Cells Flashcards
(96 cards)
1
Q
What are cells?
A
The smallest building block in an organism.
2
Q
How can cells carry out different functions?
A
They can differentiate.
3
Q
What is the ultrastructure of a cell?
A
The internal structures.
4
Q
Are cells capable of making copies of themselves?
A
Yes
5
Q
What are the three domains that include all living things?
A
Archaea, bacteria, eukaryota
6
Q
What do archaea and bacteria include?
A
All prokaryotic cells and all unicellular organisms.
7
Q
Give 5 examples of eukaryota.
A
Animals, Plants, Algae, Protists, Fungi
8
Q
How much water is a cell made up of?
A
70%
9
Q
Name two functions of proteins in a cell.
A
Enzymes in cytoplasm + organelles
Associated with the membrane
Associated with DNA in the nucleus
Associated with RNA in ribosomes.
Cytoskeleton
10
Q
Name two functions of polysaccharides in cells.
A
Associated with the membrane
Makes up cell walls
Stored for energy reserve
11
Q
Give two functions of lipids in cells.
A
Stored for energy reserve
Phospolipids make up cell membranes
Cholesterol associated with membrane and controls fluidity
12
Q
What do nucleic acids do in cells? (DNA)
A
Associated to proteins in the nucleus
12
Q
What do nucleic acids do in cells? (RNA)
A
mRNA, rRNA, tRNA - different types found in nucleus or cytoplasm or associated with proteins in ribosomes
13
Q
What is the function of the nucleus?
A
Contains DNA instructions for protein synthesis
Produces mRNA and tRNA needed for protein synthesis
Nucleolus manufactures rRNA and ribosomes
14
Q
What is the nuclear envelope?
A
Double membrane that surrounds the nucleus
15
Q
What do the nuclear pores do?
A
Allow large molecules out of the nucleus eg: mRNA
16
Q
What is the nucleoplasm?
A
Granular, jelly-like material
17
Q
What is the nucleolus?
A
Small sphere within nucleus
18
Q
What are chromosomes?
A
Linear DNA that is bound to histone proteins
19
Q
What is a chromatin?
A
When the cell is not dividing, the DNA is more loosely associated with the histones
DNA in this form is enclosed in the nucleus and is called chromatin
20
Q
When is a cell’s DNA called a chromosome?
A
When it is tightly wrapped around histones during cell division
21
Q
How can you see chromosomes in a cell?
A
Using a light microscope
22
Q
What are the rough and smooth endoplasmic reticulum made up of?
A
Folded membranes called cisternae
23
Q
What is the structure of the rough endoplasmic reticulum?
A
Continuous with the nuclear membrane
Has ribosomes on cistarnae
Cistarnae - folded membranes
24
What is the function of the rough endoplasmic reticulum?
Provides large SA for protein synthesis
Protein collects inside it and is then transported throughout the cell
(Synthesises, stores and transports proteins)
25
What is the structure of the smooth endoplasmic reticulum?
Does not have ribosomes
More tubular
26
What is the function of the smooth endoplasmic reticulum?
Synthesises, stores and transports lipids, steroids and carbohydrates
27
What is the function of ribosomes?
Site of protein synthesis
28
What is a ribosome made up of?
Ribosomal RNA and protein
29
What are the two types of ribosomes?
80S - Found in eukaryotic cells
70S - Found in prokaryotic cells, mitochondria and chloroplasts
30
What do ribosomes consist of?
A small and large subunit
31
What is the structure of the golgi apparatus?
Stacks of flattened, membrane-bound sacs or cisternae.
32
What is the structure of vesicles?
Continuously pinched off from the ends of the golgi apparatus
33
What are the proteins and lipids produced by the ER for?
Modification, processing, sorting and transportation
34
What are the 5 functions of the golgi apparatus?
Add carbohydrates to proteins or lipids produced in ER to form glycoproteins/ glycolipids
Produce secretory enzymes
Secrete carbohydrates
Transport, modify and store lipids
Form lysosomes
35
What is the structure of lysosomes?
Type of Golgi vesicle containing hydrolytic enzymes (proteases, lipases, lysozymes)
36
What are the 5 functions of lysosomes?
Digests unwanted material in the cell
Hydrolyse material ingested by phagocytic cell
Exocytosis
Digests worn out organelles
Autolysis
37
What is exocytosis?
Release enzymes to outside of cell to destroy material
37
What is autolysis?
Complete break down of cells after they have died
38
Describe how bacteria are destroyed by phagocytes
Phagocyte engulfs to form vacuole
Lysosomes empties contents into vacuole, releasing enzymes that hydrolyse bacteria
39
What is the function of mitochondria?
Site of aerobic respiration
Releases ATP during respiration - source of energy for cell activities
40
What is the structure of mitochondria?
Double membraned: Inner membrane folds to form cristae; respiratory enzymes embedded in this matrix
Fluid centre = mitochondrial matrix: Contains respiratory enzymes; contains loop of mitochondria DNA, proteins, lipids, ribosomes
41
Why is the cristae highly folded?
Highly folded so as to increase SA:Vol ratio
42
What is the function of chloroplasts?
Site of photosynthesis
43
What is the structure of chloroplasts?
Double membraned
Grana= stacks of disc-like structures called thylakoids (membranes that contain photosynthetic pigment - chlorophyll)
Stroma= fluid filled matrix containing enzymes for PHS
Contain both DNA and ribosomes
44
What is the function of the cell wall?
Provides structural support and strength
Prevents the cell from bursting under osmotic pressure
45
What is the plant cell wall made up of?
Made up of cellulose microfibrils
46
What is the algal cell wall made up of?
Made up of cellulose or glycoproteins or a mixture of both
47
What is the fungal cell wall made up of?
Chitin, glycan and glycoproteins.
48
What is the bacterial cell wall made up of?
Murein (peptidoglycan)
49
Is bacteria eukaryotic?
No
50
What is the function of the vacuole?
Makes cells turgid + provides support
Temporary store of sugars and amino acids
Pigments may give cell colour
51
What is the structure of the vacuole?
Fluid filled sac surrounded by a membrane called tonoplast
52
What is the structure of the cell-surface membrane?
Found in all cells
Phospholipid bilayer - molecules embedded within and attached on the outside (proteins, carbohydrates, cholesterol)
53
What is the function of the cell-surface membrane?
Controls the entrance and exit of molecules
54
What are the key differences between prokaryotic cells and eukaryotic cells?
The cells are much smaller
No membrane-bound organelles
No nucleus
A cell wall made of murein
55
What are the three key types of microscopes?
Optical
Transmission electron
Scanning electron
56
What is the definition of magnification?
How many times larger the image is compared to the object
57
What is the definition of resolution?
The minimum distance between two objects in which they can still be viewed as separate
58
What is the resolution in an optical microscope determined by?
The wavelength of light
59
What is the resolution of an electron microscope determined by?
The wavelength of the beam of electrons
60
How is an image created in an optical microscope?
A beam of light is condensed by a glass lens
61
Give two advantages of using an optical microscope.
Coloured images
Can view living samples
62
Give two disadvantages of using an optical microscope.
Poorer resolution than electron microscope due to light having a longer wavelength
Lower magnification than electron microscope
63
How are images created in an electron microscope?
A beam of electrons is condensed by electromagnets
64
Give two advantages of using an electron microscope.
Higher resolving power than optical microscope as electrons have a shorter wavelength
Higher magnification than an optical microscopes
65
Give two disadvantages of an electron microscope.
Black and white images
The same must be in a vacuum and therefore non-living
66
How do transmission electron microscopes work?
Extremely thin specimens are stained and placed in a vacuum
An electron gun produces a beam of electrons that passes through the specimen
Some parts absorb the electrons and appear dark
The image produced is 2D and shows detailed images of the internal structure of cells.
67
How do scanning electron microscopes work?
Specimens do not need to be thin, as electrons are not transmitted through
Electrons are beamed onto the surface and the electrons are scattered in different ways depending on contours
Produces a 3D image
68
What is the first step of calibration?
Line up the stage micrometer and eyepiece graticule whilst looking through the eyepiece
69
What is the second step of calibration?
Count how many divisions on the eyepiece graticule fit into division on the micrometer scale
70
What is the third step of calibration?
Each division on the micrometer is 10 micrometres so this can be used to calculate what one division on the eyepiece graticule is at that current magnification
71
How and why are cells broken down in cell fractionation?
They are broken down by a homogeniser so that the organelles are free to be separated
72
What are the three conditions of the solution that cells have to be kept in during homogenisation?
Cold, isotonic and buffered
73
Why must the solution that cells are kept in during homogenisation be cold?
To reduce enzyme activity to prevent the breakdown of cell components
74
Why must the solution that cells are kept in during homogenisation be isotonic?
To prevent any movement of water by osmosis, which could result in organelles shriveling or bursting
75
Why must the solution that cells are kept in during homogenisation be buffered?
To resist pH changes that could damage organelles and enzymes
76
What do you need to do once you have homogenised cells in cell fractionation?
You need to filter the solution to remove larger pieces of debris
77
How do you centrifuge a filtered homogenate solution?
Place it into a centrifuge
At first, spin it at a low speed (supernatant), pellet contains the nucleus
Then increase the speed, pellet formed from more dense organelles at start and lighter at end
78
What does a centrifuge do?
It spins at high speed to separate organelles depending on their density due to the centrifugal force.
79
How do prokaryotic cells replicate?
Binary fission
80
How does viral reproduction occur?
Occurs inside the host cells and involves the injection of nucleic acid into the cell
81
What are the three stages of interphase?
G1 - Growth
S - DNA synthesis
G2 - Growth and preparation for mitosis
82
What is interphase?
When the organelles duplicate, the cell grows and then DNA replicates
83
What is the difference between mitosis and meiosis?
Mitosis creates 2 identical diploid cells, whereas meiosis creates 4 genetically different haploid cells.
Mitosis creates cells with identical DNA for growth and repair, whereas meiosis creates gametes.
84
What is the order of stages in the cell cycle?
1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase
6. Cytokinesis
85
What happens in prophase?
The chromatins condense into chromosomes and become visible and the nuclear envelope disintegrates. In animals the centrioles separate & spindle fibre structure forms
86
What happens in metaphase?
Chromosomes align along the equator of the cell
Spindle fibres released from poles now attach to the centromere and chromatid
87
What happens in anaphase?
Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of cell
Centromere divides into two
88
What happens in telophase?
Chromosomes at each pole become longer and thinner again
Spindle fibres disintegrate and nucleus reforms
89
What happens in cytokinesis?
The cytoplasm divides into two
90
What do phospholipids form?
A bilayer
91
Why is the phospholipid bilayer an important part of the cell-surface membrane?
Hydrophilic phosphate heads point to the outside of the cell-surface membrane attracted by water on both sides.
Hydrophobic hydrocarbon tails point into the centre of the cell-surface membrane, repelled by the water on either sides.
92
What are the functions of the phospholipids in the membrane?
Allow lipid-soluble substances to enter and leave the cell
Prevent water-soluble substances entering and leaving the cell
Make the membrane flexible and self-sealing
93
What do the proteins that occur in the surface of the phospholipid bilayer do?
Some never extend completely across it and
94
