2.3 Eukaryotic Cells

Topic 2 Cells

Eukaryotic Cells2.3.1 Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell. The diagram should show free ribosomes, rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, mitochondrion and nucleus.

2.3.2 Annotate the diagram from 2.3.1 with the functions of each named structure.

2.3.3 Identify structures from 2.3.1 in electron micrographs of liver cells.

Eukaryotic Cells2.3.4 Compare prokaryotic and eukaryotic cells. Differences should include:

• naked DNA versus DNA associated with proteins• DNA in cytoplasm versus DNA enclosed in a nuclear envelope• no mitochondria versus mitochondria• 70S versus 80S ribosomes• eukaryotic cells have internal membranes that compartmentalize

their functions.

2.3.5 State three differences between plant and animal cells.

Eukaryotic Cells2.3.6 Outline two roles of extracellular components:

The plant cell wall maintains cell shape, prevents excessive water uptake, and holds the whole plant up against the force of gravity.

Animal cells secrete glycoproteins that form the extracellular matrix. This functions in support, adhesion and movement.

A Generalised Animal Cell

A Generalised Animal Cell

Ref: Advanced Biology, Roberts,Riess

Parts of a Generalised Animal Cell

You should know the function of the following parts:– Ribosomes

• Site of protein synthesis– Rough Endoplasmic Reticulum

• Transportation of proteins synthesised by the attached ribosomes– Lysosome

• Small vesicles containing digestive enzymes– Golgi Apparatus

• Packaging of proteins into vesicles– Mitochondrion

• Site of aerobic respiration– Nucleus

• Contains the chromosomes (genetic information) for the cell• Controls the activities of the cell

Mitochondria

Double membrane: – Outer membrane and

Inner membrane.

Inner membrane is folded forming cristae

The interior contains an organic matrix containing chemical compounds.

Rough Endoplasmic Reticulum and Ribosomes

A membrane system of flattened parallel cavities which are interconnected and covered with ribosomes.An intracellular transport system

Golgi Apparatus

Consists of a stack of flattened cavities which package substance produced by the cell into vesicles.These vesicles can fuse with the cell membrane (exocytosis) or become lysosomes (digestive vesicles).

Golgi Apparatus

Ref: Advanced Biology Roberts etal.

Prokaryotic vs EukaryoticFeature Prokaryotic Cells Eukaryotic Cells

Type of Genetic material

A naked loop of DNA Chromosomes consisting of strands of DNA wrapped around associated proteins (Histones)

Location of genetic material

In the cytoplasm in a region called the nucleoid

In the nucleus, inside a nuclear membrane (nuclear envelope)

Mitochondria Not present (mesosome used instead)

Always present

Ribosomes Smaller sized (70S) Larger sized (80S)

Organelles No membrane bound organelles

Many are presenteg: ER, Golgi Apparatus, lysosome

S = svedburg units. A measure of the size of organelles

Plant vs Animal Cells

Plant vs Animal Cells

Plant and animal cells have many similarities because they are both eukaryotic.They also have some differences:

Feature Animal Plant

Cell Wall Not present Present (made of cellulose)

Chloroplasts Not present Present in plant cells that photosynthesise

Carbohydrate Storage

Glycogen Starch

Vacuole Not usually present. If present they are small

Large and permanent

Plant Cell Walls

The main component of plant cell walls is cellulose.Cellulose molecules are arranged in bundles called microfibrils.The function of the plant cell wall is to provide strength and support the plant.The microfibrils are laid down in a criss-cross way across the cytoplasm.These give the cell great tensile strengthThey also allow high pressure to be built up as a result of Osmosis. This is called Turgor Pressure.

IBO guide:2.3.1 Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell.The diagram should show free ribosomes, rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, mitochondrion and nucleus. (The term Golgi apparatus will be used in place of Golgi body, Golgi complex or dictyosome).

2.3.2 Annotate the diagram from 2.3.1 with the functions of each named structure.

IBO guide:2.3.3 Identify structures from 2.3.1 in electron micrographs of liver cells.

2.3.4 Compare prokaryotic and eukaryotic cells. Differences should include:

• naked DNA versus DNA associated with proteins• DNA in cytoplasm versus DNA enclosed in a nuclear envelope• no mitochondria versus mitochondria• 70S versus 80S ribosomes• eukaryotic cells have internal membranes that compartmentalize

their functions.

IBO guide:2.3.5 State three differences between plant and animal cells.

2.3.6 Outline two roles of extracellular components:

The plant cell wall maintains cell shape, prevents excessive water uptake, and holds the whole plant up against the force of gravity.

Animal cells secrete glycoproteins that form the extracellular matrix. This functions in support, adhesion and movement.