Lecture VI/VII: The Cell Flashcards
Why are cells so small?
It has to do with the fact that larger objects have a smaller surface area to volume ratio than smaller objects.
Cells must be big enough to fit all the necessary molecules/organelles, but small enough so that the surface area of the cell is sufficient to support the metabolic activities happening inside the cell.
What is an example of an adaptation to increase the cell surface to volume ratio?
Cells making up the lining of our small intestines have small extensions on their plasma membranes called microvilli. This increases the cell surface area aiding in their primary function of absorption of digested nutrients.
What are the characteristics of Procakyrotic Cells?
Small in size 1 -10 µm
DNA in a circular loop and not enclosed within it’s own membrane, but found in the Nucleoid region of the cytoplasm.
Lack organelles
Ribosomes present
Cytoplasm fills the cell.
Cell wall present exterior to the plasma membrane.
What are the characteristics of eukaryotic cells?
Larger in size 10 -100 µm
DNA in linear strands and enclosed within it’s own membrane = nucleus
Contain many membrane bound organelles each with specialized functions.
Cytoplasm fills most of the cell, but is not found within the nucleus.
Ribosomes present
What is an Organelle?
A phospholipid membrane bound (enclosed) structure that has a lumen (space) where a specialized function is performed for the cell.
What is the difference between Plant and Animal cells? What are the components that are unique to Plant cells?
Plants and animals are structurally very different and acquire their energy and nutrients in significantly different ways. Certain cellular characteristics have evolved in each group that are not found in the other. Chloroplasts Central vacuole Cell wall Plasmodesmata
What is the plasma Membrane? What are the two main components?
A semi-permeable membrane separating the intracellular environment from the extracellular environment.
Aids in homeostasis by controlling the passage of substances into and out of the cell.
made of Proteins and Phospholipids.
What do proteins do in the plasma membrane?
Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachement to the cytoskeleton and extracellular matrix.
What is the Nucleus?
Large organelle housing the DNA of the cell (chromatin) enclosed by a double membrane called the nuclear envelope.
The nuclear envelope is studded with nuclear pores for exchange of substances between the nucleus and cytoplasm of the cell.
What is the Nucleolus?
The nucleolus is the darker region within the nucleus. It’s function is to make ribosomes. It is not considered an organelle (not enclosed by a membrane).
What is the Mitochondria and its roles?
Found in eukaryotic cells, (plants too)
powerhouse of the cell.
Double membrane (smoother outer and convoluted inner membrane)
have their own DNA and ribosomes???
Function: Cellular respiration, they harvest bond energy from glucose and other metabolites and use it to make adenosine triphosphate (ATP) the cellular energy molecule.
What are chloroplasts and their roles?
In plant cells and some protist cells only
Double membrane and have their won DNA and ribosome as well?
Contain chlorophyll within the internal structure called thylakoids
function: photosynthesis: transform light energy into bond energy forming glucose molecules.
Why do mitochondria and chloroplasts, have their own DNA and ribosomes?
If you remove the itochondriorn or the chloroplast from an eukaryotic cell you would see that they would have many simialrieties with prokaryotic cells inclusding a circular DNA moleculae and thei own ribosomes.
This leads to Endosymbiont Theory
What is Endosymbiont Theory
This theory states that an early ancestor of eukaryotic cells engulfed a bacterial cell by phagocytosis. But instead of the bacterium being digested it remained intact within the eukaryotic cell.
There is evidence supporting that this occurred 2 times independently. Once with a bacteria that could perform aerobic cellular respiration (became eukaryotic mitochondria) and then at another time with a bacteria that could perform photosynthesis (became eukaryotic chloroplasts). Over the course of time these bacteria lost their ability to live independently from the eukaryotic cell and became the organelles that we are familiar with.
These additions of prokaryotic DNA, contained within mitochondria and chloroplasts, are considered 2 distinct horizontal gene transfer events in the evolutionary history of living organisms.
What is the particularity of the reproduction of mitochondrial DNA?
Only the Mitochondrion DNA is taken from the mother.
What is peroxisomes and their role?
Contain enzymes that with the help of oxygen:
Breakdown fatty acids to be used as fuel for cellular respiration.
Breakdown cellular toxins.
What is the cytoskeleton and its role? What are the 3 types of protein fibers?
The cytoskeleton is a network of protein fibers that help organize structures within the cell as well as help with movement.
3 different types of protein fibers:
Microtubules, Intermediate filaments, and Microfilaments make up cytoskeleton components in varying quantities.
Scaffolding that supports all organelles within the cell and aids in movement of substances inside the cell.
Make up the Centrosome and spindle fibers involved in cell division.
Cilia and Flagella; specialized cytoskeleton structures which are located on the exterior surface of cells that aid in movement.
Movement within cells?
Protein fibers move organelles and vesicles from one place to another within the cell.
(view picture)
Movement of cells?
Some cells can move through their environment by cytoplasmic streaming (movement of cytoplasmic contents via cytoskeleton filaments) creating pseudopods that pull them along.
What is the Centrosome and its role?
The anchor point for the cytoskeleton.
Made up of a pair of centrioles (concentrations of microtubules).
Help direct the movement of chromosomes during cell division.
Movement exterior to the cell? Functions?
Extensions of the cytoskeleton outside of the cell’s surface.
Flagella:
Longer and whip like
Cilia:
Short and thin protrusions of the cytoskeleton.
Functions:
Motility of the cell.
Motility of substances along tissue surfaces.
Movement on tissue surfaces? (example)
Movement of the cilia removes mucus and inhaled foreign debris out of our respiratory tract.
Extracellular Components and Connections between Cells?
Exterior to the plasma membrane of cells you will find extracellular components that help the cell maintain its shape and provide a method of connecting and communicating with adjacent cells in tissues.
Plant cell walls Extracellular matrix of animal cells Cell Junctions Plasmodesmata (plant cells) Tight junctions (animal) Desmosomes (animal) Gap junctions (animal)
Role of Plant cell walls? Made of?
Protect the cell.
Allow plants to grow tall by providing structural support.
Made primarily of cellulose.
