Unit 1 Flashcards
(38 cards)
Systems Biology
An approach to studying biology that aims to model the dynamic behavior of whole biological systems based on a study of the interactions among the system’s parts
Cell theory
The theory states that all living organisms are made of cells, which are the basic unit of life. In fact, the actions of organisms are all based on the activities of cells.
Cell characteristics
Prokaryotic cells
Prokaryotic cells are found in two groups of single-celled microorganisms, bacteria (singular, bacterium) and archaea (singular, archaean). In contrast to eukaryotic cells, a prokaryotic cell lacks a nucleus or other membrane-enclosed organelles. Furthermore, prokaryotic cells are generally smaller than eukaryotic cells
Eukaryotic cells
A eukaryotic cell contains membrane-enclosed organelles (Figure 1.4). Some organelles, such as the DNA-containing nucleus, are found in the cells of all eukaryotes; other organelles are specific to particular cell types.
Organelles
Any of a number of organized or specialized structures within a living cell.
What is a DNA strand made up of?
Arranged in a double helix, each chain is made up of four kinds of chemical building blocks called nucleotides, abbreviated A, T, C, and G (Figure 1.7). Specific sequences of these four nucleotides encode the information in genes.
What is RNA?
Protein-encoding genes control protein production indirectly, using a related molecule called RNA as an intermediary. The sequence of nucleotides along a gene is transcribed into mRNA, which is then translated into a linked series of protein building blocks called amino acids.
Genome
The entire “library” of genetic instructions that an organism inherits is called its genome. A typical human cell has two similar sets of chromosomes, and each set has approximately 3 billion nucleotide pairs of DNA.
Feedback regulation
The regulation of a process by its output or end product
Negative feedback
The response reduces the initial stimulus
-Release of insulin
Positive feedback
positive feedback, in which an end product speeds up its own production.
-formation of a scab
Descent with modification
As species adapt to different environments over time, they accumulate differences from their ancestors.
Natural selection
Is a primary cause of descent with modification
Darwin reasoned that individuals with inherited traits that are better suited to the local environment are more likely to survive and reproduce than less well-suited individuals. Over many generations, a higher and higher proportion of individuals in a population will have the advantageous traits. Evolution occurs as the unequal reproductive success of individuals ultimately leads to adaptation to their environment, as long as the environment remains the same.
The Origin of Species articulated two main points
The first point was that, as species adapt to different environments over time, they accumulate differences from their ancestors. Darwin called this process “descent with modification.” Darwin’s second main point was his proposal that “natural selection” is a primary cause of descent with modification.
Cohesion
The linking together of like molecules, often by hydrogen bonds
Surface tension: cause and result
Although the arrangement of molecules in a sample of liquid water is constantly changing, at any given moment many of the molecules are linked by multiple hydrogen bonds. These linkages make water more structured than most other liquids. Collectively, the hydrogen bonds hold the substance together, a phenomenon called cohesion.
Moderation of Temperature by Water
Compared with most other substances, water has an unusually high specific heat. Because of the high specific heat of water relative to other materials, water will change its temperature less than other liquids when it absorbs or loses a given amount of heat. This makes water is effective as a heat bank because it can absorb or release a relatively large amount of heat with only a slight change in its own temperature. We can trace water’s high specific heat, like many of its other properties, to hydrogen bonding. Heat must be absorbed in order to break hydrogen bonds; by the same token, heat is released when hydrogen bonds form. A calorie of heat causes a relatively small change in the temperature of water because much of the heat is used to disrupt hydrogen bonds before the water molecules can begin moving faster. And when the temperature of water drops slightly, many additional hydrogen bonds form, releasing a considerable amount of energy in the form of heat.
Why does ice float
Hydrogen bonding in water molecules causes the molecules to become locked into a crystalline lattice, each water molecule hydrogen-bonded to four partners. The ability of ice to float due to its lower density is an important factor in the suitability of the environment for life. If ice sank, then eventually ponds, lakes, and even oceans could freeze solid
Solute vs solvent
Solute: the substance that is dissolved
Solvent: the substance dissolves
Hydrophilic
Any substance that has an affinity for water is said to be hydrophilic (from the Greek hydro, water, and philos, loving). In some cases, substances can be hydrophilic without actually dissolving.
Hydrophobic
Substances that are nonionic and nonpolar (or otherwise cannot form hydrogen bonds) actually seem to repel water. The hydrophobic behavior of the oil molecules results from a high number of relatively nonpolar covalent bonds, in this case bonds between carbon and hydrogen, which share electrons almost equally. Hydrophobic molecules related to oils are major ingredients of cell membranes.
Buffer
A buffer is a substance that minimizes changes in the concentrations of and in a solution. It does so by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted. Most buffer solutions contain a weak acid and its corresponding base, which combine reversibly with hydrogen ions.
Nucleotides
A compound consisting of a nucleoside linked to a phosphate group. Nucleotides form the basic structural unit of nucleic acids such as DNA.
