Excitation-contraction coupling refers to the series of events that begins with the excitation of the sarcolemma in response to stimulation by a neurotransmitter, and results in the release of calcium ions from the sarcoplasmic reticulum.
Hence, option D is the 1st process that starts the excitation-contraction coupling.
Recall the endosymbiosis hypothesis and recall endosymbiosis. Remember that the very first cell was a prokaryotic cell. Which engulfed chloroplast precursors and mitochondria. We all come from these cells. And how we evolved over time shows the relationship. I'm a bio major hope I helped
Different structures and functions of roots
Explanation:
Roots are the underground descending non-green part of the plant.
Root functions: Anchorages the plant to the soil, absorbs water and nutrients from the soil.
Characteristics: Positively geotropic and hydrotropic, negatively phototropic; does not have nodes, internodes or stems.
Types:
- Tap root
- Adventitious root – fibrous, foliar and true adventitious roots
Structure and functions:
- Root cap or Calyptra: Cap-like structure covering the root tip
.
- Function: protects the meristematic tissues of the root, secretes mucilage which enhances the root tips to grow into the hard soil.
- Meristematic zone or growing point sub-terminal behind root cap. These cells are inverted and looks like a dome.
- Function – helps in the root growth by adding new cells to the root tip and other basal regions
- Zone of elongation behind the meristematic zone.
- Function – helps in elongation of the root
- Root hair zone: This is the zone of differentiation where cells differentiate into vascular tissues like phloem, xylem, endodermis, cortex etc.
- The main function of root hair is to increase the total surface area of root to facilitate more absorption of water and other nutrients from the soil
- Zone of maturation: the major and mature portion of a root.
- Function - lateral roots originates from this zone and radial differentiation leads to secondary growth.
Anaphylaxis, also called allergic or anaphylactic shock, is a sudden, severe and life-threatening allergic reaction that involves the whole body. The reaction is marked by constriction of the airways, leading to difficulty breathing.
Anaphylaxis is a severe, whole-body allergic reaction to a chemical that has become an allergen. An allergen is a substance that can cause an allergic reaction.
Anaphylactic shock is a rare but severe allergic reaction that can be deadly if you don't treat it right away. It's most often caused by an allergy to food, insect bites, or certain medications. A shot of a drug called epinephrine is needed immediately.
To learn more about anaphylactic shock here
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Glycolysis, Link reaction, the Krebs cycle, and the electron transport chain.
