2.1.1 Cell Structure

What are the three types of microscopes?

• Light microscope

• Transmission electron microscope (TEMs)

• Scanning electron microscope (SEMs)

What observations can you make with light microscopes?

Structures within eukaryotic cells:

• nuclei

• sometimes mitochondria

• sometimes chloroplasts

What observations can you make with TEM microscopes?

Internal structures within cells & organelles e.g. ribosomes, endoplasmic reticulum or lysosomes

What observations can you make with SEM microscopes?

External, 3D structure of specimens

Why are stains used in slide preparation?

Stains make it easier for cells and cell structures to be seen

What is differential staining and why is it used?

A technique using two or more chemical stains to help distinguish between different organisms or organelles in a tissue sample

How do you calculate the magnification?

magnification = image size/actual size

What is magnification?

How many times bigger the image of a specimen observed is in compared to the actual size of the specimen

What is resolution?

The ability to distinguish between two separate points

What is the role of the nucleus in eukaryotic cells?

The nucleus contains chromatin (linear DNA bound to histone proteins)→form schromosomes

What is the role of the nuclear envelope in eukarytoic cells?

The nuclear envelope separates the contents of the nucleus from the cytoplasm

It is full of pores:

→ pores allow mRNA & ribosomes to leave the nucleus, & enzymes to enter

What is the roles of the nucleolus in eukarotic cells?

It is the site of ribosome production

What is the role of the rough endoplasmic reticulum (REM)?

• Surface is covered in ribosomes

• Formed from continuous folds of membrane attached to the nuclear envelope

• Processes proteins made by ribosomes

What is the role of the smooth endoplasmic reticulum?

• Does not have ribosomes on the surface

• Involved in production, processing & storage of lipids, carbohydrates, & steroids

What is the role of the golgi apparatus?

They are flattened sacs of membrane

• Modify proteins & lipids → pack them into golgi vesicles

• Vesicles transport proteins & lipids to their destination

• Proteins that go through GA are usually exported (e.g. insulin), put into lysosomes (e.g. hydrolytic enzymes) or delivered to membrane-bound organelles

What are the roles of ribosomes in eukaryotic cells?

• Site of translation - protein synthesis

• Found freely in cytoplasm of all cells or as part of the RER

What is the role of mitochondria in eukaryotic cells?

• Site of aerobic respiration

• Surrounded by double-membrane → inner membrane folds to form cristae

What are the roles of lysosomes in eukaryotic cells?

They are specialist forms of vesicles that contain hydrolytic enzymes

• enzymes break down waste materials e.g. worn-out organelles

• cells of the immune system & cells involved in apoptosis use them a lot

What are the roles of chloroplasts in eukaryotic cells?

• Site of photosynthesis

• Surrounded by a double-membrane → thylakoids (containing chlorophyll) stack to form granum

• Grana join together to form lamella

What is the role of the plasma membrane in eukaryotic cells?

The plasma membrane controls the exchange of materials between the internal cell environment & the external environment

• partially permeable & fluid

• made of phospholipids & proteins

What is the role of the cell wall in eukaryotic cells?

• Provides structural support to a cell

• Made up of polysaccharides → cellulose in plants, peptidoglycan in most bacteria

What is the role of cilia in eukayotic cells?

Cilia are hair-like projectionns made from microtubules

• Allows movement of substances over the cell’s surface

What is the role of flagella in eukaryotic cells?

Flagella contract to provide cell movement