Cells & Microscopy Flashcards
1
Q
the nucleus (3)
A
- normally spherical
- the largest organelle in eukaryotic cells (10-20nm)
- contains DNA arranged in chromosomes
2
Q
list the four parts of a nucleus
A
the nuclear envelope
nuclear pores
chromatin
the nucleolus
3
Q
the nuclear envelope (2)
A
- a double membrane that surrounds the nucleus
- controls the entry and exit of substances in and out of the nucleus
4
Q
nuclear pores
A
allow the passage of large molecules, such as mRNA, out of the nucleus
5
Q
chromatin (2)
A
- linear DNA which is histone bound
- condenses into visible chromosomes during nuclear division
6
Q
the nucleolus (2)
A
- small, spherical region of the nucleus within the nucleoplasm
- manufactures rRNA and makes ribosomes
7
Q
the nucleus: FUNCTIONS (4)
A
- stores genetic information; codes for the primary structure of polypeptides
- production of mRNA via transcription
- production of rRNA that makes up ribosomes
- location where semi conservative replication occurs
8
Q
the mitochondrion
A
where ATP is synthesised by aerobic respiration
9
Q
list the four parts of a mitochondrion
A
double membrane
cristae
intermembrane space
the matrix
10
Q
double membrane in a mitochondrion
A
controls the entry and exit of molecules in and out of the mitochondria
11
Q
cristae (2)
A
- extensions that form from folds of the inner membrane
- provide a large surface area
12
Q
the intermembrane space
A
the space between the inner and outer membrane
13
Q
the matrix (2)
A
- contains proteins, lipids, mitochondrial DNA and 70s ribosomes
- allow the mitochondrion to make its own proteins for respiration, independently of the nucleus
14
Q
state the two types of endoplasmic reticulum
A
rough endoplasmic reticulum (RER)
smooth endoplasmic reticulum (SER)
15
Q
rough endoplasmic reticulum (RER) (3)
A
- the outer surface is coated in 80s ribosomes
- large surface area for protein synthesis
- packages proteins into vesicles to transport them to the golgi
16
Q
smooth endoplasmic reticulum (4)
A
- the outer surface is not coated in ribosomes
- synthesise, store and transport lipids
- synthesise, store and transport carbohydrates
- packages them into vesicles to transport them to the golgi
17
Q
golgi apparatus (4)
A
- sorts and modifies proteins
- by adding carbohydrates or lipids onto them to form a “glycoprotein” or “glycolipid”
- these modified proteins are packaged into vesicles again
- these vesicles then fuse with the cell surface membrane, releasing their contents outside the cell via exocytosis
18
Q
lysosomes (3)
A
- contain and release hydrolytic enzymes
- also contain lysozymes (enzymes that hydrolyse the walls of certain bacteria)
- they isolate hydrolytic enzymes from the rest of the cell before releasing them
19
Q
lysosomes: FUNCTIONS (4)
A
- fuse with foreign materials ingested by phagocytic cells and then release its hydrolytic enzymes
- release enzymes to the outside of the cell in order to hydrolyse molecules there
- break down damaged and worn out organelles (the useful molecules they are made from can be reused)
- completely break down cells after they have been used (autolysis)
20
Q
what are ribosomes made up of?
A
ribosomal RNA
21
Q
what is the role of ribosomes?
A
to synthesise proteins
22
Q
where can ribosomes be found? (2)
A
- cytoplasm
- RER
23
Q
list the two main types of ribosomes
A
- 80s (larger; found in eukaryotic cells)
- 70s (smaller; found in prokaryotic cells)
24
Q
chloroplasts
A
the organelles that carry out photosynthesis
25
list the four parts of a chloroplast
double membrane
grana
thylakoids
stroma
26
**grana**
stacks of up to 100 disc like structures
27
**thylakoids** (3)
- disc like structures
- made from membranes
- within the membranes is the photosynthetic pigment called chlorophyll
28
**stroma**
a fluid filled matrix where the second stage of photosynthesis occurs
29
**cellulose cell wall** (2)
- consists of microfibrils; provides strength and rigidity to the cell wall
- prevents the cell from bursting under the pressure created by the entry of water by osmosis
30
what is a **fungi** cell wall made of?
chitin
31
state the three purposes of plant vacuoles (3)
- provide support, making cells turgid
- sugars and amino acids stored, could act as a temporary food source
- the pigments may colour petals and attract pollinating insects
32
define what a **tissue** is
a group of cells working together to perform a specific function
33
define what an **organ** is
a group of tissues working together to perform a specific function
34
what are the differences between a **prokaryotic cell** and a **eukaryotic cell**? (6)
**PROKARYOTIC**
- DNA is circular; not associated with histones
- contains no membrane bound organelles
- has no 'true' nucleus; DNA is free in the cytoplasm
- contains smaller ribosomes (70s)
- some have capsule, one or more flagella, one or more plasmids
- cell wall made of murein
**EUKARYOTIC**
- DNA is linear; associated with histones
- contains membrane bound organelles
- has a nucleus; DNA contained within nuclear membrane
- contains larger ribosomes (80s)
- do not have a capsule, flagella or plasmids
- *plant cells* have a cell wall made of cellulose
35
viruses are ___________
acellular
36
viruses: **FEATURES** (7)
- non living
- require a living cell to replicate inside
- contain DNA **or** RNA, which can be single or double stranded
- genome is surrounded by a protein called a **capsid**
- envelope contains attachment proteins
- no organelles
- has enzymes that it uses to replicate its genetic information
37
how are **retroviruses** different to viruses?
they contain an enzyme called **reverse transcriptase**, which allows them to produce a copy of DNA from viral RNA
38
what do the **attachment proteins** on the envelope of a virus do?
enable the virus to bind to host cells
39
define **resolution**
the ability to distinguish between objects that are close together
40
**light (optical) microscopes** (3)
- focussed using glass lenses
- viewed using the eye or photographic film
- cellular structures often need to be stained with a coloured dye to make them visible
41
which microscope can view both living and dead specimens?
light
42
what is a **limitation** of the light microscope?
the magnification is limited to x1500, meaning none of the smaller organelles can be observed
43
why is the magnification of a light microscope limited?
by using more lenses, a LM can magnify by a larger amount, but at these higher magnifications the microscope loses resolution
44
the ___________ the wavelength of light/electrons, the better the resolution
shorter
45
how many types of electron microscopes are there?
TWO
- transmission electron microscope (TEM)
- scanning electron microscope (SEM)
46
why does a beam of electrons have better resolution than light?
because it has a very short wavelength
47
how does a **transmission electron microscope** work? (3)
- specimens are fixed in resin and sliced thin, so they must be dead
- the electrons are fired through the specimen
- thin parts appear light, thicker areas appear darker
48
how are the specimens prepped for a TEM? (2)(+ 1)
- put in a vacuum
- stained using heavy metals
- a complex process that can create artefacts (which shouldn't be there)
49
how does a **scanning electron microscope** work? (2)
- specimens are not sliced
- electrons bounce off the surface of the specimen
50
what is the only way you can tell if the image is made in an SEM?
the image produced will be 3D
51
**CELL FRACTIONATION AND ULTRACENTRIFUGATION**: *step 1* (3)
- tissue is homogenised in a blender
- in an ice cold, isotonic, buffered solution
- to break open the cells and release organelles
52
why does the solution need to be...
**ice cold**
**isotonic**
**buffered**
**ice cold**
reduces the action of enzymes that would damage organelles
**isotonic**
same water potential to prevent osmosis so that cells don't burst (lysis) or shrivel
**buffered**
maintains pH
53
**CELL FRACTIONATION AND ULTRACENTRIFUGATION**: *step 2* (2)
- mixture is filtered to remove any large pieces of debris
- produces a solution of suspended organelles (**supernatant**)
54
**CELL FRACTIONATION AND ULTRACENTRIFUGATION**: *step 3* (4)
- differential centrifugation
- centrifuged at a low speed
- densest organelles are forced to the bottom of the tube into a pellet
- pellet is removed
55
**CELL FRACTIONATION AND ULTRACENTRIFUGATION**: *step 4* (4)
- supernatant is now centrifuged at a higher speed
- smaller, less dense organelles are forced to the bottom of the tube into a pellet
- pellet is removed
- supernatant can be centrifuged at a higher speed
