Module 2.1 - Cell structure and Microscopy

Question 1

What organelles to plant cells have extra that animal cells don’t?

Answer 1

> A cell wall with plasmodesmata (‘channels for exchanging substances with adjacent cells).
A permanent or large vacuole (compartment that contains cell sap).
Chloroplasts

Question 2

What type of cells are both plant and animal cells?

Answer 2

Eukaryotic cells.

Question 3

List all the organelles in a animal cell?

Answer 3

Plasma (cell surface) membrane, nucleus, lysosome, ribosome, rough endoplasmic reticulum (RER), smooth endoplasmic reticulum (SER), vesicle, golgi apparatus, mitochondrion, centriole, cilia and flagellum.

Question 4

What is the structure and function of a plasma membrane?

Answer 4

Structure - Consists of a lipid bilayer with embedded proteins.
Function - Regulates the movement of substances into and out of the cell and protects the cell from its surroundings. Also, has receptor molecules on it which allows it to respond to chemicals like hormones.

Question 5

What is the structure and function of a cell wall?

Answer 5

Structure - A rigid structure that surrounds plant cells and is made mainly of the carbohydrate cellulose.
Function - Supports plant cells.

Question 6

What is the structure of the nucleus?

Answer 6

Structure - A large organelle surrounded by a nuclear envelope (double membrane) which contains many pores. The nucleus contains chromatin (made from DNA and proteins) and a structure called the nucleolus (does’t have a membrane and contains RNA)

Question 7

What is the function of the nucleus?

Answer 7

Function - Controls the cell’s activities, stores the organism’s genome, transmits genetic information, ribosomes are made in the nucleolus, nuclear envelope separates content of the nucleus from the rest of the cell and the pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm.

Question 8

What is the structure and function of lysosomes?

Answer 8

Structure - A round organelle surrounded by a membrane, with no clear internal structure.
Function - Contains digestive enzymes (hydrolytic) separate from the rest of the cell and can be used to digest invading cells or to break down worn out components of the cell (for reuse).

Question 9

What is the structure of ribosomes?

Answer 9

Structure - A very small organelle (about 20 nm in diameter), made up of proteins and RNA, not surrounded by a membrane, made in nucleolus, some remain free in the cytoplasm and others attach to the rough endoplasmic reticulum.

Question 10

What is the function of ribosomes?

Answer 10

Function - The site of protein synthesis.

Question 11

What is the structure and function of the RER?

Answer 11

Structure - A system of membranes containing fluid filled cavities (cisternae) and coated with ribosomes.
Function - Folds and processes proteins that have been made at the ribosomes.

Question 12

What is the structure and the function of the SER?

Answer 12

Structure - Similar to the RER but with no ribosomes.

Function - Synthesises and processes lipids.

Question 13

What is the structure and function of the vesicle?

Answer 13

Structure - A small fluid-filled sac in the cytoplasm, surrounded by a membrane.
Function - Transports substances in and out of the cell (via the plasma membrane) and between organelles.

Question 14

What is the structure and function of the Golgi apparatus?

Answer 14

Structure - A group of fluid-filled, membrane-bound, flattened sacs. Vesicles are often seen at the edges of the sacs.
Function - It processes and packages new lipids and proteins. It also makes lysosomes.

Question 15

What is the structure of mitochondrion?

Answer 15

Structure - Usually oval shaped but can be spherical/rod-shaped/branched, they have a double membrane - the inner one is folded to form structures called cristae, inside is the matrix (contains enzymes involved in respiration).

Question 16

What is the function of the mitochondrion?

Answer 16

The site of aerobic respiration where ATP is produced . They’re found in large numbers in cells that are very active and require a lot of energy.

Question 17

What is the structure of a chloroplast?

Answer 17

A small, flattened structure found in plant cells. Surrounded by a double membrane or envelope. Contain loops of DNA and starch grains.

Question 18

What is the function of a chloroplast?

Answer 18

The site where photosynthesis takes place. Some parts happen in the grana, and other parts in the stroma.

Question 19

What is the structure and the function of centrioles?

Answer 19

Structure - Small, hollow cylinders, made of microtubules . Found in animal cells and some plant cells.
Function - Involved with the separation of chromosomes during cell division and the formation of cilia and undulipodia.

Question 20

What is the structure and function of the cilia?

Answer 20

Structure - Small, hair-like structures found on the surface membrane of some animal cells and each contain protein microtubules.
Function - The microtubules allow the cilia to move, this movement is used by the cell to move substances along the cell surface.

Question 21

What is the structure and function of the cytoskeleton?

Answer 21

Structure - A network of protein structures within the cytoplasm.
Function - Give support and mechanical strength, keep the cells shape stable and allow cell movement.

Question 22

What is the structure and function of the flagellum?

Answer 22

Structure - Like cilia but longer, stick out from the cell’s surface.
Function - The microtubules contract to make the flagellum move. Flagella are used like outboard motors to propel cells forward.

Question 23

What is the difference between prokaryotic and eukaryotic cells in size?

Answer 23

Prokaryotes are extremely small (less than 2 micrometers in diameter) whereas eukaryotes are far larger (10-100 micrometers).

Question 24

What are the other differences between eukaryotic and prokaryotic cells with their DNA storage?

Answer 24

In eukaryotic cells DNA is linear and there is a nucleus present where the DNA is stored. Whereas, in prokaryotic cells the DNA is circular and there is no nucleus so it’s free in the cytoplasm.

Question 25

What are the differences between the membranes/cell walls eukaryotic and prokaryotic cells have?

Answer 25

Eukaryotic - has no cell wall (in animals), cellulose cell wall (in plants) or chitin cell wall (in fungi).
Prokaryotic - Cell wall made of polysaccharide but not cellulose or chitin

Question 26

What are the differences between the organelles eukaryotic and prokaryotic cells have?

Answer 26

Prokaryotic have few organelles and none that are membrane-bound (e.g. no mitochondria), has a flagella of helix shape and small ribosomes and a much less developed cytoskeleton with no centrioles. Whereas, eukaryotic cells have many organelles like mitochondria, when flagella is present has a different structure and larger ribosomes.

Question 27

What is the cytoskeleton?

Answer 27

The network of protein threads running through the cytoplasm surrounding the organelles in the cell.

Question 28

What are the four main functions of the cytoskeleton?

Answer 28

> Support the cell’s organelles keeping them in position.
Help strengthen the cell and maintain it’s shape.
Responsible for the movement of materials within the cell (e.g. chromosomes).
The proteins of the cytoskeleton can also cause the cell to move (e.g. sperm cells).

Question 29

Describe the stages of protein synthesis/secreting a protein?

Answer 29

1) Transcription - happens in the nucleus. During this process a molecule of messenger RNA (mRNA) coding for a protein, is created from a DNA template.
2) Translation - New proteins produced at the RER are folded and processed. Protein is synthesised.
3) Transported to the Golgi apparatus.
4) At the Golgi apparatus protein is modified and packaged into a vesicle.
5) The vesicle containing the protein is delivered to its target or released from cell by exocytosis.

Question 30

What is the equation for magnification?

Answer 30

magnification = image size / actual size

Question 31

What is resolution?

Answer 31

Resolution of an image is the level of detail/sharpness you can see.

Question 32

What is magnification?

Answer 32

The magnification of an object describes the increase in size of the image compared to the true size of the object.

Question 33

Describe a light microscope?

Answer 33

> Uses light.
Has a lower resolution than electron microscopes, usually used for whole cells or tissues.
The maximum useful magnification of a light microscope is about x1500.

Question 34

Describe a laser scanning confocal microscope?

Answer 34

> Uses laser beams to scan a specimen which is usually tagged with fluorescent dye.
Laser causes the dye to fluorescence (give off light), focused through a pinhole onto a detector and generates an image which can be in 3D.
The pinhole means that out of focus light is blocked so produces a clearer image than a normal light microscope.
Can be used to look at objects at different depths in thick specimens.
High resolution and contrast.

Question 35

Describe electron microscopes?

Answer 35

> Use electrons instead of light to form an image.
Have a higher resolution so give more detailed images so can have a higher magnification.
Two different types, TEM and SEM.

Question 36

Describe a transmission electron microscope?

Answer 36

> Use electromagnets to focus a beam of electrons which is then transmitted through the specimen.
Denser parts of the specimen absorb more electrons, which makes them look darker on image.
Provide high resolution images.
Can only be used on thin specimens

Question 37

Describe a scanning electron microscope?

Answer 37

> Scan a beam of electrons across the specimen.
Knocks off electrons which are gathered in a cathode ray tube to form an image.
Shows surface of image and can be 3D.
Lower resolutions than TEM’s.

Question 38

Why do slides/specimens need to be stained?

Answer 38

Sometimes the object being viewed is transparent/colourless which makes the whole thing look white for all the light rays/electons just pass straight through.

Question 39

What is the resolution that can be achieved of a light microscope?

Answer 39

50-200nm

Question 40

What is the resolution that can be achieved of an electron microscope?

Answer 40

0.05-1.0nm