The of substances between the environment and the

The eight major themes of biology are seen throughout the biology course and are expressed in every chapter. In the chapters on cells (6,7,9,10,11,12, and 13), there were many examples of the themes of biology. The ones that related to these chapters the most were: Science is a process, evolution, energy transfer, relationship with structure to function, and regulation homeostasis. All of these themes are essential to be able to grasp the main concepts of biology. The theme science is a process is a way of knowing.

It either involves a discovery process using inductive reasoning, or a process of hypothesis and testing. Cell fractionation  is a process that allows for separation of the different organelles of a cell so their functions can be studied. This process begins with homogenization, which is the disruption of cells. Using a machine called a centrifuge that spins, friction  breaks down the cells without severely damaging the organelles. The centrifuge is spun at different speed and durations so that heavier pieces are separated from lighter particles.

This process is used in science so that organelles in cells are able to be separated for studying purposes and we can know more about their functions and roles in the cell. In class, we experiment to learn more about biology and understand the processes better. Our AP biology class preformed an osmosis and difusion lab that showed the role of the cell membrane in regulating the passive movement of substances between the environment and the cytoplasm. We used dialysis tubing to study the effects of difusion and osmosis through a selectively permeable membrane.

This lab showed us that substances and small molecules can move through selectively permeable membranes while large molecules cannot. Also, we were able to see that contents move from where there is more to where there is less so that it can reach a homeostasis state. In another lab, plant pigments and photosynthesis, the purpose was to separate plant pigments using chromatography and measure the rate of photosynthesis in isolated chloroplasts  to determine the best conditions for photosynthesis to occur.

By using chromatography and testing chloroplasts in different conditions, we were able to discover that certain plant pigments have different traits which allowed them to move up the filter paper at different rates, and that chloroplasts photosynthesis occurs best in light and when the chloroplasts are not denatured by heat. Using inductive reasoning and a series of tests, there were several conclusions about the experiments. Evolution is the biological change of organisms that occurs over time and is driven by the process of natural selection.

It was thought that mitochondria and chloroplasts used to be prokaryotes before they were “swallowed” by larger eukaryotes. This is called the endosymbiosis theory, where both the prokaryote and the eukaryote have a symbiotic relationship, which means they are both benefiting from it. Mitochondria and chloroplasts are thought to be prokaryotes at one point because they both contain their own DNA, ribosomes, and enzymes. This shows that all things evolve and that organisms over time are driven to become better and more stable. Plants, which take in carbon dioxide and water to form organic molecules, also have evolved over time.

Plants like C4 plants and CAM plants have adapted from C3 plants to be able to live under certain strenuous conditions like heat, dryness, and darkness. These adaptations help the plants conserve water and make the process of photosynthesis more efficient in their environment. The process of glycolysis has also evolved over time too. It was thought that the first prokaryotes used glycolysis as a sole source of ATP because they did not have oxygen. now, cells couple glycolysis with the calvin cycle and the electron transport chain if oxygen is present to make more ATP.

Discoveries like these and understanding how things evolve help us expand our knowledge about humans and other species around us. Energy is the ability to do work. All living organisms have the ability to link energy reactions to the biochemical reactions in their cells. Cellular respiration is is a process that uses oxygen as a reactant to complete the breakdown of organic molecules to make energy in the form of ATP. This transfer of energy occurs in many steps throughout cellular respiration. Through the oxidation of a glucose molecule, energy is transferred from the glucose to NAD+.

From electron carriers, the energy goes to the electron transport chain where chemiosmosis occurs and the energy is converted into ATP. In another process called photosynthesis, light energy from the sun is captured and converted into chemical energy. Energy is transferred from light waves to the chlorophyll and other pigments found in the photosystems of chloroplasts in plants. This energy then jumps up and travels to the electron transport chain where ATP is created and used in the calvin cycle to create organic molecules. Active transport also requires energy transfer. This type of transport moves against the concentration gradient.

An example of active transport is the sodium potassium ion exchange pump, which maintains the gradients of Na+ and K+ across the membrane. Animal cells have higher concentrations of K+ inside and lower concentrations of Na+ inside the cell. Sodium potassium pumps use energy from one ATP to pump three Na+ ions out and two K+ ions in. This transfer of energy helps keep the animal cell balanced with the environment surrounding it. The free energy from catabolic pathways drives anabolic ones. This is called energy coupling, which is used to transfer energy in every living organism. The structure of anything is closely related to its function.

The cell membrane, for example, is made up of phospholipid bilayer, proteins, cholesterol, and carbohydrates which all contribute to the characteristics of the membrane. The cell membrane is seletively permeable, which means that it only lets certain things in and out. Only small nonpolar molecules are allowed through the membrane, while large polar molecules must travel though specific proteins. The cholesterol in the lipid bilayer allows for the membrane to stay fluid, which is necessary for it to work properly. The structure of the cell membrane allows it to do its job: keep certain things from moving in and out of the cell.

Cell communication is key in regulating the cell activities. The enzymes used to regulate the cell’s processes are specifically shaped to bind to certain substrates. If the enzymes were not specifically structured, then they would not be able to bind to the specific substrate that causes a conformational change and a signal for a process to start or stop. In plants, most of the chloroplasts are found in the leaves for a specific reason. The leaves are where most of the light from the sun hits, which is what chloroplasts need for photosynthesis to occur.

The placement of the chloroplasts in the leaves allow photosynthesis to occur efficiently and effectively since the chloroplasts are branched out and exposed to the sun. These examples show that structure is very closely related to function. Everything from cells, to organisms, to ecosystems is in a state of homeostasis that must be controlled. In Mitosis, there are specific checkpoints in the cycle where the process stops to regulate it. The G1 checkpoint, which is the most important of the three, checks for four specific things; presence of essential nutrients, growth factors, density-dependent inhibition, and anchorage dependence.

If something goes wrong with this, the cell goes into the G0 stage, which is the “non-dividing stage”. When the cell reaches the G2 checkpoint, it stops the cycle and makes sure everything from the s-phase is copied, specifically the DNA and the organelles. At the M-checkpoint, the cycle cycle stops and makes sure and even amount of DNA goes to opposite sides of the cell before telophase and cytolinesis occurs. These examples show how everything regulates and tries to maintain stable, constant conditions.

These checkpoints also make sure nothing is out of balance and that the process is done correctly so no mutations occur. The eight major themes of biology seen throughout the book help us expand our knowledge and see the big picture. In the chapters on cells, I was able to find many examples of the themes biology. The ones that related to these chapters the most were: Science is a process, evolution, energy transfer, relationship with structure to function, and regulation homeostasis. All of these themes are essential to grasp the main concepts of biology.


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