Digestive System, Plant Physiology, and Cell Biology Lecture Review

These question-and-answer flashcards review major concepts from the lecture notes, covering human digestion, plant physiology, and cell biology. They are designed to reinforce definitions, processes, structures, and clinical or functional insights essential for exam preparation.

Which glands in the small intestine secrete intestinal juice (succus entericus)?

Intestinal glands, also called Crypts of Lieberkühn.

Name three carbohydrate-digesting enzymes found in intestinal juice.

Maltase, Lactase, and Sucrase.

Which enzyme in intestinal juice is responsible for fat digestion?

Intestinal lipase.

Where does final digestion and most absorption of nutrients occur?

In the small intestine.

What is the dual role of the pancreas?

It functions as both an exocrine gland (secreting pancreatic juice) and an endocrine gland (secreting insulin and glucagon).

List two protein-digesting enzymes present in pancreatic juice.

Trypsin and chymotrypsin.

Which pancreatic enzyme converts starch to maltose?

Pancreatic amylase.

Which salivary gland is the largest and where is it located?

The parotid gland; it lies near the ear.

What is the pH of saliva, and which enzyme does it contain?

About 6.7 (slightly acidic); contains salivary amylase (ptyalin).

Where does carbohydrate digestion begin?

In the mouth.

Name the three main cell types of gastric glands and their secretions.

Parietal cells – HCl; Chief cells – Pepsinogen; Mucous cells – Mucus.

Protein digestion starts in which organ and with which active enzyme?

In the stomach with pepsin.

Which organ secretes bile and where is bile stored?

The liver secretes bile, which is stored in the gallbladder.

Why is bile important for fat digestion?

Bile salts emulsify fats into small droplets, increasing surface area for lipase action.

Is bile acidic, neutral, or alkaline?

Alkaline.

Which enzyme does the gastric gland question commonly reference: "The stomach produces an enzyme ____"?

Pepsin.

Identify the three segments of the small intestine in order.

Duodenum, Jejunum, Ileum.

What is the approximate total length of the small intestine in adults?

About 6–7 meters (20–23 feet).

Which part of the small intestine receives bile and pancreatic juice?

The duodenum.

Which segment of the small intestine is the chief site for nutrient absorption?

The jejunum.

Which nutrients are primarily absorbed in the ileum?

Vitamin B12, bile salts, and remaining nutrients.

What are Peyer’s patches and where are they abundant?

Lymphoid nodules in the ileum that detect pathogens.

Name two structural adaptations of the small intestine that maximize absorption.

Villi and microvilli (brush border).

What is the estimated surface area of the small intestine?

About 20–25 square meters (roughly a tennis court).

Which valve regulates flow from ileum to large intestine?

The ileocecal valve.

List the four main parts of the colon in sequence.

Ascending colon, Transverse colon, Descending colon, Sigmoid colon.

Give two primary functions of the large intestine.

Absorption of water and electrolytes; formation and storage of feces.

Does the large intestine secrete digestive enzymes?

No; its main role is absorption and waste elimination.

Which vitamins are synthesized by gut bacteria and absorbed in the large intestine?

Vitamin K and some B-complex vitamins.

What two ducts unite to form the hepatopancreatic duct before entering the duodenum?

The common bile duct and the pancreatic duct.

Why is the liver called the “chemical factory” of the body?

Because it synthesizes, transforms, and detoxifies a wide range of chemicals, including bile, glycogen, plasma proteins, and drugs.

Why can the gallbladder be surgically removed without fatal consequence?

The liver can still produce bile and adjust its release directly into the duodenum.

What are chloroplasts and why are they dubbed the “kitchen of the cell”?

Green organelles where photosynthesis occurs, manufacturing food (glucose) for the plant.

Write the overall balanced chemical equation for photosynthesis.

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂ (in the presence of light and chlorophyll).

Where in the chloroplast does the light reaction occur?

In the thylakoid membranes (grana).

What three main products are generated by the light reaction?

ATP, NADPH, and O₂.

Which photosystem absorbs light best at 680 nm and splits water?

Photosystem II (PS II).

Which enzyme fixes CO₂ in the Calvin cycle?

RuBisCO (Ribulose bisphosphate carboxylase-oxygenase).

State two differences between cyclic and non-cyclic photophosphorylation.

Cyclic involves only PSI and produces ATP only; Non-cyclic involves PSI & PSII and produces ATP, NADPH, and O₂.

Give four factors that can limit the rate of photosynthesis.

Light intensity, CO₂ concentration, temperature, and water availability.

Why is the small intestine called the "site of maximum absorption"?

Its villi, microvilli, length, segmentation, and rich blood supply allow absorption of about 90 % of nutrients.

Define xylem and state its primary function.

Complex vascular tissue that conducts water and minerals upward from roots to shoots.

Name two dead cell types that compose xylem.

Tracheids and vessel elements.

Why is phloem termed the “food-conducting tissue”?

It transports photosynthetic sugars bidirectionally from leaves to other plant parts.

Which living cells assist sieve tubes in loading sugars?

Companion cells.

What is transpiration pull and which tissue relies on it?

Negative pressure created by water evaporation from leaves that pulls water up through xylem.

Define stomata.

Tiny pores on leaf surfaces surrounded by guard cells that regulate gas exchange and transpiration.

How do guard cells open a stoma during daylight?

They accumulate K⁺ ions, water enters osmotically, turgor rises, and the pore opens.

List two environmental factors that cause stomata to close.

Water stress (drought) and high internal CO₂ concentration.

What are the three main stages of aerobic cellular respiration?

Glycolysis, Krebs (citric acid) cycle, and Electron Transport Chain.

In cellular respiration, which organelle is known as the “powerhouse of the cell”?

The mitochondrion.

Differentiate between aerobic and anaerobic respiration in terms of oxygen requirement and ATP yield.

Aerobic requires O₂ and yields large ATP; anaerobic occurs without O₂ and yields much less ATP.

Arrange the genetic hierarchy from largest to smallest: cell, chromosome, gene, DNA.

Cell → Chromosome → DNA → Gene.

What is a nucleosome?

DNA wrapped around a histone octamer, forming the basic unit of chromatin.

Contrast euchromatin with heterochromatin.

Euchromatin is loosely packed and transcriptionally active; heterochromatin is densely packed and inactive.

Describe a metacentric chromosome.

A chromosome with its centromere in the middle, giving equal p and q arms.

Which centromere position results in a chromosome with virtually one arm (found in mice but not humans)?

Telocentric.

Name the four parts of the large intestine starting from the ileocecal valve.

Cecum, Colon (ascending, transverse, descending, sigmoid), Rectum, Anus.

State one key clinical condition that often affects the duodenum.

Duodenal ulcers (peptic ulcers).

What are Brunner's glands and what do they secrete?

Glands in the duodenum that secrete alkaline mucus to neutralize gastric acid.

Which two hormones secreted by the pancreas regulate blood glucose?

Insulin and glucagon.

Why is oxygen evolved during photosynthesis derived from water rather than carbon dioxide?

Water undergoes photolysis in PS II, releasing O₂; isotope tracing confirmed O₂ originates from H₂O.

What role do stomata play in plant cooling?

Evaporation of water via transpiration cools leaf surfaces.

Which nutrient element is at the center of the chlorophyll molecule?

Magnesium.

Explain the pressure-flow hypothesis in phloem transport.

Sucrose loading raises osmotic pressure, water enters from xylem, generating pressure that moves sap toward sink tissues.

Which accessory digestive organ can regenerate significantly after partial removal?

The liver.

Name the finger-like projections in the small intestine that increase surface area for absorption.

Intestinal villi.

Which lymphatic vessels inside villi absorb dietary fats?

Lacteals.

State one disorder associated specifically with the ileum.

Crohn’s disease (ileitis) or tuberculosis of the ileum.

Which endocrine portion of the pancreas contains insulin-secreting cells?

Islets of Langerhans (β-cells for insulin).