Biological Systems

  • Created by: Marvo1245
  • Created on: 15-03-20 05:01

4 main macromolecules of Life

Carbohydrates: Structure, fuel and stability.

  • Monosaccharides, glucose
  • Disaccharides, sucrose and fructose 
  • Polysaccharides, cellulose


  • Fats (energy)
  • Hormones
  • Steriods 
  • Phospholipids

Nucleic acid:

  • DNA, RNA. and amino acids
  • Store transmit and express genes 


  • Versatile building blocks and have many functions 
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Without Origin

Small inorganic molecules --> small organic molecules --> macromolecules --> Protocell 

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Life originated on another planet and was brought here by asteroid since Amino acids have been found on asteroids that do not originate on Earth.

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Carboxyl group

multiple Hydroxyl groups attached.

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Glycosidic linkage

When two sugars come together, the OH groups are hydrolysed to form a single Oxygen bond atom between the two 

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Amino Acids

Have an amino group, H,N,H and a carboxyl group OH-C=O formed with an alpha carbon.

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Carboxyl-amino group

When nthe hydrogen molecule of the amino group and the hydroxyl group of the carboxyl side hydrolyse and form a straight chain

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Primary Structure

Read the amino acids left to right, single chain

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Secondary structure

Beta pleated sheets and Alpha helix interactions. Hydrogen bonds occur between the oxygen of the carboxyl group and the hydrogen atom of the amino group 

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Tertiary Structure


  • Hydrophobic interactions
  • hydrogen bonding
  • ionic bonding
  • Disulphide bridges
  • Van Der Waal forces 

Creates overall shape of protein

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Quaternary Structure

More than two polypeptide chains interacting

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Protein denaturing

In highly acidic, high concentrations of salt or environments that are too hot, the protein can become denatured which is why fevers are dangerous

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Central Dogma

DNA -> mRNA -> rRNA -> tRNA -> protein

DNA is transcripted into RNA, RNA is transcribed into a protein

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Nucleotide bases

Guanine, thymine, adenine, cytosine, uracil. 

purines and pyramids 

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Nucleotide Composition

Nitrogenous base

pentose sugar

up to 3 phosphate groups

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introns and exons

Introns do not code

exons do code

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Having specialized organelles benefit larger cells since they can co-ordinate with each other and develop overtime

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Basic needs of a cell

- reproduce

- carry genetic information

- maintain a different internal and external environment

- have metabolic activities 

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Nucleus + nucleolus (settings)

Control centre of the body, protects DNA

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Rough Endoplasmic Reticulum (factory)

Makes proteins with ribosomes 

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Smooth endoplasmic reticulum

Makes hormones, lipids, detoxifies and stores calcium. 

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Golgi apparatus

packages and matures proteins 

digestive secretions for outside of the cell

integrates components into the cell

create lysosomes for digestion 

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catalase: makes bleach

oxidase: makes water 

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Central Vacuole

Stores water and food 

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Simple diffusion

Non-polar, uncharged and small lipids pass

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Facilitated Diffusion

polar, larger molecules with concentration gradient 

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primary active transport

Against concentration gradient, with ATP

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Secondary active transport

against and with the concentration gradient. co-transport required 

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controlling solute concentration when living in an isotonic environment 

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Turgor pressure

Cells with a cell wall pushing back onto the ECF in hypotonic environments 

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Cells with cell wall pulling away from the cell wall in hypertonic environments

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Binary fission

DNA is replicated at one point of origin, the DNA copies in both directions, the DNA supercoils with the assistance of a special protein, the cell size increases and then the cell divides. 

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Endothermic, Gibbs G and endergonic

Positive delta G value, anabolic reactions, non-spontaneous, requires energy 

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Exothermic, Giibs G, exergonic

negative Delta G, spontaneous, catabolic, releases energy 

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Inorganic molecules that assist in electron transfer. 

Iron, magnesium and zinc. 

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organic molecules that assist in electron transfer

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Behind the scenes of Evolution

-       Mutations arise from genetic DNA errors.

-       DNA polymerase: Makes an error in 1 in every 10,000,000

-       Post-replication repair: Makes error in 1 in every 1,000,000,000

-       Human genome: when a full human genome is replicated, there are usually 3 errors since they area 3,000,000,000

-       Mutation: Bad

-       Polymorphism: great or neutral

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Point mutation

Insertion: a nucleotide is inserted into the amino acid sequence 

Substitution: when a nucleotide is exchanged for another one in its place

Deletion: when a nucleotide is removed 

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Basis of evolution

Basis of evolution: In somatic cells --> mutations only affect individual, in gamete ---> mutations effect all offspring

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A change in allele frequency in a population overtime 

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In diploid organisms, two alleles usually code for every genotype 

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Darwins observations

 Members of a population vary in their inherited trait. All species produce offspring that won’t be able to reproduce. Members with inherited traits which are beneficial are advantageous because it raises the probability of survival and offspring survival.

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Descent with modification

Evolve overtime to better their environment

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Evidences of Evolution

Direct observations

morphological record

genetic homology 

fossil record 

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Direct observation

-       Galapagos finches: Beak size and shape changed with food availability and rainfall

-       Artificial selection: or selective breading. Domestication of animals for particular qualities. Different vegetables from common ancestors

-       Antibiotic resistance: Initial antibiotic almost killed all bacteria but the few that survived passed on the resilience to their offspring

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Morphological and genetic homology

Shared similarities between species to identify a common ancestor through anatomical homology

-       Molecular Homology: DNA sequence that code for similar proteins across different species

-       Amino Acid Sequence: Different species that have similar amino acid sequences that code for proteins

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Fossil record

Physical record of intermediate life forms that support descent with modification

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Mechanisms of Evolution

Natural selection

Genetic drift

Gene flow 

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Natural selection

    Natural selection: The most fit organisms reproduce more bcs they can compete better for resources. They have the most offspring who will also be well adapted thus the alleles that confer adaptive advantage increase in frequency in the population

o   Direction selection: Favours variants at one end, black mice do better than white mice

o   Disruptive selection: Favour variants at both extremes. White and black mice do well, intermediate coloured mix do not do well

o   Stabilising selection: Favours variants from the intermediate population. Tan mice do better than black or white mice

o   Maladaptation’s: Natural selection drives adaption and sometimes favours adaptions that aren’t all good. Peacock feather colouration gives its position away to predators

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Genetic drift

Fluctuations in allele frequency arising from chance events. Doesn’t always lead to adaptions since its random. Has a bigger impact with smaller populations?

-       Founder effect: A small segment of the population goes someplace different and thus the alleles are way different

-       Bottleneck effect: Occurs when population undergoes rapid decrease in size due to a natural disaster where only few live.

-       Fixation: From genetic drift, some alleles can become fixed that are really bad

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Gene flow

A result of population migration between two groups. this can diversify 

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Rock types

Igneous rock: comes from cooling magma

Sedimentary rock: Formed by accumulation of sediment

Metamorphic: One of the above charged by the environment (pressure or heat)

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Fossil Formation

Found in sedimentary rock. 

  • the carcass is buried in mud
  • The soft tissue decomposes whilst the bone remains
  • the sediment builds up top and hardens into rock 
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Fossil dating

Fossil recorded by the layer of strata they're found in 

-       Radiometric decay/dating tells us absolute age. Based on predictable decay of radioactive isotopes (expressed as t.5) = 5730 years. When an animal dies, it stops accumulating elements. Ratio of radioactive isotopes to stable isotopes is directly related to how long ago it died.

-       Fossil record bias: Subjected to bias to species that existed for a long time, were abundant and widespread and had hard-shells or skeletons

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Homology vs Analogy

Homology is a structure that is similar in related species

Analogy are structures that function the same but due to similar environment pressure, can occur in two different species that are unrelated like dolphins and sharks 

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Time determination

Fossil record/carbon dating and Mutation clock

Mutation clock: Goes back in fossil records and sees the rate of genetic mutation. The fewer mutations something has, the older it is and how long ago it diverged

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Endomembrane system

Golgi apparatus


Smooth ER

Rough ER

cellular membrane 

nuclear envelope 

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