Terms in this set (68)
In biology there is hierarchic system of organization. The system is most inclusive as kingdom and lest as species. The order is as follows:
most scientist agree that the core theme in biology today is the idea of evolution. Charles Darwin first introduced this notion in 1859 in his book On the Origin of Species. he proposed that current species arose from a process he called "descent with modification."
Science is a process. For an experiment to be performed, serveal steps must be taken. The first step is hypothesis. this is simply a statement or explanation of certain events or happenings. The second step is the experiment. This is a repeatable procedure of gathering data to support or refute the hypothesis. The final step in the scientific process is the conclusion
Water is the substance that makes life possible. The molecule itself is simply two hydrogen atoms covalently bonded to one oxygen atom. The most significant aspect of water is the polarity of its bonds.
the specific heat of a molecule is the amount of heat necessary to raise the temperature of 1 gram of that molecule by 1 degree Celsius. Water has a relatively high specific heat value, which allows water to resist shifts in temperature. One powerful benefit is the ability of oceans or large bodies of water to stabilize climates
hydrogen bonding also results in strong cohesive and adhesive properties. Cohesion is the ability of a molecule to stay bonded or attracted to another molecule of the same substance. A good example is how water tends to run together on a newly waxed car. Adhesion is the ability of water to bond to or attract other molecules or substances. When water is sprayed on a wall, some of it sticks to the wall. That is adhesion.
It is the polar nature of water that allows for hydrogen bonding between molecules. This type of intermolecular bonding has several resulting benefits. The first of these is water's high specific heat.
When water freezes
when water freezes it forms a lattice, which actually causes the molecule to spread apart resulting in the phenomenon of floating. Most moleucules, when they are in the solid form, do not float on the liquid form of the substance. If ice did not float, lakes would freeze from the bottom to the top. Life could not exist as we know it. the polarity of water also also allows it to act as a versatile solvent . Water can be used to dissolve a number of different substances.
There are multitudes of molecules that are significant to biology. the most important of these are carbohydrates, lipids, proteins, and nucleic acids.
carbohydrates are generally long chains, or polymers of sugars. they have many functions and serve many different purposes. The most important of these are storage, structure, and energy.
lipids are better known as fats, but specifically are fatty acids, phospholipids, and steroids.
Fatty acids vary greatly but simply are grouped into two categories: saturated and unsaturated. Saturated fats contain no double bonds in their hydrocarbon tail. Conversely, Unsaturated fats have on or more double bonds. As a result, saturated fats are solid whereas unsaturated fats are liquid at room temperature. Saturated fats are those the general public considers detrimental, and cardiovascular problems are likely with diets that contain high quantities of saturated fats
phospholipids consist of two fatty acids of varying length bonded to a phosphate group. The phosphate group is charged and therefore polar, whereas the hydrocarbon tail of the fatty acids is nonpolar. This quality is particularly important in the function of cellular membranes. The molecules combine in a way that creates a barrier that protect the cell.
The last of the lipids are steroids. They are a component of membranes, but, more important, many are precursors to significant hormones.
proteins are the most significant contributor to cellular function. They are polymers of 20 molecules called amino acids. Complex and consisting of several structure types, proteins are the largest of the biological molecules. Enzymes are particular types of proteins that act to catalyze different reaction or processes. nearly all cellular function is catalyzed by some type of enzyme.
nucleic acids are components of the molecules of inheritance. Deoxyribonucliec acid (dnA) is a unique molecule specific to a particular organism and contains the code that is necessary for replication. Ribonucleic acid (RNA) is used in transfer and as a messenger, in most species, of the genetic code.
metabolism is the sum of all chemical reactions that occur in an organism. In a cell, reactions take place in a series of steps called metabolic pathways, progressing from a standpoint of high energy to low energy. All of the reactions are catalyzed by the use of enzymes
the cell is fundamental unit of biology. There are two types of cells: prokaryotic and eukaryotic cells. Cells consist of many components, most of which are referred to as organelles.
cells are those containing no defined nucleus and a series of organelles that carry out the functions of the cell as directed by the nucleus.
have membrane enclosed nucleus and a series of organelles that carry out the functions of the cell as directed by nucleus. The eukaryotic cell is the more complex of the two cell types.
There are several different organelles functioning in a cell at a given time; only the major ones are considered here.
the first of the organelles is the nucleus, which contains the DNA of the cell in organized masses called chromosomes. Chromosomes contain all the material for the regeneration of the cell as well as all instructions for the function of the cell. Every organism has a characteristic number of chromosomes specific to the particular species
ribosomes are organelles that read the RNA produced in the nucleus and translate the genetic instruction to produced proteins. Cells having a high rate of protein synthesis generally have a large number of ribosomes. There are two locations ribosomes can be found. Bound ribosomes are thsoe found attached to the endoplasmic reticulum (ER), and free ribosomes are those found in the cytoplasm. The two types are interchangeable and have identical structures, although they have slightly different roles.
The ER is a membranous organelles found attached to be the nuclear membrane and consists of two continuous parts. Through an electron microscope, it is clear that part of the membranous system is covered with ribosomes. This section of the ER is referred to as rough ER, and it is responsible for protein synthesis and membrane production. The other section of the ER lacks ribosomes and is refereed to as smooth ER. It functions in detoxification and metabolism of multiple molecules.
inside the cell is a packaging, processing, and shipping organelle that is called the Golgi apparatus. The Golgi apparatus functions to transport materials from the ER throughout the cell
Intracellular digestion takes place in lysosomes. Packed with hydrolytic enzymes, the lysosomes can hydrolyze proteins, fats, sugar, and nucleic acids.
Vacuolues are membrane-enclosed structures that have various functions depending on celll type. many cells, through a process called phagocytosis, uptake food through the cell membranes, creating a food vacuole. Plant cells have a central vacuole that functions in storgae,, waste disposal, protection, and hydrolysis.
Mitochondria and chloroplasts
there are two distinct organelles that produce cell energy: the mitochondrion and the chloroplast. Mitochondria are found in most eukaryotic cells and are the site of respiration. Chloroplasts are found in plants and are the site of photosynthesis.
are found in plants and are site of photosynthesis
the cellular membrane is the most important component of the cell, contributing to protection, communicatoin, and the passage of substances into and out of the cell. The cell membrane itself consists of a bilayer of phospholipids with proteins, cholesterol, and glycoproteins peppered throughout. Because phopholipid are amphipathic molecules, this bilayer creates a hydropobic region between the two layers lipids, making it selectively permeable. many of the proteins, which pass completely through the membrane, act as transport highways for molecular movement into and out of the cell
there are two catabolic pathways that lead to cellular energy production. As a simple combustion reaction, cellular respiration produces far more energy than does its anaerobic counterpart, fementation.
C6H12O6 + 6O2 ---> 6CO2 + 6H2O. this balance equation is the simplified chemistry behind respiration. The process itself actually occurs in a series of three complex steps that are simplified for our purposes
there is one molecule that is used as the currency of the cell: adenosine triphosphate (ATP).
another compound that acts as a reducing agent and is a vehicle of stored energy is reduced nicotinamide adenine dinucleotide (NADH0. This molecule is sued as a precursor to produce greater amounts of ATP in the final steps of respiration
the first step is the conversion of glucose to pyruvate in a process called glycolysis. It takes place in the cytosol of the cell and produces two molecules of ATP, two molecules of pyruvate, and two molecules of NADH
In step two, the pyruvate is transported into a mitochondrion and used in the first of a series of reactions called the krebs cycle. This cycle takes place in the matrix of mitochondria, and for a single consumed glucose molecule, two ATP molecules, six molecules of carbon dioxide, and six NADh molecules are produced
electron transport chain
the third step begins with the oxidation of the NADh molecules to produce oxygen and finally to produce water in a series of steps called the electron transport chain. The energy harvest here is remarkable. For every glucose molecule, 28 to 32 ATP molecules can be produced. This conversion results in overall ATP production numbers of 32 to 36 ATP molecules for every glucose molecule consumed.
In the previous section the harvesting of energy by the cell was discussed. But where did that energy originated? it began with a glucose molecule and resulted in a large production of energy in the form of ATP. A precursor to the glucose molecule is produced in a process called photosynthesis. The chemical reaction representing this process is simply the reverse of cellular respiration
6CO2 + 6H2O + Light energy ----> C6h12O6 + 6O2
.the only notable difference in photosynthesis
the only notable difference is the addition of light energy on the reactant side of the equation just as glucose is used to produce energy, so too must energy be used to produce glucose.
photosynthesis consist of
photosynthesis is not as simple a process as it looks from the chemical equation. In fact, it consists of two different stages: the light reactions and the Calvin cycle. The light reactions are those that convert solar energy to chemical energy. The cell accomplishes the production of ATP by absorbing light and using that energy to split a water molecule and transfer the electron, thus creating NADPH and producing ATP. These molecules are then used in the Calvin cycle to produce sugar. The sugar produced is polymerized and stored as a polymer glucose. These sugars are consumed by organisms or by the plant itself to produce energy by cellular respiration
cells reproduce by three different processes, all of which fall into two categories: sexual and asexual reproduction
there are type of asexual reproduction. The first involves bacterial cells and is refereed to as binary fission. in this process, the chromosome binds to the plasma membrane, where it replicates. Then as the cell grows, it pinches in two, producing two identical cells.
the first involve bacterial cells and is referred to as binary fission.
another type of asexual reproduction is called mitosis. This process of cell division occurs in five stages before pinching in two in a process called cytokinesis. the five stages are prophase, prometaphase, metaphase, anaphase, and telophase.
during prophase, the chromosomes are visibly separate, and each duplicated chromosome has two noticeable sister chromatids. in prometaphase, the nuclear envelope begins to disappear, and the chromosomes begin to attach to the spindle that is forming along the axis of the cell. metaphase follows, with all the chromosomes aligning along what is called the metaphase place, or the center of the cell.
follow, with all the chromosomes aligning along what is called the metaphase plate, or the center of the cell.
begins when chromosomes start to separate. In this phase the chromatids are considered separate chromosomes.
the final phase is telophase. here chromosomes gather on either side of the now separating cell. This is the end of mitosis
the second process associated with cell division is cytokinesis. During this phase, which is separate from the phases of mitosis, the cell pinches in two, forming two separate identical cells
sexual reproduction is different from asexual reproduction. in asexual reproduction, the offspring originates from a single cell, yielding all produced cells to be identical. in sexual reproduction, two cells contribute genetic material to the daughter cells, resulting in significantly greater variation. These two cells find and fertilize each other randomly, making it virtually impossible for cells to be alike.
the process that determines how reproductive cells divide in a sexually reproducing organism is called meiosis. meiosis consist of two distinct stages, meiosis one and meiosis two, resulting in four daughter cells. Each of these daughter cells contains half as many chromosomes as the parent. preceding these events is a period call interphase.
each of these daughter cells contain half as many chromosomes as the parent. preceding these events is a period called interphase. It is during interphase that the chromosomes are duplicated and the cell prepares for division
first stage of meiosis
the first stage of meiosis consist of four phases: prophase I, metaphase I, anaphase i, and telophase i and cytokinesis. The significant differences between meiosis and mitosis occur in prophase I. During this phase, nonsister chromatids of homologous chromosomes cross at numerous locations. Small sections of DNA are transferred between these chromosomes, resulting in increased genetic variation. The remaining three phases are the same as those in mitosis, with the exceptionthat the chromosome pairs separate, not the chromosomes themselves.
After the first cytokinesis
meiosis two begins. here all four stages, identical to those of mitosis, occur the resulting four cells have half as many chromosomes as the parent cells
using garden peas, Gregor mendel discovered the basic principles of genetics. by careful experimentation, he was able to determine that the observable traits in peas were passed from one generation to the next.
from Mendel'ls studies, scientists have found that for every trait expressed in a sexually reproducing organism, there are at least two alternative versions of a gene, called alleles.
tehre are at least two alternative versions of a gene, called alleles. For simple traits, the versions can be one of two types: dominant or recessive.
if both of the alleles are the same type, the organism is said to be homozygous for that trait
if they different types, the organism is said to be heterozygous
Alleles (hesi hint)
if an allele is dominant for a particular trait, the letter chosen to represent that allele is capitalized. if the allele is recessive, then the letter is lowercased. If a dominant allele is present, then the phenotype expressed will be the dominant. The only way a recessive trait will be expressed is if both alleles are recessive
by use of a device called a Punnett square, it is possible to predict genotype (the combination of alleles) and phenotype (what traits will be expressed) of the offspring of sexual reproduction. Alleles are placed one per column for on gene and one per row for the other gene. In the example in Figure 5-2 a homozygous dominant is crossed with a heterozygous organism for the same trait. Note that all progeny will express dominance for this trait.
three of the possible combinations will be dominant, and one will be recessive for this trait
Punnett square can be used
the Punnett square can be used to cross any number of different traits simultaneously. With these data, a probability of phenotypes that will be produced can be determined. however, the more traits desired, the more complex the cross. Not all genes express themselves according to these simple rules, but they are the basis for all genetic understanding. There are many other methods of genetic expression. A few of these include multiple alleles, pleiotropy, epistasis, and polygenic inheritance.
because genetics is the study of heredity, many human disorders can be detected by studying a person's chromosomes or by creating a pedigree. A pedigree is a family tree that traces the occurence of a certain trait through several generations. A pedigree is useful in understanding the genetic past as well as the possible future.
DNA is the genetic material of a cell and is the vehicle of inheritance. In 1953, WAtson and Crick described the structure of DNA. They described a double helical structure that contains the four nitrogenous bases adenine, thymine, guanine, and cytosine.
each base of DNA
each base forms hydrogen bonds with another base on the complementary strand. The bases have a specific bonding pattern. Adenine bonds with thymine, and guanine bonds with cytosine. because of this method of bonding, the strands can be replicated, producing identical strands of DNA. During replication, the strands are separated. The, with the help of several enzymes, new complementary strands to each of the two original strands are created. This produces two new double-stranded segments of DNA identical to the original
each gene along a strand of DNA is a template for protein synthesis. This production begins with a process called transcription. In this process an RnA strand, complementary to the orginal strand of DNA, is produced.
the piece of genetic material produced is called messenger RNA (mRNA). The RNA strand has nitrogenous bases identical to those in DNA with the exception of uracil, which is substituted thymine.
functions as a messenger from the orginal DNA helix in the nucleus to the ribosomes in the cytosol or the rough ER. here, the ribosome acts as the site of translation. the mRnA slides through the ribosome. Every group of three bases along the stretch of RNA is called a codon, and each of these codes for a specific amino acid.
the anticodon is located on a unit called transfer RNA (tRNA), which carries a specific codon is sliding through the ribosome. Remember that a protein is a polymer of amino acids, and multiple tRNA molecules bind in order and are released by the ribosome. Each amino acid is bonded together and released by the preceding tRNA molecule, creating an elongated chain of amino acids.
eventually the chain is ended at what is called a stop codon. At this point the chain is released into the cytoplasm, and the protein folds onto itself and forms its complete conformation. By dictating what is produced in translation through transcription, the DNA in the nucleus has control over everything taking place in the cell. The proteins that are produced will perform all the different cellular functions required for the cell's survival