IB Biology Topic D3.1.15 Mechanisms to Prevent Polyspermy Revision Notes (HL)

IB Biology Topic D3.1.15 Mechanisms to Prevent Polyspermy Revision Notes (HL) | RevisionDojo

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Blocking Polyspermy Is Essential for a Viable Zygote

When one sperm fertilises an egg, no further sperm must be allowed to enter.
Polyspermy, the fusion of more than one sperm with a single egg, gives a zygote with too many chromosomes.
Such a zygote is not viable and cannot develop.
Two mechanisms prevent it: the acrosome reaction lets one sperm in, and the cortical reaction keeps the rest out.

Definition

Polyspermy

Polyspermy refers to the fertilization of an egg by more than one sperm.

The Acrosome Reaction Lets a Sperm Cross the Zona Pellucida

Definition

Acrosome reaction

The acrosome reaction is the first step in fertilization. It allows a sperm to penetrate the egg's protective glycoprotein layer, called the zona pellucida, to reach the plasma membrane of the egg.

The acrosome is a specialised vesicle at the tip of the sperm head.
It holds enzymes that digest the egg's protective layer, the zona pellucida.

Note

The zona pellucida is a glycoprotein layer around the egg that acts as a barrier to sperm.

Steps of the Acrosome Reaction

Sperm binding: the sperm binds to specific glycoproteins on the zona pellucida, which triggers the reaction.
Enzyme release: the acrosome releases enzymes that digest a path through the zona pellucida.

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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.

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Blocking Polyspermy Is Essential for a Viable Zygote

When one sperm fertilises an egg, no further sperm must be allowed to enter.
Polyspermy, the fusion of more than one sperm with a single egg, gives a zygote with too many chromosomes.
Such a zygote is not viable and cannot develop.
Two mechanisms prevent it: the acrosome reaction lets one sperm in, and the cortical reaction keeps the rest out.

Definition

Polyspermy

Polyspermy refers to the fertilization of an egg by more than one sperm.

The Acrosome Reaction Lets a Sperm Cross the Zona Pellucida

Definition

Acrosome reaction

The acrosome is a specialised vesicle at the tip of the sperm head.
It holds enzymes that digest the egg's protective layer, the zona pellucida.

Note

The zona pellucida is a glycoprotein layer around the egg that acts as a barrier to sperm.

Steps of the Acrosome Reaction

Sperm binding: the sperm binds to specific glycoproteins on the zona pellucida, which triggers the reaction.
Enzyme release: the acrosome releases enzymes that digest a path through the zona pellucida.

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 D3.1.15: Mechanisms to Prevent Polyspermy Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Blocking Polyspermy Is Essential for a Viable Zygote

The Acrosome Reaction Lets a Sperm Cross the Zona Pellucida

Steps of the Acrosome Reaction

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Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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Blocking Polyspermy Is Essential for a Viable Zygote

The Acrosome Reaction Lets a Sperm Cross the Zona Pellucida

Steps of the Acrosome Reaction

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