Unit 3 Reflection

In this unit, we learned about the cell. This was our first step into actual biology.

The cell theory states that 1. All living things are made up of cells. 2. The cell is the most basic unit of life. 3. New cells are generated from existing cells. In the 1600s, Zacharias Jansen and Anton von Leeuwanhok created the first microscopes. This lead Robert Hooke to give the cell its name. It also lead Mattias Schleiden to realize all plants are made up of cells, while Theodore Schwann made the same observation for animal cells. The invention of the microscope also lead to the discovery of different types of cells: the prokaryote, and the eukaryote.

Cell membranes give the cell its structure and support the cell. The membrane is made of a lipid bilayer, which also has embedded protein molecules inside. These proteins have carbohydrate molecules sticking to them. The cell membrane's function is to keep things out of the cell, to keep things in the cell, and to choose what enters and what exits the cell. For the cell membrane to complete its tasks, it must be semi-permeable, or ability to let certain things pass through but other things cannot. There are 7 membranes in a eukaryotic cell: the nuclear membrane, the lysosome, the endoplasmic reticulum, the vesicle, the golgi apparatus, the membrane in chloroplasts and mitochondria, and lastly, the cell membrane. Diffusion is the movement of very small molecules from high concentration to low concentration through a lipid bilayer. There is passive transport, which is trasportation without energy or effort from the cell, and there is active transport, which is transportation with the cell's energy required. Active transport is completed using the membranes transport proteins, and is used only when there are highly needed molecules/things by the cell, or when the cell is going against the concentration gradient. Osmosis is the diffusion of water through a semipermeable membrane. Water is a universal solvent, and solvents are small enough to pass through membranes while solutes are not. This means when there is a solution with uneven concentration, the solvent either leaves or enters the cell in various amounts until equilibrium is achieved. An isotonic solution is when the solution inside the cell has the same concentration than that outside the cell. A hypotonic solution is when the concentration of the solution outside the cell is more diluted than that inside the cell. Because of this, water goes into the cell, causing the cell to gain water and size. A hyptertonic solution is the complete opposite of this and the cell loses both water and size.

Our next important topic is how to cell makes proteins. First of all, the nucleus holds both the DNA and the genes, or specific instructions to make the proteins. The nucleus sends the genes to the ribosomes, or the assembly line. After the proteins have started being made, they are put into the endoplasmic reticulum to be finished. After this, the golgi apparatus takes control and finishes it. From the golgi apparatus, vesicles take the protein out of the cell to where ever the protein is needed.
We then talked about the evolution of the cell. When Earth was still developing and when there was very little oxygen in the atmosphere, simple prokaryotic cells were the only things that ruled the earth. These prokaryotes broke down what little oxygen there was. However, cyanobacteria evolved and started photosynthesis. They could break down oxygen and water. This lead to more oxygen being produced and thrown into the air. This changed the world, which started to lead to more change. Some heterotrophs began eating other cells, Fortunately, not all the cells were digested, and were still living in the heterotroph. The cells started to live in symbiosis, which then lead to the endosymbiotic, which is the theory that explains how a large cell ingested bacteria and became part of it. Over millions of years, chloroplasts and mitochondria have become more specialized and now cannot survive on their own.

Photosynthesis is a plants way of converting light and carbon dioxide into glucose, or food. First of all, autotorphs absorb their energy from red and blue light. Chloroplasts are organelles containing stroma and grana. the grana are stacks of thylakoids. the light dependent reaction is when the light is absorbed and energy is transferred between molecules via the electron transport chain. this produces NADPH and ATP. The light independent reaction produces sugar from carbon dioxide using ATP and NADPH from light reactions. The calvin cycle is the light independent reaction, and it rotates 6 times to produce 1 glucose molecule.

Cellular respiration is the process of cells breaking down the glucose made by photosynthesis into energy. Cellular respiration produces 36 ATP for each glucose molecule in 3 steps. First is glycolysis.  This occurs in the cytoplasm. 2 ATP is produced for every one glucose molecule. Then the Krebs Cycle converts the molecules from glycolysis into 2 ATP, 6 carbon dioxide, and NADH and FADH2. Lastly, the electron transport chain occurs within the inner membrane of the mitochondria. This uses oxygen, NADH, and FADH2 to convert ADP to ATP. The electron transport chain used the oxygen breathed in to recharge ADP to ATP. This last part creates 32 ATP. This means that in total, cellular respiration produces 36 ATP, 6 carbon dioxide, and 6 water molecules in total per 1 glucose molecule to start with.