Book 6: Topic 4 Flashcards
What is biological diversity?
Reflected in:
The vast number of species of organisms.
The variation of individual characteristics within a single species.
The variation of cell types with a single multicellular organism.
What is the cause for differences between species?
Genetic differences.
What is the cause for differences between individuals within a species?
The result of genetic factors, environmental factors or a combination of both.
What is a locus?
The particular site on a DNA molecule where a gene is located.
What does the genetic code, carried by the base sequence of each gene, determine?
The sequence of amino acids during protein synthesis.
The genetic code is the same in all organisms, what does this provide evidence for?
Evolution.
What can cause genetic diversity within a species?
Gene mutation, chromosome mutation or random factors associated with meiosis and fertilisation.
What results in species becoming better adapted to their environment?
Genetic diversity acted upon by natural selection.
What can be used to measure variation within a species?
Differences in the base sequence of DNA or the amino acid sequence of proteins.
What can be used to measure biodiversity within a community?
Species richness and an index of diversity.
What are prokaryotes?
Unicellular organisms that do not develop or differentiate into multicellular forms.
In what way do some bacteria grow?
In filaments or masses of cells. (Each cell in the colony is identical and capable of independent existence).
Why might prokaryotic cells be adjacent to one another?
They did not separate after cell division or they remained enclosed in a common sheath/slime, secreted by the cells. (Typically, there is no continuity or communication between the cells).
Where are prokaryotes capable of inhabiting?
Almost every place on earth.
How are prokaryotes distinguished from eukaryotes?
On the basis of nuclear organisation, specifically their lack of a nuclear membrane.
Other than a nuclear membrane, what else do prokaryotes lack that distinguish them from eukaryotes?
Any intracellular organelles and structures.
What takes over most of the functions of organelles in prokaryotes?
The prokaryotic plasma membrane.
Since there are no organelles in prokaryotic cells, what is the function of the cytoplasm?
Contains all the enzymes needed by the cell for all metabolic reactions.
What type of ribosomes do prokaryotic cells have?
The smaller 70 S type.
What is the nucleoid/nuclear zone in prokaryotic cells?
The region of the prokaryotic cytoplasm that contains DNA. It is not surrounded by a nuclear membrane.
Describe the DNA in the nucleoid of prokaryotic cells.
Always circular, compacted by a mechanism called “supercoiling” and it is not associated with any proteins to form chromatin. (Not to be confused with plasmids).
Describe the plasmid in prokaryotic cells.
Small circles of DNA, used to exchange DNA between bacterial cells. (Useful for genetic engineering and have a role in antibiotic engineering).
Describe the cell membrane in prokaryotic cells.
Made of phospholipids and proteins, like eukaryotic membranes.
Describe the mesosome in prokaryotic cells.
A tightly-folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis. (Can also be associated with the nucleoid).
Describe the cell wall in prokaryotic cells.
Made of murein (not cellulose as in plant cells), which is a glycoprotein/peptidoglycan (protein/carbohydrate complex). There are two kinds of cell wall that can be distinguished by a Gram stain. Gram positive bacteria - thick cell wall and stain purple. Gram negative bacteria - thin cell wall with an outer lipid layer and stain pink.
Describe the capsule/slime layer in prokaryotic cells.
A thick polysaccharide layer outside the cell wall (like the glycocalyx of eukaryotes). Used for sticking cells together, as a food reserve and as protection against desiccation (the removal of water), chemicals and phagocytosis (cell eating).
Describe the flagellum in prokaryotic cells.
A rigid, rotating helical-shaped tail used for propulsion. The motor is embedded in the cell membrane and is driven by an H+ gradient across the membrane. Clockwise rotation drives the cell forward.
What is endosymbiosis?
The idea that the organelles of the eukaryotic cell could be originally derived from prokaryotic cells that have become incorporated inside other, larger prokaryotic cells.
What are the observations that support the idea of endosymbiosis?
Prokaryotic cells are older and more diverse than eukaryotic cells.
Organelles, contain circular DNA and 70 S ribosomes like prokaryotic cells.
Organelles have double membranes, as though a single-membrane cell had been engulfed and surrounded by a larger cell.
Organelles reproduce like prokaryotic cells, by binary fission.
Organelles are very like some bacteria that are alive today.
How much larger are eukaryotic cells compared to prokaryotic cells?
About 10x the size and as much as 1000x greater in volume.
What is the major and extremely significant difference between prokaryotes and eukaryotes?
Eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place.
Describe the nucleus in eukaryotic cells.
A membrane delineated compartment that houses the cell’s DNA.
What are eukaryotic organism’s specialised structures within the cell?
Organelles, which perform dedicated functions.
How many different types of organelles are commonly found in eukaryotic cells?
A dozen.
What are some key differences of prokaryotic cell’s DNA from eukaryotic cells?
In the nucleus, DNA molecules are very long, linear and associated with proteins - “histones”.
What does a DNA molecule and its associated proteins form, in a eukaryotic cell?
A chromosome.
What is an example of part of the nuclear DNA, in eukaryotes, that does not code for polypeptides?
Non-coding multiple repeats of base sequences between genes.
Within a gene, which sequences code for amino acid sequences and which sequences are non-coding sequences?
Exons code for amino acid sequences. Exons are separated by one or more non-coding sequence, called introns.
Describe the mitochondria in eukaryotic cells.
A tubular organelle about 8 nano metres long. Surrounded by a double membrane. The outer membrane is simple and quite permeable, while the inner membrane is highly folded into cristae, which give it a very large surface area.
What is the function of mitochondria in eukaryotic cells?
It is the location where most of the reactions of aerobic respiration take place.
What similarities do mitochondria and chloroplasts in eukaryotic cells share with prokaryotic cells?
Contains short, circular DNA which is not associated with protein.
How many mitochondria organelles does a typical eukaryotic cell contain?
1000, though some will contain more depending on their rate of respiration and need for energy.
