25.1 A Review of the Eukaryotic Cell Flashcards
Describe features of the eukaryotic cell. (5)
figure 25.1 in the textbook
- energy metabolism that requires membrane stability is confined to organelles
- cytoskeleton enables cells to change shape by remodelling quickly
- nuclear membrane separates transcription and translation in eukaryotes
- vesicles building off from membranes transport materials into the cell in endocytosis, and release material from the cell in exocytosis
- network of membranes is able to change shape and package molecules and particles for transport within the cell
What organizes the eukaryotic cell?
internal protein scaffolding and dynamic membranes
All cells require a mechanisms to maintain spatial order in the cytoplasm.
What do bacteria and archaeons rely on?
What do eukaryotes rely on?
bacteria and archaeons: primarily on walls that support the cell from the outside, along with a relatively rigid framework of proteins within the cytoplasm
eukaryotes: (some eukaryotic cells have walls but many others, including the cells in our bodies, do not) mainly on an internal scaffolding of proteins to organize the cell, with most of those supports being microtubules composed of the protein tubulin and microfilaments of actin
What is the difference between a eukaryotic cytoskeleton and the protein framework of bacteria?
it can be remodelled quickly, enabling cells to change shape
What do dynamic cytoskeletons require?
dynamic membranes that enable the cell to continue functioning even as it changes shape; eukaryotes maintain within their cells a remarkably dynamic network of membranes called the endomembrane system
What does the endomembrane system include?
- nuclear envelope
- an assembly of membranes that runs through the cytoplasm called the endoplasmic reticulum and Golgi apparatus
- plasma membrane that surrounds the cytoplasm
How are all membranes of the endomembrane system interconnected?
either directly or by the movement of vesicles
many are also capable of changing shape rapidly
How are the different membranes of the endomembrane system interchangeable?
in the sense that material originally added to the ER may in time be transferred to the cell membrane or nuclear membrane
What do biologists like to say about membranes of eukaryotic cells?
they are in dynamic continuity
When are membranes stable?
only in the mitochondria and chloroplasts, as required for energy metabolism
What provides eukaryotes with new possibilities for movement?
in combination, the dynamic cytoskeleton and the membrane system
ie. amoebas extend finger-like projections that pull the rest of the cell forward
What else does the dynamic cytoskeleton and the membrane system enable?
enables eukaryotic cells to engulf molecules or particles, including other cells, in a process called endocytosis
prokaryotic cells cannot perform this
What is phagocytosis?
a specific form of endocytosis in which eukaryotic cells surround food particles and package them in vesicles that bud off from the cell membrane
when packaged this way, particles can be transported into the cell interior for digestion
*figure 25.2 textbook
What is exocytosis?
molecules or cytoplasmic waste formed within the cell are packaged in vesicles and moved to the cell surface for removal
Where are intracellular vesicles and the molecules they carry transported and how?
through the cytoplasm by means of molecular motors associated with the cytoskeleton
in this way, both nutrients and signalling molecules move through the cell at speeds much greater than diffusion allows
major consequence: eukaryotic cells can be much larger than most bacteria
Name another way that the cytoskeleton and membrane system are flexible.
a change in the expression of a few genes can change their shape and organization
this flexibility makes complex multicellularity possible
Describe gene expression in complex multicellular organisms.
patterns of gene expression can differ from cell to cell
a change in gene expression can modify the cytoskeleton and membranes of individual cells, enabling cells to function in different ways
Where is energy metabolism localized in eukaryotic cells?
in mitochondria and chloroplasts
How do eukaryotes obtain carbon and energy?
compared to prokaryotes, there are fairly limited ways:
metabolic processes that power eukaryotic cells take place only in specific organelles
- aerobic respiration in mitochondria
- photosynthesis in chloroplast
only limited anaerobic processing of food molecules takes place within the cytoplasm
What happens in the cytoplasm after eukaryotic cells engulf food particles and package them inside a vesicle to be transported to the cytoplasm?
enzymes break down the particles into molecules that can be processed by the mitochondria
What do single-celled eukaryotes feed on?
many feed on bacteria or other eukaryotic cells
What can eukaryotes exploit?
sources of food that are not readily available to bacterial heterotrophs, which feed on individual molecules
this ability opened up the great new ecological possibility of predation, which vastly increased the complexity of interactions among organisms
What does the structural flexibility of eukaryotic cells also allow?
photosynthetic eukaryotes to interact with their environment in ways that photosynthetic bacteria cannot
What can unicellular algae do?
move efficiently through surface waters vertically as well as horizontally and therefore can seek and exploit local patches of nutrients
