Cell biology Flashcards
What is stuff made of?
- All ordinary matter in the universe is made of atoms
What are atoms made of?
- protons, neutrons, electrons
What are the simplest atoms?
- hydrogen and helium
How much of the universe is made up of hydrogen and helium?
- more than 99%
When was the big bang?
- 13.7 billion years ago
When did atoms form?
- 380 000 years after the big bang
- when the universe had cooled enough for electrons to stably associate with protons and neutrons
When did Earth form?
- 4.5 billion years ago
What are the most basic chemical elements?
- the atoms on the periodic table
How do we identity atoms?
- atomic number (number of protons)
How many elements naturally occur on Earth?
- 94
What is a covalent bond?
- sharing of electrons
- do not break apart in water
What is a molecule?
- two or more atoms connected with covalent bonds
What is a chemical reaction?
- when a molecule is created, broken apart, or modified
- change in the position of electrons in the molecule
- change how molecules interact with other molecules
What is an ion?
- atom or molecule has a net electrical charge (positive or negative)
- missing or extra electron
What is an ionic bond?
- Negatively charged ions can donate an electron to positively charged ions
- break apart in water
What are salts?
- atoms and molecules connected with ionic bonds
- dissolve in water
Do water molecules or ionic bonds neutralize electrical charges better?
- water molecules
What are the 6 key chemical elements whose combination make up most of the biological molecules on Earth?
- hydrogen (59%)
- oxygen (24%)
- carbon (11%)
- nitrogen (4%)
- phosphorus
- sulfur
What are the 5 main molecules found in cells?
- water
- sugar
- fat (lipid)
- nucleotide
- amino acid
What are macro-molecules?
- chains of small molecules
- big molecules
What are carbohydrates made of?
- chains of sugar molecules
- macro molecules
What do lipid molecules form?
- cell membranes and vesicles
- macro molecules
What are nucleic acids made of?
- chains of nucleotides
- RNA and DNA are types of nucleic acids
- macro molecules
What are proteins made of?
- long chains of amino acids
- between 100 and 1000 amino acids long
- macro molecule
What are peptides made of?
- short chains of amino acids
- macro molecule
What is RNA?
- a ribonucleic acid
- naturally fold into complex 3-dimensional shapes
- some can catalyze chemical reactions
What are ribozymes?
- RNA molecules that can catalyze chemical reactions
- made of RNA
- can spontaneously interlink nucleotides to form nucleic acids (RNA and DNA) and interlink amino acids to form proteins
What are the 2 main problems with ribozymes?
- RNA is fragile. It breaks apart easily
- RNA is made of 4 different types nucleotides that are not particularly abundant on Earth
What are the main catalyst of chemical reactions?
- enzymes
What are enzymes?
- Proteins that catalyze chemical reactions
What are proteins?
- proteins are what do things in a cell
- enzymes that catalyze chemical reactions
- receptors that sense the world around us
- make up the scaffolding and roads within a cell
- mediate transport and storage and serve as messengers
What is protein synthesis?
- use the strands of RNA floating around as instructions for how to put amino acids together (in what order) to form useful proteins
What do cells need to synthesize a protein?
- 2 types of RNA (mRNA and tRNA)
- a bunch of free amino acids
What is mRNA?
- a long, unfolded strand of RNA, which represents the instructions
What is tRNA?
- a bunch of short, folded up pieces of RNA, which read the instructions
- about 76 nucleotides long
- On one end, there are 3 exposed nucleotides that can bind a complementary 3-nucleotide sequence of mRNA
- On the other side, there is pocket that is highly attractive to a free-floating amino acid
- there are unique tRNA molecules to carry each type of amino acid
How many types of amino acids are there?
- 20
How do cells make proteins?
- encouraging tRNA molecules to find a sequence of mRNA that they complement
- a chemical reaction is needed to interlink the amino acids that are held by the tRNA molecules
- based on the sequence of the genetic code (mRNA), 20 types of amino acids get strung together in different combinations to form all the proteins of life
What is a ribosome?
- the first organelle
- a molecular machine that is made of RNA and proteins
- perfected the synthesis of new proteins by stringing together the amino acids held by tRNA molecules in the order determined by free-floating strands of mRNA
interlink amino acids in the order dictated by the genetic code.
synthesize proteins by translating the RNA that was transcribed from DNA.
How do ribosomes work?
- The small subunit of the ribosome grabs a free-floating strand of mRNA
- the large subunit of the ribosome identifies free floating tRNA molecules that complement the section of mRNA held by the small subunit
- Ribosomes slide across mRNA, taking one step each time they find a tRNA molecule that complements the mRNA segment held by the small subunit
- When a ribosome finds an appropriate (complementary) tRNA molecule, it removes its amino acid and attaches it to the amino acid of the next complementary tRNA molecule
- Step by step, the ribosome links together amino acids held by tRNA molecules based on the sequence of nucleotides in free-floating strands of mRNA
Ribosomes synthesize new proteins by translating strands of mRNA, interlinking the amino acids held by tRNA molecules in the order determined by the genetic code.
What do cells use for long term information storage?
- DNA (more stable and durable than RNA)
How does DNA synthesize protein?
- All the instructions of life are stored in strands of DNA
- Sections of DNA are transcribed into mRNA
- mRNA is translated into proteins
- Protein enzymes catalyze the chemical reactions of life
What are phospholipids?
- strands of lipids with a phosphate cap
- Lipids prefer the company of other lipids
- Phosphate caps prefer to interact with water
- phospholipids form bilayer sheets if left undisturbed (in water)
What are micelles?
- soap bubbles
- formed when phospholipids are shaken
- under right conditions, can pop and reform as liposomes
What is the cell membrane?
- basically a liposome
- Diffusion through the phospholipid bilayer is limited
- Inside and outside are salt water
What are prokaryotic cells?
- the first cells
- consist of a cell membrane filled with cytoplasm
- in cytoplasm, loose strands of DNA and RNA, and ribosomes
What is cytoplasm?
- water filled with salt, sugar, nucleic acids, and amino acids
What are eukaryotic cells?
- similar to prokaryotic
- have mitochondria
- nucleus and chromosomes
What is the mitochondria?
- molecular machines that extract energy from nutrients
- generate molecules of ATP, cell’s main source of chemical energy, by digesting molecules of sugar
What is a chromosome?
- compacted strand of DNA in a nucleus
- not allowed to leave the nucleus
What is a genome?
- The genome of a cell refers to its entire collection of DNA
- provides the information necessary to synthesize all the cell’s proteins
What are genes?
- sections of the genome that get transcribed into RNA and translated into protein
- section of DNA that codes for a specific protein
- Most genes are only expressed by some cells some of the time
What happens when a gene is read?
- that segment of DNA is transcribed into RNA in the nucleus
- RNA is allowed to leave the nucleus, so it can meet up with a ribosome to be translated into a protein
How many genes do humans have in their genome?
- 20 000 protein encoding genes
- make up less than 2% of human genome
What is the cell body?
- SOMA
- where the cell’s nucleus is located
- neurons are defines by where their soma is
- made up of cytoplasm, mitochondria, microtubules
What is the cell membrane?
- defines the boundary of the cell
- consists of a phospholipid bilayer that is embedded with proteins
What are microtubules?
- allow for rapid transport of material within the neuron
What are multicellular organisms?
- all complex multicellular organisms are exclusively eukaryotic
- collections of cells stuck together (consist of more than one cell)
- cells specialize to perform distinct functions
- all cells have the same genome, but they read different parts of it
What person do you think advanced the field of neuroscience the most?
- Charles Darwin
- The theory of evolution suggested that we could learn a lot about the human brain by studying the brains of other animals
Who do humans share 98.8% of their DNA with?
- chimpanzees
- human genome is very similar to the genomes of the other great apes
What is the difference between humans and great apes?
- humans have much bigger brains and way more neurons
- neuron number generally correlates with cognitive complexity, but not always
Which mammalian species are closer to humans?
- rodents
- rodents have become the dominant species used in neuroscience research
Why do we use rodents in research?
- mammalian/rodent brain structure is highly similar to human brain structure
How are rodents like us?
- have complex decision-making abilities
- get stressed out, depressed, and anxious
What do we study in rodents?
- neural mechanisms of sensory, motor, and cognitive processes, including motivations, emotions, learning and memory, and decision-making
- model human diseases in rodents to figure out how best to treat these conditions in humans
How are human brains unique?
- develop very slowly
- brain and behaviour plastic (malleable, shapeable) far longer than other animals
- human brain grows (in weight)
- stops making new neurons halfway through its gestation in the womb
- growth of existing neurons, which continue to establish new connections with other neurons throughout life
- increases in the number of other cells in the brain (the support staff), which continue to replicate throughout the lifespan
What is neoteny?
- prolongation of maturation
- extended youth
What is the Fermi paradox?
- 40 billion earth-like planets that could support life
- some of its earth-like planets are likely way older than planet Earth
- we estimate a life-form could colonize the entire Milky Way galaxy in less than 50 million years
- 2 trillion other galaxies
- So…why haven’t we seen any aliens? Where is everybody? Could it really be just us?
- assume there’s a unique condition on Earth or the first complex cell was uniquely special
