Download Cell Processes: CRCT Review Notes

Life Science CRCT Review Notes
I. Cell Processes: Transport
1.
DIFFUSION is when particles from areas of high concentration (crowded) to areas of low
concentration (less crowded). Diffusion happens within and between living cells
3. Diffusion helps the cell bring in raw materials so that it can divide and grow --and to get rid of
wastes
4. OSMOSIS is the diffusion of WATER
5. Osmosis is important to cell functions. For example, red blood cells are surrounded by plasma.
Plasma is made up of water, salts, sugars, and other particles. The concentration of these particles is
kept in balance by osmosis
6. Diffusion and osmosis don’t require energy to work—So they are forms of PASSIVE TRANSPORT.
7. Endocytosis (bringing larger particles in) and Exocytosis (larger particles out) are forms of ACTIVE
TRANSPORT because they do require energy to work.
Section Summary
• Diffusion is the movement of particles from an area of high concentration to an area of low
concentration.
• Osmosis is the diffusion of water through a semi-permeable membrane.
• Cells move small particles by diffusion, which is an example of passive transport, and by active transport.
• Large particles enter the cell by endocytosis, and exit the cell by exocytosis.
II. Cell Processes: Photosynthesis and Respiration
1. Plants capture energy from the sun and change it into food through a process called photosynthesis.
The food that plants make supplies them with energy. This food also becomes a source of energy for
the organisms that eat
2. Animal cells have different ways of getting energy from food. One way, called cellular respiration,
uses oxygen to break down food. Many cells can get energy without using oxygen through a process
called fermentation. Cellular respiration will release more energy from a given food than
fermentation will.
the plants.
III. Cell Processes: The Cell Cycle
1. The cell cycle begins when the cell is formed and ends when the cell divides and forms new cells
2. Before a cell divides, it must make a copy of its deoxyribonucleic acid (DNA). DNA is the hereditary
material that controls all cell activities, including the making of new cells
3. The DNA of a cell is organized into structures called chromosomes. Copying chromosomes ensures
that each new cell will be an exact copy of its parent cell.
4. Prokaryotic cells (NO NUCLEUS) are less complex than eukaryotic cells are. Bacteria, which are
prokaryotes, have ribosomes and a single, circular DNA molecule but don’t have membraneenclosed organelles. Cell division in bacteria is called binary fission
5. Eukaryotic cells (HAVE a NUCLEUS) divide by Mitosis (Their sex cells by Meiosis)
6. For Eukaryotic cells that have a cell wall, such as the cells of plants, algae, and fungi. A new cell wall
forms where the cell plate was.
7. Cell division ensures that the DNA copies and becomes a part of the new cell.
8. Section Summary
• A cell produces more cells by first copying its DNA.
• Eukaryotic cells produce more cells through the four phases of mitosis.
• Mitosis produces two cells that have the same number of chromosomes as the parent cell.
• At the end of mitosis, a cell divides the cytoplasm by cytokinesis.
• In plant cells, a cell plate forms between the two new cells during cytokinesis.
IV. Heredity
1. Section Summary
• Heredity is the passing of traits from parents to offspring.
• Gregor Mendel made carefully planned experiments using pea plants that could self-pollinate.
• When parents with different traits are bred, dominant traits are always present in the first generation.
Recessive traits are not visible in the first generation but reappear in the second generation.
• Mendel found a 3:1 ratio of dominant-to-recessive traits in the second generation.
2. Section Summary
• Instructions for an inherited trait are called genes. For each gene, there are two alleles, one inherited
from each parent. Both alleles make up an organism’s genotype. Phenotype is an organism’s
appearance.
• Punnett squares show all possible (probability) offspring genotypes.
• Probability can be used to describe possible outcomes in offspring and the likelihood of each outcome.
• Incomplete dominance occurs when one allele is not completely dominant over the other allele.
• Some genes influence more than one trait (eyes).
V. SEX CELL DIVISION: Meiosis
1. Asexual reproduction - only one parent cell is needed. The DNA in the cell is copied, and then the
parent cell divides, making two exact copies. All body cells use asexual reproduction through mitosis.
Also, most single-celled organisms (prokaryotes - bacteria) reproduce asexually. Also, some plants,
potatoes, hydra reproduce asexually.
2. Human sex cells have 23 chromosomes—half the usual number. Each sex cell has only one of the
chromosomes from each homologous pair. Sex cells have only one “shoe.”
3. Sex cells are made during meiosis – a copying process that produces cells with half the usual number of
chromosomes.
4. During mitosis, chromosomes are copied once, and then the nucleus divides once. During meiosis,
chromosomes are copied once, and then the nucleus divides twice. The resulting sperm and eggs have
half the number of chromosomes of a normal body cell.
5. Males have both an X chromosome and a Y chromosome in each body cell. Meiosis produces sperm
with either an X or a Y chromosome. An egg fertilized by a sperm with an X chromosome will
produce a female. If the sperm contains a Y chromosome, the offspring will be male
6. Section Summary
• In mitosis, chromosomes are copied once, and then the nucleus divides once. In meiosis, chromosomes
are copied once, and then the nucleus divides twice.
• The process of meiosis produces sex cells, which have half the number of chromosomes. These two
halves combine during reproduction.
• In humans, females have two X chromosomes. So, each egg contains one X chromosome. Males have
both an X and a Y chromosome. So, each sperm cell contains either an X or a Y chromosome.
• Sex-linked disorders occur in males more often than in females. Colorblindness and hemophilia are
examples of sex-linked disorders.
• A pedigree is a diagram used to trace a trait through many generations of a family.
VI. Genes and DNA
1.
2.
3.
4.
5.
6.
7.
DNA is made of subunits called nucleotides, which are made up of a sugar, a phosphate, and a base
(one of 4 types of bases).
The four bases are adenine (A), thymine (T), guanine (G), and cytosine(C).
Each group of 3 bases becomes the code for specific amino acids, which form proteins
Each gene gives a set of instructions for making a protein, which determine traits.
Proteins also act as chemical triggers and messengers for many of the processes within cells
Proteins are very important to the function of cells and in determining which traits will be expressed.
A strand of DNA looks like a twisted ladder, known as a double helix
8. The base A pairs with T, and the base G pairs with C.
9. Changes in the number, type, or order of bases on a piece of DNA are known as mutations.
Sometimes a base is left out -- a deletion. When an extra base is added – insertion. When one base is
switched with another – substitution.
10. In order for the DNA to replicate, mirror-like copy of the DNA segment is made out of RNA in the
nucleus. This copy of the DNA segment is called messenger RNA (mRNA).
11. The mRNA leaves the nucleus and in the cytoplasm it is “fed through” a ribosome. Transfer RNA
(tRNA) finds and releases an amino acid when it joins with the mRNA. The amino acids then build
long chains of important proteins.
12. Genetic engineering is when genes (DNA) is transferred from one type of organism to another.
Scientists may use genetic engineering to create new products, such as drugs or foods.
Section Summary
• A gene is a set of instructions for assembling a protein. DNA is the molecular carrier of these genetic
instructions.
• Every organism has DNA in its cells. Humans have about 2 m of DNA in each cell.
• Within a gene, each group of three bases codes for one amino acid. A sequence of amino acids is linked
to make a protein.
• Proteins are fundamental to the function of cells and the expression of traits.
• Proteins are assembled within the cytoplasm through a multi-step process that is assisted by several forms
of RNA.
• Genes can become mutated when the order of the bases is changed. Three main types of mutations are
possible: insertion, deletion, and substitution.
• Genetic knowledge has many practical uses. Some applications of genetic knowledge are controversial.
VII. Evolution
1. Scientists use fossil records to find evidence of common ancestry of organisms
2. The fossil record provides evidence about the order in which species have existed (The deeper in
sedimentary rock, the older).
3. Scientists think that the ancient ancestor of whales was probably a mammal that lived on land and
that could run on four legs (tiny hip bones)
4. Similarities in bone structures suggest that cats, dolphins, bats, and humans had a common ancestor.
5. Today scientists use DNA to determine similarities and possible common ancestry.
6. Charles Darwin hypothesized that the island finches were descended from South American finches.
The first finches on the islands may have been blown from South America by a storm. Over many
generations, the finches may have evolved adaptations for the various island environments.
7. The process in which humans select which plants or animals to reproduce based on certain desired
traits is called selective breeding. Pets have been bred for various desired traits.
8. In his book, Origin of Species, Darwin proposed the theory that evolution happens through natural
selection -- process by which organisms that are better adapted to their environment survive and
reproduce more successfully.
9. The theory of natural selection has these parts:
*There are variations among species; *variations are passed down or inherited, there are
*more offspring produced than can typically survive (overproduction), there is a *struggle
to survive; those that are *best adapted survive and successfully reproduce (survival of the
fittest).
VIII. Classification
1. Biologists use a system to classify living things according to the characteristics they share.
2. Classification helps biologists answer important questions, such as the following:
• How many known species are there?
• What are the defining characteristics of each species?
• What are the relationships between these species?
3. Levels of Classification:
a. 3 Domains: Achaea, Bacteria & Eukarya
b. Kingdoms under Achaea – Archaebacteria
Prokaryotes – no nucleus
c. Kingdom under Bacteria – Eubacteria
d. Kingdoms under Eukarya – Protista, Fungi, Plantae, Animalia -- Eukaryotes – Have a
nucleus.
e. Under each kingdom, organisms are further broken down as the following
Kingdom
Phylum
Class
Order
Family
Genus
Species
4. The Genus and Species provide the scientific name of the organism. This 2-part naming system is called
binomial nomenclature.
5. A Dichotomous Key is an identification tool that uses sequential pairs of descriptive statements.
Couplets (pairs) provide a choice between two traits of the same characteristic, and the choices direct
you to the name of the organism based on these descriptions… such as:
Has brown fur…..Go to 3
Has black fur ….Go to 4
6. Fungi (molds and mushrooms), unlike plants, fungi do not perform photosynthesis – and unlike
animals, fungi do not eat food. Instead, fungi absorb nutrients from substances in their
surroundings. They use digestive juices to break down the substances.
7. Protista - protists (single-celled or simple multicellular organisms such as protozoan. algae.
slime molds.