ncea level 2 bio key ideas

bio :(

Photosynthesis

the process in which plants use sunlight, water, and carbon dioxide to produce glucose and oxygen (carbon dioxide + water glucose + oxygen)

Light-dependent reaction

light energy splits the water molecule into hydrogen and oxygen and creates ATP to drive the light-independent reaction. Occurs in the thylakoid membrane/grana

Light-independent reaction

hydrogen is combined with carbon dioxide through a series of reactions to form a glucose molecule. Occurs in the stroma

Chloroplast structures

clear membrane (controls movement of materials into and out of the cell and allows light into chloroplast); grana (contains chlorophyll which is needed to capture light); stroma (where carbon dioxide is captured in the light-independent phase, and this carbon dioxide will eventually be used to synthesise glucose)

Chloroplast labelled

Enzyme

biological catalyst that speeds up the rate of a reaction

Enzyme structure

built out of protein with an active site, which binds to the substrate to form an enzyme-substrate complex

Co-factors

molecules that bind with the enzyme to increase enzyme activity, usually by allowing the active site to bind more effectively with the substrate by changing the shape of the active site

Inhibitors

stop the enzyme from binding with its substrate by changing the shape of / binding to its active site. This would therefore slow or stop biological reactions

Denature

occurs when the temperature increases, causing the enzymes 3D protein structure to change shape and alter the active site permanently (irreversible). Therefore, substrates can no longer ‘fit’ the active site and the reaction slows/stops (THIS IS A MERIT POINT)

Active transport

the movement of a substance from an area of low concentration to an area of high concentration up/against a concentration gradient. It is an active process, so it requires energy/ATP, and this process involves ion pumps/protein channels (THIS IS A MERIT POINT)

Diffusion

the movement of a substance from an area of high concentration to an area of low concentration along/down a concentration gradient. It is a passive process, so does not require energy. Small molecules are able to move through the phospholipid bilayer (THIS IS A MERIT POINT)

Facilitated diffusion

the movement of a substance from an area of high concentration to an area of low concentration along/down a concentration gradient. It is a passive process, so does not require energy and uses a transport protein. Large substances can diffuse through the cell membrane but need a protein channel to do so (THIS IS A MERIT POINT)

Osmosis

movement of water from an area of high water concentration to an area of low water concentration along/down a concentration gradient. It is a passive process, so does not require energy and it occurs through a semipermeable membrane (THIS IS A MERIT POINT)

Mitosis

cell division that creates two new identical cells. The purpose of mitosis is to produce new cells for growth and repair

DNA replication

purpose is to produce two identical copies of the cell’s DNA. DNA must be replicated before mitosis so that the new cell has the correct amount of DNA, and has all of the genetic information needed to carry out life processes

DNA strand labelled

Cellular respiration

the process by which glucose is converted into useable energy (ATP). The purpose is to produce energy in the form of ATP for life processes

Aerobic respiration

when glucose is broken down in the presence of oxygen to form carbon dioxide, water, and 36 ATP (glucose + oxygen à water + carbon dioxide + 36 ATP). Occurs in mitochondria

Anaerobic respiration

when glucose is broken down into lactic acid and 2 ATP. No oxygen is present (glucose à lactic acid + 2 ATP). Occurs in cytoplasm

Mitochondria labelled

Meiosis

a type of cell division that produces sex cells with half the number of chromosomes (haploid) as the parent cell. Meiosis produces four genetically unique haploid daughter cells

Homologous chromosomes

are similar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same. One comes from father, the other from mother

Independent assortment

where the homologous pairs line up in a random order along the middle of the cell. Since the order is random, the maternal and paternal chromosomes are shuffled creating new combinations of alleles/recombinants, therefore each gamete has a different combination of chromosomes (THIS IS A MERIT POINT)

Crossing over

the exchange of alleles/segments of DNA between homologous chromosomes. This results in a reshuffling of alleles, creating new combinations of alleles between gametes and the parent (THIS IS A MERIT POINT)

Segregation

when homologous chromosomes are pulled apart into separate gametes. Only one chromosome from each homologous pair is placed into the gamete, resulting in only one allele from each gene going into each gamete. Therefore, each gamete has a different combination of alleles (THIS IS A MERIT POINT)

Linked genes

genes found on the same chromosome, and therefore are more likely to be inherited together

Unlinked genes

genes found on different chromosomes OR genes that are found further apart on the same chromosome, and therefore are more likely to be separated during crossing over

Somatic mutation

forms a new allele in a body cell, which may affect the individual but cannot be passed on to the offspring/not inherited

Gametic mutation

forms a new allele in sperm/egg/gametes that can be passed onto the offspring/are inherited

Phenotype

the physical expression of the genetic information of DNA

Genotype

collection of an organisms’ genes/alleles

Allele

alternative version of a gene

Test cross

used to test an individual’s genotype by crossing it with an individual of a known, homozygous recessive genotype

Incomplete dominance

when the heterozygous genotype shows an intermediate phenotype between the dominant and recessive genotypes

Complete dominance

when a phenotype is always expressed/masks the effect of recessive even if only one copy of the allele is present in the genotype

Co-dominance

when the alleles of a gene pair in a heterozygote are both fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive

Multiple alleles

alleles of which there are more than two alternatives available for one gene

Lethal alleles

an allele that causes the death of the organism

Natural selection

the process where individuals with favourable phenotypes survive and reproduce. These individuals pass the favourable alleles for these phenotypes onto the next generation, increasing the allele frequency

Mutation

random and permanent change in the DNA base sequence

Beneficial mutation

one that increases the chances of survival/reproduction in an organism. Likely to be passed onto offspring

Harmful mutation

one that decreases the chances of survival/reproduction in an organism. Likely to be eliminated from the population

Allele frequency

percentage of each allele in a population/gene pool

Gene pool

sum of all alleles in a population

Genetic variation

differences in alleles/genetic information within a population/gene pool

Genetic drift

a random change in allele frequency of a population

Bottleneck effect

a sudden reduction in the size of a population/gene pool

Founder effect

when a small group of individuals from an existing population moves to another area and are reproductively isolated from the original population

Migration

the movement of individuals/alleles from one population to another population. Immigration is the movement of individuals into the gene pool. Emigration is the movement of individuals out of a gene pool

Selection pressure

abiotic or biotic factors that will affect the survival of an organism in its environment

Mutation

random and permanent change in the DNA base sequence

Silent/same-sense mutation

when the change in the base sequence has coded for the same amino acid due to degeneracy

Nonsense mutation

the base substitution could code for one of the three STOP codons. This would shorten the length of the polypeptide chain by ending translation early. Non-functional protein is formed

Missense mutation

the base substitution could code for a different amino acid. This could replace an amino acid in the sequence or remove a STOP codon, making the polypeptide chain longer

Frameshift mutation

where after a mutation, all the triplets are incorrect as they are not ‘read’ in their correct threes (every triplet after the mutation will be incorrect)

Substitution mutation

when one base is swapped in the DNA base sequence, which may or may not result in a codon that codes for a different amino acid

Insertion mutation

when a base is inserted into the DNA sequence

Deletion mutation

when a base is removed from the DNA sequence

Point mutation

mutations that involve a single nucleotide (one base) or changes to one triplet

Environmental factor

a factor that affects gene expression/phenotype but does not change the DNA base sequence/genotype (ex. diet, temperature, etc.)

Mutagen

a physical or chemical factor that causes/increases the chance of changes to the base sequence, and therefore, the genotype of an organism (ex. smoking, UV radiation, etc.)

Genotype + environment à phenotype

Phenotype

the physical expression of the genetic information of DNA

Genotype

collection of an organisms’ genes/alleles

Gene

a section of DNA that codes for a specific protein

Metabolic pathway

a series of enzyme-controlled reactions where the product of one reaction is the substrate for the next. One gene codes for one enzyme

Enzyme

biological catalyst that speeds up the rate of a reaction

Precursor/intermediate

starting molecules or molecules within a pathway that are required for the next step in a metabolic pathway

Final product

indicates the end of the metabolic pathway

Protein synthesis

the creation of a protein in a cell using transcription and translation

Transcription

the process where mRNA is made from the template strand of DNA in the nucleus

Translation

the process where the mRNA is read by the ribosome in the cytoplasm and a polypeptide chain is created based on the codons on the mRNA

Triplet

three consecutive nucleotide bases on the DNA strand

Codon

the sequence of three consecutive nucleotides on the mRNA strand that is complementary to a triplet

Anticodon

three consecutive bases on a tRNA molecule that is complementary to mRNA codon

Start codon

initiates translation. The start codon always codes for the amino acid methionine

Stop codon

ends translation which causes the ribosome to stop translating and release the mRNA and the polypeptide chain

Ribosome

the structure that ‘reads’ the mRNA and, through the use of tRNA, adds amino acids that correspond to each codon on the mRNA until a STOP codon is reached

Base-pairing rule

states that adenine can only bind with thymine (or adenine and uracil on RNA), and cytosine can only bind with guanine

DNA

double-stranded molecule made up of a phosphate, deoxyribose sugar, and nitrogen base (A, T, C, G). Contains all the genetic information of an organism

RNA

a single-stranded short molecule made up of phosphate, ribose sugar, and nitrogen base (A, U, C, G)

mRNA (messenger RNA)

a single-stranded short molecule made up of phosphate, ribose sugar, and nitrogen bases (A, U, C, G). Made off the template strand during transcription (in the nucleus) and carries genetic information out of the nucleus

tRNA (transfer RNA)

complementary to the mRNA. Its anticodon ensures that the correct amino acid is added to the growing polypeptide chain

Amino acid

the building blocks of proteins/polypeptides

Polypeptide chain

a chain ofss amino acids which will fold together to make a protein

Template strand

the strand that the mRNA is made from. It is complementary to the mRNA strand

Gene expression

information from one gene is used to synthesize a functional protein

Redundancy/degeneracy

there are 20 amino acids and 64 codons. This means that multiple codons code for the same amino acid

The table below is a common question which asks you to create the mRNA strand and amino acid sequence from the DNA template strand.