Topic 1 Flashcards
What are the characteristics of life?
Composed of common elements, made of cells, has genetic information, grows and changes, responds to the environment, uses pre-existing molecules to make new molecules, extracts energy from the environment and uses it, exists in populations and evolves
Provide the reasons for viruses being living
They contain nucleic acids, they can replicate, they can evolve
Provides the reasons against viruses being living
They cannot replicate by themselves, do not have the same metabolic pathways as other living organisms, not made of cells, can’t extract energy
Steps of natural selection
Variation occurs in a population
Individuals with more desirable traits are more likely to survive, thrive, and reproduce
Eventually speciation may occur, where a new species forms
Two theories of how life began
Life formed spontaneously on Earth; non-living molecules created
Life came from space, such as from another planet or comet
What did the Miller-Urey experiments find?
They tried to replicate Earths atmosphere from when they believed life began. Their findings found the following could be produced.
The bases present in DNA and RNA
All 20 amino acids
Some 3 and 6 carbon sugars
Fatty acids
Vitamin B6, NAD and organic acids
What happened for life to arise?
Liquid water appeared
What happened during the Cambrian Explosion
A rapid diversification of life, which is when most of the big animal groups appeared.
What are stromatolites?
Layers of calcium carbonate that typically form in saline water. The layers trap water and debris which can be fossilised. Some fossilised bacteria has been found from 3.7 B years ago, so life must be older than that.
Properties of water that are crucial for life
High vaporisation point, high heat capacity
Why does water has such a high boiling point?
Hydrogen bonding
Cohesion
Hydrogen bonding between water molecules
Adhesions
Attraction of water to other molecules
Hydrophilic
Polar molecules are attracted to water
Hydrophobic
Non-polar molecules are attracted to each other and not water
How does pH affect life?
Influences rate of biological reactions, can affect 3D structure of molecules.
What is a macromolecule?
Polymers made up of THOUSANDS of atoms
What is a saccharide?
A sugar
What are the 3 main types of carbohydrate?
Monosaccharide, disaccharide, polysaccharide
How do monosaccharides bond together into di or polysaccharides?
Two hydroxyl groups bond together in a condensation reaction. The bond is called a glycosidic linkage.
Who determined the double helix model?
Watson and Crick (1950s)
Which bases are single ringed, and which are double-ringed?
Single: cytosine, thymine, uracil
Double: adenine, guanine
What do you need to make a nucleotide
A nucleoside ( a base and either ribose or deoxyribose) and a phosphate
How do nucleotides make nucleic acids
Condensation reactions. Hydroxyl from the third and fifth carbons bond with the phosphate next to it’s hydroxyl group. This is called a phosphodiester bond. This makes the backbone of the nucleic acid.
How do the two DNA strands bond together
The H and NH and the O and the HN groups bond together using hydrogen bonding.
Which way does the DNA go?
From the 5 prime to the 3 prime carbons
What are the types of RNA
mRNA- messenger
tRNA- transfer
rRNA- ribosomal
How do proteins form?
Amino acids bond together in a condensation reaction (OH reacts with H). The bond is called a peptide bond.
Properties of different side-chains
Non-polar, hydrophobic: dispersion forces
Polar, electrically charged, hydrophilic: ionic interactions
Polar, uncharged, hydrophilic: dipole-dipole or hydrogen bonds
What are lipids?
Large groups of molecules that are generally non-polar, and do not make long polymer chains.
Saturated fatty acids
Saturated with hydrogen, no double bonds, pack closely together, higher melting point
Unsaturated fatty acids
Double bonds instead of hydrogens, which make the backbone more flexible. Tend to have a lower melting point.
How to make a triglyceride
Glycerol plus 3 fatty acids that bond using condensation. This is an ester bond.
Phospholipids
Non-polar, hydrophilic heads, hydrophobic tails.
What was Earth’s early atmosphere like?
No oxygen, high carbon dioxide, ammonia and methane. No ozone layer so intense radiation.
Why are photosynthetic Cyanobacteria important?
They turned carbon dioxide from our atmosphere into oxygen, which meant the ozone layer could exist and more life could appear.
What are the 3 super kingdom
Archaea, Bacteria, Eukaryotes
What makes archaea and bacteria different?
Morphologically, they are the same.
When they were sequenced, archaean genes had never been seen before
Very different genetically
Archway protein synthesis more similar to eukaryotes
What do all prokaryotes contain?
A cell membrane
DNA inside a nucleoid
Cytoplasm
Ribosomes
Some features of bacteria
Capsule made of polysaccharides
Cell wall and a capsule
Flagellum (sometimes)
Pili
What is a ribosome?
Small structure made of 2 subunits of rRNA and proteins. They are responsible for protein synthesis which happens either in the cytosol or on the ER.
Features of gram positive bacteria
Stains purple, simple cell wall, single layer, thick cell wall, peptidoglycan layer is thick, no outer membrane, low levels of lipids, less toxic
What are the features of gram negative bacteria?
Complex cell wall, double layered thin cell wall, very resistant to antibiotics and often more toxic.
Difference in bacterial and archaean environments
Archaea love to live in extreme environments, only some bacteria do
What does nitrogen fixing mean?
Bacteria that turn insoluble nitrogen gas into ammonia
How is DNA stored in a prokaryote
Loosely clustered in a region called the nucleoid
When did eukaryotes evolve?
At least 2.1B years ago
Primary endosymbiosis
Prokaryote engulfs another prokaryote. DNA extracted from engulfed prokaryote and organelle formed
Secondary endosymbiosis
Eukaryote ears another eukaryote and uses the organelles that it does not have for itself. The excess organelles disappear.
What is the endomembrane system?
A system of compartments that include all membrane bound components of the cell except chloroplasts, mitochondria, microbodies
Endoplasmic reticulum
Both make carbs and lipids, but rough ER can also make proteins. The bio molecules are then secreted through the endomembrane
Golgi apparatus
ORIGAMI MASTER
packaging, collecting, distributing biomolecules. Made of golgi stacks. Receives vesicles from ER and then modified in Golgi body. Then leaves in vesicles out of Golgi and out of cell.
Vacuoles
Extremely big in plants with a membrane called the tonoplast. Contains enzymes but can also be used for storage of nutrients or maintaining cell pressure.
Lysosomes
Cell recycling bins
Break down materials via endocytosis or old organelles (like phagocytes) acidic interior, lots of enzymes.
Microbodies
Another recycle bin. Not considered part of the endomembrane system. Peroxisomes break down amino acids. Glyoxysomes break down fatty acids.
What is the cytosol and what is it’s purpose
Cytosol is a jelly like fluid that helps with structure of a cell and is the site of many biochemical processes. Many biochemical intermediates are shuttles throughout the cytoplasm.
What is the cytoskeleton and what is it’s purpose?
Scaffolding in the cytoplasm. It organises cell activities and anchors many organelles. Made of the following proteins: microtubules, microfilaments, intermediate filaments.
What are microtubules?
Hollow tubes made of tubulin molecules. They are for movement in organelles, the cell and cell division.
What are microfilaments?
Two intertwined strands of actin. Used to maintain shape in cell. Used for movement in cell and cell division. This is what creates the cleavage furrow.
What are intermediate filaments?
Fibrous proteins coiled into thicker proteins; these proteins are from the keratin family. Used for structure, anchoring organelles, formation of nuclear lamina.
