Fungi and protoctists

The nature and variety of living organisms · Characteristics and variety of living organisms · note 3 of 5

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Fungi and protoctistsSpec 1.2

Fungi

Fungi are eukaryotic organisms that are not able to carry out photosynthesis. Most have a body organised into a mycelium, made from thread-like structures called hyphae, which contain many nuclei. Some fungi are single-celled.

Their cell walls are made of chitin.
They feed by secreting digestive enzymes onto food material outside the body (extracellular secretion), then absorbing the organic products. This is called saprotrophic nutrition.
They may store carbohydrate as glycogen.

Mucor shows the typical fungal hyphal structure. Yeast is a single-celled fungus.

Mucor shown as a mycelium of branching hyphae with many nuclei and a chitin cell wall, beside a single yeast cell labelled nucleus, cytoplasm and chitin cell wall. — Two fungi: *Mucor* is made of hyphae forming a mycelium; yeast is single-celled. Both have cell walls made of **chitin**.

Protoctists

Protoctists are microscopic single-celled eukaryotic organisms. They are a varied group.

Amoeba lives in pond water and has features like an animal cell.
Chlorella has chloroplasts and is more like a plant cell.
Plasmodium is a pathogen. It causes malaria.

Two protoctists: Amoeba labelled cell membrane, nucleus, contractile vacuole, food vacuole and cytoplasm; Chlorella labelled cell wall, nucleus, cytoplasm and chloroplast. — Two protoctists: *Amoeba* is like an animal cell, while *Chlorella* has a cell wall and a chloroplast, like a plant cell.

Common mistake:

Write 'protoctists', the word used in this specification. A protoctist is single-celled, but not every single-celled organism is a protoctist: bacteria and yeast are not.