MDCAT Past Papers - Biology - UHS

541. Once an action potential reaches the membrane of a skeletal muscle fiber, what is the first event that occurs in the contraction process?

Actin and myosin form a cross bridge
Calcium is pumped back into the sarcoplasmic reticulum
Calcium is released from the sarcoplasmic reticulum
ATP is hydrolyzed by troponin

542. The public symphysis is a slightly moveable joint joined by which of the following tissue?

Elastic cartilage
Fibrocartilage
Costa Cartilage
Articular cartilage

543. In a sea plant seed color is determined by two alleles: Y (Yellow, dominant) and y (green recessive). Which parental cross would most likely result in offspring showing a 1:1 ratio of yellow to green seeds?

Yy x YY
Yy x yy
Yy x Yy
Yy x yy

544. Mendel crossed a plant with round yellow seeds (RRYY) and a plant with wrinkled green seed (rryy), what was the phenotype of all F1 offspring?

All round green
All round yellow
All wrinkled yellow
All wrinkled green

545. In a normal 28 days menstrual cycle when would you expect the LH surge to occur?

Days 7-10
Days 11-14
Days 15-18
Days 19-22

546. Which property of water helps in moderating Earth's climate and maintaining stable temperature in aquatic environment?

Low viscosity
High specific heat capacity
High surface tension
High polarity

547. Effect of increased substrate concentration on enzyme activity:

Decrease the rate of reaction
Increase the reaction rate until all active sites are saturated
Have no effect on the reaction rate
Increase the reaction rate in a straight diagonal line

548. An oligosaccharide is made up of at least:

two saccharide units
ten saccharide units
three to ten saccharide units
more than ten saccharide units

549. Which statement best explains the difference between humoral and cell mediated immune response?

Humoral immunity involves B-Lymphocytes and cell mediated immunity involves T-Lymphocytes
Humoral immunity destroys viruses and cell mediated immunity destroys bacteria
Humoral immunity is specific and cell mediated immunity is nonspecific
Humoral immunity uses antibodies and cell mediated immunity does not involve immune cells

550. Which of the following is the correct higher (left) to lower (right) sequence of molecules with respect to their amount in the cell?

DNA → rRNA → tRNA → mRNA
rRNA → tRNA → mRNA → DNA
mRNA → tRNA → rRNA → DNA
DNA → mRNA → tRNA → rRNA

551. A person in hot weather is unable to maintain body temperature. Which physiological process has failed?

Vasodilation & sweating
Vasoconstriction
Shivering
Renin secretion

552. The main idea in Darwin's Theory of "Origin of species by natural selection" is:

Inheritance of acquired traits
Use and disuse of organs
Species never change
Evolution occurs through gradual accumulation of adaptation through successive generations

553. Which of the following is a key feature of RNA?

Deoxyribose and thymine
Double stranded and thymine
Ribose and uracil
Ribose and thymine

554. Which of the following types of RNA makeup the largest proportion of total cellular RNA?

Messenger RNA
Ribosomal RNA
Transfer RNA
Catalytic RNA (ribozyme)

555. The bacterium Treponema Pallidum is responsible for which sexually transmitted disease?

Syphilis
Chlamydia
Gonorrhea
Genital herpes

556. Tissue fluid in a lymphatic system is called as:

Plasma
Matrix
Lymph
Blood

557. Which one of the following biomolecules is a polymer/polysaccharide?

Sucrose
Pentose
Lactose
Glycogen

558. Olfactory receptors are the type of:

photoreceptors
mechanoreceptors
thermoreceptors
chemoreceptors

559. Which of the following organisms eliminate nitrogenous waste mainly in the form of uric acid?

Freshwater Fish
Amphibians
Birds
Mammals

560. Which of the following cells possess Nissil's granules?

Nerve cells
WBC
RBC
Platelets