Cytology & Microscopy

Question 1

Eukaryote

Answer 1

is any organism consisting of one or more cells the contain DNA in a membrane- bound nucleus, separate from the cytoplasm (e.g animals, plants and fungi).

Question 2

Nucleus structure

Answer 2

Contains coded genetic information in the form of dna molecules. Often the biggest single organelle in the cell.

DNA is contained within a double membrane called a nuclear envelope to protect it from damage in the cytoplasm. DNA associates with protein (histones) form complex called chromatin, which coil and condense form chromosomes,

Question 3

Nucleus function

Answer 3

DNA directs the synthesis of all proteins required by the cell (but actually happens at the ribosome). DNA controls the metabolic activities of the cell, as many of these proteins are the enzymes necessary for metabolism to take place.

Question 4

Nucleolus function

Answer 4

An area within the nucleus and is responsible for producing ribosomes it is composed of proteins and RNA. RNA is used to produce ribosomal RNA (rRNA) which is then combined with proteins to form ribosomes.

Question 5

Nuclear envelope function

Answer 5

It contains nuclear pores that allow molecules to move into and out of the nucleus. DNA too large To leave the nucleus To the site of protein synthesis in the cell cytoplasm. Instead it is transcribed into smaller RNA molecules which are exported via the nuclear pores.

Question 6

Rough ER structure

Answer 6

A network of membranes enclosing flattened sacs called cisternae. It is connected to the outer membrane of the nucleus

Question 7

Rough ER function

Answer 7

They have ribosomes bound to the surface and is responsible for the synthesis and transport of proteins.

Question 8

Smooth ER structure

Answer 8

A network of membranes enclosing flattened sacs called cisternae. It is connected to the outer membrane of the nucleus

Question 9

Smooth ER function

Answer 9

They are responsible for lipids and carbohydrates synthesis, and storage. Secretory cells, which release hormones or enzymes, have more rough endoplasmic reticulum then cells that do not release proteins.

Question 10

Golgi apparatus structure?

Answer 10

Golgi Apparatus has a similar structure to the smooth endoplasmic reticulum. It is a compact structure formed of cisternae and has not contain ribosomes.

Question 11

Golgi apparatus function

Answer 11

It has a role in modifying proteins and packaging them into vesicles. These may be secretory vesicles, if the proteins are destined to leave the cell, or lysosomes, which stay in the cell.

Question 12

Ribosomes structure

Answer 12

Ribosomes can be free floating in the cytoplasm or attached to an end of placement reticulum, forming a rough endoplasmic reticulum. They are not surrounded by a membrane and they are constructed of RNA molecules made in the nucleolus of the cell.

Question 13

Ribosomes function

Answer 13

Ribosomes are the site of protein synthesis. Mitochondria and chloroplast also contain ribosomes, as the prokaryotic cells.

Question 14

Mitochondria structure

Answer 14

The number of mitochondria and if so is generally a reflection of the amount of energy it uses. Mitrochondrial have a double membrane the inner membrane is highly folded to form structures called cristae in the the interior is called the matrix. The membrane forming the cristae contains the enzymes used in aerobic respiration. Mitochondria also contain a small amount of DNA, (mt)DNA. They can produce their own enzymes and reproduce themselves.

Question 15

Mitochondria function

Answer 15

Mitochondria are essential organelles in almost all eukaryotic cells. They are the sight of final stages of cellular respiration, where the energy stored in the bonds of complex, organic molecules is made available for the sale to use by the production of the molecule ATP.

Question 16

Lysosomes structure

Answer 16

There are specialised forms of vesicles that contain hydrolytic enzymes.

Question 17

Lysosomes function

Answer 17

They are responsible for breaking down waste materials in cells including old organelles. They playing important role in the immune system as they are responsible for breaking down pathogens ingested phagocytise cells. They also playing important role in programmed cell death or apoptosis.

Question 18

Centrioles structure

Answer 18

Centrioles are a component of the cytoskeleton present in most eukaryotic cells. They are composed of microtubules.

Question 19

Centrioles function

Answer 19

To associated centrioles from the centrosome, which is involved in the assembly of organisation of the spindle fibres during cell division. In organisms with the flagella and cilia, centrioles Are thought to play a role in the positioning of the structures.

Question 20

Cilia structure

Answer 20

Cilia can be mobile or stationary. Each cilium contains two central microtubules (black circles) surrounded by nine pairs of microtubules arranged like a “wheel”. Pairs of parallel microtubules slide over each other causing the cilia to move in a beating motion

Question 21

Cilia function

Answer 21

Stationary cilia are present on the surface of many cells and have an important function to sensory organs such as the nose. Mobile cilia beat in a rhythmic manner creating a current and cause fluids or objects adjacent to the cell to move. For example they are present in the trachea and in the fallopian tubes.

Question 22

Plasma membrane structure

Answer 22

The plasma membrane is composed of a phospholipid bilayer, which is two layers of phospholipids back-to-back. Phospholipids are lipids with a phosphate group attached to them. The phospholipids have one head and two tails. The head is polar and hydrophilic. The plasma membrane is impermeable to ions and most water-soluble molecules.

Question 23

Plasma membrane function

Answer 23

The primary function of the plasma membrane is to protect the cell from its surroundings. The plasma membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix and other cells to help group cells together to form tissues. The cell membrane interacts with the cell membrane of adjacent cells e.g. to form plant and animal tissues. The cell membrane is primarily composedof proteins and lipids. While lipids help to give membranes their flexibility andproteins monitor and maintain the cell’s chemical climate and assist in the transfer of molecules across the membrane.

Question 24

Cytoskeleton structure

Answer 24

Present throughout the cytoplasm of all eukaryotic cells. A network of fibres necessary for the shape and stability of a cell. It also holds organelles in place and the cytoskeleton also controls cell movements and the movement of organelles within the cells too.

Question 25

Cytoskeleton function 
(Microfilaments)

Answer 25

Contractile to fibres formed from the protein actin. Responsible for cell movement and also cell contraction cytokinesis (cytoplasm divides to form two daughter cells).

Question 26

Cytoskeleton function 
(Microtubules)

Answer 26

Globular tubulinn proteins polymerise to Phone tubes that are used to form a scaffold like structure that determines the shape of the cell. Also at as tracks for the movement of organelles including vesicles around the cell. Spindle fibres too are composed of microtubules.

Question 27

Cytoskeleton function 
(Intermediate fibres)

Answer 27

These fibres give mechanical strength to cells and help maintain the integrity.

Question 28

Flagella structure

Answer 28

Flagella have a whip like structure In our extensions that protrude from some cell types, just like cilia (but are more hair- like ). Flagella along with and cilia, but cilia are usually present in much greater numbers.

Question 29

Flagella function

Answer 29

Flagella are used primarily to enable cell mobility. In some cells they are used as sensory organelles , detecting chemical changes in the cell’s environment.

Question 30

Differences between prokaryotic and eukaryotic cells

Answer 30

• Eukaryotic genes are generally switched on and off individually
• Much more complex
• DNA present within the nucleus and exists as multiple chromosomes (supercoiled) each one wraps around a number of proteins called histones, forming a complex for efficient packaging. Complex is called chromatin, which coils and condenses to form chromosomes.
• Membrane bound organelles (including mitochondria and chloroplast)
• Many are multicellular
• The structure of DNA is the same but it’s packaged differently. Generally only one molecule of DNA, a chromosome, which is supercoiled , more compact.
• Ribosomes are smaller
• Cell wall is made up from peptidoglycan a complex polymer formed from amino acids and sugars.
• Flagella are thinner. Energy to rotate the filament that forms the flagellum is supplied from the process of chemiosmosis, not from ATP like in eukaryotic cells.

Question 31

Resolution

Answer 31

Resolution is the ability to distinguish/ discriminate between two points

Question 32

How to calculate the total magnification

Answer 32

The total magnification is the eyepiece magnification multiplied by the objective magnification
The maximum magnification of a light microscope is x1500