cells and proteins

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allosteric enzymes

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Biology

12th

unit 1

112 Terms

1

allosteric enzymes

Enzymes that change conformation in response to a modulator

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2

alpha helix

Polypeptide chain coiled into a helix with hydrogen bonding occurring to maintain the arrangement

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3

beta pleated sheet

Polypeptide chain arranged in rows with the chain folding in parallel or anti parallel arrangements

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4

alternative RNA splicing

Removal of non coding introns from a primary mRNA transcript to leave only the coding exons; several different mature transcripts can be produced from a single primary transcript

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5

Conformation

Structural arrangement of the polypeptide chains within a protein; it can be altered by factors such as pH and the binding of ligands and modulators

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6

Co-operativity

Changes in binding of a target molecule to one subunit of a multi unit polypeptide changes the affinity of the other subunits for the target molecule

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7

disulfide bridge

a strong covalent bond that stabilises the tertiary and quaternary structures of many proteins

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8

endoplasmic reticulum

a network of membrane tubules within the cytoplasm of eukaryotic cell; continuous with nuclear membrane

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9

exon

section of RNA that is usually retained during splicing

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10

glycoprotein

a protein with a carbohydrate added by post translational modification

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11

Golgi apparatus

a series of flattened membrane discs that packages proteins into membrane bound vesicles inside the cell before they are secreted from the cell membrane

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12

hydrogen bond

attractions between polar molecules in which hydrogen is bound to a larger atom such as oxygen or nitrogen

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13

hydrolases

a class of enzyme that can use water to break chemical bonds

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14

intron

a section of RNA that is usually removed during splicing

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15

ionic bonds

a type of chemical bonding which involves the electrostatic attraction between oppositely charged ions

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16

ligand

a substance which can bind bind to a protein; the protein has a shape complimentary to the ligand to allow binding

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17

London dispersion forces

a temporary weak attraction between atoms and molecules

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18

lysosome

a modified golgi vesicle containing hydrolytic enzymes

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19

modulators

these bind to a secondary site on an enzyme to alter its conformation; positive modulators activate enzymes and negative modulators deactivate enzymes.

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20

monomers

a molecule that can bind chemically to other monomers to form polymers

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21

non coding RNA genes

a gene that codes for RNAs other than mRNA, so do not code for a protein

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22

phospholipid

component of cell membranes

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23

polymer

a macromolecule composed of many repeated subunits (monomers)

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24

post-translational modification

addition of chemical groups to, or modification of, a protein to allow a particular function

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25

prosthetic group

a non-protein unit tightly bound to a protein and necessary for its function

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26

protein kinase

catalyse the transfer of a phosphate group from a donor molecule (usually ATP) to an acceptor

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27

protein phosphatases

an enzyme that removes a phosphate group from its substrate

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28

primary structure

sequence in which amino acids are found within a protein

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29

secondary structure

hydrogen bonding occurring within a polypeptide forming alpha helices or beta-pleated sheets

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30

tertiary structure

bonding of many types occurring between R groups of amino acids within a protein

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31

quaternary structure

the arrangement of multiple folded polypeptides connected together

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32

proteolytic cleavage

a major form of post-translational modification; it occurs when a protease cleaves one or more bonds in a target protein to activate, inhibit or destroy the protein's activity

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33

proteome

the entire set of proteins expressed by a genome; it is much larger than the genome

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34

Rough Endoplasmic Reticulum

organelle made up of membranes with ribosomes attached

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35

signal sequence

a short stretch of amino acids at one end of the polypeptide that determines the eventual location of a protein in a cell

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36

Smooth Endoplasmic Reticulum

a membranous organelle found in most eukaryotic cells; its main functions are the synthesis of lipids and steroid hormones

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37

turns

secondary structure that reverses the direction of a polypeptide chain

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38

vesicles

small membrane bound compartments filled with liquid

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39

electrochemical gradient

a gradient of electrochemical potential, usually for an ion that can move across a membrane, consisting of the difference in solute concentration and the difference in charge across a membrane

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40

facilitated diffusion

the passive transport of substances across the membrane through specific transmembrane proteins

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41

fluid mosaic model

a model that describes the structure of the plasma membrane as a mosaic of components including a phospholipid bilayer, which gives the membrane a fluid character, and cholesterol, proteins and carbohydrates

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42

gated channels

channel forming proteins controlled by signalling molecules or ion concentration

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43

Glucose symport

an integral membrane protein involved in transport of glucose and sodium ions across the cell membrane at the same time and in the same direction

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44

integral membrane proteins

they have one or more segments that are embedded in the phospholipid bilayer

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45

ligand gated channels

transmembrane protein channels controlled by the binding of signal molecules

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46

membrane potential

an electrical gradient that forces ions to move passively in one direction; positive ions are attracted by the negative side of the membrane and negative ions by the positive one

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47

peripheral membrane proteins

proteins that bind to the membrane without passing through it

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48

sodium-potassium ATPase

the enzyme that acts as the sodium-potassium pump, removing three sodium ions from the cell and taking two potassium ions into the cell during a cycle of action

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49

transmembrane proteins

Integral proteins that span the membrane and act as channels or transporters of ions

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50

transporter proteins

a membrane protein involved in the movement of ions, small molecules, and macromolecules (such as another protein) across a membrane

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51

voltage gated channels

a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel

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52

action potential

a wave of electrical excitation along a neuron's plasma membrane

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53

cones

photoreceptor cells responsible for colour vision; they only function in bright light

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54

cyclic GMP (cGMP)

a second messenger for visual transduction; it is present in high concentrations in photoreceptor cells

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55

depolarisation

an electrical state in an excitable cell whereby the inside of the cell is made less negative relative to the outside than it is at the resting membrane potential

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56

diabetes mellitus

an inability to regulate blood glucose levels; in type 1 there is a failure to produce insulin; in type 2 there is a loss of function in insulin receptors on a cell surface

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57

extracellular signalling molecule

cues (such as growth factors, hormones, cytokines and neurotransmitters) designed to transmit specific information to target cells

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58

GLUT 4 glucose transporter proteins

the insulin regulated glucose transporter; insulin triggers the movement of GLUT 4 transporters to the membrane surface, increasing uptake of glucose to be converted to glycogen

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59

G-proteins

also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior

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60

hormone response elements (HREs)

a short sequence of DNA within the promoter of a gene that is able to bind a specific hormone receptor complex and therefore regulate transcription.

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61

Hormone Receptor Complex

formed when steroid hormones bind to specific receptors in the cytosol or the nucleus; they bind to specific sites on DNA and affect gene expression

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62

hydrophilic

having a strong affinity for water

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63

Hydrophobic

the tendency of non-polar substances to aggregate in aqueous solution and exclude water molecules; it is responsible for cell membrane and vesicle formation

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64

hydrophilic signalling molecules

signalling molecules that are not able to pass through the membrane; the signal is transduced across the membrane by receptor molecules on the cell surface

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65

hydrophobic signalling molecule

signalling molecules that can diffuse through membranes, so their receptor molecules can be within the nucleus

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66

ion concentration gradient

gradients created by ion pump enzymes that transport ionic solutes, such as sodium, potassium, hydrogen ions and calcium, across the membrane; energy is required to produce a gradient, so the gradient is a form of stored energy

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67

opsin

a light-sensitive protein molecule found in the animal kingdom

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68

Phosphodiesterase (PDE)

enzyme that catalyses the hydrolysis of cyclic GMP (cGMP)

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69

phosphorylation

the addition of a phosphate group to a molecule

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70

phosphorylation cascade

a series of events in which one kinase activates the next one in a sequence phosphorylation cascades can result in the phosphorylation of many proteins as a result of the original signalling event

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71

photon

the basic unit of light

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72

photoreceptor cells

cells (rods and cones) found in the retina that are capable of visual phototransduction (converting light - visible electromagnetic radiation - into electrical signals)

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73

repolarisation

restoration of a membrane potential following depolarisation (restoring a negative internal charge)

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74

resting membrane potential

the difference in ion concentration between the inside and outside of a cell

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75

retinal

a light sensitive molecule within the eye that binds with opsin to form photoreceptors in the eye

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76

rhodopsin

the retinal-opsin complex in rod cells

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77

rods

photoreceptor cells in the retina that function in dim light and respond to low light intensities; they do not allow colour vision

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78

signal transduction

conversion of extracellular signals into an intracellular response

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79

threshold value

when the depolarisation reaches about -55mV, a neuron will fire an action potential- this is the threshold; if the neuron does not reach this critical threshold level, the action potential will not fire

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80

transcription factor

a protein that binds to specific DNA sequences, thereby controlling the rate of transcription of genetic information from DNA to messenger RNA.

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81

transducin

A protein naturally expressed in vertebrate retina rods and cones and it is very important in vertebrate phototransduction (colour vision).

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82

affinity

the degree to which a substance is attracted and tends to bind to another

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83

affinity chromatography

a technique used to separate and purify proteins based on a specific binding interaction between an immobilised ligand and its binding partner

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84

antigen

a specific protein with which antibodies can bind in an immune response

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85

aseptic technique

procedures in place to prevent contamination, including sterilising equipment and work surfaces

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86

bright-field microscopy

microscopy commonly used to observe whole organisms, parts of organisms, thin sections of dissected tissues or individual cells

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87

buffer

a solution used to set and maintain a particular pH

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88

centrifugation

a process which uses centrifugal forces to components of different densities in a mixture

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89

colorimeter

a device used to measure the absorbance of a specific wavelength of light by a solution

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90

culture media

a nutrient-rich culture media growth medium providing the basic requirements for cell growth

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91

fluorescence microscopy

microscopy technique that uses specific fluorescent labels to bind to and visualise certain molecules or structures within cells or tissues

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92

gel electrophoresis

technique used to separate samples of nucleic acid and protein by size; introduced to a gel, the move through it due to an electric current; smaller fragments move further than larger fragments

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93

growth factors

proteins that promote cell growth and proliferation

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94

inoculum

starting material used to grow a culture from, fro example a bacterial culture

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95

serum

vitally important as a source of growth factors, hormones, lipids and minerals for the culture of cells

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96

haemocytometer

microscopic grid used to estimate the total number of cells within a sample

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97

hazard

anything that poses potential risk or threat to an individual or the environment

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98

immunoassay

technique used to detect and identify specific proteins; antibodies linked with reporter enzymes

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99

isoelectric point (IEP)

the pH at which a soluble protein has no net charge and will precipitate out of solution

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100

linear dilution series

a series of dilutions that differ by an equal interval

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