GATE BT flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Km definition

The substrate concentration at which reaction velocity is half of Vmax. It reflects enzyme–substrate affinity: lower Km means tighter binding and higher affinity, and it is independent of enzyme concentration.

Competitive inhibition effect

Inhibitor binds free enzyme at the active site. Apparent Km increases while Vmax is unchanged, because high substrate can outcompete the inhibitor. Lineweaver–Burk lines intersect on the y-axis.

Non-competitive inhibition

Inhibitor binds enzyme or ES complex at a site other than the active site, reducing effective Vmax without changing Km. Lineweaver–Burk lines intersect on the x-axis.

Uncompetitive inhibition

Inhibitor binds only the ES complex, lowering both Vmax and apparent Km by the same factor. Lineweaver–Burk lines are parallel, since the slope Km/Vmax is unchanged.

Doubling time from μ

In exponential batch growth, doubling time td equals ln2 divided by the specific growth rate μ, approximately 0.693/μ. A μ of 0.693 per hour gives td of one hour.

Monod Ks meaning

Ks is the limiting substrate concentration supporting half of μmax in Monod growth kinetics. It is analogous to Km and indicates how efficiently an organism scavenges a limiting nutrient.

Chemostat washout condition

Washout occurs when dilution rate D exceeds the critical value μmax·S0/(Ks + S0). At steady state before washout, D equals μ and residual substrate S = D·Ks/(μmax − D).

Decimal reduction time D

D is the heating time at a given temperature that reduces viable spore count tenfold. It relates to the first-order death constant k by D = 2.303/k, and D falls tenfold per z-degree rise.

z value in sterilization

The temperature increase in degrees Celsius required to reduce the decimal reduction time D by a factor of ten. For typical spores z is about 10 °C, used in F0 lethality calculations.

kLa determination by dynamic method

After stopping aeration or sparging nitrogen, dissolved oxygen falls; on re-aeration the slope dCL/dt = kLa(C* − CL) − qO2X allows kLa estimation from the initial re-aeration rate.

Respiratory quotient values

RQ equals CO2 evolved divided by O2 consumed. It is about 1.0 on carbohydrate, above 1.0 on organic acids or lipid-rich substrate, and below 1.0 on highly reduced substrates such as alkanes.

Degree of reduction

A measure of electrons available per carbon atom, computed as 4C + H − 2O − 3N for a molecule's formula. It is conserved in balanced growth and used to check elemental balances.

PCR product yield

After n successful cycles starting from N0 template molecules, the theoretical copy number is N0·2^n. Efficiency below 100 percent gives N0(1 + E)^n, where E is fractional efficiency.

Restriction fragment frequency

A restriction enzyme recognizing an n-base-pair site cleaves on average once every 4^n base pairs in random DNA. A 6-base cutter averages one site per 4096 bp.

Chromatographic resolution formula

Resolution Rs equals 2(tR2 − tR1)/(w1 + w2), using retention times and baseline peak widths. Rs of 1.5 corresponds to essentially complete baseline separation of two peaks.

Gel filtration Kav

Kav equals (Ve − V0)/(Vt − V0), where Ve is elution volume, V0 void volume, and Vt total bed volume. Large molecules have small Kav and elute first; fully included solutes approach Kav of 1.

HETP and plate number

Height equivalent to a theoretical plate is column length divided by plate number N. N is calculated as 16(tR/w)^2 from retention time and peak width, and higher N means sharper, better-resolved peaks.

Semiconservative replication

Each daughter DNA duplex contains one parental strand and one newly synthesized strand. Meselson–Stahl demonstrated this with density-gradient centrifugation after labeling DNA with heavy nitrogen.

DNA melting temperature factors

Duplex Tm increases with G+C content because three hydrogen bonds per G–C pair stabilize the helix. Tm also rises with monovalent salt concentration and falls with base mismatches or denaturants.

Lineweaver–Burk intercepts

In the double-reciprocal plot, the y-intercept equals 1/Vmax and the x-intercept equals −1/Km. The slope is Km/Vmax, allowing graphical determination of kinetic constants from velocity data.

Biomass yield coefficient

Yx/s is grams of biomass formed per gram of substrate consumed, equal to ΔX/ΔS. It links carbon source utilization to cell production and is used in material balance and medium design.

Maintenance energy

Substrate consumed for functions other than growth, such as ion gradients and repair. It is modeled by 1/Yx/s = 1/Yx/s(max) + m/μ, where m is the maintenance coefficient.

Oxygen uptake rate relation

OUR equals the specific oxygen uptake rate qO2 multiplied by cell concentration X. At steady state in a fermenter, OUR equals the oxygen transfer rate kLa(C* − CL).

Fed-batch feeding rationale

Nutrient is added during the run to keep substrate low, avoiding overflow metabolism, catabolite repression, and oxygen demand spikes while extending product formation and raising final biomass and product titre.

Enzyme unit definition

One international unit of enzyme activity converts one micromole of substrate per minute under defined assay conditions. Specific activity is units per milligram of protein, indicating enzyme purity.

Protein A chromatography use

Affinity chromatography with immobilized Protein A binds the Fc region of IgG antibodies. It is a capture step in monoclonal antibody purification, followed by low-pH elution and viral inactivation.

SDS-PAGE separation principle

SDS denatures proteins and imparts uniform negative charge per mass, so migration depends mainly on molecular weight in a polyacrylamide gel. Smaller proteins migrate farther toward the anode.

Southern versus Northern blot

Southern blotting detects specific DNA sequences after restriction digestion and gel transfer. Northern blotting detects RNA, revealing transcript size and abundance, and is used to assess gene expression.

ELISA sandwich format

Capture antibody immobilizes antigen, a detection antibody binds a second epitope, and an enzyme conjugate produces a colorimetric signal. It quantifies antigen concentration with high specificity.

Biosensor response principle

A biological recognition element such as an enzyme or antibody generates a signal transduced optically or electrochemically. Signal magnitude relates to analyte concentration through a calibration curve.

Immobilized enzyme advantage

Immobilization allows enzyme reuse and continuous operation and often improves stability. Activity may fall due to mass transfer limitation or conformational change, described by an effectiveness factor.

Thiele modulus meaning

It compares intrinsic reaction rate to diffusion rate within a porous catalyst or immobilized enzyme particle. Large values indicate diffusion limitation, and the effectiveness factor falls below one.