Cell Structure, Magnification and Mitosis Flashcards
1
Q
What are the two main types of organisms?
A
Eukaryotes and Prokaryotes
2
Q
What are prokaryotic cells?
A
single- celled organisms that are small and simple eg bacteria
3
Q
What are eukaryote?
A
Any organism consisting of one or more cells that contain DNA in a membrane bound nucleus – separate from the cytoplasm.
4
Q
What are example of eukaryotes?
A
Animals, Plants, Fungi, Protists
5
Q
What is the structure of an animal cell?
A
6
Q
What is the structure of plant cell (practice on white board)
A
7
Q
What makes a fungal cell different from a plant cell?
A
- Their cell walls are made of chitin
- They don’t have chloroplasts (they don’t photosynthesize)
8
Q
Where is the cell surface membrane found? (description)
A
- Surface of animal cells
- Inside cell wall of other cells
9
Q
What is the cell surface membrane made of?
A
Mainly lipids and protein
10
Q
What is the function of the cell surface membrane?
A
- Regulates movement of substances in and out of the cell.
- Has receptor molecules - Allows it to respond to chemicals like hormones
11
Q
What is the description of a nucleus?
A
- Surrounded by nuclear envelope (double membrane) - contains many pores
- Contains chromatin to form chromosomes
- contains nucleolus which is the site of ribosome synthesis
12
Q
What is the function of a nucleus?
A
- Controls cell’s activities
- Pores allow substances to move between nucleus and cytoplasm
- Nucleolus makes ribosomes
- Contains DNA in form of chromosomes
13
Q
Describe a Mitochondrion
A
- Usually oval - shaped
- Double membrane - inner one folded to form cristae
- Inside is the matrix - contains enzymes involved in respiration
14
Q
What is the function of mitochondrion?
A
- Site of aerobic respiration where ATP is produced.
- Found in large numbers in cells that are very active and require a lot of energy
15
Q
Describe Chloroplasts
A
- Small and flattened - found in plant and algal cells
- surrounded by double membrane
- Membranes inside - Thylakoid membranes
- Membranes stacked up in parts of chloroplasts to form grana
- Grana linked together by lamellae
- Lamellae - thin, flat, pieces of thylakoid membrane
16
Q
What is the function of chloroplasts?
A
- Site of photosynthesis
- 1st stage of photosynthesis happens in the grana (light photosynthesis)
- 2nd stage happens in stroma- sugar photosynthesis (thick fluid found in chloroplasts)
17
Q
What is the description of Golgi Apparatus?
A
- Group of fluid-filled membrane-bound flattened sacs.
- Vesicles often seen at the edges of the sacs.
18
Q
What is the function of Golgi apparatus?
A
- Processes and packages new lipids and proteins
- Makes lysosomes
19
Q
What is the description of Golgi vesicle?
A
- Small fluid-filled sac in the cytoplasm
- Surrounded by a membrane
- Produced by Golgi Apparatus
20
Q
What is the function of Golgi vesicle?
A
- Stores lipids and proteins made By Golgi Apparatus
- Transports them out of the cell (via cell-surface membrane)
21
Q
What is the description of Lysosome?
A
- Round organelle surrounded by a membrane
- Type of Golgi vesicle
22
Q
What is the function of Lysosomes?
A
- Contains digestive enzymes called lysozymes - kept separate from cytoplasm by surrounding the membrane
- Lysozymes can be used to digest invading cells or break down worn out components of the cell
23
Q
What is the description of ribosome?
A
- Very Small
- Floats free in cytoplasm or attached to rough endoplasmic rectum
- Made up of proteins and RNA
- NOT SURROUNDED BY MEMBRANE
24
Q
What is the function of Ribosomes?
A
- Site where proteins are made
25
What are the two types of ribosomes?
70S - found in prokaryotes
80S - found in eukaryotes
26
What is the description of Rough Endoplasmic Rectum?
- A system of membranes enclosing a fluid-filled space.
- The surface is covered with ribosomes.
27
What is the function of rough endoplasmic rectum?
Folds and processes proteins that have been made at the ribosomes
28
What is the structure of smooth endoplasmic rectum?
Similar to rough endoplasmic reticulum, but with no ribosomes.
29
What is the function of smooth endoplasmic rectum?
Synthesises and processes lipids
30
What is the structure of a cell wall?
- A rigid structure that surrounds cells in plants, algae and fungi.
- In plants and algae it's made mainly of the carbohydrate cellulose.
- In fungi, it's made of chitin.
31
What is the function of Cell wall?
Supports cells and prevents them from changing shape.
32
What is the structure of Cell vacuole?
- A membrane-bound organelle found in the cytoplasm of plant cells.
- Contains cell sap - a weak solution of sugar and salts.
- The surrounding membrane is called the tonoplast.
33
What is the function of a vacuole?
- Helps to maintain pressure inside the cell
- Keeps cell rigid - stops plant wilting
- Isolates unwanted chemicals in cell
34
What is the difference between Plants and animal cells?
Plants have a cellulose cell wall with plasmodesmata, vacuole and chloroplasts
35
What is plasmodesmata?
‘channels’ for exchanging substances with adjacent cells
36
What is the difference between unicellular and multicellular organisms?
unicellular - all the functions necessary for life must be carried out in one cell.
multicellular - can delegate jobs to particular group of cells
37
What is differentiation?
The process by which a cell becomes specialized to perform a specific function
38
Do all cells contain the same DNA?
YES but different genes are switched on
39
What are specialized cells?
Cells that have adapted to a specific function
40
What are the two key types of microscopes?
Light and electron
41
What are the two types of electron microscope?
transmission and scanning
42
What does magnification mean?
how many times larger the image is compared to the actual size of the object.
43
What is resolution?
The ability to distinguish between two separate points
44
How is resolution determined in light and electron microscopes?
- In light microscopes, it's determined by the wavelength of light
- in electron microscopes, by the wavelength of the electron beam.
45
What is the main source of light in a light microscope?
A beam of light from a lamp or a mirror.
46
Why do light microscopes have lower resolution than electron microscopes?
light has a longer wavelength compared to electrons.
47
What type of images can light microscopes provide?
Color images and can use living samples.
48
What must specimens be in for electron microscopes to work?
A vacuum.
49
What is the formula for calculating magnification?
Image size = actual size × magnification.
50
What is the difference between transmission and scanning electron microscopes?
- Transmission passes electrons through the specimen for 2D images
- scanning reflects electrons off the surface for 3D images.
51
What is the purpose of an eyepiece graticule?
allows for precise measurements and analysis of microscopic specimens.
52
Why must the eyepiece graticule be calibrated?
Because the value of the divisions changes with different magnifications.
53
What is a stage micrometer?
A glass slide with a scale used to calibrate the eyepiece graticule.
54
How do you use a stage micrometer to calibrate the eyepiece graticule?
- Line it up with the eyepiece graticule
- Count how many divisions fit into one division of the stage micrometer.
55
What is an advantage of knowing the actual size of structures in microscopy?
It allows for accurate measurements of cells and organelles under the microscope.
56
How do prokaryotic cells replicate compared to eukaryotic cells?
by binary fission, not mitosis.
57
How do viruses replicate?
by injecting their nucleic acid into host cells.
58
What are the main stages of the cell cycle?
interphase G1 (Gap Phase 1), S (Synthesis), and G2 (Gap Phase 2). nuclear division (mitosis or meiosis), and cytokinesis.
59
During which phase does the cell spend most of its cycle?
(about 90%) is spent in interphase.
60
What happens during the G1 phase of interphase?
organelles double, and the cell grows in preparation for division.
61
What occurs in the S phase of interphase?
DNA replication
62
What is checked in the G2 phase of interphase?
The cell checks DNA for mutations in G2 and destroys the cell if mutations are found.
63
What are the four key stages of mitosis?
prophase
metaphase
anaphase
and telophase.
64
What happens during prophase in mitosis?
- Chromosomes condense and become visible
- chromosomes consists of sister chromatids (identical)
- centrioles move to opposite poles
- the nuclear envelope disintegrates.
65
What happens in metaphase?
Chromosomes align along the metaphase plate of the cell, and attach to spindle fibres via centromeres.
66
What happens in anaphase?
Spindle fibers retract, pulling chromatids to opposite poles, and this process requires ATP.
67
what happens in telophase?
- Chromosomes reach opposite poles
- become longer and thinner
-spindle fibers break down, and the nuclear envelope reforms.
68
What is cytokinesis?
the final step where the cytoplasm splits, resulting in two genetically identical cells.
69
What is the mitotic index, and how is it calculated?
- the ratio of cells in mitosis to the total number of cells.
- It’s calculated by dividing the number of cells in mitosis by the total cells in view.
70
What is the purpose of Mitosis?
for growth and repair, such as when replacing old cells or creating new cells.
71
How many daughter cells are produced in mitosis, and how many divisions occur?
two daughter cells through one division.
72
How is cancer related to mitosis?
Cancer is caused by uncontrolled cell division, leading to excessive cell growth and tumor formation.
73
What role do genes play in cell division?
They regulate cell division; mutations in these genes can lead to uncontrolled cell division.
74
How do most cancer treatments work?
restricting cell division, targeting rapidly dividing cancer cells more than normal cells.
75
Why do cancer treatments affect cancer cells more than normal cells?
Cancer cells divide more frequently
76
Method for measuring cells
- Calibrate eyepiece graticule using stage micrometer
- Measure cell length
- Repeat measurements and calculate a mean
77
Method for measuring cells
- Calibrate eyepiece graticule using stage micrometer
- Measure cell length
- Repeat measurements and calculate a mean
78
Why should a sample be thin and transparent
to allow light pass through
79
why do we use stains ?
to see the cells more clearly
80
Why are there lots of different types of stain?
- Some don’t work on other cells
- Specific stain for different cells
81
What is a plasma membrane, and where is it found?
structure surrounding both cells and certain organelles, like mitochondria.
82
What is the "fluid mosaic model"?
- describes the membrane's structure
- where "fluid" refers to the mobility of molecules
- “mosaic" refers to the variety of components.
83
What are the main components of the plasma membrane?
phospholipids, proteins, glycoproteins, glycolipids, and cholesterol.
84
What is the phospholipid bilayer, and how is it structured?
The bilayer consists of two layers of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward.
85
Describe the structure of a phospholipid
- hydrophilic head (containing a phosphate group)
- hydrophobic tails (made of fatty acid chains).
86
What role does cholesterol play in the plasma membrane?
- restricts the lateral movement of molecules, making the membrane less fluid and more stable at high temperatures.
87
Differentiate between peripheral and integral proteins in the membrane.
- Peripheral proteins are on one side of the membrane
- integral proteins span the entire membrane.
88
What are glycoproteins and glycolipids, and what is their function?
- Glycoproteins (proteins with carbohydrates)
- glycolipids (lipids with carbohydrates)
function as receptors and help in cell recognition.
89
What is the difference between channel proteins and carrier proteins?
- Channel proteins form a pore for water-soluble ions to pass through
- carrier proteins bind and transport larger molecules across the membrane.
90
What is meant by the plasma membrane being "partially permeable"?
- Only certain molecules, like lipid-soluble substances and small molecules (e.g., oxygen, CO₂), can diffuse directly through the bilayer.
91
Which molecules cannot pass through the membrane via simple diffusion?
- Large polar substances like glucose and ions
- water-soluble substances
92
What are the size and structure differences between prokaryotic and eukaryotic cells?
Prokaryotic cells are smaller, lack membrane-bound organelles, and have simpler structures
93
Do prokaryotic cells have membrane-bound organelles?
NO
94
What kind of ribosomes do prokaryotic cells have?
70S ribosomes, while eukaryotic cells have 80S ribosomes.
95
In which eukaryotic organelles might you also find 70S ribosomes?
mitochondria and chloroplasts of eukaryotic cells.
96
Describe the DNA structure in prokaryotic cells.
have circular DNA that is free within the cytoplasm
97
How does the nucleus in eukaryotes compare to prokaryotes?
Eukaryotes have a nucleus with a nuclear envelope, nucleoplasm, and linear chromosomes with histones; prokaryotes lack a nucleus.
98
What are prokaryotic cell walls made of?
glycoprotein called murein.
99
What are the differences in cell walls among prokaryotes, plants, and fungi?
- Prokaryotes have murein
- plant cell walls are made of cellulose
- fungi have chitin-based cell walls.
100
What is a plasmid in a prokaryotic cell?
a small loop of additional DNA that may contain genes, like antibiotic resistance genes.
101
What is the capsule, and what are its functions?
a slimy protein layer that prevents drying out and helps protect bacteria from the host's immune system.
102
What is a flagellum, and what does it do in some prokaryotic cells?
tail-like structure that rotates to propel the bacterium, allowing it to "swim."
103
Are capsules and flagella found in all prokaryotic cells?
NO
104
What is cell fractionation?
a process that isolates different organelles from cells to study them individually.
105
three main steps in cell fractionation?
homogenization, filtration, and ultracentrifugation.
106
What occurs during homogenization?
Cells are broken open in a solution to release organelles, often using a blender or homogenizer.
107
Why is the solution kept cold, isotonic, and buffered during homogenization?
Cold: To reduce enzyme activity and prevent damage.
Isotonic: To prevent organelles from bursting or shrinking.
Buffered: To maintain a stable pH and avoid damage from pH changes.
108
What is the purpose of filtration in cell fractionation?
To remove large cell debris, leaving a liquid with organelles.
109
What is ultracentrifugation?
A process that separates organelles by spinning them at high speeds.
110
In what order do organelles separate during ultracentrifugation?
Organelles separate by density:
- first nucleus, then mitochondria, followed by lysosomes, endoplasmic reticulum and finally ribosomes (from heaviest to lightest)
111
Why are multiple centrifugation speeds used in ultracentrifugation?
Each speed allows different organelles to settle out based on their density and size.
112
What forms at the bottom of the tube during ultracentrifugation?
A pellet of organelles forms at the bottom, with lighter components remaining in the supernatant.
113
What three properties must the solution have during cell fractionation?
cold, isotonic, and buffered.
114
What force does a centrifuge generate to separate organelles?
Centrifugal force.
115
What is the supernatant in ultracentrifugation?
The liquid remaining above the pellet after centrifugation.
116
What happens to the supernatant in differential centrifugation?
It is re-spun at a higher speed to separate the next dense organelle.
117
How are organelles separated in differential centrifugation?
By spinning the supernatant at increasing speeds to isolate each type of organelle.
118
In plant cells, what is found in the second pellet during centrifugation?
Chloroplasts.
119
If asked to separate chloroplasts from plant cells, what is a key step?
Spin once to remove the nucleus, then re-spin to isolate chloroplasts in the second pellet.
120
Are viruses considered living cells?
NO
121
Where do viruses replicate?
Inside of a host cell
122
Why are viruses challenging to treat with medicine?
Destroying the virus would also require destroying the host cell.
123
Why can't antibiotics destroy viruses?
Antibiotics target specific cellular processes like protein synthesis or cell walls, which viruses lack.
124
What does the structure of a virus lack compared to bacterial cells?
organelles and certain chemical reactions found in bacteria.
125
What are the main structural components of viruses?
protein envelope, a capsid, and genetic material (DNA or RNA).
126
Describe Binary fission in bacteria
- Replication of DNA
- Replication of plasmids
- Division of cytoplasm to produce daughter cells
127
during cell fractionation a detergent can be used - why?
Cell membranes made of phospholipids
Detergent dissolves membranes
Releasing cell contents
128
In an investigation about diffusion and plasma membranes (beetroot discs) why would you ensure the beetroot discs were shaken?
- To ensure all the discs exposed to water/ all discs fully submerged
- maintain concentration/diffusion gradient
