c9

"Q: What are red blood cells also called

and how long do they live?"

"Q: Do red blood cells have a nucleus?"

"A: No

"Q: Since RBCs have no nucleus how are they replaced

They are continuously replaced through hemopoiesis in the red bone marrow, where stem cells differentiate into new RBCs.

"Q: What key molecule is inside red blood cells and what does it do

hemoglobin - carries oxygen to tissues and some CO₂ back to the lungs.

"Q: What are the structural features of hemoglobin?"

"A: It is made of iron and protein and has 4 binding sites that bind oxygen loosely and reversibly."

"Q: What shape are red blood cells and why is it important?"

"A: Biconcave

Increases surface area for efficient oxygen and carbon dioxide exchange.

• Allows flexibility to squeeze through narrow capillaries.

"Q: How many RBCs are there compared to white blood cells?"

"A: RBCs outnumber WBCs 1000 to 1."

"Q: Why are RBCs efficient oxygen carriers despite lacking mitochondria?"

"A: They produce energy anaerobically

"Q: What happens when iron levels are low?"

"A: Low iron → low hemoglobin → low oxygen levels."

"Q: How many hemoglobin molecules are in each red blood cell and how much oxygen can they carry

• Each red blood cell contains about 270 million hemoglobin molecules.

• Each hemoglobin molecule can carry 4 oxygen (O₂) molecules, so one RBC can carry roughly 1 billion O₂ molecules.

"Q: What happens when RBCs get old or damaged?"

"A: They undergo hemolysis (breakdown) and are phagocytized by macrophages in the spleen and liver."

"Q: What happens to the components of hemoglobin during RBC breakdown?"

"A: • Iron → reused in bone marrow or stored in liver\n• Globin (protein chains) → broken into amino acids and reused or used for energy\n• Heme pigment → converted to bilirubin in the liver → becomes bile

"Q: What triggers red blood cell production?"

"A: A low oxygen level (hypoxia) signals the kidneys to release erythropoietin

"Q: What type of feedback controls RBC production?"

"A: A negative feedback mechanism maintains stable RBC levels."

"Q: When does erythropoietin release stop?"

"A: When oxygen levels return to normal and tissue needs are met."

"Q: What nutrients and factors are needed for erythropoiesis?"

"A: • Iron (for hemoglobin)\n• Folic acid (vitamin B9) to keep RBCs healthy\n• Vitamin B12

"Q: What are intrinsic and extrinsic factors in RBC health?"

"A: • Intrinsic factor: produced by the stomach lining; required to absorb B12\n• Extrinsic factor: vitamin B12 itself

"Q: What is erythropoiesis?"

"A: The development of red blood cells in the bone marrow."

"Q: How many protein chains and iron atoms are in a hemoglobin molecule?"

"A: Each hemoglobin has 4 protein chains and 4 iron atoms."