Ever wondered how your body creates new cells, repairs damage,... Show more
Biology361 views·Updated May 18, 2026·15 pagesUnit 1 Higher Human Biology: Key Facts and Flashcards
ava🪱@avasnotes
1 / 10
1
of 10
Cell Division and Stem Cells
Your body contains two main types of cells that behave very differently. Somatic cells are basically any body cell not involved in reproduction - think skin, muscle, or liver cells. These divide through mitosis to create identical diploid copies of themselves.
Germline cells are the reproductive game-changers - these are your gametes (sperm and egg cells) and the stem cells that create them. When they divide by mitosis, you get more diploid germline cells, but when they divide by meiosis, you get four haploid gametes with half the chromosomes (23 instead of 46).
Stem cells are your body's ultimate multitaskers - unspecialised cells that can either self-renew or differentiate into specialised cell types. Embryonic stem cells are pluripotent (can become any cell type), whilst tissue stem cells are multipotent (can only become cells of their specific tissue). Through cellular differentiation, genes are expressed to create proteins that give each cell type its unique characteristics and functions.
Key Point: Remember the difference - diploid cells have 46 chromosomes (23 pairs), whilst haploid cells have just 23 chromosomes (one set).
2
of 10
Stem Cell Applications and Cancer
Tissue stem cells have three crucial jobs: growth, repair, and renewal. They're already being used in medicine for things like corneal repair and skin regeneration after burns. Embryonic stem cells can self-renew indefinitely in lab conditions, making them powerful tools for research.
Scientists use stem cells as model systems to understand how diseases develop and test new drugs. However, this raises ethical concerns since using embryonic stem cells requires destroying embryos - a major debate in medical research.
Cancer happens when cells go rogue and fail to respond to the body's regulatory signals, dividing excessively to form tumours. Things get dangerous when cancer cells within a tumour fail to stick together properly - they can break away and spread throughout the body, forming secondary tumours.
Real-world Application: Stem cell therapy is already helping patients with conditions like corneal blindness and severe burns - this isn't just theoretical future medicine!
3
of 10
DNA Structure and Replication
DNA is made up of nucleotides, each containing three components: a deoxyribose sugar, a phosphate group, and one of four bases (adenine, thymine, guanine, or cytosine). These nucleotides link together through complementary base pairing - adenine always pairs with thymine, and guanine always pairs with cytosine.
The two DNA strands are antiparallel (running in opposite directions) and twist together to form the famous double helix. One strand has a phosphate group at the 5' end and a deoxyribose sugar at the 3' end.
Before cell division, DNA replication must occur. The double helix unwinds and hydrogen bonds break, creating two template strands. DNA polymerase adds new nucleotides to the 3' end of the forming strand, but it needs primers to get started.
Memory Tip: Think of DNA polymerase as a builder who can only add bricks (nucleotides) to one end of the wall, and needs a foundation (primer) to start building.
4
of 10
DNA Replication Process and PCR
DNA replication happens differently on each strand. The leading strand replicates continuously, whilst the lagging strand must be built in fragments because DNA polymerase can only work in one direction. These fragments are then joined together by DNA ligase.
Polymerase Chain Reaction (PCR) is a brilliant technique that amplifies tiny amounts of DNA. It uses primers - short DNA sequences that bind to specific target sequences at both ends of the DNA section you want to copy.
PCR involves three temperature stages: heating to 92-98°C separates the DNA strands, cooling to 50-65°C allows primers to bind to their target sequences, and heating to 70-80°C lets heat-tolerant polymerase replicate the DNA region. This process repeats many times, exponentially increasing the amount of DNA.
Real-world Application: PCR is used everywhere - solving crimes through DNA evidence, paternity testing, and diagnosing genetic disorders from tiny tissue samples.
5
of 10
RNA and Gene Expression
Gene expression converts DNA information into proteins through two stages: transcription and translation. Unlike DNA's double helix, RNA is single-stranded and contains ribose sugar instead of deoxyribose. In RNA, adenine pairs with uracil instead of thymine.
There are three types of RNA, each with specific jobs. mRNA carries genetic information from the nucleus to ribosomes. tRNA brings specific amino acids to the ribosome and has an anticodon (three bases) that pairs with mRNA codons. rRNA combines with proteins to form ribosomes.
RNA polymerase starts transcription by unwinding DNA and breaking hydrogen bonds between base pairs. Free RNA nucleotides then pair with the template strand through complementary base pairing, forming a primary transcript.
Key Concept: Think of mRNA as a photocopy of the DNA recipe, tRNA as delivery trucks bringing ingredients, and ribosomes as the kitchen where everything gets assembled.
6
of 10
From Transcript to Protein
The primary transcript isn't ready for translation yet. It contains introns that must be removed and exons (coding regions) that need joining together. RNA splicing removes introns and joins exons to create a mature mRNA transcript.
Translation begins at start codons and ends at stop codons. tRNA molecules bring amino acids to the ribosome, where their anticodons pair with mRNA codons through complementary base pairing. Peptide bonds join amino acids together, forming polypeptides.
Alternative RNA splicing allows one gene to produce different proteins by retaining different exons in various combinations. As polypeptides form, they fold into specific 3D shapes held together by hydrogen bonds and interactions between amino acids.
Amazing Fact: One human gene can produce multiple different proteins through alternative splicing - it's like getting several different recipes from the same cookbook page!
7
of 10
Protein Function and Mutations
The 3D shape of a protein determines its function, and proteins produced through gene expression ultimately determine your phenotype (observable characteristics). When things go wrong with DNA, we get mutations - changes in the DNA sequence.
Single gene mutations affect individual nucleotides and come in several types. Substitution mutations include missense (changes one amino acid), nonsense (creates a stop codon producing shorter proteins), and splice-site mutations (affect intron removal and exon inclusion).
Frameshift mutations (insertions and deletions) are particularly serious because they change all codons after the mutation point, completely altering the amino acid sequence. Chromosome structure mutations include duplication (adding chromosome sections), deletion (removing sections), inversion (reversing sections), and translocation .
Important: Frameshift mutations often have more severe effects than substitutions because they change the entire protein sequence downstream from the mutation.
8
of 10
Chromosome Mutations and Genomes
Chromosome mutations can be lethal because they affect large amounts of genetic material. Deletion mutations remove chromosome sections entirely, whilst inversion mutations reverse chromosome sections. Translocation mutations move chromosome sections to non-homologous partners, often disrupting normal gene function.
Your genome contains all hereditary information encoded in DNA - both genes and non-coding sequences that don't produce proteins. Genomic sequencing can determine the sequence of bases in individual genes or entire genomes.
Computer programs help identify genes by comparing sequences to known genes in databases. This field, called bioinformatics, uses computer and statistical analyses to compare genome sequence data and make sense of the massive amounts of information generated by modern sequencing techniques.
Future Medicine: Understanding genomes is revolutionising medicine - soon doctors might analyse your genome to predict disease risk and choose the best treatments for you personally.
9
of 10
Genomics and Personalised Medicine
Individual genome analysis can predict your likelihood of developing certain diseases before symptoms appear. This information helps doctors make better decisions about prevention and early treatment strategies.
Pharmacogenetics studies how genome information influences drug choice and effectiveness. Different people respond differently to medications based on their genetic makeup, so knowing someone's genome helps doctors select the most effective treatments.
Personalised medicine uses your individual genome sequence to choose the most effective drugs and dosages for treating your specific condition. This approach reduces side effects and improves treatment outcomes by tailoring medical care to your genetic profile.
Real Impact: Personalised medicine is already helping cancer patients receive treatments specifically designed for their tumour's genetic characteristics, dramatically improving survival rates.
10
of 10
Metabolic Pathways and Enzymes
Metabolic pathways are integrated networks of enzyme-controlled reactions within cells. Anabolic reactions build small molecules into larger ones (requiring energy), whilst catabolic reactions break large molecules into smaller ones (releasing energy).
These pathways are controlled by enzyme presence and regulation of reaction rates. Enzymes work through induced fit - their active sites change shape to better accommodate substrates. Substrates have high affinity for active sites, whilst products have low affinity, allowing them to leave easily.
Enzymes lower the activation energy needed for reactions to occur. Increasing substrate concentration speeds up reactions until all enzyme active sites are occupied. However, increasing end product concentration can reduce reaction rates, stop reactions, or even reverse them.
Key Understanding: Think of enzymes as specialist tools that make chemical reactions happen faster and more efficiently - they're essential for all life processes.
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Biology361 views·Updated May 18, 2026·15 pagesUnit 1 Higher Human Biology: Key Facts and Flashcards
ava🪱@avasnotes
Ever wondered how your body creates new cells, repairs damage, or even how DNA works? This guide breaks down the fascinating world of cells, DNA, and genetics in a way that'll actually make sense for your A-levels.
1
of 10Sign up to see the content. It's free!
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- Join milions of students
Cell Division and Stem Cells
Your body contains two main types of cells that behave very differently. Somatic cells are basically any body cell not involved in reproduction - think skin, muscle, or liver cells. These divide through mitosis to create identical diploid copies of themselves.
Germline cells are the reproductive game-changers - these are your gametes (sperm and egg cells) and the stem cells that create them. When they divide by mitosis, you get more diploid germline cells, but when they divide by meiosis, you get four haploid gametes with half the chromosomes (23 instead of 46).
Stem cells are your body's ultimate multitaskers - unspecialised cells that can either self-renew or differentiate into specialised cell types. Embryonic stem cells are pluripotent (can become any cell type), whilst tissue stem cells are multipotent (can only become cells of their specific tissue). Through cellular differentiation, genes are expressed to create proteins that give each cell type its unique characteristics and functions.
Key Point: Remember the difference - diploid cells have 46 chromosomes (23 pairs), whilst haploid cells have just 23 chromosomes (one set).
2
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Stem Cell Applications and Cancer
Tissue stem cells have three crucial jobs: growth, repair, and renewal. They're already being used in medicine for things like corneal repair and skin regeneration after burns. Embryonic stem cells can self-renew indefinitely in lab conditions, making them powerful tools for research.
Scientists use stem cells as model systems to understand how diseases develop and test new drugs. However, this raises ethical concerns since using embryonic stem cells requires destroying embryos - a major debate in medical research.
Cancer happens when cells go rogue and fail to respond to the body's regulatory signals, dividing excessively to form tumours. Things get dangerous when cancer cells within a tumour fail to stick together properly - they can break away and spread throughout the body, forming secondary tumours.
Real-world Application: Stem cell therapy is already helping patients with conditions like corneal blindness and severe burns - this isn't just theoretical future medicine!
3
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
DNA Structure and Replication
DNA is made up of nucleotides, each containing three components: a deoxyribose sugar, a phosphate group, and one of four bases (adenine, thymine, guanine, or cytosine). These nucleotides link together through complementary base pairing - adenine always pairs with thymine, and guanine always pairs with cytosine.
The two DNA strands are antiparallel (running in opposite directions) and twist together to form the famous double helix. One strand has a phosphate group at the 5' end and a deoxyribose sugar at the 3' end.
Before cell division, DNA replication must occur. The double helix unwinds and hydrogen bonds break, creating two template strands. DNA polymerase adds new nucleotides to the 3' end of the forming strand, but it needs primers to get started.
Memory Tip: Think of DNA polymerase as a builder who can only add bricks (nucleotides) to one end of the wall, and needs a foundation (primer) to start building.
4
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
DNA Replication Process and PCR
DNA replication happens differently on each strand. The leading strand replicates continuously, whilst the lagging strand must be built in fragments because DNA polymerase can only work in one direction. These fragments are then joined together by DNA ligase.
Polymerase Chain Reaction (PCR) is a brilliant technique that amplifies tiny amounts of DNA. It uses primers - short DNA sequences that bind to specific target sequences at both ends of the DNA section you want to copy.
PCR involves three temperature stages: heating to 92-98°C separates the DNA strands, cooling to 50-65°C allows primers to bind to their target sequences, and heating to 70-80°C lets heat-tolerant polymerase replicate the DNA region. This process repeats many times, exponentially increasing the amount of DNA.
Real-world Application: PCR is used everywhere - solving crimes through DNA evidence, paternity testing, and diagnosing genetic disorders from tiny tissue samples.
5
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
RNA and Gene Expression
Gene expression converts DNA information into proteins through two stages: transcription and translation. Unlike DNA's double helix, RNA is single-stranded and contains ribose sugar instead of deoxyribose. In RNA, adenine pairs with uracil instead of thymine.
There are three types of RNA, each with specific jobs. mRNA carries genetic information from the nucleus to ribosomes. tRNA brings specific amino acids to the ribosome and has an anticodon (three bases) that pairs with mRNA codons. rRNA combines with proteins to form ribosomes.
RNA polymerase starts transcription by unwinding DNA and breaking hydrogen bonds between base pairs. Free RNA nucleotides then pair with the template strand through complementary base pairing, forming a primary transcript.
Key Concept: Think of mRNA as a photocopy of the DNA recipe, tRNA as delivery trucks bringing ingredients, and ribosomes as the kitchen where everything gets assembled.
6
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
From Transcript to Protein
The primary transcript isn't ready for translation yet. It contains introns that must be removed and exons (coding regions) that need joining together. RNA splicing removes introns and joins exons to create a mature mRNA transcript.
Translation begins at start codons and ends at stop codons. tRNA molecules bring amino acids to the ribosome, where their anticodons pair with mRNA codons through complementary base pairing. Peptide bonds join amino acids together, forming polypeptides.
Alternative RNA splicing allows one gene to produce different proteins by retaining different exons in various combinations. As polypeptides form, they fold into specific 3D shapes held together by hydrogen bonds and interactions between amino acids.
Amazing Fact: One human gene can produce multiple different proteins through alternative splicing - it's like getting several different recipes from the same cookbook page!
7
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Protein Function and Mutations
The 3D shape of a protein determines its function, and proteins produced through gene expression ultimately determine your phenotype (observable characteristics). When things go wrong with DNA, we get mutations - changes in the DNA sequence.
Single gene mutations affect individual nucleotides and come in several types. Substitution mutations include missense (changes one amino acid), nonsense (creates a stop codon producing shorter proteins), and splice-site mutations (affect intron removal and exon inclusion).
Frameshift mutations (insertions and deletions) are particularly serious because they change all codons after the mutation point, completely altering the amino acid sequence. Chromosome structure mutations include duplication (adding chromosome sections), deletion (removing sections), inversion (reversing sections), and translocation .
Important: Frameshift mutations often have more severe effects than substitutions because they change the entire protein sequence downstream from the mutation.
8
of 10Sign up to see the content. It's free!
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- Improve your grades
- Join milions of students
Chromosome Mutations and Genomes
Chromosome mutations can be lethal because they affect large amounts of genetic material. Deletion mutations remove chromosome sections entirely, whilst inversion mutations reverse chromosome sections. Translocation mutations move chromosome sections to non-homologous partners, often disrupting normal gene function.
Your genome contains all hereditary information encoded in DNA - both genes and non-coding sequences that don't produce proteins. Genomic sequencing can determine the sequence of bases in individual genes or entire genomes.
Computer programs help identify genes by comparing sequences to known genes in databases. This field, called bioinformatics, uses computer and statistical analyses to compare genome sequence data and make sense of the massive amounts of information generated by modern sequencing techniques.
Future Medicine: Understanding genomes is revolutionising medicine - soon doctors might analyse your genome to predict disease risk and choose the best treatments for you personally.
9
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Genomics and Personalised Medicine
Individual genome analysis can predict your likelihood of developing certain diseases before symptoms appear. This information helps doctors make better decisions about prevention and early treatment strategies.
Pharmacogenetics studies how genome information influences drug choice and effectiveness. Different people respond differently to medications based on their genetic makeup, so knowing someone's genome helps doctors select the most effective treatments.
Personalised medicine uses your individual genome sequence to choose the most effective drugs and dosages for treating your specific condition. This approach reduces side effects and improves treatment outcomes by tailoring medical care to your genetic profile.
Real Impact: Personalised medicine is already helping cancer patients receive treatments specifically designed for their tumour's genetic characteristics, dramatically improving survival rates.
10
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Metabolic Pathways and Enzymes
Metabolic pathways are integrated networks of enzyme-controlled reactions within cells. Anabolic reactions build small molecules into larger ones (requiring energy), whilst catabolic reactions break large molecules into smaller ones (releasing energy).
These pathways are controlled by enzyme presence and regulation of reaction rates. Enzymes work through induced fit - their active sites change shape to better accommodate substrates. Substrates have high affinity for active sites, whilst products have low affinity, allowing them to leave easily.
Enzymes lower the activation energy needed for reactions to occur. Increasing substrate concentration speeds up reactions until all enzyme active sites are occupied. However, increasing end product concentration can reduce reaction rates, stop reactions, or even reverse them.
Key Understanding: Think of enzymes as specialist tools that make chemical reactions happen faster and more efficiently - they're essential for all life processes.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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92,6130
English LiteratureMacbeth: Guilt and Ambition
Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.
918,780390
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