Meat is a significant dietary source of high-quality protein, which contains all the essential amino acids required by the human body for muscle repair, enzyme production, and immune function. While meat also contains varying amounts of lipids (fats), protein is the defining macronutrient that characterizes meat as a nutritional source. It is essential for growth and maintenance of body tissues.

Gastric juice is a complex mixture secreted by the glands in the stomach lining. It primarily consists of hydrochloric acid, pepsinogen (which is converted to the enzyme pepsin), mucus, and intrinsic factor. This acidic environment is essential for protein digestion and for killing pathogens that may be ingested with food.

Glycolysis is the initial stage of cellular respiration occurring in the cytoplasm. It is an anaerobic process that converts one six-carbon glucose molecule into two three-carbon pyruvate molecules. This pathway is essential for energy production in both aerobic and anaerobic organisms, providing a small amount of ATP and NADH for further metabolic processes.

Holozoic nutrition is the process by which organisms ingest complex organic substances, such as solid or liquid food, which are then broken down internally through digestion. This mode is characteristic of most higher animals, which rely on consuming other organisms or organic matter to obtain the necessary nutrients for energy and growth, unlike autotrophs that synthesize their own food.

Lipase is the enzyme specifically secreted by the pancreas and other organs to break down dietary fats (lipids). It catalyzes the hydrolysis of triglycerides into monoglycerides and free fatty acids, which can then be absorbed by the intestinal lining. Amylase breaks down carbohydrates, while trypsin and pepsin are involved in protein digestion.

Gastrin and secretin are key gastrointestinal hormones. Gastrin stimulates the secretion of gastric acid in the stomach, while secretin stimulates the pancreas to release bicarbonate-rich fluid to neutralize acidic chyme in the duodenum, facilitating efficient digestion within the digestive tract.

The provided answer is factually incorrect as a standard adult heart beats roughly 60-100 times per minute, totaling approximately 100,000 beats per day. The option '70 times/day' is a significant underestimation. This discrepancy may arise from a confusion between beats per minute and total daily beats. We retain the provided answer key as requested.

Lymphocytes and monocytes are classified as agranulocytes because their cytoplasm lacks the prominent, visible granules found in other white blood cells like neutrophils, eosinophils, and basophils. These cells play critical roles in the adaptive and innate immune responses, respectively, and are characterized by their distinct nuclear shapes and lack of cytoplasmic staining granules.

Neutrophils are the most abundant type of white blood cell and act as the body's first line of defense. They are highly mobile phagocytes that migrate to sites of infection to engulf and destroy invading pathogens, particularly bacteria, through the process of phagocytosis.

In clinical medicine, the standard reference for normal systolic blood pressure in a healthy young adult is approximately 120 mmHg. Systolic pressure represents the force exerted against arterial walls during the contraction of the heart ventricles. While individual variations exist based on health, age, and activity, 120/80 mmHg is widely accepted as the benchmark for normal blood pressure.