BIOSCI 107 CELL STRUCTURE AND FUNCTION

cytoplasm

material within a cell excludes nucleus

cytosol

aqueous component of cytoplasm

cytoplasm

material within a cell excludes nucleus

cytosol

aqueous component of cytoplasm

plasma membrane

double layer of phospholipids

integral membrane proteins

proteins that are inserted into the membrane

transmembrane proteins

spans entire membrane so is in contact with the extracellular and cytoplasmic environments

peripheral membrane proteins

associated with the membrane but not actually embedded in it

glycoprotein

has a carbohydrate group attached and faces the extracellular side of cell

nucleus

largest, distinct structure inside cell which contains DNA and is where rRNA and ribosome production occurs

nuclear lamina

lines nuclear envelope

nucleolus

site of rRNA production and assembly of the small and large subunits of ribosomes

ribosomes

consists of small and large subunits which are made in the nucleolus and function to produce proteins

endoplasmic reticulum

extensive network of tubes and tubules stretching out from the nuclear membrane

smooth endoplasmic reticulum

extends from rough ER and functions to produce lipids and carbohydrates, house tissue specific proteins in the liver and store enzymes

rough endoplasmic reticulum

dotted with the attached ribosomes and functions to process, sort and package proteins produced by the ribosomes

Golgi apparatus

complex of a number of flattened membranous sacs called cisternae

cisternae

sacs which contains enzymes of different functions

lysosomes

vesicles from the golgi apparatus which functions to digest substances

mitochondria

made up of inner and outer mitochondrial membrane with folds called cristae and a mitochondrial matrix. Functions to generate ATP

cytoskeleton

fibres and filaments that help to maintain the size, shape and integrity of a cell

microfilaments

part of cytoskeleton comprised of actin molecules assembled in two long chains twisted around each other. Found around periphery and lining of the interior. Functions to bear tension and weight

intermediate filaments

part of cytoskeleton comprised of a range of materials like keratin. Found in the cytoplasm. Functions to bear tension and weight as well as act as a scaffold for organelles

microtubules

part of cytoskeleton comprised of tubulin dimers coiled to form a tube. Found extending from the centriole. Functions to support cell shape and size, guide movement of organelles and support movement of cilia and flagella

DNA

heritable material used to store and transmit information from generation to generation

RNA

acts as a messenger to allow the information stored in the DNA to be used to make proteins

proteins

carry out cellular functions

transcription

synthesis of RNA from a DNA template

basal transcription factor

protein which initiates transcription

RNA polymerase II

enzyme which catalysed RNA synthesis

promotors

specific nucleotide sequences at the start of a gene which initiates RNA synthesis by assembling a complex of polymerase and transcription factors

exons

coding regions

introns

non-coding regions

spliceosome

molecular machine which removes introns and splices together exons

small nuclear ribonuclear proteins + proteins

assembles the spliceosome

translation

translating the sequence of mRNA to a sequence of amino acids

aminoacyl tRNA synthetase

enzyme which attaches the appropriate amino acids to the tRNA

a site

acceptor site for an aminoacyl tRNA in which it binds to the mRNA codon

p site

peptide bonds formed between amino acids forming a polypeptide chain

e site

where tRNA no longer bounds to an amino acid and exits the ribosome

primary structure

polypeptide chain as an unbranched polymer held together by peptide bonds

secondary structure

alpha helix or beta sheets coiled or pleated to form a spiral or sheet structure held by hydrogen bonds

tertiary structure

alpha helix or beta sheets superimposed on itself to form a compact globular molecule held by intramolecular bonds

quaternary structure

two or more polypeptide chains each with its own tertiary structure which combine to form a functional protein

phosphorylation

addition of phosphate group

methylation

addition of methyl group

ATP cycle

transfers energy between complex and simple molecules with ATP as the mediator

energy stored

transferred from complex molecules to ATP

energy used

transferred from ATP to complex molecules

glycolysis

anaerobic process which occurs in the cytoplasm in which a glucose molecule is oxidised to produce two pyruvate molecules of acid and 2 ATP and 2 NADH

krebs cycle

aerobic process which occurs in the mitochondrial matrix and produces 1 ATP, 2 CO2, 1 FADH2+ and 3 NADH

electron transport chain

series of complexes that transfers electrons from electron donors to acceptors via redox reactions and couples this electron transfer with the transfer of protons across a membrane

diabetes mellitus

disease in which the bodies ability to produce and respond to the hormone insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood

insulin

produced by beta cells of islets of langerhans in pancreas and functions to promote glucose uptake in cells

glucagon

produced by alpha cells of islets of langerhans in pancreas and functions to stimulate breakdown of glucose to increase blood sugar levels

protein kinase

catalyses phosphorylation of a target protein by ATP

cyclin

controls progression of cells through cell cycle by activating cyclin dependent kinase enzymes

proto oncogenes

genes that produces a protein that promotes progress through the cell cycle functioning normally

oncogenes

genes that produces a protein that promotes progress through the cell cycle but functioning abnormally

tumor suppressor genes

genes that produces a protein which functions to halt cell cycle when appropriate so that checkpoints operate correctly

mutated tumor suppressor genes

genes that produces a protein which functions to allow progression through the cell cycle inappropriately

signal receptors

proteins that change their conformation when a hormone binds to them

steroid hormones

binds to the receptor protein

cytosolic or nuclear receptors

primary messenger which are generally hydrophobic and small

membrane bound or cell surface receptors

primary messenger which are generally hydrophilic and large

autophagy

digestion of broken down organelles

autolysis

digestion of entire cells

amphipathic

contains both polar and non-polar parts

centromere

holds chromatid pairs together

kinetochore

protein complex which is outside of each centromere

chromatin

the entire complex of DNA and proteins that is the building material of chromosomes

protein phosphatases

enzymes that can rapidly remove phosphate groups from proteins in a process called dephosphorylation

transcription factors

controls which genes are turned on

second messengers

small, non-protein, water-soluble molecules or ions E.g. Ca2+ and cyclic AMP

adenylyl cyclase

enzyme embedded in the plasma membrane which converts ATP to cAMP in response to an extracellular signal