2.1 CELLS

Question 1

What does cell theory state?

Answer 1

Cell theory sates that:
- both animals and plant tissue is composed of cells
- cells are the basic unit for all life
- cells only develop from existing cells

Question 2

What is the development of cell theory?

Answer 2

The development of cell theory is:
1665- cells first observed
1674-1683- first living cells observed
1832- evidence for origin of new plant cells
1833- nucleus first observed
1837-1838- birth of a universal cell theory
1844- evidence for origin of new animal cells
1860- spontaneous generation disproved (germ theory)

Question 3

Configuration of compound light microscope.

Answer 3

A compound light microscope:
- has 2 lenses (objective lens which produces a magnified image, and eyepiece lens which magnifies the image again)
- objective/eyepiece lens configuration allows for much higher magnification and reduced chromatic aberration than a simple light microscope

Question 4

Why is staining used?

Answer 4

Staining is used as it provides contrast because different organelles and structures stain

Question 5

What are the different types of staining?

Answer 5

The different types of staining are:
- gram staining (sample stained with crystal violet and fixed with iodine, washed with alcohol, safarine (counterstain) added. gram negative bacteria= ‘red’ stain, gram positive bacteria= ‘crystal violet’ stain)
- acid fast staining (sample stained with carbolfuchsin, heated to fix, washed with alcohol, methylene blue (counterstain) added. non acid fast bacteria= ‘blue’ stain, acid fast bacteria= ‘red’ stain)

Question 6

What are the types of sample preparation?

Answer 6

Types of sample preparation:
- dry mount (viewed thinly sliced or whole. e.g hair, pollen dust)
- wet mount (suspended in liquid e.g living/aquatic things)
- squash slides (wet mount first, sample gently squashed. e.g root tip)
- smear slides (sample smeared. e.g blood)

Question 7

What are the stages of sample preparation?

Answer 7

The stages of sample preparation are:
1. fixation- process to preserve specimens (e.g chemicals such as formaldehyde)
2. sectioning- specimens dehydrated with alcohol and placed in a wax block before being thinly sliced with a microtome
3. staining- different stains allow different structures to be viewed
4. mounting- specimens are secured to a microscope slide with a coverslip

Question 8

What is the magnification equation?

Answer 8

Magnification equation:
magnification = image size / actual size

Question 9

How do you calculate the eyepiece graticule?

Answer 9

Calibrating the eyepiece graticule:
1. put stage micrometer in place
2. get scale on stage micrometer into clear focus
3. align stage micrometer with scale on eyepiece graticule. take multiple readings to determine scale
4. choose 2 intersecting points to create a scale
5. recall size of each micrometer divisions and calculate how many micrometers in scale
6. 1 graticule division = number of micrometers in scale / number of graticule divisions in scale
7. value of single graticule division = magnification factor
8. measure specimen on graticule and work out actual size

Question 10

What is an artefact?

Answer 10

An artefact is an object or structure seen through a microscope that have been created through the processing of the specimen, but are not an actual feature of the specimen

Question 11

What is the magnification and resolution of a light microscope, TEM, SEM, and laser scanning confocal microscope?

Answer 11

light- magnification= x1500-x2000, resolution= 200nm
TEM- magnification= x500,000-x2,000,000, resolution= 0.05-2nm
SEM- magnification- x100,000-x500,000, resolution= 5-50nm
laser scanning confocal- magnification= high, resolution= high

Question 12

What are the function of vesicles?

Answer 12

Vesicles are sacs that have storage and transport roles and have a single membrane

Question 13

What are the function of flagella and cillia?

Answer 13

Flagella and cillia are both extensions that protude from some cells. Flagella primarily enable mobility and can detect chemical changes in the environment. Stationary cillia have important functions in the nose, mobile cillia beat in a rhythmitic manor which causes currents and causes fluids or objects adjacent to the cell to move. Cillia keep air passages clean and move egg cells from the ovary to the uterus

Question 14

What is the function of the cell surface membrane?

Answer 14

The cell surface membrane provides protection for the cell

Question 15

What is the function of the cytoplasm?

Answer 15

The cytoplasm gives a cell its shape and allows organelles to move within the cell, provides mechanisms in which the cell itself may move

Question 16

What is the function of ribosomes?

Answer 16

Ribosomes are the site of protein synthesis

Question 17

What is the function of centrioles?

Answer 17

Centrioles come in pairs to form a centrosome and are involved in assembly and organisation of the spindle fibres used in cell divison

Question 18

What is the function of mitochondria?

Answer 18

Mitochondria are where the final stages of cellular respiration takes place. Mitochondria release ATP

Question 19

What is the function of the golgi apparatus?

Answer 19

The golgi modifies and packages proteins into vesicles

Question 20

What is the function of the ER?

Answer 20

The ER (endoplasmic reticulum) is composed of the:
- RER (contains ribosomes, responsible for synthesis and transport of proteins)
- SER (does not contain ribosomes, responsible for synthesis and transport of other biological molecules)

Question 21

What is the function of the nucleus?

Answer 21

The nucleus contains the genetic material (DNA) of the cell

Question 22

What is the function of a lysosome?

Answer 22

Lysosomes contain hydrolytic enzymes that break down waste material

Question 23

What is the function of the cytoskeleton?

Answer 23

The cytoskeleton is comprises of intermediate fibres, microfilaments and microtubles. They each work together to maintain the cells shape and internal organisation. Intermediate fibres offer the cell support and stability. Microfilaments hold the organelles in place and contribute to their movement ocasionally, contributes to movement of chromosomes using spindle fibres. Microtubles help change the shape of the cell during processes such as cytokinesis and muscle contraction, contributes to movement of cillia and flagella

Question 24

What are the steps of protein production?

Answer 24

The steps of protein production are:
1. the transcription of DNA occurs in the nucleus, mRNA leaves the nucleus
2. proteins are synthesised from the mRNA strand on the ribosomes bound to the RER
3. proteins are passed through the cisternae and are packaged through transport vesicles
4. vesicles move towards the golgi apparatus via the cytoskeleton
5. vesicles fuse with cis-face of golgi and proteins enter
6. proteins are structurally modified before leaving the golgi through the trans-face
7. secretory vesicles carry proteins to be released from the cell- these fuse with the cell surface membrane, releasing contents by exocytosis
8. some vesicles form lysosomes which contain hydrolytic enzymes for use in the cell

Question 25

What is the function of the cell wall?

Answer 25

The cell wall is freely permeable and gives shape and rigidity to the cell and provides defence against pathogens

Question 26

What is the function of the vacuole?

Answer 26

The vacuole contains cell sap which keeps the cell turgid

Question 27

What is the function of the chloroplasts?

Answer 27

Chloroplasts are responsible for photosynthesis

Question 28

What is the theory of endosymbiosis?

Answer 28

Endosymbiosis is the leading theory of the origin of eukaryotic cells from prokaryotic organisms

Question 29

What are the differences between prokaryotic and eukaryotic cells?

Answer 29

Differences between eukaryotes and prokaryotes:
- euk have nucleus, pro do not
- euk have a linear DNA shape, pro have a circular
- euk are mostly multicellular, pro are mostly unicellular
- euk reproduce sexually or asexually, pro reproduce via binary fission