The Cell Flashcards
4 Tenets of Cell Theory
1: All living things are composed of cells
2: The cell is the basic functional unit of life
3: Cells arise only from preexisting cells
4: Cells carry genetic information in the form of deoxyribonucleic acid (DNA). This genetic material is passed on from parent to daughter cell
How do viruses violate the tenets of cell theory?
Viruses violate the 3rd and 4th tenets of cell theory because they can only replicate by invading other organisms and they may use ribonucleic acid (RNA) as their genetic information.
Eukaryotic cells
Contain a true nucleus enclosed in a membrane
Prokaryotic cells
Do not contain a membrane bound nucleus (they have a nucleoid)
Cytosol
Surrounds the cell organelles in eukaryotes
Allows for diffusion of molecules throughout the cell
Cytosol is specifically the the fluid contained in the cell’s cytoplasm. The cytoplasm is the entire content within the cell membrane.
Membranes of eukaryotic cells
- are made up of phospholipid bilayers
meaning its surfaces that interact with the extra and intracellular environments of the cell are hydrophilic and have electrostatic interactions with the surrounding aqueous environment while the inside of the membrane is hydrophobic.
-This makes these phospholipids amphipathic.
Nucleus
- contains genetic material that is encoded in deoxyribonucleic acid (including all of the genetic material necessary for cellular replication) with is then organized into chromosomes
- surrounded by a nuclear membrane or envelope
- a subsection of the nucleus is the nucleolus which is where the ribosomal RNA (rRNA) is synthesized. This takes up 25% of the nucleus and is a darker spot under a microscope
Nuclear pores
pores in the nuclear membrane that allow for selective two way exchange between the material in the cytoplasm and the nucleus
Packaging of genetic material in the nucleus
- genes are coding regions within the larger DNA molecules
- linear DNA is wrapped around positively charged proteins called histones
- then these histones are further organized into condense chromosomes.
Mitochondria
- extremely important metabolically
- creates ATP with ATP synthase at the end of the electron transport chain (ETC)
- contains inner and outer membranes
- the outer membrane serves as a barrier between the cytosol and the inner environment of the mitochondrion and the inner membrane, folded into cristae, contains the molecules and enzymes of the ETC.
- Cristae increase the surface area for the ETC enzymes
- the inter-membrane space is the area between the outer membrane and the inner membrane
- the mitochondrial matrix is the space inside the inner membrane
Nuclear membrane
- a double membrane that keeps the nuclear environment separate and distinct from the cytoplasm
- contains nuclear pores
- allows for the compartmentalization of transcription and translation in the nucleus (in eukaryotes)
Cytoplasmic or Extranuclear inheritance
the transmission of genetic material independent of the nucleus
- mitochondria are an example of this because they are semi-autonomous and replicate independently of the nucleus via binary fission
Apoptosis triggered by mitochondria
mitochondria can trigger apoptosis (programmed cell death) by releasing the enzymes from the ETC
Lysosomes
- contain hydrolytic enzymes that are capable of breaking down many different substrates (such as things ingested through endocytosis and cellular waste products)
- membrane bound structures that keep the hydrolytic enzymes separate from the rest of the cell to prevent cellular degradation
- work with endosomes
Endosomes
- intracellular sorting organelles that transport, package and sort cell material traveling to and from the membrane
- can also transport things to the lysosomal pathway for degradation
Apoptosis triggered by Lysosomes
- autolysis of lysosomes releases these hydrolytic enzymes into the interior of the cell and leads to apoptosis because the released enzymes lead directly to degradation of cellular components
Endoplasmic Reticulum (ER)
- as series of interconnected membranes that are contiguous with the nuclear envelope.
- has a double membrane that is folded into multiple invaginations, crating complex structures with a smooth central lumen
- two types of ER: smooth and rough
Rough Endoplasmic Reticulum (RER)
the RER is studded with ribosomes which can perform translation of proteins destined for secretion directly into it lumen
Smooth Endoplasmic Reticulum (SER)
the SER lacks ribosomes and is used for lipid synthesis (like the membrane phospholipids), detoxification and the transport of proteins from the RER to the golgi apparatus
Golgi Apparatus
- consists of stacked membrane bound sacs
- it modifies and sorts cellular products before they are sent to their correct cellular location
- example: materials from the ER can be transported the to golgi apparatus where they may be modified by the addition of groups like phosphates, carbohydrates and sulfates. Signal sequences cam also be added which direct the delivery to a certain cellular location
Peroxisomes
- its primary function is to breakdown long chain fatty acids via beta-oxidation
- beta-oxidation is the catabolic process where the beta carbon of the fatty acid undergoes oxidation to a carbonyl group
- this process produces H2O2, hydrogen peroxide, which then helps with further fatty acid break down
- participates in the synthesis of phospholipids
Cytoskeleton
- provides structure to the cell, helps it maintain its shape, and provides a conduit for the transport of materials around the cells
- 3 components: microtubules, microfilaments and intermediate filaments
Microfilaments
- made up of solid polymerized rods of actin
- resistant to compression and fracture so they provide protection for the cell
- use ATP and interact with myosin to aid in muscle contractions
- help form the cleavage furrow in cytokinesis
Microtubules
- hollow polymer of tubulin proteins
- radiate throughout the cell and provide primary pathways along which motor proteins such as kinesin and dynein (nonenzymatic proteins)
