DNA, Macromolecules (Proteins, Enzymes) & Bodily systems Flashcards
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What is deoxyribonucleic acid? (DNA)
DNA stores the information that directs all the complex processes an organism must carry out.
It does this by containing genes that code for all of the organism’s proteins
What does DNA consist of?
DNA is made up of 2 strands of polynucleotides that form a double helix.
Each strand of DNA has a sugar-phosphate backbone, and bases that bind to complementary bases on the other strand by weak hydrogen bonds.
What are the bases of nucleotides and which complement each other?
The bases from one strand bind (by weak hydrogen bonds) to their complementary bases on the complementary strand.
ATCG
Adenine <–> Thymine
Cytosine <–> Guanine
DNA vs. RNA?
DNA:
- Stores genetic information
- Double stranded
- Bases: Thymine, adenine, guanine, cytosine
RNA:
- Involved in protein synthesis
- Single stranded
- Bases: Uracil, adenine, guanine, cytosine
What is the hierarchy of synthesis from DNA to amino acid?
DNA - made up of nucleotides provides the code for the cellular activities
RNA - also made up of nucleotides converts DNA code into RNA molecules to synthesise proteins to carry out cellular functions
Protein - made by the code on RNA molecules and carry out the cellular functions
What is the process of protein synthesis and gene expression?
Step 1: Transcription (DNA to mRNA)
Genetic information in a gene is copied (transcribed) to messenger RNA (mRNA).
The part of the DNA to be transcribed unwinds, the two strands separate, and free floating RNA nucleotides assemble at the template DNA strand to form an mRNA molecule.
The main enzyme involved is called RNA polymerase.
mRNA carries the genetic message from the DNA to ribosomes in the cytoplasm for protein synthesis (translation).
Step 2: Translation (mRNA to protein)
Messenger RNA (mRNA) is transported from the nucleus to ribosomes in the cytoplasm.
The genetic message on the mRNA is translated into a sequence of amino acids (forming a polypeptide)
Polypeptides then fold into proteins
The genetic message in RNA is in the form of codons (three bases) that each code for a specific amino acid
Each amino acid is carried by a specific tRNA (transfer RNA) to a ribosome to add to the growing polypeptide chain.
Each tRNA has a specific set of three bases (anticodon) that complements each codon on the mRNA template
In the ribosome, tRNA molecules, carrying specific amino acids, bind (via their anticodons) to complementary codons in the mRNA. This adds amino acids to the growing polypeptide chain in the correct sequence.
Many antibiotics (chemicals that are anti-bacterial) work by inhibiting protein synthesis at the ribosome.
What are macromolecules?
All organisms use four different types of large molecules:
Carbohydrates, Lipids, Protein and Nucleic acids (DNA and RNA)
What are organic compounds?
Organic compounds contain carbon (C) and hydrogen (H) (can also contain O, N, S, and P)
They can be very complex (big)
What are polymers?
Polymers are composed of many smaller molecules called subunits (monomers), that join together to make long chains.
What are nucleic acids?
Nucleic acids (DNA & RNA) store, and help express the information that directs all the metabolic processes in organisms.
There are 2 types of nucleic acids:
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Nucleic acids are polynucleotides that are made of subunits called nucleotides
What is DNA made up of?
DNA is made up of 2 polynucleotide strands that form a double helix.
Each strand has a sugar-phosphate backbone, and bases that bind to complementary bases on the other strand by weak hydrogen bonds.
What are genes and what do they do?
Genes are segments of DNA that provide the code to make the sequence of amino acids (polypeptides) for all the proteins in an organism.
Genes can also make RNA (that don’t code for proteins)
What does RNA do?
Ribonucleic acid (RNA) helps convert the codes in DNA to the sequence of amino acids for all the proteins in an organism.
The flow of genetic information in a cell:
DNA (genes) → RNA → protein
RNA molecules also form structures (including ribosomes)
What are the functions of proteins in the body?
Structural (eg, cytoskeleton, hair, nails, tendons, ligaments and skin)
Catalyse reactions (enzymes)
Movement (muscle fibres)
Transport (haemoglobin carrying O2, membrane transport proteins)
Defence (antibodies produced by white blood cells)
Communication (hormones and membrane receptors)
What are proteins?
Proteins are made up of one or more polypeptide chains that are long chains of amino acid subgroups.
There are 21 different amino acids, each with different chemical properties, making up all the different proteins in your body.
How is protein structure classified?
- Primary structure
- the sequence (order) of amino acids in a polypeptide chain - Secondary structure
- the coiling or folding of parts of the polypeptide chain into helices and sheets.
- Held in place by hydrogen bonds - Tertiary structure
- the 3D shape of the entire folded polypeptide
- helices and sheets (held together by hydrogen bonds) folded into one globular mass - Quaternary structure
- the association of two or more polypeptide chains (only some proteins have a quaternary structure)
What are carbohydrates?
Carbohydrates (saccharides) are molecules that contain carbon (C), hydrogen (H) and oxygen (O).
Made of simple sugars, such as glucose that are converted into usable energy (ATP) in cells
Monosaccharides
Simple form of an organic sugar.
Eg. Glucose, Fructose, Galactose
Disaccharides
Consist of 2 monosaccharides bound together.
Eg. Sucrose (1 glucose + 1 Fructose)
Polysaccharides
Long chains of monosaccharides bound together.
Eg. Starch (many glucose)
What are the functions of carbohydrates/polysaccharides?
Polysaccharides (long chains of sugars) are used by organisms for either storage or structural purposes.
Storage of energy
Starch (in plants)
- Allows plants to stockpile surplus glucose for later use
- Most animals (including humans) can breakdown starch (from potato tubers, grains) into glucose for the cells’ energy.
Glycogen (in animals)
- Stockpile of surplus glucose in liver and muscle tissue
Cellulose (in plants)
- Major component of cell walls in plants
- Herbivores rely on cellulose-digesting microorganisms to digest it.
- In our diet cellulose is the main source of ‘dietary fibre’
What are lipids?
The compounds called lipids are grouped together because they do not mix with water - they are hydrophobic. They have a hydrophilic head, but a hydrophobic tail.
There are 2 main types:
- Fats/oils (triglycerides)
- Phospholipids
What are enzymes?
Enzymes are proteins that act as biological catalysts.
They dramatically speed up metabolic reactions without being consumed (they can be reused)
Most enzymes are intracellular, however some are extracellular (eg. digestive enzymes in the gut).
How do enzymes work?
Each enzyme has an active site that has a complementary shape to a specific substrate
When the substrate binds to the active site the site changes shape and improves the fit (induced-fit model)
The reaction occurs because the active site provides a suitable environment for the reaction to begin
How does pH impact enzyme function?
Low pH (acidic) or high pH (alkaline) environments can denature enzymes.
Each enzyme has an optimal pH
Eg, most work best at neutral pH (7),
pepsin in the stomach, works best in an acidic environment (pH 2).
What does the graph of enzyme activity for pH look like?
An exponential increase toward the optimum pH, where the line is then mirrored back down after the point of optimum pH. Almost looks like a parabola.
How does temperature impact enzyme function?
Low temperatures decrease enzyme activity because the enzyme and substrate are moving at slower speeds and therefore collide and bind less often
High temperatures decrease enzyme activity because H-bonds are disrupted leading to the denaturation of the enzyme
