Study Guide Homeostasis

8th Grade Living EnvironmentMr. Ardito's Classes

Study Guide - Homeostasis Unit1. Characteristics of Life2. Homeostasis3. Cells4. Photosynthesis/Cellular Respiration5. Diffusion

1. Characteristics of LifeThis is the set of processes that a living thing must do in order to be considered alive.

M -- Metabolism -- The total of all chemical reactions within the organismR -- Regulation -- Being able to respond to changes in the internal and externalenvironment.L -- Locomotion -- Moving from place to place in search of food, water, shelter, and mates.S -- Synthesis -- Building big things from small things.T -- Transport -- Moving materials within the organismR -- Respiration -- Burning food for energyN -- Nutrition -- Obtaining energy from the environmentG -- Growth -- More cells and bigger cellsE -- Excretion -- Removing wasteR -- Reproduction - The organism makes copies of itself

2. HomeostasisThis is the process by which living things maintain the optimal internal environment forthemselves.One example we talked about in class was thermoregulation, which is managing bodytemperature. The chemical reactions within our bodies work best and at all only at certaintemperatures. So, our bodies work to keep our core body temperature within certain levels.

Feedback MechanismsThese are the processes that living things use to maintain homeostasis.We studied two types:Negative Feedback LoopsPositive Feedback Loops

Negative Feedback LoopsThis is a situation where one thing happening causes another thing to stop happening.

Here is an example:

Ardito Homeostasis Study Guide 1

Positive Feedback Mechanisms

This is a situation where one thing happening causes another thing to happen more.

In class, we used the examples of arguing or putting a microphone to a speaker. One thinghappening causes more of that thing to happen.

3. CellsCells are the smallest living things.They have to perform all of the Characteristics of Life in order to function.The cell organelles are parts of the cell that carry out these life processes.


Cell OrganellesCell Wall - Surrounds the plant cell and provides structure to the cellCell Membrane -- Found in both plant and animal cells. Determines what goes in and out ofthe cell.Nucleus -- Considered the control center of the cell. Houses the chromosomes and thenucleolus.Chromosomes -- Found in the cell nucleus. Contains the genetic information for the cell (therecipes it needs to do everything it needs to do to function).Nucleolus -- Found in the nucleus. Makes the ribosomes.Ribosomes -- Found in the cytoplasm. Makes proteins.Endoplasmic Reticulum -- Found in the cytoplasm, just outside the nucleus. Finishes up theproteins made by the ribosomes.Cytoplasm -- A jelly like fluid that contains all the other organelles.Mitochondria -- The powerhouse of the cell. This is where the cells burn glucose for fuel. Thehome of cellular respiration.Golgi apparatus -- The post office of the cells. It packages up materials made by the cell.Vacuoles - Storage containers within the cell. In plant cells, they are very big and helpprovide structure for the cell.Lysosomes -- Little vessels that break down waste produced by the cells.Chloroplasts -- Found in plant cells only. They are the place where photosynthesis takesplace.

4. Photosynthesis/Cellular RespirationThese are two of the most important chemical reactions performed by living things. If itwere not for these two reactions, there would be no life on Earth.

PhotosynthesisThis is performed by plants. Photosynthesis happens in the chloroplasts.In photosynthesis, plants convert some of the Sun's energy into a form that can be used byall living things.In photosynthesis, inorganic molecules (carbon dioxide and water) are converted into an


organic molecule (glucose).The energy that is converted from sunlight is stored in the bonds connecting the carbons inglucose.

Formula for Photosynthesis:Carbon Dioxide + Water ---SUNLIGHT-----> Glucose + Oxygen + WaterCO2 + H20 ---SUNLIGHT-----> C6H12O6 + O2 + H2O

Cellular RespirationThis is performed by both plants and animals. Cellular Respiration happens in themitochondria.In cellular respiration, cells combine glucose and oxygen to release energy. This energy is inthe form of another molecule called ATP (which stands for adenosine triphosphate). ATP isthe form of energy that cells use to perform all of their life functions.

Formula for Cellular RespirationGlucose + Oxygen ------------> Carbon Dioxide + Water + ATP

C6H12O6 + O2 ------------> CO2 + H20 + ATP

5. Diffusion

Diffusion is the process where stuff moves from where there is more of it to where there isless, unless a balance (or equilibrium) is reached.Diffusion is the process by which substances move across the cell membrane. The cellmembrane is called semi-permeable, because it lets some things through and keeps otherthings out.

Three types of DiffusionOsmosis - the diffusion of water across the cell membrane. This process uses NO ENERGY.Diffusion (passive transport) - the diffusion of substances other than water across the cellmembrane. This process uses NO ENERGY.Active Transport -- This is the movement of substances across the cell membrane fromwhere there's less to where there's more (the opposite of what normally happens in


diffusion). This process uses ENERGY.Active transport is how your nerve and muscle cells work.


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Study Guide Homeostasis