2.1 cell structure definitions

Question 1

Centrioles

Answer 1

Hollow cylinder structures found in the cytoplasm containing a ring of microtubules arranged at right angles to each other that produce spindle fibres during mitosis

Question 2

Chloroplasts

Answer 2

Organelles found in plants and algae that are the site of photosynthesis. Contain their own DNA and ribosomes so can make their own protiens

Question 3

Cilia

Answer 3

Small hair-like structures that project from the surface of cells made of 9 + 2 arrangement of microtubules.

Question 4

Laser Confocal microscopy

Answer 4

A type of microscopy that uses lasers to scan a specimen point by point to produce an image

Question 5

Cytoskeleton

Answer 5

A mesh of protein fibres found in the cytoplasm of eukaryotic cells providing mechanical strength/ support as well as aiding transport within cells (intracellular transport) and enabling cell movement

Question 6

Differential staining

Answer 6

Using multiple different stains to distinguish different parts of a specimen.

Question 7

Eukaryotic cell

Answer 7

A type of cell that contains a nucleus along with membrane bound organelles.

Question 8

Flagella

Answer 8

A whip-like structure found on bacterial cells that is used for cell movement.

Question 9

Golgi apparatus

Answer 9

An organelle found in eukaryotic cells that is involved in the modification and packaging of proteins and lipids. It is a fluid filled, flattened & curved sacs with vesicles surrounding the edges. It also produces lysosomes.

Question 10

Light microscope

Answer 10

A type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen

Question 11

Lysosomes

Answer 11

Membrane-bound vesicles found in the cytoplasm that contains a hydrolytic (digestive) enzyme called lysozyme

Question 12

Magnification

Answer 12

How much bigger an image appears compared to the original object.
Mag = image/actual

Question 13

Mitochondrion

Answer 13

An organelle found in eukaryotic cells it is oval shaped, bound by a double membrane called the envelope. The inner membrane is folded to form projections called cristae with matrix on the inside containing all the enzymes needed for aerobic respiration

Question 14

Nuclear envelope

Answer 14

A double membrane that surrounds the nucleus

Question 15

Nucleolus

Answer 15

A structure found inside the nucleus that contains proteins and RNA and is involved in synthesizing new ribosomes

Question 16

Nucleus

Answer 16

Found in eukaryotic cells. stores the genetic information of the cell as chromosomes and is surrounded by a double membrane called the nuclear envelope. contains pores which allow molecules to enter and leave the nucleus. also contains nucleolus and chromatin

Question 17

Plasma membrane

Answer 17

A semipermeable lipid bilayer studded with proteins that surrounds the cell and many organelles.

Question 18

Prokaryotic cell

Answer 18

A unicellular that does not contain any membrane bound organelles or a nucleus but do contain DNA

Question 19

Resolution

Answer 19

The ability to distinguish two different points in a specimen

Question 20

Ribosomes

Answer 20

Organelles found either free in the cytoplasm or membrane bound to the RER that are the site of protein production. composed of two sub units. Found in both prokaryotes and eukaryotes (70s in prokaryotes and 80s in eukaryotes)

Question 21

Rough endoplasmic reticulum (RER)

Answer 21

A membrane-bound organelle that is involved in the synthesis and packaging of proteins by folding and processing them. It is a series of flattened sacs enclosed by a membrane with ribosomes on the surface.

Question 22

Scanning electron microscope (SEM)

Answer 22

A type of microscope that passes a beam of electrons over the surface of a specimen to produce an image

Question 23

Smooth endoplasmic reticulum (SER)

Answer 23

A system of membrane-bound sacs. an organelle involved in lipid synthesis.

Question 24

Transmission electron microscope (TEM)

Answer 24

A type of microscope that passes a beam of electrons through a sample to produce an image.

Question 25

cell wall (prokaryote)

Answer 25

Rigid outer covering made of peptidoglycan

Question 26

Capsule (prokaryote)

Answer 26

Protective slimy layer which helps the cell to retain moisture and adhere to surfaces

Question 27

Plasmid DNA (prokaryotes)

Answer 27

Circular loop of DNA

Question 28

Flagellum (prokaryotes)

Answer 28

a tail like structure which rotates to move the cell made of 9+2 microtubules

Question 29

Pili (prokaryotes)

Answer 29

Hair-like structures which attach to other bacterial cells

Question 30

Transport of proteins (6-9 marks)

Answer 30

Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum (1).
They then pass into its cisternae and are packaged into transport vesicles (2).
Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport function of the cytoskeleton (vesicles)(3,4).
The vesicles fuse with the cis face of the Golgi apparatus and the proteins enter.(5)
The proteins are structurally modified before leaving the Golgi apparatus in vesicles from its trans face (6).
Secretory vesicles carry proteins that are to be released from the cell. (7)
The vesicles move towards and fuse with the cell-surface membrane, releasing their contents by exocytosis.(8)
Some vesicles form lysosomes these contain enzymes for use in the cell (9)

Question 31

Outline how a student could prepare a temporary mount of tissue for a light microscope

Answer 31

1) slice thin section of tissue using ultratome or by maceration
2) place plant tissue in a drop of water
3) stain using iodine (or equivalent) to make structures visible
4) add cover slip at 45degrees ensuring not to trap air bubbles. (mounted needle could be used for this)

Question 32

Describe how a light microscope works

Answer 32

1) lenses focus rays of light and magnify the view of a thinly sliced specimen
2) different structures absorb different amounts and wavelengths of light
3) reflected light is transmitted to the observer via the objective lens and eyepiece

Question 33

Describe how a transmission electron microscope (TEM) works

Answer 33

1) high energy beams of electrons are fired and pass through the thin sliced specimen
2) more dense structures seem darker as they absorb more electrons
3) focus image onto fluorescent screen or photographic plate using magnetic lenses

Question 34

Describe how a scanning electron microscope (SEM) works

Answer 34

1) focus a beam of electrons onto a specimens surface using electromagnetic lenses
2) reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate

Question 35

Describe how a laser scanning confocal microscope works

Answer 35

1) focus a laser beam onto a small area of a sample’s surface using objective lenses
2) fluorophores (fluorescent chemical compound) in the sample emit photons
3) photomultiplier tube amplifies the signal onto a detector where the image is then produced pixel by pixel in the correct order

Question 36

Rules when doing a biological drawing

Answer 36

Sharp pencil
no sketching lines/shading
include scale bar
annotate visible structure
use a ruler for lines 
no arrow heads
Use more than 50% of the paper given
Ensure correct proportions
Label lines should no cross
Label lines should be parallel to the top of the page

Question 37

why do samples need to be stained for light microscopes

Answer 37

coloured dye binds to cell structures
facilitates absorbtion of wavelengths of light to produce an image
differerntial staining: contrast between heavy and lightly stained areas to distinguish structures

Question 38

State the mag and res of a compound optical microscope

Answer 38

mag x2000

res 200nm

Question 39

state the mag and res of a TEM

Answer 39

mag x500,000

res 0.5nm

Question 40

state the mag and res of a SEM

Answer 40

mag x500,000

res 3-10nm

Question 41

How do you calculate a graticule division

Answer 41

Number of eyepiece divisions / number of micrometres

Question 42

Permanent Vacuole (plant cells)

Answer 42

Membrane lined sacs in the cytoplasm containing cell sap. Maintain turgor pressure and Ridgid structure

Question 43

Tonoplast

Answer 43

Membrane of a vacuole in a plant cell that is selectively permeable allowing small molecules to pass

Question 44

Stroma

Answer 44

Fluid enclosed in a chloroplast

Question 45

Thylakoids

Answer 45

Internal network of membranes which form flattened sacs

Question 46

Granum

Answer 46

Several thylakoids stacked together joined together by lamellae. They contain the chlorophyll pigments

Question 47

Where is starch produced by photosynthesis present

Answer 47

Starch grains within the chloroplast

Question 48

Similarities and differences between prokaryotes and eukaryotes

Answer 48

PROKARYOTE
No nucleus
Circular DNA (plasmids)
Non membrane bound organelles
Cell wall = peptidoglycan
70s ribosomes
Simple cytoskeleton
Reproduce via binary fission
Unicellular
Cell surface membrane present

EUKARYOTES
Nucleus present
Linear DNA
extra DNA only present in mitochondra and chloroplasts
Membrane bound and non membrane bound
Cell wall = chitin in fungi, cellulose in plants and not present in animals
80s Ribosomes
Complex cytoskeleton
Reproduced asexually or sexually
Unicellular and multicellular
Cell surface membrane present

Question 49

Theory of endosymbiosis

Answer 49

Mitochondria and chloroplasts were formerly free living prokaryotes that got taken inside another cell as an endosymbiont which lived within the cell leading to the evolution of eukaryotic cellss