Passive transport does not require energy input from the cell. Which of the following is an example of passive transport?

Correct Answer: B

Rationale: Passive transport refers to the movement of molecules across a cell membrane without the input of energy. Diffusion of small molecules across a concentration gradient is a classic example of passive transport, as it occurs spontaneously from an area of high concentration to an area of low concentration. Active transport (option A) requires energy input in the form of ATP to move substances against their concentration gradient. Movement of large molecules using vesicles (option C) involves processes like endocytosis and exocytosis that require energy in the form of ATP. Endocytosis of particles into the cell (option D) is an active process that requires energy expenditure by the cell to engulf and internalize extracellular substances.

Correct Answer: B

Rationale: Melanocytes are the cells responsible for producing melanin, the pigment that determines skin color. Melanin gives skin its color and protects it from the harmful effects of UV radiation. Keratinocytes produce keratin, a tough protein that forms the outer layer of the skin, hair, and nails. Sebocytes produce sebum, an oily substance that helps moisturize and protect the skin. Langerhans cells are a type of immune cell found in the skin that play a role in protecting against infections and foreign substances but do not produce melanin.

Correct Answer: A

Rationale: Eczema is a skin condition characterized by red, itchy, and inflamed patches. It is a common condition that can vary in severity and often presents with symptoms such as dry, scaly skin, and sometimes oozing or crusting. Psoriasis, on the other hand, presents with red, scaly patches but is not typically described as itchy. Melanoma is a type of skin cancer characterized by the development of abnormal moles, while keloid is a type of raised scar that can occur after an injury to the skin. Therefore, the correct answer is eczema due to its specific symptom presentation of red, itchy, and inflamed patches.

Correct Answer: B

Rationale: Ligaments are the tough, fibrous tissue that connects bones at joints, providing stability and support to prevent excessive movement and potential injury. Cartilage is a smooth, rubbery connective tissue that covers bone ends at joints. Tendons connect muscles to bones, enabling movement. Fascia surrounds muscles, blood vessels, and nerves, providing support and structure to these tissues. In this context, ligaments are specifically the connective tissues that bind bones together at joints, not cartilage, tendons, or fascia.

Correct Answer: D

Rationale: The vertebral column, also known as the spine, is the curved bone in the back that provides support and attachment for muscles. It consists of individual vertebrae stacked on top of each other, forming a flexible and protective structure for the spinal cord. The sternum, scapula, and clavicle are bones in the chest and shoulder regions, not in the back where the vertebral column is located. Therefore, the correct answer is the vertebral column (Option D). Options A, B, and C are incorrect as they are bones situated in the chest and shoulder areas, not in the back where the vertebral column is found.