Download Bio Core 40 Review

Bio Core 40 Review
Basic Biochemistry
Three main types of bonds
•
Ionic bond – a “magnetic” attraction that is formed when one atom loses an electron (so it is positive), and the other atom gains an electron
(so it is negative)
•
Covalent bond – a bond that is formed when two atoms share electrons
o Covalent bonds can be “polar,” which means that the shared electrons are closer to one atom than to the other atom. Because of
this part of the compound will have a slight positive charge, and part of it will have a slight negative charge. Water is an example
of a polar molecule.
o Covalent bonds that have an equal sharing of electrons are neutral are called “non-polar.” These are neutral and do not have
positive and negative areas.
•
Hydrogen bond – a weak attraction between two different polar molecules
Advanced: Covalent bonds require energy to form, so when some bonds are broken and others are created, energy may either be released or stored.
Living things use energy to create organic molecules. When the molecules are split and the resulting atoms form new bonds, energy is released.
Major components of organic molecules
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Carbon – this is the main one!!!
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Hydrogen, Oxygen.
•
(Nitrogen, Sulfur, and Phosphorus are also important, but in much smaller amounts)
Four major categories of organic compounds
Carbohydrates are made up of one or more sugar molecules stuck together. They have many functions. Glycogen is a carbohydrate that is
used by animals to store energy for short term use. Starch is a carbohydrate that stores energy for plants. Cellulose is a carbohydrate that is
used for cell walls in plants.
Sugars are simple carbohydrate molecules that most living organisms use for immediate energy. They are made of Carbon,
Hydrogen, and Oxygen atoms. Examples of sugars are fructose, sucrose (table sugar), and glucose.
Proteins are compounds made up of units called “amino acids.” These amino acids all have Carbon, Hydrogen, Oxygen, and Nitrogen atoms;
and some also have Sulfur atoms. They play a part in every process of cells, and are the main component of muscle. Meats have lots of
proteins.
Lipids include oils, fats, phospholipids, steroids, and waxes. They are used to help form cell membranes (phospholipids), and for long term
energy storage (fats).
Nucleic acids are used to store information for your cells. DNA and RNA are examples of nucleic acids. They are made of units called
nucleotides.
**Enzymes are proteins that are used to speed up a chemical reaction. Amylase is an example of an enzyme. It is present in saliva, and it helps to
break down starch into sugar molecules. The enzyme itself doesn’t break down.**
Cell Basics
Prokaryotes (bacteria) are simple cells – no nucleus and missing most organelles. They have circular DNA, cell membrane and wall.
Eukaryotes (plants, animals, fungi, etc.) are more advanced. They have a nucleus. They have linear DNA, and lots of membranes within the cell
(lysosomes, nucleus, golgi complex, endoplasmic reticulum, etc.)
Animal cells and plant cells have many of the same parts – but animal cells do not have chloroplasts or cell walls. Plant cells have both. Plant cells
also usually have one large vacuole. Animal cells do not.
Important cell parts
Mitochondria – carries out cellular respiration (energy source). Has its own DNA and ribosomes
Chloroplast (only in plant cells) – carries out photosynthesis
Ribosome – makes proteins (with the help of mRNA and tRNA) – in both prokaryotes and eukaryotes
Golgi Complex – packages and sends cell products out of cell
Endoplasmic reticulum – final processing of proteins, and moves things around the cell
Cell membrane – protects cell and controls what comes in and out – made of a “phospholipid bilayer”
o Membrane has protein channels to let in certain substances that won’t go through the membrane
Cell Division
Cell Cycle – There are four parts of the cell cycle. “G1” is when the cell grows. “S” is when the cell copies its DNA. “G2” is when the cell grow
some more. “M” is when the cell actually divides (mitosis)
Mitosis
Normal Cell Division, makes two exact copies of the cell.
Prophase, (Prometaphase), Metaphase, Anaphase, Telophase
Each chromosome has been duplicated. They are held together by centromeres, and are called sister chromatids
The chromosomes split in metaphase, and each new cell will get one copy.
In humans, there are 23 types of chromosomes. You get two of each type, so there are 46 total in each cell
Meiosis
Cell Division for gametes (egg or sperm)
Reduces number of chromosomes to half of the normal number (a human egg or sperm has 23)
o One of each chromosome type instead of two
o “Haploid” means one of each chromosome type, “Diploid” means two of each chromosome type
Energy
Cellular Respiration
Sugar is broken down for energy to make ATP (the form of energy used by the cell
Takes in sugar and oxygen (aerobic respiration), and lets off carbon dioxide and water
o Starts in the cytoplasm, but mostly takes place in the mitochondria
Can make energy without oxygen (anaerobic respiration), but not nearly as much
Photosynthesis
Sunlight is converted from light energy and stored in chemical bonds
Takes in carbon dioxide and water, and produces oxygen and glucose (sugar)
Two cycles - “Light cycle” produces ATP, “Dark cycle” uses that ATP to make the sugar
DNA
Double Helix – looks like a twisted ladder. The sides of the molecule are made up by a sugar and a phosphate; the “rungs” are the bases
The two sides are held together with hydrogen bonds that link the bases together
Four Bases – Adenine (A) binds with Thymine (T); Cytosine (C) binds with Guanine (G) (A-T, C-G)
When DNA copies and makes another DNA molecule, this is called replication
Protein Synthesis
DNA copies on to mRNA – this is called transcription – it happens in the nucleus
o RNA is only a single strand, not a double strand. It also uses Uracil (U) instead of Thymine (T)
The mRNA goes out of the nucleus into the cytoplasm to the ribosome
Every three base unit on the mRNA is called a codon – each codon matches up with one tRNA
tRNA molecules bring in amino acids, and match up with the codons on the mRNA
The amino acids are bonded together to make a complete protein.
Genetics
A gene is a section of DNA that holds information for a specific trait (like the color of a flower)
An allele is the actual information that is written there (like red or white)
Most organisms have two copies of each DNA, so they have two alleles
Often, one allele is dominant, and it is recessive. If an organism has one dominant allele and one recessive allele, the dominant one is the
one that is expressed
The phenotype is what the organism looks like. The genotype is a list of alleles.
If red is dominant, and white is recessive, we might use “R” to be red and “r” to be white
A flower with the genotype Rr would have the phenotype red.
Homozygous means that an organism has two of the same allele (like RR or rr)
Heterozygous means that an organism has two different alleles (like Rr)
Gregor Mendel was a monk who discovered lots of rules about genetics through his work with pea plants.
Evolution
Every species has variety (members of the species have differences from each other)
Mutations can increase this variety because they make new changes in DNA
Some varieties may reproduce better than others. This can happen for a couple of reasons
o They may survive better, so they are able to reproduce more (natural selection)
o They might be more attractive to members of the opposite sex, allowing them to reproduce more (sexual selection)
When some varieties reproduce more, they are more common in the next generation. In several generations, the whole population changes
Origin of Life (This is the scientific / naturalistic explanation of how life developed from the beginning. It is fine for you to believe that
there are other explanations that are better, but you need to understand this explanation). Here is the theory:
o All life on earth started as a single cell. Over time, this cell divided into many different cells.
o Mutations caused different cells to develop different characteristics. Some cells developed into more complex organisms.
o With more changes, various forms of life developed – fungi, plants, animals, etc.
o Over time, some species or forms of life died off. Others survived and multiplied.
o Since survival depended being adapted to the environment, we can see life forms today that are well suited to their environment.
Implications of this theory:
o Since one cause of evolution is that some types organisms survive better than others, evolution would happen most rapidly in difficult
living conditions, when survival is touch to begin with!
o Since evolution is about changes in a whole population, not just one organism, evolution would happen most quickly in small
population groups. The larger the group, the longer it would take for the change to work its way through the whole population.
o Since the changes have to spread through the population, evolution should happen faster in a species that a shorter reproductive cycle.
Evidence supporting the history of evolution. (Note – these pieces of evidence can all be explained in other ways. Therefore, they do not
prove that all life forms came from an original single cell. If any student would like to hear about other explanations for the evidence, I
would be happy to talk to you about this. But for purposes of the class, you need to know how scientists use the evidence to support the
scientific theories about the origin of life.)
o DNA – similar organisms have similar DNA. Since we get our DNA from our parents, grandparents, etc., many scientists believe that
this means that different organisms have a common ancestor.
o Homologous structures – different organisms have similar bone structures, even though they are used for different purposes. This is
what we would expect to see if organisms descended from a common ancestor.
o Vestigial organs –organs in some animals that seem to be useless. These are often similar to useful organs in other animals. Many
scientists believe that these organs exist because they were useful to an ancestor species, and they are “leftovers” from evolution.
o Fossils – we have found many fossils from extinct species. We have also found some fossils that many scientists believe to be
examples of a transitional life form – for example, an organism that shows a step in the evolution from dinosaurs to birds.