Eukaryotic Cells�STUDENT NOTES

2.4 Eukaryotic Cells

Lesson Objectives:

Learners should be able to demonstrate and apply their knowledge and understanding of:

• The ultrastructure of eukaryotic cells and the functions of the different cellular components
• Photomicrographs of cellular components in a range of eukaryotic cells
• The importance of the cytoskeleton

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Monday, 12 March 2018

Turn to pages 26 and 27 in the OUP Textbook

Bell Task

• Label the diagram of the animal cell

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• Which features can you identify from year 9

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This document may have been altered from the original

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Week 2

List the functions of the organelles you have studied at Högstadiet

• Nucleus
• Mitochondria
• Ribosomes
• Cell Membrane
• Cytoplasm

What is a eukaryote?

A eukaryote is any organism consisting of one or more cells that contain DNA in a membrane-bound nucleus, separate from the cytoplasm.

• plants

• a diverse group known as the protists (or protoctists).

All eukaryotic cells contain a large number of specialized, membrane-bound organelles.

Eukaryotes include:

• fungi

• animals

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Relative Sizes

Nucleolus

Chromatin

Nuclear Envelope

The Nucleus

Nucleus – Structure & Function

• Nucleus – houses nearly all the cell’s genetic material
• Chromatin – consists of DNA and proteins
• Nucleolus – makes RNA, which is made into ribosomes and ribosomes
• Nuclear envelope – has nuclear pores going through the envelope to let relatively large molecules pass through. In the nuclear envelope there is nucleoplasm.

Nucleus – The Facts

• The largest organelle in the cell
• Consists chromatin which contains DNA and proteins
• Chromatin is seen as darkened patches when seen on a light micrograph
• Some of these proteins regulate the cell’s activity
• Makes ribosomes
• Has holes called nuclear pores which allow exchange of substances in and out of the cell

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Nucleolus – The Facts

• The most obvious structure in the nucleus is the nucleolus
• The nucleolus produces ribosomes, which move out of the nucleus to latch onto the outside of the rough endoplasmic reticulum where they produce proteins

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Nuclear envelope

• It is a dense spherical structure
• Surrounds the nucleolus
• A structure made of two membranes (inner and outer) with fluid separating them
• The nuclear envelope is marked with nuclear pores which allow for exchange of relatively large molecules

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Mitochondria

The mitochondrion is an energy-generating organelle.

The inner membrane is coated in enzymes, which catalyze the reactions of aerobic respiration to produce ATP.

It is surrounded by two membranes. The inner layer folds inwards to form the cristae. The cristae project into a liquid called the matrix.

outer membrane

matrix

inner membrane

cristae

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Mitochondrion (2-5 µm long)

© Pearson Education Ltd 2008

This document may have been altered from the original

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Week 2

Please note that magnification sizes are subject to variation on different screens

Look at the diagram of the mitochondria.

• What is the function of the mitochondria?
• How does the function of the mitochondria relate to this function?

The Mitochondria contains is one DNA

• Suggest why the Mitochondria has its own DNA?

• They are tiny organelles which can be found in cytoplasm or bound to rough endoplasmic reticulum.
• Each ribosome consists of two sub-units.
• They are the site of protein synthesis in a cell, which is where proteins are made. It acts as an assembly line for coded information form the nucleus to be used to make proteins from amino acids.

Ribosomes

Golgi Apparatus

• The Golgi Apparatus is a stack of membrane- bound flattened sacs.
• Its single membrane is similar to that of a cell membrane in that it has two layers.
• Its membrane surrounds an area of fluid where the complex molecules are stored and changed.

Golgi Apparatus - Function

• Golgi Apparatus receives proteins from the ER and modifies them.
• It may add sugar molecules to them.
• The Golgi apparatus then packages the modified proteins into vesicles that can be transported.
• Some modified proteins may go to the surface of the cell so that they may be secreted.

• They are spherical sacs surrounded by a single membrane.
• They are specialised vesicles
• They contain powerful digestive enzymes and their role is to break down materials.

Lysosomes

Rough Endoplasmic Reticulum

• Consists of a series if flattened membrane – bounds sacs called cisternae.
• They are studded with ribosomes.
• It transports proteins that were made on the attached ribosomes.
• Some of the proteins will be secreted by the cell whilst the others will be placed on the surface of the cell membrane.

Smooth Endoplasmic Reticulum

• They have the same structure as a rough endoplasmic reticulum but it does not have ribosomes.
• It is involved in making the lipids that the cell needs

Endoplasmic Reticulum

Centrioles

• Centrioles are �self-replicating organelles made up of nine bundles of microtubules and are found only in animal cells.
• They help in organizing cell division, but aren't always needed in the process.

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Cilia and Flagella

• For single-celled eukaryotes, cilia and flagella are essential for the locomotion of individual organisms.
• In multicellular organisms, cilia function to move fluid or materials past an immobile cell as well as moving a cell or group of cells.

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Eukaryotic organelles

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The Nucleus

Mitochondria

Note: Mitochondria can be shown as round

Golgi Apparatus

Endoplasmic Reticulum

• What are the two types?

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• Rough
• Smooth

Lysosomes

Organelles without membranes

Review Questions

Answer the exam questions on the sheet