Living Environment - Regents Review Notes
Topic 1
- Organelles → Cells → Tissues → Organs → Organ Systems → Organism (simplest to most complex)
- Human Systems: digestive, respiratory, reproductive, circulatory, excretory, muscular, nervous, endocrine (coordination), and immune systems.
- These systems interact to perform life functions and maintain homeostasis.
- Functions of Human Systems:
- Digestive: Breaks down molecules and makes nutrients available.
- Circulatory: Carries nutrients and oxygen to cells.
- Respiratory: Exchange of gases.
- Excretory: Removal of metabolic wastes (water, carbon dioxide, salts, and urea).
- Nervous: Sends messages throughout the body; organisms detect and respond to stimuli.
- Endocrine: Glands release hormones into the bloodstream. (Both the nervous and endocrine systems are involved in communication and coordination).
- Example: The circulatory system moves nutrients (from digestion) throughout the body.
- Disruption in any system affects homeostasis. (Diseases of the Systems: ulcers, heart attack, emphysema, kidney stones, multiple sclerosis)
- Cells of the body are very different (stomach cell vs. liver cell) but all cells of the body are coordinated and work together.
- Cell Membrane: Separates cell from the outside environment, controls what enters and leaves the cell.
- Diffusion:
- Requires no energy.
- Molecules move from high to low concentration; down the concentration gradient.
- Osmosis:
- Diffusion of water.
- Salt solution effect on a plant cell: cell membrane and cytoplasm shrink to the middle of the cell while the cell wall remains intact; the salt draws the water out of the cell.
- Active Transport:
- Requires ATP (energy from glucose is transferred to the bonds of ATP).
- Molecules move from a low to high concentration; against a gradient.
- Receptor molecules: Embedded in the cell membrane to recognize hormones and neurotransmitters. Involved with coordination and cell communication. If hormone or neurotransmitter (nerve signal) are blocked from binding to receptor molecules, cellular communication is disrupted.
- Target cells have receptors that are specific for that hormone.
- Large organic food molecules must be broken down in order to enter cells. Enzymes are responsible for this process.
- Example: Starch is broken down into simple sugars & Proteins are digested to amino acids.
- Organelles:
- Nucleus: Controls activities of the cell, stores genetic information - DNA.
- Mitochondria: Cell respiration occurs here; energy is extracted from nutrients.
- Ribosomes: Site of protein synthesis.
- Cytoplasm: Liquid portion of the cell - molecules can be moved from one part of the cell to another.
- Vacuole: Food or wastes are stored here.
- Chloroplasts: Site of photosynthesis.
- Cell membrane: Controls the movement of molecules into and out of the cell.
- Organelles that work together:
- nucleus and ribosome
- cell membrane and chloroplasts
- Organelles carry out similar functions as the human body systems:
- nucleus - nervous system (brain)
- mitochondria - muscular system
- cytoplasm - circulatory system (blood)
- vacuole - digestive system (stomach)
- cell membrane - respiratory system (alveoli of the lungs for exchange of materials)
Topic 2
- Energy for life comes primarily from the Sun.
- Photosynthesis provides a vital connection between the Sun and the energy needs of living things.
- Plant cells and one-celled organisms (algae) contain chloroplasts (site of photosynthesis).
- Equation for photosynthesis:
- Energy in organic molecules (glucose) is released during cellular respiration and stored in the bonds of ATP. This event occurs in the mitochondria.
- Equation for cellular respiration:
- Energy from ATP is used to do work for the cell (Example: active transport).
- Enzymes: proteins, biological catalysts (affect the rate of chemical reactions), involved in the breakdown and synthesis of molecules.
- Rate of enzyme activity is affected by pH (pH lower than 7 is acidic and a pH greater than 7 is basic). and temperature.
- High Temperatures slow down the activity of the enzyme. The shape of an enzyme is very important to its function. It will bind to a substrate. At high temperatures, the enzyme denatures or changes shape and can no longer bind to its substrate. If high temperatures continue, enzymes will no longer work and chemical reactions in the body would stop.
- Molecules that are specific in terms of their shape and what they can react with:
- a) enzymes b) antibodies c) receptor molecules
- Shape influences how they function.
- Homeostasis can be threatened by: bacteria (strep), viruses (flu, common cold, HIV), fungi (athlete's foot), parasites (tapeworm)
- Immune System: protects you against antigens (protein molecules on the surface of pathogens). These antigens serve as an ID tag and your body recognizes these pathogens as "non-self" and prepares an immune response.
- White Blood Cells: can engulf invaders or produce antibodies that attack invaders (pathogen)
- Vaccinations: person is given weakened microbes/pathogen to stimulate the immune system to react and produce antibodies.
- Steps to creating a vaccine:
- Obtain pathogen
- Weaken it
- Inject weakened pathogen into organism
- Organism produces antibodies against the pathogen and will remember the pathogen, in case of any future attacks.
- AIDS: weakened immune system; victims are more likely to get secondary infections and cancer.
- Allergic Reactions: body produces antibodies to usually harmless environmental substances (dust, pollen, animal hair)
- Immune system can attack own cells (autoimmune disease)
- Immune system can attack transplanted organs. So, the individual must take immunosuppressants, so they don't reject the organ.
- Causes of Disease: a) inheritance (cancer and diabetes can be inherited), b) toxic substances, c) poor nutrition, d) organ malfunction, e) high-risk behaviors
- Cancer: uncontrolled cell division resulting from gene mutation.
- Cell exposure to radiation and/or chemicals increases chances of gene mutation
- Feedback mechanisms help to maintain homeostasis (dynamic equilibrium)
- Examples:
- The maintenance of blood sugar levels by insulin (lowers blood sugar level) and glucagon (raises blood sugar level) from the pancreas.
- Exercise, Carbon dioxide level, Change in breathing rate :(an increased level of carbon dioxide resulting from cell respiration causes an increase in your breathing rate. The brain detects this increased level of carbon dioxide in the blood and sends a message to breathe heavier. When carbon dioxide decreases, brain detects this and sends a message to slow down breathing rate.)
- Plants: guard cells and stomates (pores or openings); guard cells regulate the amount of water loss and regulate gas exchange (carbon dioxide into the leaf and oxygen out)
Topic 3
Genes are inherited but gene expression can be changed by interactions with the environment. For example:
- Himalayan rabbit (cool temperatures turn on the black pigment gene)
- identical twins separated at birth - one growing up in a small suburb and the other growing up in a busy industrial city where there are many factories. They may both have a cancer gene but the one living in the city may get that gene turned on.
All the cells in your body contain the same genetic information but yet carry out very different functions. This is due to gene expression.
In different cells, certain genes are "turned on" (expressed) and certain genes are "turned off' (not expressed).
Heredity: passage of coded instructions from one generation to the next
Hereditary information is contained in genes, located in the chromosomes of each cell
A trait can be determined by one or more genes.
A single gene can affect more than one trait.
Asexual Reproduction: all genes come from one parent and offspring are genetically identical to the parent. Carried out by mitotic cell division (mitosis).
Sexual reproduction: the new individual receives half genetic information from mother(egg) and half from father (sperm). Offspring often resemble parents but are not identical.
Advantage of sexual reproduction over asexual: sexual reproduction offers genetic variation. Variation increases an organism's chances of survival in a changing environment.
4 bases of DNA: A, G, C, T (weak chemical bonds separate the two strands of DNA)
DNA Replication:
- Template / Pattern or guide for a new DNA strand
Genetic information stored in DNA is used to direct the synthesis of proteins. The base sequence of DNA affects the amino acid sequence of protein.
You should be familiar with the Protein Synthesis Picture in review book p. 43 Fig.3-5
Messenger RNA: A, U, G, C
You can use the messenger RNA codons to determine the sequence of amino acids, using the chart.
Genes are segments of DNA.
Mutations:
- change in DNA sequence
- inserting, deleting, or substituting DNA segments can alter genes.
- mutations in gametes can be passed on to offspring
Proteins: long folded chains of amino acids in a specific sequence. The sequence of the amino acids affects or influences the shape of the protein. The shape of the protein then influences the function.
Selective Breeding: to produce offspring with favorable traits
Altering the genetic makeup of an organism:
- Genetic Engineering: transferring DNA from one organism to another
- Ex: transferring the human insulin gene into bacterial DNA and inserting this into a bacterial cell. Many copies of the human insulin gene can be made at a low cost. Reduction in cost and side effects. Human insulin can be used to treat people with diabetes.
- Enzymes are used to cut, copy, and move segments of DNA.
Human Genome Project:
- scientists hope to cure and/or diagnose diseases
- scientists can replace defective genes with normal genes (gene therapy)
Genetic disease: sickle cell anemia