What are the 3 parts making up ATP?
organic base
Ribose sugar
Phosphate groups
How does ATP store energy?
By its three phosphate bonds (but the bonds have are unstable so they’re easily broken)
They release lots of energy when bonds broken
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What are the 3 parts making up ATP?
organic base
Ribose sugar
Phosphate groups
How does ATP store energy?
By its three phosphate bonds (but the bonds have are unstable so they’re easily broken)
They release lots of energy when bonds broken
What are the uses of ATP?
synthesis of protein , DNA , RNA , fat , carbohydrates
Active transport of ions and metabolites
Movement
How does ATP work?
ATP diffused to the part of the cell that needs energy
ATP broken down into ADP by hydrolysis reactions breaking the phosphate group bonds to release energy
This hydrolysis reaction is catalyses by the enzyme ATP hydrolase
The released inorganic phosphate can be added to other compounds
Where is ATP made?
It is made continuously in the mitochondria (in the inner membrane) of cells when required
Why is ATP a better source of energy in cells than glucose?
ATP only uses a single simple reaction to release energy whereas glucose uses a complex serious of enzyme controlled reactions
ATP doesn’t leave the cell, meaning it always has a constant supply of energy
ATP contains a small manageable amount of energy so no energy is lost as heat
ATP is a small soluble molecule that can be easily transported around the cell
What is the structure of DNA?
a double helix with two polynucleotide chains held together by hydrogen bonds
What is the role of DNA?
it contains all the DNA needed to make a new copy of the cell and to control the activities of the cell
What is the role of RNA?
it transfers gentic information from the DNA to the ribosomes
What is the role of the rough endoplasmic recticulum?
a series of thin intricate channels formed by a phospholipid membrane and it continuous with the nuclear membrane
so, materials can be moved easily through the channels between each membrane
What is the role of the smooth endoplasmic recticulum?
a tubular phospholipid membrane where lipids are synthesised and processed due to the ribosomes on the SER’s surface
What is the role of the golgi apparatus?
to take enzymes and other synthesised proteins and package them into membrane bound vesicles where they are then transported to other parts of the cell
What are the monomers making up DNA called?
nucleotides
What do nucleotides consist of?
phosphate group
pentose sugar called deoxyribose
organic nitrogenous base
What are the 4 nitrogenous bases?
adenine (A)
thymine (T)
cytosine (C)
guanine (G)
A and T bind by 2 hydrogen bonds
C and G bind by 3 hydrogen bonds
What does DNA and RNA stand for?
DNA - deoxyribonucleic acid
RNA - ribonucleic acid
What are ribosomes formed from?
RNA and proteins
What is the Penrose sugar called in DNA compared to RNA?
DNA - deoxyribose
RNA - ribose
What’s the difference in organic bases in RNA compared to DNA?
RNA has U (uracil) instead of Thymine which is in DNA
So, A + U bind and C + G bind
What are the three forms of RNA?
mRNA - several thousands nucleotides long (messenger RNA)
tRNA - less than 100 nucleotides long (transfer RNA)
rENA - several thousands nucleotides long (ribosomal RNA)
What is difference in shape of RNA compared to DNA?
DNA is a double helix
RNA is single stranded
What’s the purpose of RNA?
RNA transfers genetic information from DNA to the ribosomes
RNA is found in the cytoplasm
What is the function of mRNA?
They are copied sections of DNA that can pass through the nuclear pores to reach ribosomes in the cytoplasm
What is transcription?
It involved the synthesis of mRNA using the code on the sense strand part of the DNA
DNA unwinds and hydrogen bonds between bases break
A free nucleotide bonds to an exposed complementary base, creating pre-mRNA
the mRNA is released and the DNA returns to a double helix
How are the hydrogen bonds between the DNA bases broken?
Due to the enzymes DNA helicase where the region of the gene being transcribed is
What are the complementary bases joined up by?
RNA polymerase from condensation reactions, forming phosphodiester bonds between the ribose sugar of one nucleotide and the phosphate group of the next
What happens after transcription?
Splicing takes place - the removal of introns (useless parts of gene) and the exons joining together to form mRNA strands
After, the mRNA Then leaves the nucleus
What is translation?
The process which the protein is assembled from the mRNA (happens in cytoplasm of cell)
Involved tRNA and rRNA
What is the role of tRNA is translation?
Anticodons are linked to its complementary codon for the amino acid created from the mRNA
What is the role of rRNA in translation?
the ribosomes link amino acids together in the order specified by the codons of mRNA to form polypeptide chains
Ribosomes consist of small (where mRNA binds and decoded) and large (amino acids get added) sub units
How does translation work?
mRNA moves into the cytoplasm and attached to a ribosome
Anti codons in tRNA bind to vacant codons in the ribosome
The attached amino acids (located at top of the tRNA) form a peptide bond
as mRNA moves through ribosome, it releases the tRNA that aren’t bound to an amino acid and then the steps are repeated until the end of the mRNA
What is rRNA?
They are the site of protein synthesis, made of protein and RNA in the nucleolus
They are free in the cytoplasm or attached to the RER
What is a polysome?
When several ribosomes are attached to a single mRNA molecule
What happens when gametes fuse?
a zygote is formed containing 46 chromosomes
Zygote grows into an adult by repeatedly dividing by mitosis
Eventually a ball of 100 cells are formed (a blastula) that aren’t yet differentiated
Chromosomes are still active and called stem cells
What happens in the process of semi conservative replication?
The enzyme DNA helicase breaks the hydrogen bonds between the 2 polynucleotide strands
Free floating DNA nucleotides join to the exposed bases by the enzyme DNA polymerase, forming hydrogen bonds
The active site of DNA polymerase is only complementary to the 3’ end of the new DNA strand
Who are Watson and Crick?
They built the DNA modem to explain the unit of inheritance
What are the three theories of replication?
Semi conservative
Conservative
Dispersive
What is cell division needed for?
It is needed for growth
What are the two types of cell division?
mitosis → where daughter cells are genetically identical to the parent cell
Meiosis → where each daughter cell contains half the number of chromosomes of the parent cell, leading to the production of gametes
What organisms does mitosis and meiosis happen in?
Mitosis - in multicellular organisms for growth and repair and in unicellular organisms for asexual reproduction
Meiosis - all organisms that reproduce sexually
What is the cell cycle?
The series of event involving the growth, replication and division of a eukaryotic cell
What are the three stages of the cell cycle?
Interphase including G1, S, G2
Nuclear division (notification division of nucleus
Cell division nitric cell division
What are the stages of the cell cycle?
GO phase - DNA is relaxed (chromatin) and not yet started to divide
G1 phase - cell starts making proteins and organelles, growing larger
S phase - chromosomes containing genetic code are copied
G2 phase - cell checks DNA and prepares to start splitting into two cells
M phase - cell splits into two new cells
What are centrioles?
They are cylinder shaped cell structure made of microtubles and are involved in the organization of the spindle (where centromeres attach to)
What are sister chromatids?
Copies of the same chromosome attached to the centromere
What are the 4 phasers in the mitotic phase?
Prophase → chromosomes become visible in nucleus, DNA been replicated so nuclear membrane breaks up and fibrous soundly forms from centrioles
Metaphase → chromosomes attach to spindle by centromere, nuclear membrane has broken down
Anaphase → sister chromatids separate and spindle fibres shorten causing chromatids to move to opposite poles of cell
Telophase → spindle disintegrates, nuclear membrane forms and chromosomes unravel to become chromatin
Cytokinesis → produces 2 daughter cells and cell membrane contracts to split apart cell into 2
What is cancer?
A mutation in genes that cause uncontrolled cell growth and division
How does chemotherapy treat cancer?
prevents the synthesis of the enzyme needed for DNA replication
This prevents the cell entering the S phase, causing it to die
Inhibits metaphase by altering the way spindle fibres work so no division of chromatids and no daughter cells formed
What is a problem of chemotherapy?
they aren’t selective and target dividing cells = normal dividing body cells affected
e.g hair cells affected = hair loss
What is secondary cancer?
parts of the tumour can break away if it isn’t enclosed in a membrane
The broken off section can move somewhere else through the blood or lymphatic system and grow another tumour
This is metastasis
What is angiogenesis?
the cancer cells that make up a tumour attract blood vessels to grow into the tumour
These blood vessels nourish the tumour
What is the difference between benign and malignant tumours?
Benign:
has a membrane
No metastasis
They put pressure on things (non invasive)
Non cancerous
Slow growing
Malignant:
no membrane
Metastasis
Secondary tumours are likely formed
Invasive
cancerous
Fast growing
How is meiosis and mitosis different?
Mitosis produced 2 identical daughters cells whereas meiosis produced 4 non identical cells and form gametes
What are haploid cells?
Sex cells that have only one copy of each chromosome from parents
What are diploid cells?
Sex cells that have 2 copies of each chromosome from parents
What is the process of meiosis?
Before meiosis starts dna unravels and replicates forming chromatids
DNA condenses forming sister chromatids joined by centromere
Meiosis 1: chromosomes arrange into homologous pairs and then seperate
Meiosis 2: sister chromatids making up each chromosome separated creating 4 haploid cells
What is the advantage of meiosis?
Increases amount of genetic variation allowing survivors to pass on their successful gene combinations onto offspring
What 3 ways can combinations of alleles be produced by?
independang assortment
Random fertilisation
Crossing over
What is independent assortment?
Homologous pairs of chromosomes can be reshuffled in any combination during meiosis
What is random fertilisation?
Any male gamete can join with any female gamete who each have chromosomes carrying different alleles
What is crossing over (chiasmata)?
Homologous chromosomes line up together and the chromatids cross over each other and join together, the links are called Chiasmata
What does non disjunction result in?
More than 2 copies of chromosomes being created → leads to disorders like Down syndrome
What is genetic diversity?
The number of different alleles of genes in a species or population.
When does evolution happen?
When the genetic composition (allele frequency) of a population changes over successive generations
What is the structure for a natural selection question?
I solation mechanism
V ariation
A dvantageous
M utation
P ass it on
S eperate species
What are the 3 main ways in which natural selection acts on the phenotypes in a population?
Stabilising selection → always occurs in an unchanging environment and eliminated extreme variations and favours the average phenotypes e.g human birth mass
Directional selection → favours the extreme phenotypes usually in a changing environment e.g antibiotic resistance
Disruptive selection → favours 2 extreme populations causing a bimodal distribution , new species may arise due to accumulation of different mutations within a species
What is allopatric and sympatric?
Allopatric = physical barrier separating the populations
Sympatric = no physical barrier
What is the founder effect?
occurs when a few individuals from a population colonise a new region and give rise to populations that are genetically distinct from the populations they left behind → these new populations can then develop into new species over time
This new population shows less genetic diversity than the populations they came from
The seperate species they develop into over time is less able to adapt to changing conditions due to having fewer alleles
What is classification?
The arrangement of organisms into groups of various sizes on the basis of shared features
What is taxonomy?
A form of classification that focuses on physical similarities between different species
What is phylogeny?
The classification of organisms by these evolutionary relationships, so that every group shares a common ancestor
What are the basic forms of classification?
artificial classification → divided organisms according to their differences that are useful to them e.g colour, size → however it ignores genetic info
natural classification → divides organisms into according evolutionary relationships and into a hierarchy with no overlaps
What is a phylogenetic tree?
Evolutionary history of organisms that shows their common ancestors → closely related organisms have diverged more recently from their common ancestor
What are some examples in shared characteristics?
fossil records show similarities
Similarities in protein/ amino acid structure
Similarities in behaviour
What are homologous structures?
Structural similarities that are inherited from a common ancestor e.g hands from cats, humans, frogs
What are analogous structures?
Those with the same purpose thag have evolved independently due to similar evolutionary pressures e.g wing shape
How does the binomial system name organisms scientifically?
genus (like last name) is the first letter of the first part of the name and is always capitalised and underlined when written
Species (like first name) is the second part and not capitalised but is underlined when written
What are the advantages of using the binomial system?
for brevity → earlier systems used more descriptive terms so were much longer
It’s widespread → it is used internationally
For clarity → the same name for the same species despite its geographical spread
What is the order of the binomial hierarchy?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What are the three subcategories in the domain division?
archaea → simple single cells
Bacteria → prokaryotic cells
Eukaryota
What are species?
2 organisms that are able to produce fertile offspring
Why is it difficult to give a definite answer for species?
they change and evolve over time becoming new species
There can be considerable variation in the same species e.g dogs
Many species are extinct and left no fossil data
How are evolutionary relationships determined?
by studying:
DNA sequences using DNA hybridisation
Anatomy e.g hologous features
Fossil records
Behaviour
What do DNA comparisons allow us to do?
identify numbers and types of differences between species
The more closely 2 species are related, the shorter the amount of time has passed since they shared a common ancestor
What are the steps to carry out DNA hybridisation?
Hybrid strands soeafsfed and temperature is increased in stages
At each stage the percentage of stow strands that are linked together are measured
If 2 species are closely related they will share many complementary nucleotide bases
The larger the number of hydrogen bonds, the stronger the hybrid strand will be
The higher the temperature needed to split the hybrid strand, the more closely the two species are leafed and vice versa
why is courtship behaviour carried out by organisms?
To attract a mate of the right species
What are some simple courtship behaviours?
releasing a chemical e.g pheromones released
Using sound
Visual displays e.g male peacocks
What are some complex courtship behaviours?
dancing
Building
Why are courtship behaviours necessary?
to recognise members of their own species
To identify a mate capable of breeding
To form a pair bond
What is the stimulus response chain order?
Make communicates a courtships signal
This acts as a visual stimulus for the female
The females nervous system detects and responds with a specific behaviour of her own
This acts as a stimulus to the male
The male responds
The cycle repeats