Bio Unit 6 Section 2

Hemoglobin (Hb)

Iron-rich protein found in RBCs that carries O₂, CO₂, and H⁺

~200 million per RBC; made of 4 polypeptide chains + 4 heme groups

Oxyhemoglobin

Hemoglobin bound to oxygen (HbO₂)

Forms in the lungs; releases O₂ at tissues: HbO₂ → Hb + O₂

Carbaminohemoglobin

Hemoglobin bound to CO₂ (HbCO₂)

Forms at tissues; releases CO₂ at lungs: HbCO₂ → Hb + CO₂

Deoxyhemoglobin (HHb)

Hemoglobin bound to H⁺ ion

H⁺ + Hb → HHb; releases H⁺ at the lungs

Carboxyhemoglobin

Hemoglobin bound to carbon monoxide (CO)

CO blocks O₂, CO₂, and H⁺ binding — inhibits respiration

Carbonic anhydrase (CA)

Enzyme that catalyzes: H₂O + CO₂ ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

Present in red blood cells; speeds up both directions of reaction

Bicarbonate ion (HCO₃⁻)

Buffer that keeps blood pH constant

Most CO₂ is transported in the blood as HCO₃⁻

Internal respiration

Gas exchange between blood and body tissues/organs

O₂ released to tissues, CO₂ picked up; HbO₂ → Hb + O₂

External respiration

Gas exchange between blood and the lungs (alveoli)

CO₂ exhaled, O₂ loaded onto Hb: Hb + O₂ → HbO₂

Hb & temperature/pH rule

Hb binds O₂ more readily at lower temp & basic/neutral pH (lungs); releases O₂ more easily at higher temp & acidic pH (tissues)

Active tissues are warmer and more acidic → O₂ released there

Alveoli

Tiny air sacs in the lungs where gas exchange occurs

One cell layer thick; surrounded by capillary beds; secrete lipoprotein to prevent collapse; high SA:V ratio

Inspiration (inhalation)

Diaphragm + intercostal muscles contract → chest volume increases → pressure decreases → air flows in

Negative pressure maintained by the pleural membrane

Expiration (exhalation)

Diaphragm + intercostal muscles relax → chest volume decreases → pressure increases → air forced out

Air moves from high pressure inside to lower pressure outside

Pleural membranes

Membranes lining the outside of chest walls and inside of lungs

Fluid between them creates an air-tight seal and maintains pressure difference

Medulla oblongata

Breathing control center in the brain

Detects CO₂/H⁺ via chemoreceptors; sends nerve impulses to diaphragm & intercostal muscles

Tidal Volume (TV)

Amount of air inhaled or exhaled during normal quiet breathing (~500 mL)

Vital Capacity (VC)

Total air forcibly exhaled after maximum inspiration

= IRV + TV + ERV

Residual Volume (RV)

Air remaining in lungs after a maximal exhalation

Cannot be exhaled — keeps alveoli from collapsing

Plasma

Liquid component of blood (55%)

Contains water, plasma proteins (albumin, fibrinogen, globulin), gases, nutrients, salts, wastes, hormones

Erythrocytes (RBCs)

Red blood cells — transport O₂, H⁺, CO₂; no nucleus; >95% of formed elements

Contain ~200 million hemoglobin molecules each

Leukocytes (WBCs)

White blood cells — fight infection; two types: granular and agranular

Granular: basophils, neutrophils, eosinophils; Agranular: monocytes, lymphocytes

Thrombocytes (platelets)

Cell fragments that participate in blood clotting

Activated by injury; release clotting factors

Neutrophil

Granular WBC that identifies and destroys pathogens via phagocytosis

First responder to infection

Basophil

Granular WBC that releases histamine during allergic/inflammatory responses

Triggered by bradykinin (BK) released from injured tissues

Eosinophil

Granular WBC with toxic proteins that kill parasites; promotes inflammation

Causes swelling and itching at injury sites

Monocyte

Agranular WBC that patrols for infection; becomes macrophages to engulf dead/damaged cells

Stimulates release of other WBCs from bone marrow

Lymphocyte

Agranular WBC that recognizes/remembers antigens, produces antibodies

3 types: B cells, Helper T cells, Cytotoxic T cells

B cells

Lymphocytes that produce antibodies

Activated by Helper T cells

Helper T cells

Lymphocytes that activate B cells to produce antibodies

Cytotoxic T cells

Lymphocytes that destroy cells infected with pathogens

Bind to cells displaying specific antigens on their surface

Antigen

Protein or carbohydrate on the surface of a pathogen that triggers an immune response

e.g. protein coat of a virus or bacteria

Antibody (immunoglobulin)

Protein made by lymphocytes that binds to a specific antigen (lock-and-key) to neutralize a pathogen

Variable region binds antigen; constant region held together by disulfide bonds

Bradykinin (BK)

Chemical released by injured tissues that causes basophils to release histamine

Also stimulates nerves, causing pain

Histamine

Chemical released by basophils that dilates and increases permeability of capillaries

Causes swelling that isolates pathogens from further tissue contact

Blood clotting steps

1. Injury → prothrombinase released (needs Vit. K) →

2. prothrombin → thrombin (needs Ca²⁺) →

3. fibrinogen → fibrin →

4. fibrin network forms clot

Platelets + activated by injury; fibrin strands trap RBCs

Inactivated vaccine

Contains a dead virus — cannot cause disease but triggers immune response

Attenuated vaccine

Contains a weakened (live) virus — may cause mild symptoms but builds immunity

mRNA vaccine

Injects mRNA coding for a viral protein → cells produce the protein → immune system makes antibodies against it

mRNA is destroyed by the body in 1–3 days; does NOT alter DNA

Albumin

Plasma protein secreted by the liver; transports nutrients and waste

Also helps maintain blood osmotic pressure

Fibrinogen

Plasma protein secreted by the liver; involved in blood clotting

Thrombin converts fibrinogen → fibrin to form clot