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