Cell theory 2 Flashcards
Ribosome function
not organelles (no membrane) composed out of rRNA and proteins (formed in the nucleus) – made out of big and small subunit and there are 70S and 80S (Svedberg is the unit indicating how fast something sediments when centrifuged) – proteins synthesized on free ribosomes stay inside the cell and those synthesized on bound ribosomes get transported outside of the cell
Plastid (example structure)
a family of double-membraned organelles like chloroplast (green) also exist red, orange, yellow… but only in plant cells – e.g. chloroplast surrounded by a double membrane, thylakoid membrane containing chlorophyll and other pigments, it is the site of photosynthesis (stroma, outer membrane, inner membrane, granum, thylakoids)
Centrioles
elongated cylindrical structures present only in animal cells
Mitochondria
the site of CR, surrounded by a double membrane (ribosomes, matrix, inner membrane, outer membrane, intermembrane space, starch grains, cristae, mDNA)
Cilia and flagella
project from the cell surface, cilia are only present in animal cell and have the same function as pili in prokaryotic cells (attachment) while flagella is used for locomotion (movement)
Do animals, fungi, and plants have these structures:
1) cell wall
2) vacuoles
3) plastids
4) centrioles
5) cilia
6) flagella
1) no, yes, yes
2) small, large, large
3) no, no, yes
4) yes, no, no
5) some, no, no
6) some, some, some
What does the endosymbiotic theory say?
eukaryotes evolved from an anaerobic, one-celled common ancestor (with a nucleus) that reproduced either asexually by mitosis or sexually by meiosis and fertilization – mitochondria were formed by the endocytosis of aerobic heterotrophic bacteria by the common ancestor and chloroplasts by the endocytosis of photoautotrophic bacteria by the common ancestor
What is the evidence for the endosymbiotic theory?
1| 70S ribosomes
2| Double membrane (vacuole)
3| Circular, naked DNA
4| Mitochondria divide by binary fission
Cell differentiation
when cells develop along different pathways despite the same genome due to different gene expression because different chemical signals in the environment impact them
How are tissues formed?
cells in the same environment (area) get influenced by the same chemicals and express the same genes (specialize for the same function) – cells of the same tissue interact and connect by cell-to-cell adhesion proteins (the integrity of the tissue is maintained) in all tissues except blood
Housekeeping vs other genes
genes active in all cells that are required for basic life processes – other genes are expressed in only some cells because they cause the development of specialized structures, e.g. genes for the synthesis of hemoglobin only expressed during the development of erythrocytes
Advantages of cell differentiation
1| Form can match function more specifically
2| A Specialist performs a function of life more efficiently than a generalist
Advantages of multicellularity
1| Longer lifespan of the organism (death of one cell does not impact its survival
2| Larger body size possible (plants competing for light, predatory animals)
3| Effectiveness due to cell differentiation (more complex body forms can develop)
Shared vs different features in viruses
shared:
1) non-cellular (no cytoplasm, metabolism or enzymes)
2) obligate intracellular parasites
3) no shared ancestor
4) small, fixed size (lack structural features, do not grow)
5) nucleic acid as genetic material (same genetic code as the host so that proteins can be synthesized)
6) capsids made of protein subunits
diverse features are in genes (no genes occur in all viruses) and structure (can be enveloped or non-enveloped)
Viruses only have enzymes for:
1| Replication of genetic material
2| Infection of the host cells
3| Lysis (bursting host cells)
Which genetic material can viruses have?
double/single-stranded DNA/RNA which can be circular/linear and can either be positive/negative sense (if it’s single-stranded)