Cell structure and microscopes

Question 1

What is the structure and function of Lysosomes?

Answer 1

They are vesicles that contain hydraulic enzymes( lysozymes) to break bonds and break down molecules.

Question 2

What is the structure and function of Centrioles?

Answer 2

They are paired barrel shaped organelles located in the cytoplasm of animal cells near the nuclear envelope. They organise microtubules that serve as the cells skeletal system.

Question 3

What is the structure and function of the cytoskeleton?

Answer 3

Its made up of microtubules, actin filaments and intermediate filaments/ a network of protein fibres. They form cell shape, allow cell to move and allows organelles to move within the cell.

Question 4

What is the structure and function of cell surface membrane?

Answer 4

Plasma membrane - partially permeable. It separates the interior of the cell from the surrounding environment

Question 5

What is the structure and function of ribosomes?

Answer 5

They are very small (20nm), spherical structures which are free in the cytoplasm. They make/assemble proteins for protein synthesis and make/assemble protiens which are going to be used inside the cell.

Question 6

What is the structure and function of the rough endoplasmic reticulum?

Answer 6

It continues with the outer nuclear membrane. It is folds of membrane that have ribosomes on their outer surface. It produces proteins from ribosomes on its surface and sends them to another organelle to be packaged and sent out of the cell.

Question 7

What is the structure and function of the Golgi apparatus?

Answer 7

It is fused cisternae, flattened membrane. It modifies (adds molecules to proteins), packages and labels substances like proteins before sending them in Golgi vesicles to different parts of the cell.

Question 8

What is the structure and function of the smooth endoplasmic reticulum?

Answer 8

Its a long network of folded tube like structures. It makes, moves and packages lipids and carbohydrates.

Question 9

What is the structure and function of the nucleus?

Answer 9

It contains DNA which is linear and is tightly wound around histone proteins to form thread like structures called chromosomes.

Question 10

What is the structure and function of the nucleolus?

Answer 10

It is the largest structure in the nucleus. It makes ribosomal RNA to form functioning ribosomes.

Question 11

What is the structure and function of the nuclear envelope?

Answer 11

The nucleus is surrounded by a double membrane called the nuclear envelope which contains nuclear pores. It allows some molecules to move out of the nucleus NOT DNA.

Question 12

What is the structure and function of mitochondria?

Answer 12

Double membrane - cristae, matrix, outer and inner membrane, inter membrane space. Its the site of aerobic respiration - produces ATP

Question 13

What is the structure and function of the cytoplasm?

Answer 13

Cytosol - gel like substance.
Where all the chemical reactions in the cell take place and where all the membrane bound organelles are held.
It separates the organelles from the external environment.

Question 14

What is the difference between a prokaryotic and a eukaryotic cells?

Answer 14

Eukaryotic cell: contains a nucleus and membrane bound organelles.
Prokaryotic cell: No membrane bound organelles, no nucleus so genetic material free floating.

Question 15

What is the cell wall in a prokaryotic cell made from?

Answer 15

Peptidoglycan

Question 16

What is the structure and function of a capsule in a prokaryotic cell?

Answer 16

Around the outside of cell, helps prokaryotic cell cling to each other and various surfaces, its a defence against host cells and prevents cell from drying out.

Question 17

What is the structure and function of pili in a prokaryotic cell?

Answer 17

They are short hair like structures on cell surface which increase surface area, they are involved in adherence to surfaces - facilitates infection, they have a role in movement.

Question 18

What is the structure and function of a flagellum in a prokaryotic cell?

Answer 18

Some prokaryotic cells have them, they help an organism in movement, they are sensory organs so they detect temperature and pH and they get energy from chemiosmosis which is movement of H+ across a biological membrane - generates ATP

Question 19

What is the structure and function of free chromosomal DNA in a prokaryotic cell?

Answer 19

Nucleoid region
allows direct connection to translation and transcription
contains genetic material

Question 20

What is the structure and function of a ribosome in a prokaryotic cell?

Answer 20

Smaller than 70s
Different type of ribosome made of proteins - tRNA

Question 21

Explain the cell surface membrane of a plant cell

Answer 21

made out of cellulose - beta glucose chains hold together by hydrogen bonds. fully permeable to and contents of the cell push against it allowing it to support the cell and those around it. If there is not enough water present the cell wall holds onto the water and supports - stops cell from collapsing, if there is too much water present the cell wall prevents lysis
(cell bursting)

Question 22

Explain the structure and function of chloroplasts

Answer 22

They are found in the areas above ground in plants. They have a double membrane, fluid in the centre in the stomata. Internal membranes are made of flattened sacs called thylakoids and stacked to make grana. The grana contain photosynthetic pigments like chlorophyll

Question 23

Explain the structure and function of the permanent vacuole

Answer 23

Membrane bound sac containing cell sap. The membrane is often called tonoplast. It stores cell sap and may also store nutrients and proteins. Keeps cell turgid (swollen and hard). Some play a similar role to lysosomes - digest

Question 24

What organelles does a plant cell have that a animal cell doesn’t?

Answer 24

vacuole
chloroplasts
cellulose cell wall

Question 25

What organelles does an animal cell have that a plant cell doesn't?

Answer 25

Centrioles lysozymes

Question 26

What happens first in the process 'organelles involved in protein synthesis'

Answer 26

Proteins are synthesised at the ribosomes.

Question 27

What happens second in the process 'organelles involved in protein synthesis'

Answer 27

Proteins pass into the cisternae of RER and are packaged into vesicles.

Question 28

What happens third in the process 'organelles involved in protein synthesis'

Answer 28

Vesicles move towards the Golgi via the cytoskeleton.

Question 29

What happens fourth in the process 'organelles involved in protein synthesis'

Answer 29

Vesicles fuse with cis surface of Golgi. Proteins enter and are modified. They leave in vesicles via the trans face of the Golgi.

Question 30

What happens fifth in the process 'organelles involved in protein synthesis'

Answer 30

Vesicles move to plasma membrane to release proteins that are needed are needed outside of the cell. Some are transported round the cell to where they are needed.

Question 31

What is the equation for magnification?

Answer 31

Magnification= size of image/actual size

Question 32

What is magnification?

Answer 32

It is the number of times greater than that an image is than the object.

Question 33

What is resolution?

Answer 33

It is the ability to distinguish between two objects very close together, the higher the resolution the better the detail that can be seen.

Question 34

What is a TEM?

Answer 34

Transmission electron microscope

Question 35

What is a SEM?

Answer 35

Scanning electron microscope

Question 36

Describe light microscopy

Answer 36

>coloured images >living specimens >requires a light source >not very detailed images >easy to use >affordable

Question 37

Describe TEM microscopy

Answer 37

>electrons pass through sample >electromagnets > max resolution = 0.5 nm

Question 38

Describe SEM microscopy

Answer 38

>electrons reflected off the surface >image of only the surface > max resolution = 3-10 nm

Question 39

What are the similarities between a light microscope and a TEM?

Answer 39

>2D Images >Thin samples

Question 40

What are the similarities between a light microscope and a SEM?

Answer 40

>Objective lens >Use reflection

Question 41

What are the similarities between a SEM and a TEM?

Answer 41

> Difficult to use > Electron guns > Detailed > Black and white > Stream of electrons > Large > Expensive > Dead specimen > Viewed in a vacuum > Maximum magnification = 500,0000

Question 42

What are the similarities between a light microscope, a SEM and a TEM?

Answer 42

> Stream of energy to view stream > Make sample appear bigger

Question 43

What are the features of a laser scanning confocal microscope?

Answer 43

Maximum resolution = 200 nm 2D/3D Image Coloured images Used to observe an object at a certain depth within a cell Can view living cells

Question 44

How does an image produced by laser scanning confocal microscope differ from that produced by an electron microscope?

Answer 44

It has a lower resolution Can see movement

Question 45

What is the average magnification and resolution of a light microscope?

Answer 45

Magnification = 1500 x Resolution = 200nm

Question 46

What is the average magnification and resolution of a TEM?

Answer 46

Magnification = 500000 x Resolution = 0.2nm

Question 47

What is the average magnification and resolution of a SEM?

Answer 47

Magnification = 100 000 x Resolution = 0.2nm

Question 48

Explain how to measure the diameter of the nucleus of a cell when observing cells through a light microscope

Answer 48

> calibrate eye piece graticule using stage micro meter - calculate the length of one epu. > measure the diameter of the nucleus in epu (graticule units) > take repeat measurements and calculate a mean diameter > use calibrated epu to calculate diameter of nucleus in um.

Question 49

What needs to be done on a drawing of image of something observed under a microscope?

Answer 49

> A scale > Labels > Sharp pencil > Title > No shading/cross hatching

Question 50

What is the formula for the volume of a sphere?

Answer 50

V = 3/4 x Pi x r^3

Question 51

Why do we stain samples?

Answer 51

To provide a contrast - different parts of the cell take up different amounts of stain.

Question 52

What is differential staining?

Answer 52

It can be used to differentiate between types of cells that otherwise cannot be distinguished. E.g; gram staining - two different bacteria one pink, one purple, one +1, one -1

Question 53

What is a dry mount?

Answer 53

Is used to view thin slices which are cut with a sharp blade, no liquid - such as hair samples, pollen and insects.

Question 54

What is a wet mount?

Answer 54

Is when the specimen is covered with a drop of liquid such as water, oil or a stain. A cover slip is gently placed over the sample at an angle to stop any air bubbles.

Question 55

What is a squash slide?

Answer 55

When a sample is squashed between the slide and the cover slip. Its a type of wet mount and is used for soft tissues such as root tips.

Question 56

What is a smear slide?

Answer 56

Is when a slide is used to smear the sample across another slide such as a thin layer of blood.

Question 57

What are two examples of positively charged stains?

Answer 57

Crystal violet and methylene blue - they are attracted to the negatively charged components such as organelles.

Question 58

What are two examples of negatively charged stains?

Answer 58

Nigrosine and Congo red - are attracted to the outside of cells.

Question 59

How to use a light microscope?

Answer 59

1. Prepare the slide - glass slide and cover slip 2. Adjust the light - light source and adjust intensity 3. Start with low power - lowest mag objective lens to locate specimen 4. Focus - roughly focus with coarse focus knob then fine-tune with fine focus knob 5. Increase magnification - switch mag higher for more detail - refocus when changing 6. Analyse the specimen - noting its structure and details 7. Record observations - for later reference