Cell Structure And Microscopy

Question 1

What are prokaryotic cells?

Answer 1

They are single celled organisms with no nucleus. They are smaller and simpler

Question 2

What are eukaryotic cells?

Answer 2

They are more complex cells and include plant and animal cells.

Question 3

What is the cell ultra structure?

Answer 3

The organelles and internal structure of cells

Question 4

What are animal and plant cells?

Answer 4

Both eukaryotic

Question 5

What are the typical organelles of an animal cell?

Answer 5

-Plasma membrane
-Rough endoplasmic reticulum
-Nucleolus
-Nucleus
-Smooth endoplasmic reticulum
-Mitochondria
-Cytoplasm
-Golgi apparatus
-Nuclear envelope
-Ribosomes

Question 6

What are the typical organelles of a plant cell?

Answer 6

-Plasma membrane
-Rough endoplasmic reticulum
-Smooth endoplasmic reticulum
-Nucleolus
-Nucleus
-Nuclear envelope
-Mitachondria
-Cytoplasm
-Golgi apparatus
-Ribosomes
-Lysosome
-Plasmodesmata
-A vacuole
-Chloroplast

Question 7

What is the plasma membrane and what does it do?

Answer 7

It is the membrane found on the surface cells. This is mainly made of lipids and proteins.
It regulates the movement of substances through the membrane and has receptor molecules which allow responses and detection of chemical messengers.

Question 8

What is a cell wall and what is its function?

Answer 8

A rigid structure on plant cells mainly made of the carbohydrate cellulose. It supports plant cells

Question 9

What is a nucleus and what does it do?

Answer 9

A nucleus is a large organelle surrounded by a nuclear envelope with pores. It contains chromatin and often a nucleolus. It controls the cells activities and the nucleolus makes ribosomes.

Question 10

What is a lysosome and what is its function?

Answer 10

It is a round organelle surrounded by a membrane with no clear internal structure. It contains digestive enzymes and keeps these separate from the cytoplasm

Question 11

What is a ribosome and what is its function?

Answer 11

It is a very small organelle that is made of proteins and RNA. It is not surrounded by a membrane. It is also the site where proteins are made.

Question 12

What is the rough endoplasmic reticulum and what does it do?

Answer 12

It is a system of membranes enclosing a fluid filled space. The surface is covered in ribosomes. It folds and processes proteins.

Question 13

What is the smooth endoplasmic reticulum and what does it do?

Answer 13

It is a system of membranes enclosing a fluid filled space. These Synthesis and process lipids.

Question 14

What is a vesicle and what does it do?

Answer 14

It is a small fluid filled sac in the cytoplasm surrounded by a membrane. It transports substances around, and into and out of a cell.

Question 15

What is the Golgi apparatus and what does it do?

Answer 15

It is a group of fluid filled membrane bound flattened sacs that process and package new lipids and proteins. It also makes lysosomes.

Question 16

What is the mitachondria and what does it do?

Answer 16

It is usually oval shaped and has a double membrane. The inner one is folded to form structures called cristae. Inside is the matrix which contains enzymes involved in respiration. It is the site of aerobic respiration.

Question 17

What is a chloroplast and what does it do?

Answer 17

It is a small flattened structures found in plant cells surrounded by a double membrane. It has membranes inside called thylakoid membranes. These are stacked uo in some parts to form grana, which can be stacked up to form granum. Grana are linked together by lamellae which are thin flat pieces of thylakoid membrane. Chloroplasts are the site of photosynthesis. Some happens in the grana and others occur in the stroma, which is a thick fluid found in chloroplast.

Question 18

What is a centriole and what does it do?

Answer 18

They are small hollow cylinders made of microtubules. They are involved in the separation of chromosomes during cell division.

Question 19

What are cilia and what do they do?

Answer 19

Small hair like structures found on the surface of some membranes. They have 9 pairs of microtubules on the outside and 2 microtubules on the inside. These move substances along a membrane.

Question 20

What is a flagellum and what does it do?

Answer 20

They are like cilia. They stick out from the cell surface and are surrounded by the plasma membrane. They have 2 microtubules on the inside and 9 pairs on the outside. These contract to make the flagellum move which can propell the cell forwards.

Question 21

Explain the process of protein production in a eukaryotic cell.

Answer 21

Proteins are made at ribosomes either on free floating ones or ones on the rough endoplasmic reticulum. New proteins produced at the RER are folded and processes then transported in a vesicle to the golgi apparatus. They then undergo further processing and packaging. They are then packaged into a vesicle and transported around or out of the cell.

Question 22

What is the cytoskeleton?

Answer 22

A network of fibres necessary for the shape and stability of a cell

Question 23

What components make up the cytoskeleton and wjat do they do?

Answer 23

1) Microfilaments:
Contractile fibres formed by the protein actin. These are responsible for cell movement and contraction during cytokenesis
2) Microtubules:
Globular tubulin proteins polymerase to form tubes that are used to form scaffold like structures that determine the shape of a cell. They also act as tracks for organelle movement.
Spindle fibres are also composed of microtubules.
3) Intermediate fibres:
Give mechanical strength to cell to help maintain their integrity

Question 24

What are the functions of the cytoskeleton?

Answer 24

-Supports cells organelles
-Give strength to help the cell maintain its shape
-Responsible for Transporting organelles
-Can help the whole cell to move

Question 25

What are the features of prokaryotic cells?

Answer 25

-Less that 2 micrometres -DNA is circular -No nucleus -Cell wall made of a polysacchride but not cellulose or chitin -Few organelles -Flagella made of flagellin -Small ribosomes -Capsule around the outside -Pili (hairs) on the outside for attachment to other cells or surfaces -plasmids

Question 26

Wjat are the features of eukaryotic cells?

Answer 26

-Larger (10-100 micrometres) -linear DNA -Nucleus -No cell wall in animal cells but cellulose in plants and chitin in fungi -Many organelles -Flagella made of 9+2 formation microtubules -Larger ribosomes

Question 27

What ribosomes do prokaryotic and eukaryotic cells have?

Answer 27

Prokaryotic cells have 70s ribosomes and eukaryotic cells have 80s ribosomes.

Question 28

What is magnification?

Answer 28

How many times larger the image is compared to the actual object

Question 29

What is resolution?

Answer 29

The minimum distance at which two separate objects appear as separate images. It is the ability to see in detail

Question 30

What is the formula for magnification?

Answer 30

Size of image÷real size of object

Question 31

What is a light microscope?

Answer 31

They use light to produce an image. They have a lower magnification and resolution so are usually used to look at whole cells or tissue

Question 32

What is an electron microscope?

Answer 32

They use electrons to form an image. They have a higher resolution and magnification so therefore produce more detailed images.

Question 33

What are the types of electron microscope?

Answer 33

-Transmitting electron microscope -Scanning electron microscope

Question 34

What is a transmittion electron microscope

Answer 34

They use electromagnets to focus a beam of electrons through a specimen which is detected to produce a 2D image. Desperate parts absorb more electrons making them darker on the image.

Question 35

What is a scanning electron microscope?

Answer 35

They scan a beam of electrons across the surface of the specimen. This knocks of electrons which are gathered in a cathode ray tube to form an image. This produces a 3D image but at a lower resolution.

Question 36

What are the advantages and disadvantages of light microscopes?

Answer 36

Advantages: -Can observe living things -No harsh chemicals -Easy to set up -Cheap Disadvantages: -Low resolution -Low magnification (only x1500) -Low resolution (max 0.2 micrometres)

Question 37

What are the advantages and disadvantages of transmittion electron microscopes?

Answer 37

Advantages: -High resolution (up to 0.2 nanometres) -High magnification (up to x500,000) -Can see the ultrastructure Disadvantages: -Expensive -Harsh chemicals -Can only see dead material

Question 38

What are the advantages and disadvantages of scanning electron microscopes?

Answer 38

Advantages: -High magnification (up to x100,000) -High resolution (up to 0.2 nanometres) -Can see surface details Disadvantages: -Uses harsh chemicals -Expensive -Can only see dead material

Question 39

How are electron micrograms produced?

Answer 39

Samples are treated with heavy metals. This is because the metal ions act to scatter the electrons to give a contrast between structures.

Question 40

What does Methylene blue stain?

Answer 40

DNA

Question 41

Hoe do you prepare a dry mount?

Answer 41

-Take a thin slice of your specimen -Place the specimen on the slide -Put a cover slip on top

Question 42

How do you prepare a wet mount?

Answer 42

-Pipette a small drop of water onto the slide -Stand the cover slip upright then carefully tilt and lower it so that no air bubbles become trapped -Add your stain by placing a small drop on the edge of the slip and put a piece of paper towel on the other edge so it gets drawn across.

Question 43

Describe how to use a light microscope

Answer 43

1) Clip the slide containing the specimen to the stage 2) Select the lowest power objective lens 3) Use the course focus to bring the stage up just before the slide 4) Look down the eyepiece and move the stage down until it is roughly in focus 5) Use fine focus to fully focus the image 6) Repeat this with each objective lens

Question 44

What is the eyepiece graticule?

Answer 44

It is fitted to the eyepiece. It is like a ruler with no units.

Question 45

What is a stage micrometre?

Answer 45

It is places on the stage. It is a slide with an accurate scale and is used to work out the divisions on the eyepiece graticule at a particular magnification.

Question 46

Describe how to calibrate an eyepiece graticule to a stage micrometre

Answer 46

1) 1 small division on the stage micrometre is 0.1mm which is 100 micrometres 2) Count the eyepiece divisions in this area. 3) each division eyepiece division will be 100 micrometres ÷ no. Eyepiece divisions (At that magnification)

Question 47

What is differential staining?

Answer 47

Using more than one chemical stain

Question 48

What is gram staining?

Answer 48

A technique which catagorises and identifies bacteria based on the composition of their cell walls

Question 49

Wjat are the rules of biological drawings?

Answer 49

-Use a sharp pencil -Clear continuous lines -No shading or colouring -Use at least 50% of the space -Draw with accuracy -State the magnification -Give an informed title -Lable with annotations -Rule with horizontal lines -Ads a scale bar -Only draw whole cells

Question 50

What stains can be used?

Answer 50

1) Methylene blue: Stains DNA 2) Giemsa: Used to differentiate different types of blood cells. Red blood cells stained red and nuclei in white blood cells stained purple 3) Haematoxylin: Stains RNA and DNA present in cells blue/purple 4) Eosin: Dyes the cytoplasm pink

Question 51

What is a confocal microscope?

Answer 51

A type of advanced light microscope that uses lasers and fluorescence to produce high resolution images in 3D. It produces clearer images and can observe living cells