Unity of Life - Chapter 1 Flashcards
What does the unity of life reveal?
All organisms arise from a common ancestor.
Which naturally occurring elements make up 98% of the atoms in an organism?
oxygen, hydrogen, and carbon
What reaction using biological fuels provides the energy to power the cell?
combustion, the reaction of oxygen with biological fuels to produce carbon dioxide and water
Why is carbon compared to silicon? Why is carbon better suited for life compared to silicon?
Although silicon is much more plentiful in the Earth’s crust and can form 4 covalent bonds, carbon-carbon bonds are stronger than silicon-silicon bonds.
- Carbon’s stronger bonds are more stable, enabling the building of large molecules.
- More energy is released when carbon-carbon bonds undergo combustion, making it a better fuel.
- After combustion, carbon dioxide remains in biochemical circulation due to being readily soluble in water and its ability to exist as a gas.
Why is carbon dioxide in biochemical circulation? Why isn’t silicon?
It is readily soluble in water and can exist as a gas. In contrast, silicon is insoluble after combustion, causing it to permanently remain out of circulation.
What are proteins?
biological macromolecules composed of linear array of 20 amino acids joined by peptide bonds to form long, unbranched polymers that fold into specific 3D structures to facilitate biochemical functions
What are nucleic acids?
biological macromolecules constructed of 4 nucleotides that store and transfer information in the cell
Name some of the functions of proteins.
- Catalysis as enzymes
- Transmission of signals as signal molecules and receptors
- Structural
- Mobility
- Defense against environmental dangers
Describe the structure of a nucleic acid.
five-carbon sugar (either deoxyribose or ribose) attached to a heterocyclic ring structure (a base) and a phosphoryl group
What are the two differences in DNA and RNA’s composition?
- Thymine is used in DNA and uracil is used in RNA.
- Ribose contains an additional hydroxyl group than deoxyribose.
What are the four deoxyribonucleotides?
adenine, cytosine, guanine, and thymine
How is information contained in DNA?
contained in the sequence of nucleotides linked together by phosphodiester linkages
How is mRNA different from DNA?
mRNA is an RNA and is frequently broken down after use. DNA is conserved to store information.
How do the sizes of proteins, lipids, and nucleic acids compare?
Lipids are much smaller. Proteins and nucleic acids can have weights of thousands-millions g mol^-1, lipids generally have a molecular weight of 1300 g mol^-1.
What allows the development of the inside and outside of a cell?
Lipids’ dual nature (hydrophobic and hydrophilic regions)
What are lipids?
a biological macromolecule with hydrophobic and hydrophilic regions that allow the formation of barriers; serves as a storage form of energy and a signal molecule
What are carbohydrates?
a biological macromolecule that serves as fuel and can be used for cell-cell recognition and interaction
How is glucose stored in animals? In plants?
as glycogen in animals
as starch in plants
Describe the structure of glycogen.
Glycogen is a branched polymer composed of glucose molecules.
What is the central dogma?
What is replication? What catalyzes it?
the process of copying the genome
DNA polymerases
What are the discrete units DNA is packaged into?
genes
What is transcription?
process of transcribing DNA into RNA to make its information accessible, catalyzed by RNA polymerase
What defines the function of a tissue or cell?
The selective transcription of certain genes
What is translation?
the process of translating nucleic acid sequence information from RNA to protein (a functional form); occurs on ribosomes
What is a plasma membrane?
a membrane is a lipid bilayer that separates the inside of a cell from its environment; impermeable to most substances, the plasma membrane has selective permeability due to presence of proteins that permit the entry and exit of certain molecules and information
How are membranes organized?
Membranes are lipid bilayers with two layers of lipids organized with hydrophobic chains interacting with each other between hydrophilic head groups that interact with the environment.
What are the differences between eukaryotes and prokaryotes?
Eukaryotes have membrane-enclosed compartments (organelles); prokaryotes don’t.
Describe the structure of prokaryotes.
Surrounded by 2 membranes separated by periplasmic space
What is a microbiome?
aggregate microorganisms that inhabit us; vital for good health; consists of approximately 40 trillion prokaryotes (equal to # cells in human body)
What allows the plasma membrane to be selectively permeable?
Proteins embedded or attached to the membrane that permit the entry and exit of certain molecules and information.
What are the two requirements for a cell to be considered a cell?
- Barrier that separates the cell from its environment
- Inside that is chemically different from the environment and that accommodates the biochemistry of living
What is the cytoplasm?
the fundamental intracellular material between the plasma membrane and the nuclear membrane that is not enclosed by other membranes; site of most biochemical processes, including initial stage of glucose metabolism, fatty acid synthesis, and protein synthesis
What is the plant cell wall made of?
cellulose - a long, linear polymer of glucose molecules
We used to think the cytoplasm was a soup of biomolecules? What are we starting to realize?
The cytoplasm is highly organized by a network of cytoskeleton (structural filaments).
What is the cytoskeleton?
structural filaments that construct the cytoplasm; in eukaryotes, is a network fo actin filaments, intermediate filaments, and microtubules that all support the structure of the cell, serve as molecular highways, and help localize some biochemical activities
What are the 3 kinds of protein fibers that constitute the eukaryotic cytoskeleton?
Actin filaments
Intermediate filaments
Microtubules
What is the largest organelle?
the nucleus
What is the nucleus?
the information center of a eukaryotic cell; double membrane enclosed compartment that contains most of a eukaryotic cell’s DNA
How do things make it in and out of the nucleus? Give an example.
via pores in the nuclear membrane
The proteins that synthesize DNA and RNA are made in the cytoplasm, but operate within the nucleus.
What is the mitochondrion?
oval-shaped organelle that is the site of oxidative phosphorylation, the enzymes of the citric acid cycle, and the enzymes of fatty acid oxidation
the powerhouse of the cell
Describe the structure of the mitochondrion.
outer membrane that touches the cytoplasm
intermembrane space between 2 membranes
highly invaginated inner membrane that defines the matrix
How does the mitochondrion work?
combustion of fuel molecules into carbon dioxide and water, along with ATP
What is the chloroplast?
a double-membrane bounded organelle found in plant cells; site of photosynthesis
What is the endoplasmic reticulum? What is the difference between the rough and smooth ER?
a series of membranous sacs
RER - region that binds ribosomes, where proteins are produced
SER - region devoid of ribosomes, processes exogenous chemicals (ex. drugs)
How does drinking more alcohol impact your cells?
The more drugs ingested, the greater the quantity of smooth ER found in the liver.
How does the location of the ribosome influence the use of the created protein?
Free ribosomes make proteins for use inside the cell.
Ribosomes on the rough ER make proteins that will either be inserted into the cell’s membranes or secreted from the cell.
Describe the secretory pathway.
- Proteins are transported into the lumen of the ER during translation.
- Inside the lumen, the protein folds into a final 3D structure with help from chaperones and are often modified (with addition of carbohydrates).
- The proteins are then put on regions of the RER lacking ribosomes, which bud off as transport vesicles and travel into the Golgi complex.
- After fusing with the Golgi, the proteins are further processed and sorted to different fates.
- A vesicle filled with proteins for secretion buds off the Golgi, forming a secretory granule, which is directed towards the plasma membrane.
- After receiving a signal, the secretory granule undergoes exocytosis by fusing with the plasma membrane and dumping its cargo into the extracellular environment.
What is the Golgi complex? What is its structure?
major sorting center for proteins in a cell; a stack of membranous sacs
What is an endosome?
component of the receptor-mediated endocytotic pathway, derived from coated vesicles that lose the clathrin coat
What is endocytosis used for?
to bring important biochemicals into the cell (ex. iron ions, vitamin B12, cholesterol)
What is phagocytosis? How is it different from endocytosis?
when large amounts of material is taken into the cell (compared to endocytosis, which only happens through small regions of the plasma membrane)
What is a lysosome?
an organelle containing a wide array of digestive enzymes that degrades and recycles damaged cellular components or material brought in via endocytosis
How is lysosome formation different from secretory granule formation?
The formation is analogous, but lysosomes fuse with endosomes rather than the plasma membrane.
What are plant vacuoles?
a storage-organelle only present in plant cells
Can eukaryotes be unicellular?
yes
What does a DNA polymerase do?
replicates DNA
What does RNA polymerase do?
transcribes RNA from DNA
Where does translation occur?
within ribosomes
