bio yr 10 exam

Cells and Genetics

Cells

  • Basic functional unit of all living organisms


Cell theory

  1. All living things are composed of cells

  2. Cells are basic unit of structure and function of life

  3. New cells come from pre existing cells




Eukaryote cell

  • Complex cell type

  • Eu - ‘true’  kary - ‘nucleus’

  • Multi cellular

  • Plant + animal cell

  • Membrane (has specific function) bound organelle


Eukaryote plant cell

Nucleus: stores DNA

Ribosome: protein synthesis

Chloroplast: photosynthesis

Mitochondria: creates energy

Cell wall: provides structure 

Cell membrane


Eukaryote animal cell

Mitochondria: create energy

Nucleus: stores DNA, linear

Ribosome: protein synthesis

Cell membrane


Prokaryote

  • Pro- ‘before’  kary- ‘nucleus’

  • Simple cell type e.g bacteria

  • Small

  • Unicellular


Prokaryote cell

Cell wall: structure

Circular DNA: not in a nucleus

Ribosome: protein synthesis

Fla-gella: helps swim

Cell membrane


Cell membrane


Diffusions

  • Movement of particles form areas of high concentration to areas of low concentration


Surface area: total area of external environment/membrane 

Volume: total internal space

Small intestines contain villi which maximise absorption of nutrients

Alveoli made of smaller sacs to maximise the surface area for gas exchange


Osmosis 

  • Diffusion of water across semi permeable membrane from high water concentration to low water concentration

Hypotonic

  • Solute concentration is lower than cell

  • Water enters cell

  • Volume increases


Isotonic

  • Solute concentration equal to cell 

  • No water movement

  • Volume remains stable


Hypertonic

  • Solute concentration 


Genetics


Deoxy Ribonucleic acid

  • Stores genetic information 

  • Provides instructions for proteins


DNA has double helix made up of nucleotides



Nucleotides

  • Phosphate group (the circle)

  • Deoxyribosome sugar (pentagon part)

  • Nitrogenous base ( adenine, thymine, guanine, cytsone)


Gene

  • Sequence of dna that codes for protein


Chromosome

  • Long condeseded strands of DNA wrapped proteins called histoines

Structure:

  • Telomere: representative base sequence at  the end of chromosomes to protect

  • Centromere: holds chromotids together 

  • Sister chromotids: replicated chromosomes withidentical strands of dna

  • Dna molecule: dna coiled tightly around histoine proteins

Facts

  • 46 chromosomes for humans 

  • Homologus chromosomes: same size, same centromere location and gene loci

  • XX - female

  • XY - male

  • Karyotyping: arrangement of chromosomes found in an organisms nucleus that allows us to analyse organisms chromosomes

  • Aneuploidy: person with too few or too many chromosomes


Somatic cell (body cells) - 2 set of chromosomes (diploid)

E.g. skin, muscle, heart cells


Gamets (sex cells) - 1 set of chromosmes (haploid)

E.g. sperm, egg


Cell cycle

  • Series of events that lead to division and duplication of a cell to produce two genetically identical daughter cells

  • Cell cycle can allow for development and growth, cell replacement/regeneration and aesexual reproduction

Interphase

Gap 1 (G1): 

  • Increase volume of its cytosol

  • Synthesising proteins for DNA replication

  • Replicating its organelles

Synthesis (S):

  • Chromosomes duplicate chromotids

  • Become double stranded

  • All each daughter cell to rec one chromatin


Cap 2 (G2):

  • Increase volume of cytosol

  • Synthessing proteins for mitosis


Binary fission

  • Used to reproduce prokaryotic organisms 

  • Uses DNA replication, e,ongation, septum formation, cell division

  • Allows a single bacterial cell to into millions of bacteria quickly


Mitosis

  • Produces 2 idnetical daughter cells (somatic cells)


Prophase: 

  • chromosomes are duplicated

  • nuclear membrane breaks down 

  • Proteins spindle between the centrosomes


Metaphase

  • Chromosomes align in centre 


Anaphase

  • Chromotids separate at the centromere by proteins


Telophase

  • Nuclear membranes reform around each set of chromosomes


Cytokines

  • Cells are divided into two daughter cells each with a nucleus


Meiosis

  • Produces 4 daughter cells (gamete cells)

  • Errors include non dijunction: chromosomes fail to split leading to extra or too little chromosomes in each cell


Prophase 2: 

  • chromosomes are duplicated

  • nuclear membrane breaks down 

  • Proteins spindle between the centrosomes


Metaphase 2:

  • Chromosomes align in centre 


Anaphase 2:

  • Chromotids separate at the centromere by proteins


Telophase 2:

  • Nuclear membranes reform around every set of chromosomes


Cytokines 2:

  • Cells are divided into 4 daughter cells each with a nucleus


Crossing over

  • In prophase 1 when genetic material is exchanged between homologus chromosomes

Indepemdant assortment

  • In metaohase 1 when a random arrangement of chromosomes leads to different alleles and genetic combinations

Downsyndrome is from the presence of extra chromosomes


Alleles

  • different form of the same gene  

  • Genotype

  • Set of alleles

Dominant traits: given capital letter

Recessive traits: given lowercase letters

Homozygous

  • Geneotype consisting of 2 identical alleles 

Hetrozygous

  • Genotype with different alleles

Phenotype

  • Physical expression or chrararistic of a trait

  • How genotypes expressed

  • Observable 


Punnett square

  • Expresses how traits can be passed down generations

Sex linked traits

  • Traits that are carried on sex chromosomes


Males must have Y chromosme so the mother dictates the type of X chromosome they receive.

If X chromosome has recessive allele the male will be hemizygosus

Evolution & Immunity


Selection

Lamark founded a false verison of evolution theory

Darwin and Walace founded the supported theory of evolution


Natural selection 

  • Under normal conditions members of a population compete with each other (intraspecific competition) for access to living space, energy supplies and mating partners.

  • Species with alleles that are compatible with the environment will thrive (selective advantage) whereas species with


Allele: variant of a gene

Gene pool: all alleles in a population

Allele frequency: proportion of allele in a gene pool


Fitness: phenotype that has the greatest advantage to an individual

Selection pressure:a factor that affects the reproductive success of an organism

Gene flow: migration taht introduces new allele to populations

Genetic drift: external events affect the allele (does not favor anything)

Founder effect: new population formed by small number of individuals


Population bottleneck: event that results in the loss of a phenotype/allele 


Artificial selection

  • Human intervention to increase desirable traits

  • Individuals aren’t fitter to their environment


Speciation

  • Formation of new species 


  1. Population speareted leading to reproductive isolation due to lack of gene flow

  2. Separated populations expose dto different selction pressures

  3. Populations accumulate different alleles according to different environments

  4. Populations are sufficiently different


Same species

  • Produce viable and fertile offspring

  • Similar DNA

  • Same physical characteristics

Hybrid animal: species that share same family 


Evolution


Biogeography

  • is the study of the distribution of organisms and is another type of evidence for the theory of evolution.


Comparitivie morphology

  • Study of structural similarities and idfferneces in organisms in order to analyse their evolutionary relationships


Hologus structures: similar structures but different functions (distant common ancestor)

Analogous structures: different structure but same function (very distant related) 

Vestigial structures: remenant structures that has lost most/all function


Divergent evolution: common ancestor to 2+ new species

Convergent evolution: very similar traits because same selection pressures not same common ancestor


Fossil

  • Preserved remains, impression or any trace of living things from past geological age


When a microgranism dies and on the rare occasion the remains become preserves as a fossil

  • occur when part or whole organisms die and get covered in sediment


Types of fossils

Mold: cavity left by decomposed organism

Cast: a mold that has been filled with material

Trace: indirect evidence of an organism (footprint, tracks, marks)


Stratigraphy

  • Studying layers of rocks

  • Stratum (bottom layer) has fossils that are older than top layer


Index fossils

  • Helps identify the age of other fossils

Requirements

  • Wide geographical distribution

  • Short geologic time range

  • Abundance

  • Easily recognisable


Transitional fossils

  • Shows characteristics of more than 1 animal 


Infectious and non-infectious disease


Immune system

  • complex set of organs, tissues, cells and chemicals that work together to defend us against infection


Lymphatic systems

  • Removes access fluid from your tissue and returns it to the bloodstream

  • Helps absorb fat

  • Protects against invaders/ pathogen 


Primary lymphoid organ: 

  • bone marrow (most immune cell made here) 

  • Thymus (t cells made here)


Secondary lymphoid organs

  • Lymph nodes (acts as filter)

  • Spleen (stop immune cells)

  • Tonsils (store immune cells/ stop infections in mouth and naval)


Infectious disease

  • pathogens that can spread directly or indirectly

Pathogen: microorganism that can cause diseases


Bacteria: pathogens treated with antibiotics 

Fungi: eukaryotic microgranims cured with antifungal medication

Virus: non living pathogens that reproduce in the cells of the hosts by inserting their DNA, treated through antivirals


Noninfectious diseases 

  • Diseases without pathogens that are caused by genetics, malnutrition, environment and lifestyle


Lines of Defence


First line defense (non specific reponse)

  • Prevents pathogens from entering the body

E.g. skin (intact), stomach acids, tears


Second line of defence (non specific response)

  • innate /non specific response to a pathogen that may be cellular or non cellular

  • Phagocites engulf entering pathogens to which they recieve MHC-II from the pathogen

  • The phagocytes undergo antigen presentation which is when they present MHC-I and MHC-II to the body


Noncellular responses (second line defense) 

  • Fever - core temp increases to kill pathogens

  • Cytokinesis - signal phagocytes to invade pathogens in a site of infection or activate immune cells

  • Natural killer cells ( NK cells): recognise and detsroy cells that have lost or dont have a MHC-I marker


Third line of defese (specific response) (Lymph node)

  • A T helper cell that is complementary to the phagocyte is selected and sends cytokenisis to the b cell that is complementary to the complementary T cell to replicate itself (colonial expansionism) and attach to the antigens and activate the b cell


Colonial expansionism will lead to the replicated b cells producing plasma cells (cells that produce antibodies) and memory b cells (allow for a faster and larger response on re - exposure



Inflamation (second line defence)

  • Immune cells release a chemical message (histamine) at site of infection

  • Histamine increases permeability of blood vessels increasing number of immune cells to remove pathogen


MHC-I: “self marker” in all nucleated cells

Phagocytopsis: white blood cells that engluf and digest invading pathogens


Antibody: Y shaped protein that can be complementary to antigens (found on b cells)

Antigens: a substance that can trigger an immune response in the body (found on pathogens)


Humoral response

  • recognise specific pathogens by the antibodies binding to specific antigens (usual response)

  1. Their membrane bound antibodies recognise and bind to an antigen in the lymphatic system or blood (T cell independent activation).

  2. An antigen is presented to T helper cells by an antigen presenting cell. The T helper cell then “selects” a specific B cell that recognises the antigen The B cell will then produce antibodies.


Cytotoxic cells

  • After antigen presentation a complementary T helper cell is selected to which it send cytokenisis to other complementary T helper cells to replicate themselves through expansion

  • Various complementary T helper cells are created as well as memory T cells and cytotoxic T cells


Cell mediated response 

  • Responds to infected cells

  • Infected cells withholds a MHC-I marker that tells the body it’s infected/sick and should be destroyed 

  • A cytotoxic T cell that is complementary to the antigen will then induce apoptosis ( destroy the infected cell)



Antibodies and Vaccines


Natural immunity

  • Active: Immune response to contact with a pathogen ( creating antibodies and memory cells)

  • Passive: introduction of new antibodies from external and natural source


Artificial immunity

  • Active: immune system created antibodies and memory cells due to medicine intervention

  • Passive: introduction of new antibodies from external and artificial source


Antibiotic resistance

  • Antibiotics is becoming less effective and dependant due to bacteria becoming more resistant


Vaccines

  • Antigens or inactive pathogens are entered to the body so that the body produces more memory cells and b cells against the pathogen to therefore fight pathogens easier


Booster vaccines

  • Booster vaccines are used to strengthen and upkeep the immune system and fight against incoming pathogens


Herd immunity

  • If a large part of the population is vaccinated it can lead to protection from diseases to those who havent been vaccinated 


Disease modelling

  • describes the spread of a disease and forecast future spread of a disease, and how to combat a disease