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Living Environment Essay

* All living things must maintain homeostasis in order to stay alive. * Homeostasis: A balanced state in an organism’s body. * Failure to maintain homeostasis results in disease or death. * Homeostasis is often maintained using feedback mechanisms. * Feedback mechanisms are cycles in which the product of one reaction causes another to start or stop. * While organisms are balanced, they are not unchanging. The term used to describe the balanced state is dynamic equilibrium. * Dynamic Equilibrium: A balanced state created by many small, opposing changes.

* Life Processes: All living things carry out the same basic chemical processes. Taken together, these processes make up an organism’s metabolism. * Metabolism: All the chemical processes that take place in an organism. * Nutrition: Using nutrients for growth, synthesis, repair and energy. * Respiration: Converts energy in food into a usable form (ATP). * Synthesis: Making complex chemicals from simple substances. * Transport: Absorbing and distributing materials throughout the body. * Regulation: The control and coordination of life processes. * Excretion: Removing of wastes produced by metabolic activities. * Reproduction: Passes on genes to offspring.

* Inorganic Chemicals: Simple compounds
* Water ( H2O) : Most common substance in all living things (about 60% of body mass) * Needed for chemical reactions ( which won’t happen in “dry” conditions) * Dissolves other molecules into solution, allowing them to be transported through the body.

* Oxygen (O2): Needed by most (not all) organisms for cellular respiration. * Released by plants and algae as a waste product of photosynthesis. * Aerobic respiration: Process that uses oxygen to extract energy from glucose (sugar). Used by most organisms. * Anaerobic respiration: Process that extracts energy from glucose without using oxygen. Gives less energy, so only used by some simple organisms (some bacteria, yeast). These organisms do not need to breathe in oxygen.

* Carbon Dioxide (CO2):
* With water, used by plants to make glucose (photosynthesis).
* Waste product of aerobic respiration.

* Nitrogen (N2):
* Most common gas in air (70%)
* Needed to make protein.
* Converted into nitrates by soil bacteria. Nitrates are absorbed by plants and then eaten by animals
. * Excreted as waste in urine.

* Acids and Bases:
* Measured by the pH scale
* pH can affect rates of chemical reactions; for example, digestive enzymes work fastest in acidic environments, which is why we make stomach acid (hydrochloric acid, or HCl).

* Organic Compounds: Larger, more complex chemicals. Always contain the elements carbon (C) and hydrogen (H). Synthesized from simpler substances (building blocks). * Carbohydrates: Sugars and starches

* Building blocks: Simple sugars
* Functions:
* A starch (A) is broken down by an enzyme (B) into two simple sugars (C, D). This is also a good example of the lock and key model. A starch (A) is broken down by an enzyme (B) into two simple sugars (C, D). This is also a good example of the lock and key model. Provides energy

* Stores energy in plants (starch)

* Lipids: Fats, oils and waxes
* Functions:
* Stores energy (animal fat)
* Insulation
* Water proofing
* Cell membrane

* Proteins: Complex compounds that carry out all the body’s activities. * Building blocks: Amino acids * Have many different functions as determined by their shape. * Lock and Key Model: Proteins must have the right shape to “fit” with other molecules. * Changing the shape of a protein will change what it can interact with its function. * Important types of proteins:

* Hormones and neurotransmitters – carry messages through the body. * Cell receptors – in cell membrane; receive hormones and neurotransmitters. * Antibodies – attack foreign pathogens

* Enzymes- act as catalysts, controlling all chemical reactions in the body. * High temperatures will cause enzymes to denature (lose their shape) and stop functioning. This is why high fevers are dangerous.

* Nucleic Acids (DNA and RNA): Make up genes and chromosomes. * Building blocks: Nucleotides; molecular bases (ATCGU)

Topic Two: The Cell
I. Definition: The basic unit of structure and function in all living things.

II. Cell Theory has three parts:
1. All living things are made of one or more cells. * Unicellular – single celled organisms (amoeba, paramecium) * Multicellular – have more than 1 cell; may be only a few cells, or many trillions of cells. Almost all structures in multicelled organisms are made of or by cells. 2. Cells carry out all life processes.

* Everything you do is the result of the work of your cells – walking, talking, even thinking and feeling. When you get sick, it is because your cells are not working correctly.

3. All cells come from preexisting cells.
This seems obvious now, but at one time people believed in spontaneous generation, the idea that living things regularly emerged from nonliving things.

A) Exceptions to the Cell Theory
4. Viruses are not made of cells. However, they also do not carry out all life processes; so many biologists do not consider them true living things. 5. The first cell obviously could not come from another cell.

III. Organization
B) Atoms
C) Molecules
D) Organelles – Cell structures
E) Cells
F) Tissues – Cells with the same structure and function. G) Organs – Made of different tissues working together for the same function. H) Organ Systems – Groups of organs that work together. I) Organism

IV. Cell Organelles: These are the tiny cell parts that make up a cell. 6. Nucleus
* Controls the cell
* Contains hereditary material (chromosomes, genes, DNA) 7. Cytoplasm (technically not an organelle)
* Fluid/liquid in the cell – mostly water
* Helps transport material
8. Mitochondrion
* Carries out cellular respiration.
* Gives cell energy (Powerhouse of the cell).
9. Ribosome
* Makes proteins from amino acids.
10. Vacuole
* Stores food, water and waste
* Food vacuoles may digest large molecules.
* Waste vacuoles may excrete waste out the cell membrane 11. Chloroplast
* Carries out photosynthesis
* Plant and algae cells only
12. Cell Wall
* Gives shape, structure and protection.
* NEVER found in animal cells.
13. Cell Membrane
* Separates cell interior from environment
* Controls what enters and leaves the cell using transport proteins.
* Has receptor molecules that pick up signals from
other cells. * Has antigens which are protein “tags” that identify the cell (see immune system).

Topic Three: Nutrition, Photosynthesis and Respiration
Reminder: All life processes are chemical activities which make up your metabolism.
* Nutrition: Taking in nutrients (food) for various activities including:
* growth
* healing
* synthesis
* respiration (energy)
A) Ingestion: To take nutrients into the body.
B) Digestion: To break down nutrients into smaller pieces. 1. Nutrients must be broken down into smaller parts so that they can be absorbed into the blood and cells of organisms. * Starches are digested into simple sugars.

* Proteins are digested into amino acids.

C) Autotrophic Nutrition: Organisms take inorganic materials (CO2, H2O) and convert them into organic nutrients (carbohydrates). 2. Auto = self ; troph = food; so Autotroph = self feeding 3. Photosynthesis is most common form of autotrophic nutrition 4. Plants, algae and blue-green bacteria (cyanobacteria) are common autotrophs.

D) Heterotrophic Nutrition: Organisms must consume nutrients from other organisms. 5. Hetero = other so Heterotroph = feeds on others. 6. All animals and fungi are heterotrophs.

7. Includes:
* Carnivores: eats mostly animals
* Herbivores: eats mostly plants or algae
* Omnivores: eats both plants and animals
* Decomposers: breaks down dead matter and waste
* Decomposers are important for recycling nutrients *

I. Photosynthesis: Process in which sun’s energy is trapped in the chemical bonds of sugar. E) Requires sunlight, water and CO2.
F) Makes glucose (C6H12O6) as food.
G) Water and oxygen are waste products.
H) Benefits:
8. Provides food for all plants, animals and other organisms. 9. Provides oxygen to breathe.
10. Removes CO2 from atmosphere.
I) Plant adaptations:
11. Chloroplast: Cell organelle that does photosynthesis
12. Gas exchange:
* Stomata : Pores under a leaf; let gases in and out * Guard cells: open and close stomata to prevent dehydration
13. Transport:
* Xylem and Phloem: “tubes” transport food and water throughout the plant.

Two different views of the stomates and their guard cells (X).

Two different views of the stomates and their guard cells (X).

II. Cellular Respiration: Process that takes energy from sugar molecules and places it in molecules of ATP. J) ATP is the molecule all life uses for energy.
* No organism can get energy from sunlight or sugar without first putting the energy into ATP. K) Requires oxygen, glucose and water.
L) Carbon dioxide and water are waste products.

M) Most organisms carry out aerobic respiration (uses oxygen) in their mitochondria. N) Anaerobic respiration does not require oxygen, but gives less ATP (energy) for each molecule of sugar. * When exercise causes human muscles to run out of oxygen, their cells will do anaerobic respiration. The waste product, lactic acid, causes muscles to “ burn” so that you will stop.

O) Photosynthesis and Cellular Respiration are opposite reactions! They are also important in cycling oxygen, carbon, hydrogen and water through the environment

P) Common mistakes:
* “Plants use photosynthesis, animals use respiration.” All organisms, including plants, use respiration to get their energy.

* “Respiration is breathing.”
Breathing is not respiration. Breathing exchanges the gases needed for respiration. Inhaling and exhaling does not give you ATP.

* “Oxygen is used to breathe.”
This is backwards. Breathing is used to get oxygen which is used for respiration. Without oxygen, you have no respiration, no ATP, and no energy. * “All living things need oxygen/need to breathe.” Anaerobic organisms do not need oxygen, and do not have to breathe.

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