Hypothesis – an explanation for a question or problem that can be formally tested.
Experiment – an investigation performed by a scientist that tests a hypothesis by the collecting of information under controlled conditions.
Independent Variable – “I change” variable; the variable the experimenter changes in an experiment. The independent variable is the only factor that affects the outcome of a controlled experiment. This is why only one variable can be tested in a controlled experiment. If you tested two variables in one experiment, the experiment would be invalid.
Dependent Variable – the variable measured at the end of the experiment. Changes in response to the independent variable.
Ex: To test the affect of different soils on plant growth, I would place plants in containers with different types of soil. At the end of the experiment I would measure the height of the plants. Ind. Var: the different types of soil. Dependent Var: the height of the plants
Control – the part of the experiment that is the standard against which results are compared. The control receives no experimental treatment.
Data – Information obtained from investigations. (aka experimental results) Data may be quantitative, involving numerical information – or – data may be qualitative, meaning that it is expressed verbally (like describing what animals may do in their natural habitat and how they respond to changes in their environment.
Observation – the process of gathering information about events or processes in a careful, orderly way using the five senses.
Inference – a logical interpretation based on an observation, prior knowledge, or experience.
Prediction – the expected outcome of an experiment. May prove to be accurate or not.
When conducting a controlled scientific experiment, the sample size must be large enough to generate meaningful data. Control groups are groups of samples that receive no experimental treatment. When scientists publish the results of their experiments, they must be descriptive enough that other scientists can replicate their experiments and achieve the same results. It must be possible for different scientists to repeat another scientist’s experiment. Other scientists offer peer reviews that analyze the procedure, examine the evidence, identify faulty reasoning, point out statements that go beyond the evidence, and suggest alternative explanations for the same observations.
Safety is another important factor that scientists consider when carrying out investigations. Biologists try to minimize hazards to themselves, the people working around them, and the organisms they are studying. A safety symbol is a symbol that warns you about a danger that may exist from chemicals, electricity, heat, or procedures you will use.
Inorganic molecules do not contain carbon. Examples include salt (NaCl), water (H2O), oxygen (O2)
Organic molecules contain carbon. Carbon is an element found in all living organisms.
A molecule is a group of atoms – it is the smallest unit of most chemical compounds.
A macromolecule can also be called a polymer. It is a giant molecule made up of thousands or even hundreds of thousands of smaller molecules (monomers). Monomers join together to form polymers.
Polymer / Monomercarbohydrates / monosaccharide
lipids / 3 fatty acids & 1 glycerol
proteins / amino acid
nucleic acids / nucleotide
Carbohydrates are the main source of quick energy for living things.
Glucose (C6H12O6) is a monosaccharide. Other monosaccharides are galactose (in milk) and fructose (in fruit). Benedict’s solution is the food test for monosaccharides. Remember, many sugars end in the suffix “-ose”.
Glycogen is a carbohydrate (stored in the liver & muscles; monosaccharide of glycogen is glucose). Cellulose is another example of carbohydrate. Cellulose is found in the cell walls of plant cells and is the main component of wood and paper.
Iodine is the test for carbohydrates (remember the iodine dropped on the saltine turned it purplish-black.)
Lipids are fats, oils, and waxes. The function of lipids is to store energy (long-term energy storage). Some lipids are important parts of biological membranes and waterproof coverings (like the cell membrane).
Proteins contain nitrogen along with carbon, hydrogen, and oxygen. Amino acids are the monomer for proteins. There are over 20 different amino acids. Proteins are made on the ribosome where the amino acids are put together by peptide bonds. A chain of amino acids is called a polypeptide. Once the polypeptide is folded it can be called a protein.
Hemoglobin is the protein in red blood cells that holds onto oxygen molecules.
Functions of proteins: Some proteins control the rate of reactions (these are called enzymes) and regulate cell processes. Some proteins are used to form bones and muscles. Others transport substances into or out of cells or help fight disease (antibodies).
Biuret’s is the food test for protein.
Enzymes are a special type of protein. They act as biological catalysts. A catalyst is a substance that speeds up the rate of a chemical reaction, so enzymes speed up chemical reactions in living things. Enzymes bind substrates on the active site.
Enzymes are re-usable. The enzyme and substrate fit together at the active site like a lock and key. Enzymes, like all proteins, can become denatured (destroyed) by high temperatures and changes in pH (acid/base level).
Remember, many enzymes end in the suffix
“-ase”.
Nucleic acids store and transmit hereditary, or genetic, information. The two examples of nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
The monomer, or building block, of nucleic acids is the nucleotide. A nucleotide has three parts:
1. A 5-carbon sugar
2. A phosphate group
3. A nitrogenous base
DNA is double-stranded. The sugar in the nucleotide of DNA molecules is deoxyribose. The four nitrogen bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
Adenine and thymine pair up and are held together by weak hydrogen bonds. Cytosine and guanine pair up and are also held together by weak hydrogen bonds.
DNA is always found in the nucleus of eukaryotic organisms. DNA is circular and found in the cytoplasm of prokaryotes. These circular pieces of DNA in prokaryotes are called plasmids. They can be used in genetic engineering.
The nitrogen bases of DNA are held together by weak hydrogen bonds. When DNA makes an exact copy of DNA (replication) the hydrogen bonds break to allow more DNA to be made. Replication occurs in the nucleus because DNA only exists in the nucleus!
RNA is single-stranded. The sugar in the nucleotide of RNA molecules is ribose. The four nitrogen bases in RNA are adenine (A), uracil (U), cytosine (C), and guanine (G).
Adenine and uracil go together Cytosine and guanine go together.
There are three types of RNA:
1. mRNA (messenger RNA) – This is the single-stranded RNA made in the nucleus. mRNA wriggles out of the nucleus into the cytoplasm where it seeks out a ribosome so it can go on to assist with making protein.
It contains the nitrogen bases A, U, C, & G.
Three nitrogen bases on a strand of mRNA form the triplet (aka codon) that determines which amino acid needs to be brought to the ribosome during protein synthesis.
2. tRNA (transfer RNA) – This is the molecule of RNA that brings (or transfers) the amino acid to the ribosome. The triplet of nitrogen bases on the tRNA is called the anti-codon.
3. rRNA (ribosomal RNA) – This is simply the ribosome. The ribosome is made of RNA.
The cell is the basic unit of all living things. There are seven organelles you need to know:
1. nucleus – the control center of the cell; found in eukaryotic cells only; contains the DNA.
2. cell membrane (aka plasma membrane) – controls what enters and leaves the cell. Made of a phospholipid bilayer. Also provides protection and support for the cell
q The cell membrane is considered to be semi-permeable because it allows some molecules to enter the cell while keeping other molecules out of the cell. Think of a screen door that allows air to enter a room, but keeps the bugs out.
3. cell wall – found only in plant cells. Provides structure and protection for plant cells.
4. mitochondria – site of cellular respiration; Convert food energy into cellular energy in the form of ATP. The “mighty mitochondria”.
5. vacuoles – storage site for nutrients, water, salts, and wastes. Plant cells have one big central vacuole while animal cells have many, small vacuoles.
6. chloroplasts – site of photosynthesis in autotrophs. This is where light energy gets trapped and converted into chemical energy (glucose - C6H12O6)
7. ribosomes – site of protein synthesis (translation). All cells have ribosomes because all cells need protein.
Main differences between plant cells and animal cells:
q Plant cells have chloroplasts, a cell wall, and a central vacuole.
q Animal cells lack chloroplasts, lack a cell wall, and have many, small vacuoles.
A group of cells forms a tissue. A group of tissues forms an organ. A group of organs forms an organ system:
Cells ® Tissue ® Organ ® Organ System
Chemical signals from one cell influence the activity of another.
Cell Transport:
Diffusion – the movement of molecules from an area of high concentration to an area of low concentration; a form of passive transport since no energy is required.
Osmosis – the diffusion of water; the movement of water molecules from an area of high concentration (of water molecules) to an area of lower concentration (of water molecules); a form of passive transport since no energy is required.
Active Transport – the movement of molecules from an area of low concentration to an area of high concentration. Considered to be “active” because it requires energy to move molecules against a concentration gradient (from low to high concentration).
Homeostasis: the process by which organisms maintain a relatively stable internal environment. (temperature, pH level, blood glucose levels, water balance, salt balance)
Determine total magnification of a light microscope by multiplying the magnification of the eyepiece lens with the magnification of the objective lens. So if the eyepiece lens magnification is 10X and the objective lens magnification is 40X the total magnification is 10 x 40 = 400X.
Objects in a microscope appear to get turned upside-down and backwards. So, the letter “p” would look like the letter “d” through a microscope.
Cellular respiration (aerobic respiration) is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. It occurs in the mitochondria and produces cellular energy (ATP):
O2 + C6H12O6 ® CO2 + H2O + ATP
oxygen glucose carbon water cell
dioxide energy
Cellular respiration (aerobic respiration since oxygen is present) produces a total of 36 ATP molecules.
Autotrophs and heterotrophs both do cellular respiration. (Plants have mitochondria.)
Anaerobic respiration releases energy from food by making ATP when oxygen is not present. Fermentation is another name for anaerobic respiration. There are two types of fermentation:
1. Alcoholic fermentation – yeast performs alcoholic fermentation. Remember that yeasts are unicellular members of Kingdom Fungi.
Alcoholic fermentation produces alcohol and carbon dioxide. Used in the production of bread (carbon dioxide makes bread rise), beer, and wine.
2. Lactic Acid fermentation - occurs in your muscles when you do strenuous exercise and the body cannot supply enough oxygen to the tissues. Prokaryotes also perform lactic acid fermentation. Cheese, yogurt, buttermilk, sour cream, pickles, and sauerkraut are all produced thanks to lactic acid fermentation.
Fermentation produces a net total of 2 ATP molecules. Aerobic respiration produces 18x as many ATP molecules than anaerobic respiration. Aerobic respiration is much more efficient than anaerobic respiration.
Photosynthesis – the production of chemical energy from light energy. It occurs in the chloroplasts. The pigment in chloroplasts is chlorophyll.
CO2 + H2O ® O2 + C6H12O6
carbon water oxygen glucose
dioxide
Autotrophs – organisms that can make their own food. All plants are autotrophs.
Heterotrophs – organisms that must consume other organisms for food. All animals are heterotrophs.
*Remember plants must do both photosynthesis and cellular respiration!
Genetic Mutations:
Any change in the DNA or RNA code is a genetic mutation.
A point mutation occurs when one nitrogen base is replaced with the wrong nitrogen base. This causes one incorrect amino acid to be placed in the chain of amino acids (protein). Sickle cell anemia is caused by a point mutation.
A frameshift mutation occurs when a nitrogen base is either inserted or deleted from the DNA or RNA. This type of mutation causes all amino acids pulled into the protein after the mutation to be incorrect.
Chromosomal Mutations:
Occurs when there is a change in the number of structure of chromosomes. For example, Down syndrome is caused by having three copies of chromosome #21 instead of two copies. It is considered to be a trisomy.
Cell Division:
Mitosis – the way body cells reproduce. A cell makes an exact copy of itself. Stages of mitosis (IPMAT):
Interphase, Prophase, Metaphase, Anaphase, Telophase.
Human body cells have 46 chromosomes. Body cells are diploid (2n) meaning they have one pair of each chromosome (homologous chromosomes). So when a human body cell undergoes mitosis, it splits into two identical body cells. The process of DNA replication causes the chromosome number to double. Then the cell splits.
Remember, mitosis: double ® split
92 ® 46
Mitosis produces 2 diploid cells.
Meiosis – the way sex cells (gametes) reproduce. The gametes are the eggs for females and the sperm for males. Sex cells are haploid (n) meaning they only have one copy of each chromosome. Human sex cells have 23 chromosomes. The process of DNA replication occurs prior to meiosis. The chromosome number doubles and then splits twice:
double ® split ® split
92 46 23
Meiosis produces 4 haploid cells.
Genetics:
Tt x Tt
T / tT / TT / Tt
t / Tt / tt
Genotype is the genetic makeup of an organism. There are 3 possible genotypes with a Tt x Tt cross: TT (homozygous dominant), Tt (heterozygous), tt (homozygous recessive).