IB Biology Topic D3.1.17 Pregnancy Testing by Detection of Human Chorionic Gonadotropin Secretion Revision Notes (HL)

IB Biology Topic D3.1.17 Pregnancy Testing by Detection of Human Chorionic Gonadotropin Secretion Revision Notes (HL) | RevisionDojo

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Pregnancy Tests Detect hCG, a Hormone Made Only After Implantation

Definition

Human chorionic gonadotropin (hCG)

Human chorionic gonadotropin (hCG) is a hormone essential for sustaining early pregnancy. It ensures that the uterine environment remains suitable for the developing embryo by maintaining the production of progesterone.

hCG is a hormone secreted by the trophoblast of the developing embryo, and later by the placenta.
It maintains early pregnancy by signalling the corpus luteum to keep secreting progesterone.
The trophoblast starts secreting hCG around 6 to 7 days after fertilisation, just before implantation.
Because only the embryo and placenta make hCG shortly after fertilisation, its presence is a reliable early marker that implantation has occurred.

Note

Without hCG, the corpus luteum would break down, causing menstruation and loss of the embryo.
See D3.1.16 for how the blastocyst implants and starts secreting hCG.

Monoclonal Antibodies Bind hCG to Give a Visible Line

Pregnancy tests detect hCG in urine using monoclonal antibodies.
Monoclonal antibodies are identical antibodies, specific to a single antigen, made by one clone of cells.

Definition

Monoclonal antibodies

Monoclonal antibodies are lab-engineered antibodies designed to bind to a specific target—in this case, hCG.

Tip

Antibodies are proteins that recognise and bind to specific molecules called antigens.

The Three Zones of a Test Stick

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Pregnancy Tests Detect hCG, a Hormone Made Only After Implantation

Definition

Human chorionic gonadotropin (hCG)

hCG is a hormone secreted by the trophoblast of the developing embryo, and later by the placenta.
It maintains early pregnancy by signalling the corpus luteum to keep secreting progesterone.
The trophoblast starts secreting hCG around 6 to 7 days after fertilisation, just before implantation.
Because only the embryo and placenta make hCG shortly after fertilisation, its presence is a reliable early marker that implantation has occurred.

Note

Without hCG, the corpus luteum would break down, causing menstruation and loss of the embryo.
See D3.1.16 for how the blastocyst implants and starts secreting hCG.

Monoclonal Antibodies Bind hCG to Give a Visible Line

Pregnancy tests detect hCG in urine using monoclonal antibodies.
Monoclonal antibodies are identical antibodies, specific to a single antigen, made by one clone of cells.

Definition

Monoclonal antibodies

Monoclonal antibodies are lab-engineered antibodies designed to bind to a specific target—in this case, hCG.

Tip

Antibodies are proteins that recognise and bind to specific molecules called antigens.

The Three Zones of a Test Stick

Reaction zone

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic D3.1.17: Pregnancy Testing by Detection of Human Chorionic Gonadotropin Secretion Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Pregnancy Tests Detect hCG, a Hormone Made Only After Implantation

Monoclonal Antibodies Bind hCG to Give a Visible Line

The Three Zones of a Test Stick

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Pregnancy Tests Detect hCG, a Hormone Made Only After Implantation

Monoclonal Antibodies Bind hCG to Give a Visible Line

The Three Zones of a Test Stick

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account