cells and microscopy

Question 1

what is the function of the nucleus

Answer 1

• stores genetic information
• location where semi-conservative replication occurs

Question 2

explain the 4 parts of the nucleus

Answer 2

• the nuclear envelope - double membrane that surrounds the nucleus. It controls the entry and exit of substances in and out of the nucelus
• nuclear pores - allow the passage of large molecules such as mRNA out of the nucelus
• chromatin - linear DNA which is protein(histone) bound
• nucleolus- manufactures rRNA and makes ribosomes

Question 3

what is the function of the mitochondria

Answer 3

• where ATP is synthesised by aerobic respiration

Question 4

what are the 4 structures a mitochondrion is made up of and explain them

Answer 4

• the double membrane - the 2 membranes control the entry and exit of molecules
• cristae - provide a large surface area for enzymes such as ATP synthase
• intermembrane space - the space between the inner and outer membrane
• matrix - contains proteins, lipids, mitochondrial DNA and 70s ribosomes

Question 5

what is the difference between the rough and the smooth endoplasmic reticulum

Answer 5

the rough has ribosomes on the outer surface membrane

Question 6

what are the 2 functions of the rough endoplasmic reticulum

Answer 6

• synthesis of proteins
• package proteins into vesicles

Question 7

what are the 2 functions of the smooth endoplasmic reticulum

Answer 7

• synthesis, store and transport lipids
• synthesis, store and transport carbohydrates

Question 8

what is the function of the golgi apparatus

Answer 8

sorts and modifies proteins which are then packages into vesicles

Question 9

what are the functions of lysosomes

Answer 9

• they contain and release hydrolytic enzymes

1. fuse with foreign materials ingested by phagocytic cells and then release its hydrolytic enzymes
2. release enzymes to the outisde of the cell in order to hydrolyse and breakdown molecules outside of the cell
3. they breakdown damages and worn out organelles so the useful molecules can be reused
4. break down cells after they have died

Question 10

what is the function of ribosomes

Answer 10

• synthesise proteins

Question 11

what are the 2 different types of ribosomes and explain them

Answer 11

1. 80s ribosomes - larger, found in eukaryotic cells
2. 70s ribosomes - smaller, found in prokaryotic cells

Question 12

what is the function of the cell surface membrane

Answer 12

controles the passage of molecules in and out of the cell

Question 13

what are the 3 additional organelles called in a plant cell

Answer 13

• chloroplasts
• cell wall
• vacuole

Question 14

what is the function of the chloroplast

Answer 14

carry out photosynthesis

Question 15

explain the structure of chloroplasts

Answer 15

• double membrane surrounds the organelle known as the chlorplast envelope
• inside the chlorplasts, the grana are stacks of up to 100 disk like structures called thylakoids
• within the membrane is the photosynthetic pigment called chlorophyll

Question 16

what is the function of the cell wall

Answer 16

provide strength and rigidity

Question 17

what are the functions of vacuoles

Answer 17

• provide support, making cells turgid
• sugars and amino acids stored
• pigments may colour petals and attract pollinating insects

Question 18

what are the different organisation levels in an organism

Answer 18

1. specialised cell
2. tissue
3. organ
4. organ system
5. organism

Question 19

give 4 differences between prokaryotic cells and eukaryotic cells

Answer 19

1. prokaryotic cells have circular DNA whereas eukaryotic cells have linear DNA
2. prokaryotic cells have no membrane-bound organelles whereas eukaryotic has membrane-bound organelles
3. prokarytoic cells have no ‘true’ nucleus and the DNA is free in the cytoplasm whereas eukaryotic cells have a nucleus and the DNA is contained in a nuclear membrane
4. prokaryotic cells contain 70s ribosomes whereas eukaryotic cells contain 80s ribosomes

Question 20

what are features of viruses

Answer 20

• non-living
• require a living cell to replicate inside
• contain DNA or RNA
• the envelope contains attachment proteins
• they have no organelles

Question 21

what is meant by resolution

Answer 21

the ability to distinguish between two objects that are close together

Question 22

what are the two types of electron microscopes

Answer 22

TEM and SEM

Question 23

explain how we can see specimens using a TEM

Answer 23

• the specimens are in a vacuum and stained using heavy metals
• specimens are fixed in resin and sliced thin
• electrons are fired through the specimen to enable the viewing of internal structures
• it is 2D

Question 24

explain how we can see specimens using a SEM

Answer 24

• the electrons bounce off the surface of the specimen
• they produce a 3D image

Question 25

compare light microscopes and electron miscroscopes by the following: 1. illumination 2. maximum magnification 3. what can you observe 4. specimens 5. staining process

Answer 25

Light on the left, Electron on the right 1. light rays, beam of electrons 2. x1500, x500000 3. larger organelles, smaller organelles 4. living, dead 5. easy, complex

Question 26

give the three structural features found in all virus particles and describe the function of one of these features (3 marks)

Answer 26

* capsid * genetic material * attachment proteins * **capsid - protects the genetic material**

Question 27

explain why viruses are described as accelular and non living (2 marks)

Answer 27

* can only reproduce inside a host cell * dont have a cell surface membrane

Question 28

describe two functions of the gologi apparatus in a eukaryotic cell

Answer 28

* package, modify ahnd trasnport lipids * package, modify and transport proteins