Ch. 4.1 Flashcards
Eukaryotic Overview
What is the endosymbiotic theory?
The evolution of eukaryotes as a series of sequential, cell-merging events between an ancient eukaryotic ancestor and certain prokaryotes.
The cells involved were
1) the ancient eukaryotic cell
2) an ancient Rickettsia-like prokaryote- these together formed a protoeukaryote. The Rickettsia-like cell became the mitochondria of our current eukaryotic cells.
3) Later, these proteukaryotic cells merged with photosynthetic prokaryote (possible cyanobacteria), which became the cells chloroplast.
What kind of DNA and ribosomes do mitochondria and chloroplasts have?
Circular DNA and 70S ribosomes?
What are the four main groups of eukaryotic cells?
Plants, animals, protists, and fungi.
Define eukaryotic organisms types.
Unicellular: Protists and yeast (type of fungi)
Multicellular: Animals, plants, and most fungi
Define eukaryotic size
Usually much larger than prokaryotes
Define types of eukaryotic cell division
Asexual mitosis and sexual meiosis
What substance does the eukaryotic plasma membrane contain that prokaryotic plasma membrane lacks?
Often contains sterols
What kinds of eukaryotic cells have a cell wall?
Those of plants, protists, and certain fungi.
Does a eukaryotic cell have a nucleus?
Yes
Describe types of ribosomes present in eukaryotes, and where they are located.
80S: Cytoplasm and rough endoplasmic reticulum
70S: Mitocondria and cholorplasts
Eukaryotic genetic material type
DNA
Chromosome type and arrangement
Multicellular and arranged linearly.
Membrane bound organelles present?
Yes
Define mitosis
Asexual reproduction in which one parent cell produces two identical offspring cells with the same number of chromosomes as the parent cell. All human cells except for eggs and sperm divide using mitosis. This is the most common way eukaryotic cells divide.
Define meiosis
Sexual reproduction in which the parent cell splits into four genetically unique gametes with half the number of chromosomes as the parents. A gamete must combine with it’s complimentary gamete to form a zygote.
What methods do eukaryotes use to move things in and out of the cell?
Osmosis, diffusion, endocytosis and exocytosis.
What are the three main mechanisms of endocytosis?
Pinocytosis, phagocytosis, and receptor-mediated endocytosis.
Define pinocytosis
This is the endocytosis of substances in small vesicles. Eukaryotes are constantly doing this to survive.
Define Phagocytosis
This is the endocytosis of undissolved substances. This is when a eukaryote engulfs a cell or virus. This involves large vesicles and is usually mediated by receptors on the cells surface. features on the surface of the cell being eaten often bond to these receptors. Antibodies and other immune system factors can also coat cells “marking” them for clearance into the cell via phagocytosis.
Describe what happens to an engulfed cell during phagocytosis.
The engulfed cell is wrapped in a phagosome and as it enters the cell, it is fused with a lysosome that has hydrolytic enzymes in it. This combination is called a phagolysosome.
Describe receptors mediated endocytosis
Ligands (target substances such as hormones, nutrients, or pathogens), bind to specific cell surface receptors.
Describe clatherin-mediated endocytosis
When a ligand binds to a receptor on the cell surface, the receptor “anchor” on the interior of the cell is coated in a protein called clatherin. The clatherin polymerizes forming a pit that then pinches off from the inner surface of the inner plasma surface. This forms a clatherin coated vesicle which still has the target ligand inside it. The clatherin coat is then shed and it combines with an endosome (a small vesicle with an acidic interior). This combination of endosome with clatherin-coated vesicle changes the PH which separates the receptor from the ligand. The receptors and the ligands are then taken to their target destinations within the cell or back on the cells surface. Alternatively, the endosome can fuse with a lysosome forming an endolysosome- similar to phagocytosis.
Describe exocytosis
When vesicles deliver their contents to the plasma membrane. The vesicle fuses with the plasma membrane to expel its contents (i.e. water products or neurotransmitters). When the vesicle fuses with the plasma membrane, it uses it’s mass to repair damage to the plasma membrane that was caused by endocytosis.
