A2.2 Cell Structure

Question 1

functions of life

Answer 1

Metabolism,
reproduction,
homeostasis,
movement,
growth,
response to stimuli,
excretion (removal of metabolic waste),
nutrition

Question 2

Cell theory

Answer 2

Living organisms are composed of cells
Cells are the smallest unit of life
Cells come from pre-existing cell

Question 3

Magnification

Answer 3

the ability to enlarge an object’s image

Question 4

Resolution

Answer 4

the ability to differentiate two separate objects

Question 5

Light Microscopes

Answer 5

Use lenses to bend light and magnify images by a factor of roughly 100-fold

Question 6

Electron microscopes

Answer 6

Use electromagnets to focus electrons resulting in significantly _greater magnifications and resolutions__

Transmission electron microscopes (TEM) pass electrons through specimen to generate a cross-section

Scanning electron microscopes (SEM) scatter electrons over a surface to differentiate depth and map in 3D

Question 7

Light Microscope advantages

Answer 7

Can observe living specimen
Cheap to use
Portable
Easy to used
Can observed colored specimen

Question 8

light microscope disadvantages

Answer 8

Low Resolution
Only produced a two- dimensional image

Question 9

electron microscope advantages

Answer 9

Can view finer details (Higher resolution)

Question 10

electron disadvantages

Answer 10

Expensive
Difficult to prepare specimen
Not portable
May produce artifacts (structure that is not present in specimen) due to heavy metal staining
Cannot observed colored specimen. (The ‘color’ observed are ‘false-color scanning)

Question 11

structures of prokaryotic cell

Answer 11

Capsule (Glycocalyx)
Cell wall
Cell membrane
Cytoplasm
Pili
Flagella
Nucleoid region
Plasmid
70S ribosome

Question 12

capsule (glycocalyx)

Answer 12

Protect the cell from external environment

Question 13

cell wall (prokaryotic)

Answer 13

Act as a structural support, made up of peptidoglycan

Question 14

Cell membrane

Answer 14

Control substances going in and out of the cell

Question 15

cytoplasm

Answer 15

Contain enzymes, site for metabolic reactions

Question 16

pili

Answer 16

Responsible for exchange of plasmid between bacteria (horizontal gene transfer/sexual reproduction)

Question 17

Flagella

Answer 17

Responsible for locomotion of the bacterium

Question 18

Nucleoid region

Answer 18

Contain genetic material of the bacterium

Question 19

Plasmid

Answer 19

Circular DNA in the cytoplasm

Question 20

70S ribosome

Answer 20

Site for protein synthesis

Question 21

Asexual Reproduction of Prokaryotes

Answer 21

binary fission

Question 22

binary fission

Answer 22

The circular DNA is replicated.

The membrane elongates and pinches off (cytokinesis), forming two cells.

The way of transferring gene is called _vertical gene transfer__

Question 23

Sexual Reproduction of Prokaryotes

Answer 23

Formation of Conjugation

Question 24

formation of conjugation

Answer 24

Pili of the donor will be connecting to the recipient.

Conjugation is formed between the donor and recipient.

Replication of the donor plasmid.
Plasmid is transferred to the recipient, and it comes a new donor

Question 25

structure Eukaryotic Cell – Animal Cell

Answer 25

Nucleus Cytoplasm Cell membrane Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Mitochondria Golgi Apparatus Vesicles Lysosome Peroxisome 80S ribosome Cytoskeleton Centriole

Question 26

nucleus

Answer 26

Contain DNA, control cellular activity

Question 27

cytoplasm

Answer 27

Contain enzymes, site for metabolic reactions

Question 28

cell membrane

Answer 28

Control substances going in and out of the cell

Question 29

Rough Endoplasmic Reticulum

Answer 29

Site for protein synthesis (extracellular proteins)

Question 30

Smooth Endoplasmic Reticulum

Answer 30

Site for lipid synthesis

Question 31

mitochondria

Answer 31

Site for aerobic respiration, produces ATP

Question 32

Golgi Apparatus

Answer 32

Site for modifying and repackaging protein

Question 33

Vesicles

Answer 33

Transport of substances, mainly protein

Question 34

Lysosome

Answer 34

Contain hydrolytic enzyme, breaking down pathogens or worn-out organelles

Question 35

Peroxisome

Answer 35

Responsible for breaking down of lipid

Question 36

80S ribosome

Answer 36

Site for protein synthesis (intracellular proteins)

Question 37

Cytoskeleton

Answer 37

Structural support of the cell

Question 38

Centriole

Answer 38

Responsible for the formation of spindle fibers

Question 39

Atypical Eukaryotes

Answer 39

red blood cells Fungal hyphae Phloem sieve tube Skeletal muscle

Question 40

red blood cells

Answer 40

Carries oxygen Contains _haemoglobin_ _biconcave_ shape Do not have a nucleus

Question 41

fungal hyphae

Answer 41

Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called _septa_ Some fungi are not partitioned by septa and hence have a _continuous cytoplasm_ along the length of the hyphae Challenges the idea that living structures are composed of _discrete cells_

Question 42

Phloem sieve tube

Answer 42

In charge of translocation Specialized cell for _transportation_ of sucrose and amino acid in plant End wall with _pores_ and __ cellular components Can only remain alive with the help of _companion cell_

Question 43

Skeletal muscle

Answer 43

Muscle cells fuse to form fibres made up of _specialised protein_ that may be very long (>300mm) Tubular cells with _multiple nuclei_ despite being surrounded by a single, continuous plasma membrane Allowing more coordinating protein molecules

Question 44

Prokaryotic Cell vs Eukaryotic Cell (1)

Answer 44

Nucleus absent No membrane bounded organelles Capsule present Contain plasmid Naked DNA (histone is the clothes, DNA without histone) 70S ribosome Divide by binary fission

Question 45

Prokaryotic Cell vs Eukaryotic Cell (2)

Answer 45

Nucleus present Contain membrane bounded organelles Capsule absent No plasmid DNA associate with histone protein (chromosome) 80S ribosome Divide by mitosis and meiosis

Question 46

Endosymbiotic Theory (theory only)

Answer 46

The _origin of eukaryotic cells__ can be explained by the endosymbiotic theory. Mitochondria are believed to have evolved from _aerobic prokaryotes_ that were engulfed by anaerobic cell. Chloroplasts are believed to be evolved from _photosynthetic bacteria_ that were engulfed by heterotrophic cell.

Question 47

Endosymbiotic Theory – Evidence

Answer 47

Mitochondria and chloroplasts have _their own DNA_ which is naked and circular Mitochondria and chloroplasts have _ribosomes_ that are similar to prokaryotes (70S) Mitochondria and chloroplasts have a _double membrane_, and the inner membrane has _proteins_ that are similar to prokaryotes Mitochondria and chloroplasts are roughly the _same size_ as bacteria and are susceptible to the _antibiotic_ chloramphenicol

Question 48

Cell Differentiation

Answer 48

All the cells in our body contain the _same DNA_. (Except sex cell) Based on the _position_ of the cell, different cells will have different expression Depending on where the cell is, only some genes in the cell are _expressed_. The cell is said to be specialized or differentiate.

Question 49

Difference between cilia and microvilli

Answer 49

Cilia are motile Microvilli are non-motile Cilia involved in movement Microvilli increase surface area for absorption Cilia are found in the lumen of the respiratory tract (trachea) and the lumen uterine tube Microvilli are found on the epithelial cells of the small intestine (villi) and kidney tubules

Question 50

Central vacuole / Large vacuole

Answer 50

Primarily store water but nutrients, salts, ions, minerals, proteins, pigments, etc. may also be found depending on the type of plant cell The water inside the vacuole helps to maintain the turgor pressure (the force within the cell that pushes the plasma membrane against the cell wall) within the plant cell (increase the turgidity of the plant cell) When water goes in and there are no ions inside the cell, it will go out of the cell through osmosis