Cell Structure

Question 1

Nucleus

Answer 1

Contains DNA and controls cells growth and reproduction

Question 2

Cytoplasm

Answer 2

Liquid that fills cell
Holds everything together, where chemical reactions take place

Question 3

Lysosome

Answer 3

-Contain digestive enzymes capable of breaking down all types of polymers
-Hydrolyse material ingested by phagocytic cells
-Digest worn out cells so that the useful chemicals they are made of can be re-used
-Break down dead cells
-Digest macromolecules (carbs, lipids, proteins, nucleic acids)
-Cell membrane repairs

Question 4

Centrosome

Answer 4

Regulates cell motility
Adhesion and polarity in interphase
Facilitates organisation of spindle poles during mitosis

Question 5

Nuclear Membrane

Answer 5

Barrier to separate contents of nucleus from cytoplasm

Question 6

Mitochondria

Answer 6

Produce energy through cellular respiration

Question 7

Pinocytic Vesicle

Answer 7

Carriers of the extracellular fluid into the cellq

Question 8

Cell Membrane

Answer 8

Hold cell together and control what goes in and out

Question 9

Nucleolus

Answer 9

Produce and assemble cell’s ribosomes

Question 10

Golgi apparatus

Answer 10

Add carbohydrates + proteins to form glycoproteins
Produce secretory enzymes
Secrete carbohydrates
Transport, modify and store lipids
Form lysosomes

Question 11

Rough endoplasmic reticulum

Answer 11

large SA for synthesis of proteins and glycoproteins
Provide a pathway for transport of materials (especially proteins)

Question 12

Smooth endoplasmic reticulum

Answer 12

Synthesise store and transport lipids and carbohydrates

Question 13

Nerve cell adaptations

Answer 13

Cell body for protein synthesis
Extensions of cytoplasm cytoplasm from cell body = dendrites and axons, allowing neurones to communicate
Axon = myelin sheeth to speed impulses

Question 14

MUscle cell adaptations

Answer 14

Layers of protein filaments = slide over eachother causing muscle contraction
High density of mitochondria = sufficient energy for muscle contraction
SKeletal muscles fuse together = form multinucleated cells that contract in unison

Question 15

Sperm cells adaptations

Answer 15

Acrosome = contains digestive enzyme to break outer layer of egg cell so haploid nucleus can enter to fuse with eggs nucleus
Mid piece lots of mitochondria = rlease energy for tail movement
Tail rotates = allow move towards egg

Question 16

Root hair cells adaptations

Answer 16

Root hair increase surface area = high rate of water uptake by osmosis
Thin walls = water moves through easily
Permanent vacuole = cell sap more concentrated than soil water maintaining water potential gradient
Mitochondria = actove transport of mineral ions

Question 17

Xylem vessels adaptations

Answer 17

No top and bottom walls = water drawn towards leaves by transpiration
Dead cells = free movement of water
Lignin thick outer walls = support plant

Question 18

Phloem vessel cells adaptation

Answer 18

Living companion cells
Joined end to end contain holes in end cell walls so sugars and amino acids flow easily
Few subcellular structures to aid flow of materials

Question 19

What are plasmids

Answer 19

Loops of DNA
Contian genes that can be passed ebtween prokaryotes

Question 20

Capsule

Answer 20

Some prokaryotes surrounded by final outer layer known as capsule
Helps protect bacteria from drying out from attack by cells of the immune system of host organism

Question 21

Describe optical light microscope

Answer 21

Use light, limiting the resolution
Cannot be used to observe smaller organelles such as ribosomes, endoplasmic reticulum or lysosomes

Question 22

Electron microscopes

Answer 22

Use electrons
High resolution because smaller light wavelength
Two types transmission electron miscroscope and scanning electron microscope

Question 23

Transmission electron microscope advantages

Answer 23

High resolution images
Allowing internal structures within cells to be seen

Question 24

Transmission electron microscopes disadvantages

Answer 24

Used with thin specimen or thin sections of obkect
Cannot be used to observe live speciments
Lengthy treatment
Do not produce colour image

Question 25

Scanning elecrtron microscope advantage

Answer 25

Used on thick pr 3D speciments Allow external 3D structure ot speciments to be observed

Question 26

Scanning electron microscope disadvantages

Answer 26

Lower resolution Cannot be used to observe live speciments Do not produce a colour image

Question 27

Light vs electron

Answer 27

Light: alive or dead, shine light through objective lense, better fr whole cells, small plant and organism Electron: dead, useful for organelles viruses and DNA, higher frequency of wavelength so better resolution and magnification

Question 28

3 stages of cell frctionation

Answer 28

homogenisation Filtration Utracentrigufation

Question 29

Describe homogenisation

Answer 29

Cold = reduce activity of enzymes isotonic = same water potential so organelles dont damage from osmosis Buffer = prevent protein denaturing Use a homogeniser = grind up cells Use a homogenate = breaks plsama membrane to release organelles

Question 30

Describe filtration

Answer 30

Homogenate filtered through gauze Separate large cell debris not broken up Organelles much smaller than debris not filtered out Leaves solution that contains a mixture of organelles

Question 31

Describe ultracentrifugation

Answer 31

Placed in centrifuge and spins Cause largest to settle at bottom in thick sediment knows as a pellet Solution = supernatant Rest of organelles stay suspended in solution Filter and drain supernatant drained off formimg new supernatant after second spin Spun at higher speed Repeated until organelle present are separate

Question 32

Why do you repeat the centrifuge at different speeds

Answer 32

Some organelles (e.g. mitochondria) are lighter than others (nucleus) so needs to be spun at higher speeds

Question 33

How is the inner membrane of mitochondria adapted

Answer 33

Has cristae Which is folded to increase surface area for respiration

Question 34

Key terms when answering ribosome questions comparisons of prokaryotic and eukaryotic

Answer 34

Comparign bacteria to eukaryotic Must say ribosomes 80S, denser, heavier or large ribosomes