Chapter 2: Kelp structure

Jelly Fish GIF by Monterey Bay Aquarium

Welcome back! This week we will be discussing the structure of kelp! Kelp is a multicellular protist. Kelps lack the complexity that plants have so they cannot be fully considered plants! They can grow up to 215 feet tall. Kelp normally lives in temperate areas.

Image result for kelp structure

The parts of the kelp are the blade, gas bladder, stipe, and holdfast. The function of the blade is for photosynthesis which is similar to land plants. The production of food is done there with a combination of sunlight energy and nutrients from the water. The gas bladder is used to be able to do maximum photosynthesis on the top surface. The stipe is for supporting the blades.Last but not least is the holdfast. Plants have roots which keep them grounded and allow for the absorption of nutrients, but kelp is different. The kelp grows in rocky areas, so the holdfast is used as the anchor for the kelp on these surfaces.

Image result for brown algae cell

Kelp fall under the category of brown algae. The outside cell wall of the brown algae is made from cellulose, alginates, and laminarin. These components are important because, in recent studies of kelp, it was discovered that these molecules could be used in anti-inflammatory and antioxidant activities. Studies are also researching on how it could be used in anti-cancer and anti-infection responses. Another component of the cell wall is alginic acid which is used to reinforce the cellulose wall.

The organelles that brown algae have are mitochondria, nucleus, nucleolus, nuclear envelope, Golgi bodies, cytoplasmic endoplasmic reticulum, chloroplast, nuclear endoplasmic reticulum, and physodes. The physodes are vesicles which contain phenolics which are in the life cycle of the algae. One organelle that plants and the kelp have in common is chloroplast. The chloroplast is used to help with photosynthesis and stores the Chlorophylls a and c.  There is also a pyrenoid sac present where reserve carbohydrates are synthesized and polymerized.


Dotson, J. D. (2019, March 22). Does Kelp Have Many Different Cells? Retrieved from

Kelp Forests. (2012). Retrieved from


2 Responses

  1. lgranger1 at |

    When I went to the Georgia Aquarium to find my microorganism, I remember seeing the kelp and being confused at how a microorganism could be so macroscopic. The fact that they can grow to be 215ft is insane! I also think it’s interesting that they have a gas bladder to keep them floating towards the surface. Sharks evolved a swim bladder so they could have control of their depth in the water and it is crazy that something as simple as a protist could evolve similar machinery.

  2. lhughes19 at |

    I remember going to the aquarium here thinking that Kelp was actually seaweed because it was so tall. I find it extremely interesting that they would rather grow out of rocks than in the sand or other parts of the ground, since it is so plant like.


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