Biology 2 - Genes and Health

define osmosis

the net movement of water from an area of lower concentration to higher concentration through a partially permeable membrane, which doesn’t use energy from respiration

define diffusion

the movement of particles from an area of higher concentration to and area of lower concentration

define active transport

the movement of particles from an area of lower concentration to an area of higher concentration against the concentration gradient while using energy from respiration

what proteins are involved in facilitated diffusion?

carrier and channel

what molecules pass across a membrane via facilitated diffusion?

charged molecules (channel proteins) and large molecules (carrier proteins)

what is endocytosis?

a substance is taken across a membrane by being engulfed by the membrane and pinched off into the cell creating a vesicle

what is exocytosis?

a substance is released from a cell when the vesicle fuses with the membrane and releases the substance out of the cell

what is a membrane made of?

phospholipid bilayer, glycolipids/proteins, cholesterol

what is Fick’s law?

rate of diffusion = (surface area x concentration difference)/thickness of membrane

how are lungs adapted for rapid gas exchange?

massive surface area (alveoli), short diffusion pathway, moist surfaces

what is ATP used for?

the cell can’t get all its energy from glucose so the energy released from glucose is used to make ATP which stores and releases energy

what is ATP often known as?

universal energy currency

where is ATP formed?

mitochondria via aerobic respiration

what is the role of cholesterol in a membrane?

provides structure and support

what is the role of protein in a membrane?

selective transport of molecules, and communication

what is the role of glycoproteins in a membrane?

act as receptors, bind to signalling molecules

what is the role of glycolipids in a membrane?

cell recognition and stability

what is the role of phospholipids in a membrane?

controls the cell’s internal environment

what is the aqueous environment inside the cell?

cytoplasm

what is the aqueous environment outside the cell?

tissue fluid

what are the two 3D structures that a protein could have?

globular or fibrous

what are the characteristics of globular structure?

round, compact, multiple polypeptide chains, coiled, hydrophilic inside, hydrophobic outside, soluble

what are the characteristics of fibrous structure?

long insoluble polypeptide chains, tightly coiled around each other, lots of bonds makes it strong, often found in supportive tissue

what is the order of polypeptides structure?

primary (sequence of amino acids), secondary (alpha helixs, beta pleated sheets), tertiary (3D specific shape), quaternary (2+ polypeptides forming a protein)

what is the function of DNA?

to store genetic information

what is the function on RNA?

to transfer genetic information

how do ribosomes work with RNA?

they read RNA to make polypeptides (translation)

what are DNA and RNA types of?

nucleic acids

what is a gene?

a length of nucleotide bases that provides a code to sequence amino acids to form a polypeptide

what are exons?

coding regions of DNA (genes)

what are introns?

non-coding regions of DNA

what is DNA made up of?

two polynucleotide strands (made up of mononucleotides)

what is RNA made of?

a single stranded polynucleotide

what are two examples of RNA?

messenger and transfer

when is RNA made?

it’s copied from DNA for protein synthesis

what is transcription?

the process of DNA being copied into mRNA to transfer genetic information to the ribosomes

what is a gene?

a length of nucleotides that provides a code for a sequence of amino acids in a polypeptide 

what is the role of DNA polymerase?

it forms hydrogen bonds between the nucleotide bases during DNA replication to join the strands-

what is the name of Meselson’s and Stahl’s experiment?

semi-conservative replication

how are proteins formed?

amino acids linked by peptide bonds to make a polypeptide

what are the differences between DNA and RNA?

DNA double helix - RNA single stranded, DNA’s sugar is deoxyribose - RNA’s sugar is ribose, DNA has thymine - RNA had uracil

what are the 4 DNA nucleotide bases?

adenine, guanine, cytosine, thymine

what 3 things are mononucleotides made of?

sugar (deoxy/ribose), phosphate, nucleotide base

how are bases bonded in the DNA double helix?

hydrogen bonds

what practical investigates the effect of alcohol on cell membranes?

beetroot test

what model is often used to show the structure of cell membranes?

fluid mosaic model

what are the properties of gas exchange surfaces in living organisms?

large surface area to volume ratio, thickness of surface, difference in concentration

what is an enzyme?

a biological catalyst that reduces activation energy

what is the difference between intra/extracellular enzymes?

intra - catalyses reactions inside cells

extra - catalyses reactions outside of cells

what are mutations caused by?

a change in the nucleotide base sequence in DNA (substitution, deletion, insertion, duplication, inversion)

how does cystic fibrosis occur?

by a mutation in a gene that codes for CFTR protein (Cystic Fibrosis Transmembrane conductance Regulator)

what is an allele?

a version of a gene

what is a genotype?

the alleles a person has

what is a phenotype?

the observable characteristics in an organism

what is incomplete dominance / codominance?

both alleles present are expressed in phenotype

what is the diagram often used to display inheritance?

pedigree diagram

what does cystic fibrosis do to gas exchange?

thick mucus is unable to move up cilia so airways can become blocked by mucus and gas exchange can’t take place in the area below the blockage

what does cystic fibrosis do to the digestive system?

the tube connecting the pancreas to the small intestine can become blocked by mucus, which prevents digestive enzymes from pancreas reaching the small intestine so the person won’t digest food well and won’t get as many nutrients

what does cystic fibrosis do to the reproductive system?

men - the tubes to the testicles can be absent or become blocked by mucus so sperm cannot reach the penis

women - mucus can prevent the sperm reaching the egg

what is the strand of DNA that mRNA copies bases from?

template strand

what is a stop codon?

the stop codon is the last 3 nucleotide bases of a gene that mark the end of the polypeptide chain

what are anticodons?

an anticodon is the 3 bases on a tRNA that are complementary to the codon

what is the nature of the genetic code?

triplets, non-overlapping, degenerate

what is the structure of an amino acid?

amino group, variable r group, carboxyl group

what does the primary structure of a protein determine?

the amino acid sequence

what does the secondary structure of a protein determine?

folding patterns (alpha helixs, beta pleated sheets)

what does the tertiary structure of a protein determine?

the 3D shape of the polypeptide chain

what does the quaternary structure of a protein determine?

joining with other polypeptide chains to make a protein

what model is used to show the active site and substrate?

induced fit model (replaced lock and key model)

3 reasons why genetic screening is used?

identification of carriers, preimplantation genetic diagnosis, prenatal testing

what are two types of prenatal testing?

amniocentesis and chorionic villus sampling

explain amniocentesis

a sample of amniotic fluid is obtained, DNA from fetal cells is analysed, 1% chance of miscarriage, usual results take 2-3 weeks but rapid test is 3-4 days (but rapid test only looks for a few common disorders)

explain chorionic villus sampling

cell sample taken from chorionic villi and DNA analysed, 1-2% chance of miscarriage, main results in a few days but in depth results in a few weeks