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Biology Unit 3 - Coggle Diagram
Biology Unit 3
How do cellular processes work?
Plasma membranes
Roles
Helps cell maintain shape
Selectively permeable barrier between intracellular and extracellular
Has receptor and marker molecules that enable intercellular communication
Phospholipid bilayer
Phospholipid orientation: phosphate heads (hydrophilic, polar) face outward, lipid tails (hydrophobic, non-polar) face inward
Phospholipids are amphipathic
Cholesterol scattered between phospholipids
Maintains optimal membrane flexibility
Transport proteins
Protein channel
Carrier protein
Glycolipids
Allow intercellular communication
Movement across
Passive transport
Simple diffusion
Net movement of molecules along their concentration gradient
From an area of higher solute concentration to an area of lower solute concentration
Only relatively small, polar and uncharged molecules can diffuse across plasma membrane via simple diffusion
E.g. O2, CO2, ethanol, urea
Osmosis
Net movement of free water molecules from hypotonic region to hypertonic region through selectively permeable plasma membrane; purpose of making regions isotonic
Hypotonic
Lower solute concentration, higher FREE WATER molecule concentration than compared solution
Hypertonic
Higher solute concentration, lower FREE WATER molecule concentration than compared solution
Isotonic
Two compared solutions have same solute concentration
Facilitated diffusion
Net movement of molecules or ions along its concentration gradient via transport proteins through plasma membrane
Channel proteins
Carrier proteins
E.g. absorption of small charged calcium ions into neurons by carrier proteins
Active transport
Movement of molecules or ions through the plasma membrane against their concentration gradient via transport proteins, requires the input of energy
Channel proteins
Form a water filled pore which can open and close
Specialises in small, charged molecules and ions
Carrier proteins
Change shape to carry substances across semi-permeable membrane
Specialises in large uncharged molecules
Bulk active transport
Movement of very large substances through the plasma membrane along or against its concentration gradient
Endocytosis
Transport into cell via endocytic vesicles
Exocytosis
Transport out of cell via exocytic vesicles
E.g. macrophages engulfing foreign material like a bacterial cell via endocytosis
E.g. absorption of large, polar, uncharged glucose molecules from gut into intestinal cells through carrier proteins
Nucleic acids and proteins
Condensation polymerisation
The process of binding monomers to each other with covalent bonds to make a polymer
Water molecule released
Linking 'n' monomers together to make 'x' number of polymer chains, you'll need 'n - x' covalent bonds.
One water molecule released for each bond, so you will get 'n - x' water molecules in the process
Bonds can be broken through a hydrolysis reaction, where molecule of water is added
Proteins
Proteome
All proteins present within a cell or organism
Made up of: C, H, O, N, and sometimes S
Cats Have One Need (Sometimes)
Polymers that consist of amino acid monomers joined via covalent bonds (specifically peptide bonds) formed through condensation polymerisation
Amino acids
Monomers/building blocks of proteins
20 different amino acids, distinguished by unique R group
Levels of structure
Primary structure
Specific sequence of amino acids in 2D polypeptide chain
Secondary structure
Coiling and pleating of polypeptide as a result of hydrogen bond formation within polypeptide
Alpha helices
Beta pleated sheets
Tertiary structure
3D structure of polypeptide folds due to R group chemical interactions
Quaternary structure
2 or more individual polypeptide chains bond together to form final 3D protein
Only some proteins have this structure e.g. haemoglobin
Denaturisation
The permanent change in 3D structure of a protein by disrupting the bonds that maintain it
Causes
Extreme heat or pH exposure disrupts tertiary structure bonds
Change to specific shape usually results in loss of function
Two classifications
Fibrous
Generally insoluble
Lacking in 3D structures
Usually serves structural function in organisms
Globular
Usually soluble
Complex 3D structures
Involved in cell communication and metabolic reactions
Roles
Structural
Collagen
Transport
Haemoglobin
Signalling molecules
Neurotransmitters
Receptor
Membrane glycoproteins
Defensive (immunity)
Antibodies
Enzymes
Lipase, amylase, protease
Regulatory
Gene regulator proteins
Nucleic acids
Genome
All the DNA present in a cell or organism
Made up of C, H, O, P, N
Chopn' nucleic acids
Polymers that consist of nucleotide monomers joined via covalent bonds (specifically phosphodiester bonds) formed through condensation polymerisation
Two types
DNA
Double stranded, double helix, antiparallel, wrapped around histone proteins to make chromosomes
Deoxyribose sugar
A, T, G, C
Contains hereditary information in the form of instructions that code for cell's proteome
Triplets
Sequence of 3 nucleotides that corresponds to a specific amino acid
Degenerate/redundant
More than one triplet can code for the same amino acid
Universal
The same triplet will code for the same amino acid in almost all organisms
RNA
Single stranded
Ribose sugar
A, U, G, C
Subtypes
mRNA
RNA copy of DNA
tRNA
Bring in amino acids in order specified by mRNA and rRNA to build polypeptide chain
rRNA
Structural component of ribosomes
Nucleotides
Made of a phosphate group, nitrogenous base, both bonded to a pentose sugar
Nitrogenous bases
Pyrimidines
One ring
Cytosine, uracil, thymine
Smaller
Purines
Two rings
Guanine, adenine
Larger
A > T and A > U pair together with 2 hydrogen bonds
G > C pair together with 3 hydrogen bonds
End of polymer starting with phosphate group is 5' prime, other end is 3' prime
Protein synthesis
Transcription
Transcription initiation: RNA polymerase attaches to promoter upstream of the gene and begins unwinding the gene's double helix to expose nucleotide bases of DNA template/antisense strand. This strand starts at 3' and ends at 5' end, and is complementary to non-template/coding/sense strand (starts at 5' ends at 3')
Transcription elongation: moving in 3' to 5' direction according to the template strand, RNA polymerase catalyses condensation polymerisation of free mRNA nucleotides. mRNA built in 5' to 3' direction.
Transcription termination: RNA polymerase hits STOP triplet and mRNA transcript detaches from RNA polymerase
Prokaryotes
mRNA goes directly to ribosomes in cytoplasm for translation
Eukaryotes
Post-transcriptional modification
Add methylated 5' cap and poly-A tail to respective ends of pre-mRNA
Introns are spliced out of pre-mRNA and exons are spliced together. This mRNA then moves into cytoplasm via nuclear pores for translation.
Translation
Translation initiation: ribosome attaches to 5' end of mRNA
Translation elongation:
Structure and regulation of biochemical pathways
Photosynthesis
Cellular respiration
How do cells communicate?
Cellular signals
Types of signalling
Endocrine
Between cells that are in different parts of the body
Hormones
Plant hormones
Similarities to animal hormones
Organic
Signalling molecules
Target tissue distant to source
Differences to animal hormones
Don't travel in general circulation
Not produced in endocrine glands
Not biomacromolecules
Paracrine
Between adjacent cells
Neurotransmitters
E.g. acetylcholine
Cytokines
E.g. Th cell secreting interleukin to activate Tc cell
Autocrine
Cells signalling to themselves
Cytokines
When a Th cell secretes interleukin to activate Tc cell, but also activates itself
Exocrine
Pheremones
Stimulus-response model
Stimulus
A intracellular or extracellular change that induces transduction
Transduction
Receptor
Usually a protein
Binding of signalling molecule causes receptor protein to change shape
Intracellular receptor
Inside the cell, hydrophobic molecules
Extracellular receptor
On the surface of the plasma membrane, hydrophilic molecules
Effector
Molecules that produce a response
Second messenger
Signal amplification
One signalling molecule is responsible for producing a much bigger signal cascade inside the cell
Response
Cellular-level response
Apoptosis
Programmed cell death
Intrinsic pathway (mitochondrial)
Mitochondria damaged
Release cytochromes
Act as signalling molecules for receptors inside cell that initiates apoptosis
Extrinsic pathway (death receptor)
Death ligand (FasL)
Secreted by cytotoxic T cell
Binds to FasR on exterior of cell membrane
Cascade to form a caspase
Caspase binds to proteins of cytoskeleton, so cell collapses and blebs
Removal of cells no longer needed, or that are a threat
Mediated by caspases (enzymes)
Processes
Blebbing
Cell shrinkage
Nuclear fragmentation
Breaking down of nucleus
Chromatin condensation
Chromatin starts to thicken and condense
Chromosomal DNA fragmentation
DNA broken up into pieces
Malfunctions
Can lead to cancer
Uncontrolled division of cells
Apoptosis happens when it shouldn't
Apoptosis doesn't happen when it should
Responding to antigens
Antigens
Self
MHC I
All cells except red blood cells
MHC II
B cells
T cells
Macrophages
Dendritic cells
Red blood cells
A/B/O blood types
Non-self
Pathogen
A disease causing agent
Cellular
Bacteria
Shapes
Baccilus
Rod
Coccus
Sphere
Spirochaete
Spiral
Spirillium
Spiral shaped
Flagella
Unicellular, prokaryote
Fungi
Multicellular parasites
Non-cellular
Virus
DNA or RNA
Protein capsid
Lipid envelope
Prions
Viroids
Single, circular RNA strand
Only known to infect plants
Innate immune system
First line of defence
Physical barriers
Animals
Intact skin
Ciliated mucous membranes
Stomach acid
Coughing or sneezing
Secretions (mucous, saliva, tears, earwax, urine)
Plants
Intact layer of cells over surface of leaf (epidermis)
Waxy cuticle over epidermis
Chemical barriers
Plants
Animals
Microbiological barriers
Second line of defence
Adaptive immune system (third line of defence)
Immunity
Natural
Receiving antibodies via breastmilk or crossing the placenta
Becoming infected by a pathogen
Artificial
Receiving a vaccination
Active
Becoming sick
Receiving a vaccination with foreign antigen
Live attenuated
Virulent genes manipulated/removed
Usually viruses with small genomes
Advantages
Easy to create
Usually single dosage gives life long immunity against pathogen
Disadvantages
Can cause disease if weak immune system
Can cross placenta and infect baby
Inactivated
Killed vaccine
Heat, radiation, toxic chemical exposure
Cannot reproduce
Advantages
Can be used for bacteria
Whole pathogen included so more antigens
Safer for people with weaker immune systems
Disadvantages
Might need a booster shot for life long immunity
Risk that not all pathogens will be fully killed
Active means via own adaptive immune response
Passive
Receiving antibodies via a vaccine
Antiserum (serum that contains antibodies)
Serum (fluid part of blood that contains antibodies)
Receiving antibodies via breastmilk or across placenta
Immediate, short term protection
Antibodies from one organism to another
Immunity definition: The ability for an organism to have adequate biological defences against pathogens and a tolerance to allergies and autoimmune diseases.
Vaccination programs
Series of ages where specific dosages of vaccines should be given
Aim to reduce rate of, or eradicate, disease
Aim for herd immunity
Herd immunity definition: how hard it is for a disease to spread across a population
Difficult = High
Easy = low
Aim for 95% vaccination rate
Protect those who may not be able to get vaccinated
Very old
Very young
Immunocompromised
Immunological memory
Ability of adaptive immune system to 'remember' antigens after primary exposure