotic cells. The nuclear membrane consists of two layers of lipids / fats - that separate it from the cytoplasm. It controls and regulates the activities of the cell. It contains threads of chromatin (a combination of DNA / Deoxyribonucleic Acid molecules and proteins). In mitosis / when a cell divides, the chromatin undergo condensation (when chromatin cells are compacted when they are organized to fit into a smaller space) - forming chromosomes, which are more tightly coiled.

The nucleolus is located inside of the nucleus. It is not enclosed by any membrane. The nucleolus contains RNA / Ribonucleic Acid. The RNA is typically a single stranded molecule (while DNA is typically double stranded). The RNA carries genetic information / instructions from DNA (which controls growth, development, and reproduction) and delivers them to proteins. The nucleolus is also responsible for creating and assisting ribosomes, by delivering proteins.

The ribosomes are essentially a combination of RNA and proteins, thus they are created by the nucleolus. They are not enclosed by any membrane. They decode the messenger RNA / mRNA sequence (unzipped part of DNA) into a string of amino acids (the building blocks of proteins - that are able to form them by linking together in polypeptide chains). The ribosomes could be found floating in the cytoplasm, or they can be attached to the rough ER / endoplasmic reticulum.

The mitochondria are organelles enclosed by a double membrane, found in eukaryotic cells. The mitochondria has their unique DNA, different from the nucleus. The mitochondria generates ATP / adenosine triphosphate - a currency of energy for the cell, in the process of cellular respiration. Cellular respiration is a metabolic pathway which breaks down food molecules like glucose and oxygen to create energy.

• 1 glucose molecule (six-carbon sugar) → 2 molecules of pyruvate (three-carbon organic matter)
• NAD+ (oxidized form ; accepts / carries electrons that break down glucose) → NADH (reduced form ; gives electrons that break down glucose) Some energy captured during this process

uuhh i'll cover the rest of the organelles ok? ok  sorry i've been busy because of schoolwork

A concentration gradient is the difference in density between two fluids. The difference can be expressed as a diagonal line (x and y axis represent high and low concentrations respectively); which the steeper the slope; the greater the difference and speed in the process of diffusion. The direction of movement is typically downward, however the reverse happens in active transport.

Active transport is the movement of solute against a concentration gradient. It happens when a substance moves from an area of low concentration to an area of high concentration. This process requires ATP (energy stored within cells) and proteins in order to occur.

• An example of active transport is when water and nutrients are reabsorbed at the PCT of a nephron. In the process, a sodium-potassium pump is formed – when ATP atom is split (to produce energy) in order to release 3 sodium ions out of a cell and transport 2 potassium ions into a cell (low concentration to high concentration of potassium). (I learned this because of an assignment lol)

Osmosis

Osmosis is essentially when a liquid or gas (rarely) moves from a side with a high concentration of solute to a side with a lower concentration of solute parted by a semi permeable membrane. It is a type of diffusion. The process of osmosis aims to achieve an equal concentration of solute between both solutions, concluding when the state of equilibrium is achieved.

Diffusion happens when particles of a liquid or gas in a highly concentrated area shifts to a lower concentrated area, and distributes itself evenly throughout the given space. This process continues until all of the particles are spread out evenly.

Osmosis and diffusion are have some differences:

• Solute — Osmosis typically only occurs with fluids. While it is possible for gases to undergo Osmosis, it is incredibly rare. However, diffusion occurs with many liquids and gases.
• Solvent — Osmosis occurs in fluids, while diffusion may occur in gases, liquids, and solids.
• Membrane — Osmosis requires a semi permeable membrane, while diffusion does not need one.
• Goal — Osmosis aims to achieve an equal concentration of solute throughout multiple mediums separated by a semi permeable membrane, whilst diffusion aims to achieve an equal concentration of solute throughout a singular medium.