Biology - Key terms (all topics)

A level

monomer

a molecule that can be bonded to another identical molecule

polymer

molecule made up from a large number of monomers joined together

macromolecule

large molecules formed by condensation reactions between smaller molecules

monosaccharide

monomer of saccharide (glucose)

disaccharide

two monomers of saccharide (maltose)

polysaccharide

long chain of saccharide (amylose)

amphipathic

both hydrophobic and hydrophilic

amphoteric

a molecule with both basic and acidic properties

glycoproteins

carbohydrate prosthetic group

lock and key

exact complementory fit

catabolic

break down larger substrates

anabolic

build up smaller substrates

induced fit

not a perfect match between enzyme and substrate

denaturation

active site changes

aquaporins

protein lined by hydrophilic amino acid residuals

histone proteins

packaging proteins (8 histone molecules = bead)

unipotent

cells only produce one type of cell

multipotent

cells divide and produce different cells in one type of tissue

carcinogen

any agent that could cause cancer

transcription

copies the gene to MRNA and moves it out of nucleus

translation

takes the the MRNA and binds it to the ribosome and turns it into polypeptides

splisosome

cuts the preMRNA

introns

non coding RNA

extrons

coding RNA

pyrimidines

cytosine, thymine, uracil

purines

adenine, guanine

telomere

repeated replications on chromosomes so that DNA is not lost as the chromosomes shorten

meiosis

sexual reproduction - forms gametes

haploid

daughter cells have ½ number of chromosomes as parent cells

mitosis

asexual reproduction - cell growth

diploid

daughter cells genetically identical + same number of chromosomes as parent cell

cytokenisis

animal cells - starts by constriction of the edges of cell

plant cell - cell wall is laid already

daughter cells have same number of cells as parent cell and genetic make up

mitosis then continues

cell cycle G1

cell grows by producing proteins and cell organelles

cell cycle S

cell growth continues as replication of DNA occurs

histone are synthesised

each chromosome becomes 2 chromatids

cell cycle G2

cell growth continues by proteins and cell organelles

organelle synthesis

mitochondria + chloroplasts (plants) divide

spindle begins to form

metaphase (brief)

chromosomes line up in the centre of the cell, spindle fibres attach to them

anaphase (brief)

sister chromatids separate and move to opposite ends of the cell

telophase (brief)

new nuclei form at each end, chromosomes uncoil, nuclear envelope starts reforming

helicase

unzips the DNA

semiconservative replication

half the DNA strand is used to make a new one

MRNA

messenger RNA carries DNA message to ribosomes

TRNA

transfer RNA transfers the amino acids to the ribosomes

RRNA

ribosomal RNA is what makes up the ribosomes-protein factories of the cell

silent mutations

despite mutation the codon will still code for the same amino acid

insertion mutation

a base is added so shifts the whole order over

deletion mutation

a base is removed so shifts the grouping of codons

substitution mutation

bases replace each other (where a lot of silent mutations occur)

nonsense mutation

when a stop codon is made in the middle of the sequence so rest of protein isn’t made

truncated

the small protein made after the nonsense mutation

glandular trichomes

specialised hairs on plants that release oils(eg. lavender / rosemary)

stinging trichomes

specialised hairs on plants that sting (eg. stinging nettles)

vascular bundles

made up of two groups, the xylem and phloem, transports water and minerals

epidermis

outermost layer of cells inn plants, includes specialised cells like guard cells, trichomes, root hair cells

cortex

region in a stem or root between epidermis and vascular tissue mainly made of parenchyma cells

parenchyma cells

store food in the stems and roots, can also help transport water and nutrients, found in the cortex and pith

pith

located in the centre of dicot stems, not roots, function as storage

palisade mesophyll cells

just below upper epidermis, tightly packed and rich in chloroplasts, main site of photosynthesis

spongy mesophyll cells

below the palisade layer, lots of air spaces between them, aid gas exchange

waxy cuticle

reduces water loss

central stele

vascular tissue in roots

endodermis

layer of cells around the central stele

Suberin

waxy strip on radial walls of endodermis (casparien strip)

pericycle

layer of cells immediately below the endodermis

lignin

makes crosslinks with hemicelluloses that fill gaps between cellulose and cell walls, strengthening the xylem cell walls, makes them impermeable to water

tracheids

water conducting tissue in ferns and cone bearing trees, form large pits in lateral walls where water can be passed

sieve tubes

found in phloem tissue, no nucleus, rely on companion cells for metabolic support, sieve plates at their ends

sieve plates

perforated end walls between sieve tubes

companion cell

supports metabolic functions of sieve tubes, helps in active transport of substances during translocation

plasmodesmata

strands of cytoplasm that pass through narrow gaps in the cell walls

apoplast pathway

transport of water from the root hairs to the xylem by the free spaces between cellulose fibres

symplast pathway

water transport from the root hairs to the xylem where water diffuses through the plasmodesmata, slower due to organelles in the way.

aerial parts of plants

stems, leaves, flowers, fruits/seeds, buds (parts seen on plants)

stomata

pores in the epidermis of leaves, consists of 2 elongated guard cells with a pore between them

guard cells

specialised cells surrounding each stoma, changes opening with water pressure

cohesion

attraction between water molecules, helping water move in a continuous column through xylem

adhesion

attracting between water molecule and the walls of the xylem vessels

transpiration stream

continuous movement of water from the roots through the xylem to the leaves where it evapourates

root pressure

pressure generated buy active transport of ions in the root xylem

capillarity

the movement of of water in narrow spaces due to cohesion and adhesion

assimilates

sugars and amino acids (sap)

translocation

process where assimilates are moved around the plant by phloem vessels from source to sink

source

part of plants where sugars are produced or released into phloem (eg. mature leaves)

sink

the part of the plant where sugars are used or stored (eg. roots)

pressure flow hypothesis

current theory for explaining translocation, sugar loading causes water uptake, creating pressure that drives sap flow from source to sink

sink unloading

the removal of sucrose out of companion cells, sucrose then moves out of phloem tissues via the apoplectic or symplastic pathway into a sink

proton pump

membrane bound protein that requires ATP to function, used to pump hydrogen ions out of the cytoplasm into the cell wall

cotransporter protein

where hydrogen ions diffuse back into the cytoplasm, pulling sucrose molecules in against the concentration gradient.

tunica externa

(tunica adventitia) - made of collogen (elastic fibres as well for arteries), outside layer of blood vessels

tunica media

made of smooth muscle and elastic fibres to allow muscles contract, stretch and recoil, this allows blood vessels to control blood flow and maintain pressure

tunica intima

made of endothelium, helps reduce friction to maintain blood flow, allows faster diffusion

endothelium

smooth squamous epithelial cells

lumen

NOT A LAYER, the central cavity of blood vessels

arteries

carry blood AWAY from the heart to organs

Capillaries

carries blood between arteries and veins, delivering nurtients

veins

carry blood TOWARDS the heart from the organs

vein valves

prevent back flow under low pressure

arterioles

joining arteries and capillaries

plasma

liquid part of blood, transports nutrients, hormones, waste products

platelets

small cell fragments that clot at injury sites

albumin

most abundant plasma protein, regulates blood water potential, and helps transport lipids and iron

carbaminohaemoglobin

formed when CO2 binds to amino groups

thrombocytes

blood plotters produced in bone marrow by megakaryocyte fragmenting