2.1.1 Cell Structure

Question 1

A)What are the microscopes you need to know

Answer 1

• light/optical microscopes
• Transmission electron microscopes
• Scanning electron microscopes

Question 2

A)what does a light ( optical ) microscope do

Answer 2

• they helps to understand cell structure
• optical microscopes uses light (wavelength 400-700 nm) which is focused by glass.
• the photo of the image produced is called a photomicrograph

Question 3

A) what are the advantages of using a light / optical microscopes

Answer 3

• linear magnification (x50 means 50 times larger)
• cheap
• easy to use
• portable
• stains are not necessary

Question 4

A) what are the disadvantages of a light/optical microscope

Answer 4

• limited resolution so some organelles cannot be seen ( eg ribosomes)

Question 5

A) how does a transmission electron microscope work

Answer 5

• a beam of electron ( wavelength 0.004nm) from a cathode passes through the specimen and are focused by magnets onto a screen/photographic plate
• produces a 2B black and white photomicrograph

Question 6

A) what are the advantages to transmission electron microscopes

Answer 6

• very high magnification ( x2 000 000 max)
• 0.1 nm resolution
• Ultrastructure seen

Question 7

A) what are the disadvantages of transmission electron microscopes

Answer 7

• large
• expensive
• needs skills and training to use
• specimen needs to be in a vacuum
  -specimens needs to be dehydrated and stained with metal salt (may be dangerous)

Question 8

A) How does a scanning electron microscope work

Answer 8

• use of a beam of electrons from a cathode ( 0.004nm wavelength) that bounces of a specimen and then focussed by magnets.
• this makes a 3D black and white electron micrograph ( colour can be added by computer)

Question 9

A) what are the advantages of using a scanning electron microscope

Answer 9

• high magnification achieved (x15 - x200,000)
• 0.1 nm resolution
• whole specimen can be used

Question 10

A) what are the disadvantages of scanning electron microscopes

Answer 10

• large
• expensive
• need skill and training to use
• cannot be used to study living organisms
• specimen needs to be viewed while in a vacuum

Question 11

B) how do you prepare the wet mount slide for light microscopes

Answer 11

• place a drop of water on the slide
• place your sample specimen in your drop of water
• set a cover slip over the sample specimen at a 45 degree angle

Question 12

B) how do you prepare the stained slides for light microscopes

Answer 12

• Set a cover slip over the sample specimen at a 45o angle.
  -Place 1 drop stain on the other side of the cover slip.
  -The staining agent will begin to seep under the cover slip as the paper towel draws water out from the other side.

Question 13

B) what and how does an eye piece graticule work

Answer 13

• an eye piece graticule is a small transparent ruler used to see the size of the object you are looking at

Question 14

B) what is a stage micrometre

Answer 14

a microscope slide with a slide divided scale marked on the surface used to calibrate the eye piece graticule

Question 15

(c) what are stains

Answer 15

stains are coloured chemicals that bind to molecules which allows the different structures in specimens to become more visible

Question 16

(C) what is meant by differential staining

Answer 16

using different stains which are used so different tissues are stained different colours

Question 17

what are the conversions between cm, mm, micrometres, nanometres

Answer 17

cm -> mm x10
mm -> micrometre x1000
micrometre -> nanometres x1000

Question 18

what should biological drawing include and not include

Answer 18

Biological drawings should not:
Include shading or colouring
Include arrow heads for labels
Involve lines overlapping each other

Biological drawings should:
Include a title
State the magnification or scale
Be drawn with a sharp pencil
Include smooth, continuous lines
Include labels
Include accurate sizes of observable structures

Question 19

what is the magnification formula

Answer 19

image size= magnification x actual size
i = am

Question 20

define resolution

Answer 20

Resolution is the ability to distinguish between two separate points (or how detailed the image is).

Question 21

define magnification

Answer 21

Magnification is how many times larger an image is than the object.

Question 22

what are the components of a eukaryotic cell

Answer 22

-nucleus
-nucleolus
-nuclear envelope
-rough and smooth endoplasmic reticulum (ER)
-Golgi apparatus
-ribosomes
-mitochondria
-lysosomes
-chloroplasts
-plasma membrane
-centrioles
-cell wall
-flagella
-cilia

Question 23

what are eukaryotes

Answer 23

multicellular organisms made up of eukaryotic cells like animals, plants, fungi, and protists.

Question 24

what are prokaryotes

Answer 24

These are single-celled organisms made up of prokaryotic cells like bacteria.

Question 25

what is the structure and function of the nucleus, nucleolus and nuclear envelope

Answer 25

Animal+plant Structure - surrounded by a nuclear envelope ( double membrane) containing pores - contains genetic information in the form of chromosomes - contains the nucleolus Function - Controlling the cell's activities - It contains DNA with instructions to produce proteins. - Synthesis of ribosomes - The nucleolus makes ribosomal RNA - substances can enter and leave the nucleus via the pores in the nuclear envelope - stores organisms genome and transmits genetic information

Question 26

what is the structure and function of the rough endoplasmic reticulum

Answer 26

animal+plant Structure - a system of membrane with fluid-filled cavities ( cisternae) that is continuous with the nuclear envelope and is coated with ribosomes function - RER is used as a transport system where ribosomes make the proteins and the cavities transport the proteins - provides a large surface area for the ribosomes for protein synthesis

Question 27

what is the structure and function of the smooth endoplasmic reticulum

Answer 27

animal+plant Structure - system of cisternae continuous with the nuclear envelope but no ribosomes - contains enzymes that catalyse reactions involved with lipids Function - used for the synthesis, storage and transport of lipids and carbohydrates - for example: cholesterol and steroid hormones

Question 28

what is the structure and function of the Golgi apparatus

Answer 28

animal+plant Structure - contains fluid filled, membrane bound sacs know as cisternae, and contains smaller vesicles - the vesicles being substances to and from the Golgi apparatus Function - Process and package lipids and proteins - Carried out by the cisternae. -Store and transport lipids and proteins - Carried out by the vesicles. -Synthesise lysosomes - Specialised vesicles.

Question 29

what is the structure and function of the ribosomes

Answer 29

animal+plant Structure - made up of proteins and ribosomal RNA - consists of a large and small subunit - not surrounded by a membrane Function - site of protein synthesis - involved in the process of translation

Question 30

what is the structure and function of the mitochondria

Answer 30

animal+plant Structure - contains an enzyme - rich liquid known as the matrix - surrounded by a double membrane in which the inner membrane is folded to form structures known as cristae - contains their own DNA and ribosomes Function - site of aerobic respiration - produces ATP

Question 31

what is ATP used for

Answer 31

it is used for energy in process such as ion transport, muscle contraction and nerve impulse propagation

Question 32

what is the structure and function of lysosomes

Answer 32

Animal Structure - Round organelles with no clear internal structure - contains hydrolytic enzymes - surrounded by a membrane to keep enzymes separate from the cytoplasm of the cell Function - Digest pathogens - using enzymes - break down waste material ( including old organelles and cells)

Question 33

what is the structure and function of chloroplast

Answer 33

plant Structure -found in the green parts of plants - contains fluid - filled sacs known as thylakoid which are stacked up to form grana - surrounded by a double membrane, enclosing a fluid known as stroma - contains its own DNA and ribosomes Function - a site of photosynthesis - reactions take place in the grana and stroma

Question 34

what is the structure and function of the cell surface membrane/ plasma membrane

Answer 34

animal+plant + bacteria Structure - found on the surface of animal cells - mainly made up of lipids and proteins Function - controls the movement in and out of the cell as the membrane is partially permeable - cell signalling - receptors can detect signals from other cells

Question 35

what is the structure and function of centrioles

Answer 35

animal Structure - they are hollow cylinders containing a ting of microtubules arranged at right angles to each other - spindle fibres form the centrioles Function - involved in cell division, when the cell is dividing the centrioles go to opposite ends of the nucleus

Question 36

what is the structure and function of the cell wall

Answer 36

plant + bacteria Structure - made up of cellulose - contains channel ( gaps_ known as plasmodesmata Function - supports the cell, contents of the cell press against the cell wall to make it rigid - prevents the cell from bursting as the cell wall can withstand high osmotic pressure - allows exchange of substances between cells as the channels connects to neighbouring cells

Question 37

what is the structure and function of the vacuole

Answer 37

plant Structure - Contains cell sap ( salt and sugar solution) - surrounded by selectively permeable membrane known as tonoplast Function - Helps to maintain pressure within then cell, which keeps the cell rigid and stops the plant from wilting

Question 38

what is the structure and function of the flagella

Answer 38

Bacteria Structure - a long, hair - like structure Function - attached to the cell membrane and rotates to push the cell around its environment

Question 39

what is the structure and function of the cilia

Answer 39

animal Structure - protrusions from the cell surface membrane containing microtubules Function - to sweep substances along

Question 40

what is the relationship between some o the organelles involved in the production and secretion of protiens

Answer 40

- mRNA copy of the gene is made in the nucleus and leaves via the nuclear envelopes nuclear pores - the mRNA attaches to a ribosome connected to RER - the ribosome reads instructions to assemble amino acid chains - proteins are then transported from the RER to the golgi apparatus in vesicles. - they are then modified in the Golgi apparatus - vesicles pinched off to the plasma membrane where it fuses with the membrane and the contents are releases via exocytosis

Question 41

what is the cytoskeleton

Answer 41

- it is present in the cytoplasm and gives structure and support to the cell

Question 42

what is the importance of the cytoskeleton

Answer 42

- made of microfilaments which is involved in cell movement and locomotion such as muscle contraction - made of microtubules which form a scaffold structure throughout the cell and acts as tracks for intracellular transport of vesicles and organelles - made of intermediate filaments which is responsible for the mechanical strength of certain tissues such as skin and hair

Question 43

what are the similarities and differences in structure and ultrastructure of eukaryotic and prokaryotic cells

Answer 43

Organism prokaryotes - bacteria cells eukaryotes - animal, plant size prokaryotes - 0.1 - 0.5 micrometres eukaryotes - 10 to 100 micrometres DNA prokaryotes -circular DNA free in the cytoplasm eukaryotes - linear DNA in the nucleus Ribosomes prokaryotes - smaller ribosomes (70s ribosomes) eukaryotes - bigger ribosomes (80s ribosomes) Organelles prokaryotes -contains a few non membrane-bound organelles eukaryotes - contains membrane-bound and non-membrane bound organelles Cell walls prokaryotes - made up of murein eukaryotes - made up of cellulose (plants) or chitin ( fungi)