3.1 - 3.3 Biology - Cell Theory + Eukaryotic Cells

Organelles in all living organisms

• Cytoplasm

• Ribosome

• Cell membrane

• DNA

Ultrastructure

The internal structure of cells

Animal cells only organelles

• Microvilli

• Centrioles

Plant Cells ONLY Organelles

• Chloroplasts

• Vacuole

• Cellulose Cell Wall

Microvilli

Folded regions of the cell surface membrane that increase cell surface area for absorption

Cell Surface Membrane Function

Controls the exchange of materials between the internal cell environment and the external environment

- ALWAYS say cell SURFACE membrane

What contains the nucleus?

a double membrane called the nuclear envelope

Nuclear pores - Function

• Allows mRNA and ribosomes to travel out of the nucleus

• Allows enzymes and signalling molecules to travel into the nucleus

What are chromosomes made from?

• chromatin

• Sections of linear DNA tightly wound around proteins called histones

Nucleolus function

ribosome production

Mitochondria Function

Site of aerobic respiration

What surrounds the mitochondria?

• A double membrane

• Inner membrane folded to form cristae

What does the matrix of mitochondria contain?

• Enzyms needed for aerobic respiration

mitochondrial DNA

replication of mitochondria before cell division

Where can ribosomes be found?

• rough endoplasmic reticulum

• Cytoplasm

What are ribosomes?

Complex of ribosomal RNA and proteins

Riboosome function

Site of translation

Size of ribosomes in eukaryotic cells

80s ribosomes

Size of ribosomes in prokaryotes

70s ribosomes

What organelles contain 70s ribosomes?

• mitochondria

• chloroplasts

Rough endoplasmic reticulum - what is it made of?

• folds of membrane continuous with the nuclear envelope

• surface covered in ribosomes

RER Function

• folds and processes proteins in the lumen, made on the ribosomes

Smooth Endoplasmic Reticulum Function

the production, processing and storage of lipids, carbohydrates and steroids

SER - what is it made from?

• folds of membrane

• no ribosomes on surface

Golgi apparatus

• flattened sacs of membrane

• regular, stacked

Golgi Apparatus Function

• modify proteins and lipids

• packaging them into Golgi vesicles

• vesicles transport the proteins and lipids to their required destination

What makes up the lysosome?

• specialist forms of vesicle which contain hydrolytic enzymes

Lysosome Function

• break down waste materials such as worn-out organelles

• used by cells of the immune system and in apoptosis

Microtubules

• filaments of protein

• used to move substances around inside a cell

• to support the shape of a cell from the inside

Centrioles formed from what?

microtubules

Centriole Function

• Two centrioles at right angles to each other form a centrosome

• Centrosome organises the spindle fibres during cell division

Organelles

specialised parts of a cell that carry out a particular function

Packaging and transporting proteins in a cell

1. The DNA in the nucleus is used to make an mRNA copy of the gene.

2. This leaves the nucleus through a Nuclear pore

3. A ribosome on the RER attaches to the mRNA.

4. Ribosomes synthesise the protein.

5. Transport vesicles containing the proteins are pinched off from the Rough endoplasmic reticulum

6. These vesicles fuse with the membrane of the Golgi apparatus, and proteins are released into this organelle.

7. Inside the Golgi apparatus, the proteins are

processed, modified and packaged for release.

8. Vesicles containing the modified proteins are pinched off from the Golgi apparatus.

9. These travel to the cell surface membrane and fuse with the cell surface membrane.

10. The modified proteins are released to the outside of the cell by exocytosis