1.2 cell structure and organisation Flashcards
1
Q
What is the cell theory?
A
States that all organisms are composed of cells. Cells are the basic unit of life
2
Q
What are unicellular organisms
A
Amoeba and bacteria
3
Q
What are multicellular organisms?
A
Plants and animals
4
Q
How are new cells made
A
Arise from pre existing cells
5
Q
How are specialised cells formed?
A
Specialised cells arise from undifferentiated stem cells.
6
Q
What did Antonie van Leeuwenhoek do?
A
Learned to grind lenses and assemble them into simple microscopes
7
Q
What did Robert Hooke do?
A
Used a simple microscope to observe and draw cork cells.
8
Q
What did Matthais Jacob Shleiden do?
A
Recognised that plants are composed of cells.
9
Q
What did Theodor Schwann do?
A
Realised that animals were also composed of cells.
10
Q
What did Rudolf Virchow do?
A
Proposed that all living cells arise from pre-existing cells.
11
Q
Examples of Eukaryotic cells?
A
Animal and plant cells.
12
Q
What do Eukaryotic cells have?
A
A nucleus and membrane bound organelles.
13
Q
What makes a Eukaryotic cell different?
A
Each part has a different function.
14
Q
What’s the difference between rough endoplasmic reticulum and smooth endoplasmic reticulum?
A
Rough endoplasmic reticulum have ribosomes attached to them
15
Q
What is the nucleus?
A
A membrane-bound organelle found in eukaryotic cells. The largest organelle.
16
Q
Diameter of a nucleus?
A
10-20 micrometres (μm)
17
Q
What does the nucleus contain?
A
The nucleic acids DNA and RNA
18
Q
What does DNA do?
A
Controls protein synthesis.
DNA is replicated in the nucleus.
DNS provides a template for the production of mRNA during transcription.
19
Q
What is the nucleus surrounded by and what does it do?
A
Surrounded by a double membrane with nuclear pores. The pores allow the transport of large molecules out the nucleus
20
Q
The nucleoplasm is inside the nucleus. What does it contain?
A
Contains chromatin, which is made up of coils of DNA bound to protein
21
Q
What happens to chromatin during cell division?
A
Chromatic condenses to form chromosones.
22
Q
What is the small spherical body in the nucleus?
A
The nucleolus
23
Q
What does the nucleolus contain?
A
Pure DNA where RNA and ribosomes are produced.
24
Q
What is the rough endoplasmic reticulum?
A
Network of fluid filled, flattened, membrane bound sacks which are connected to the nuclear membrane
25
What are ribosomes essential for?
Essential for protein synthesis (building proteins)
26
What's the function of the rough endoplasmic reticulum
To package, modify, store and transport proteins to the Golgi body in transport vesicles
27
How is the Golgi body formed?
Transport vesicles are formed and merge to form the Golgi body
28
How are transport vesicles formed?
The ends of the rough endoplasmic reticulum are pinched off
29
What is transcription?
The genetic code in DNA is transcribed (copied) into mRNA molecules
30
What is translation?
The code carried by the mRNA is then translated by the ribosomes into a polypeptide (sequence of amino acids).
31
What are the two parts of the ribosome
Large subunit (at top) and small subunit (small subunit)
32
What two chemical components make up a ribosome?
Protein, rRNA
33
Where in the cell are ribosomes synthesised?
Nucleolus
34
Where are ribosomes located in eukaryotic cells?
On the outer surface of the rough endoplasmic reticulum
35
What does a smooth endoplasmic reticulum do?
Synthesizes, packages and transports fatty molecules called steroid and lipids.
36
How are functional proteins formed?
Polypeptides are further modified. E.g. Carbohydrate chains are added to form glycoproteins, digestive enzymes, and lysosomes.
37
What does the golgi body do?
Stores, packages and transports modified proteins
38
How are modified proteins transported?
Packaged into secretory vesicles, pinched off Golgi body, and transported to the cell membrane.
39
What is exocytosis?
Secretory vesicles fuse with the cell membrane and the modified/functional proteins are secreted from the cell.
An active process that uses ATP
40
What are lysosomes?
vesicles containing strong digestive enzymes.
41
How are lysosomes formed?
When portions of the Golgi body are pinched off
42
What do lysosomes do?
Fuse with organelles which are worn out/not functioning. Digestive enzymes released into the organelle and it is destoryed.
43
What does a lysosome do when a whole cell needs to be destroyed?
Lyses/bursts releases the digestive enzymes into the cytoplasm
44
How do phagocytes use lysosomes?
Use lysosomes to digest bacteria they've engulfed by phagocytosis.
Phagocyte forms a vacuole around the bacterial cell and the lysosome discharges its contents into the food vacuole and digests the bacteria
45
What does the mitochondria do?
Produces ATP by aerobic respiration
46
Length of the mitochondria?
1-10 micrometres (μm)
47
What do mitochondria have?
Double membrane separated by a narrow fluid-filled inter-membrane space
48
What are the folds in the inner membrane?
Extensions called cristae
49
What does cristae do?
Increase surface area of the inner membrane for more ATP production
50
What is the mitochondria filled of?
Organic matrix, containing protein, lipids and other chemical compounds
51
What does DNA in the matrix do?
Allows mitochondria to control the production of their own proteins and replicate new organelles.
52
Why do mitochondria sometimes appear sausage shaped/round in an electron micrograph?
Lying in different planes, or could be different ages/stages of development.
53
Where are mitochondria most abundant in?
Cells with a high energy demand/high metabolism. e.g liver and muscle cells.
54
What is a cytoskeleton?
A network of 3D protein microfilaments and microtubules
55
What does a cytoskeleton do?
Anchors and facilitates movement of organelles within the cell
56
Where are centrioles found?
All animal cells and most protoctists, but not in cells of higher plants.
Located just outside the nucleus in the centrosome in the cytoplasm
57
How are centrioles formed?
From two circles of microtubules which make two hollow cylinders positioned at right angles to each other.
58
What happens to centrioles during cell division?
Divide and move to the opposite poles of the cell where they synthesize the microtubules of the spindle
59
Flagella
100 μm. Used to move cells or organelles
60
Cilia
5-10μm long and move substances such as mucus
61
Are plant cells eukaryotic or prokaryotic?
eukaryotic
62
What do the cell walls do?
Strengthen and support plant tissues
63
What are cell walls composed of?
Mainly composed of the structural polysaccharide cellulose
64
Why does cellulose have a high tensile strength?
Prevents cellysis and maintains cell turgor/strength
65
What is high tensile strength?
High maximum strength that a material can withstand while being stretched or pulled without breaking or bursting the cell
66
What does plasmodesmata do?
Allows transport of substances between cells via the cytoplasm.
67
What are plasmodesmata?
Cytoplasm filled canals which cells are connected by and which cross the cell wall
68
What do plasmodesmata cross through?
Cellulose cell walls
69
Why do plasmodesmata cross cellulose cell walls
To allow the transport of substances from cell to cell via the cytoplasm (symplastic pathway)
70
What are vacuoles?
sacks full of cell sap with their own membranes
71
What is the vacuole's membrane called
Tonoplast
72
What do vacuoles do?
The vacuole is the storage site for chemicals like glucose.
Helps support the cell and plant tissues
73
How do vacuoles help support the cell and plant tissues
Fills with water by osmosis until the cell is turgid
74
What do chloroplasts do?
Carry out photosynthesis
75
Structure of chloroplasts
Each chloroplast surrounded by a double membrane. Fluid filled stroma that contains some of the products of photosynthesis.
76
What does the stroma contain
Ribosomes, lipids, circular DNA and other structures like large starch grains
77
What does DNA do in the chloroplast?
Allows replication of the chloroplast
78
What are thylakoids
flattened sacks within the stroma.
79
How is grana formed
By stacking thylakoids
80
What is a single stack of thylakoids?
A granum.
Each granum consists of 2-200 of these closed, parallel, flattened sacks.
81
What do the thylakoid membranes contain
Photosynthetic pigments like chlorophyll
82
What does chlorophyll do?
Absorbs light energy
83
What do folded membranes provide?
A large surface area for the absorption of more light energy
84
What are prokaryotic cells
Cells which do not have membrane bound organelles
85
What organelles do prokaryotic cells not have
No nucleus, rough endoplasmic reticulum, golgi apparatus, mitochondria, or chloroplastd
86
What does the flagella do
Helps a prokaryotic cell move/swim
87
Function of mesosome
Site of aerobic respiration
88
What does pili do in prokaryotic cell
Helps cell stick to substances
89
What does capsule do in prokaryotic cells?
Makes them less vulnerable to antibiotics
90
Compare prokaryotic and eukaryotic cells
P are smaller (1-10um), E are larger (10-100um).
P have no membrane bound organelles, E have membrane bound organelles (mitochondria and nucleus).
P have circular DNA, E have linear DNA.
P cell wall made of peptidoglycan, E cell wall made of cellulose
91
Viruses don’t have..
Cell membrane, cytoplasm, organelles, or chromosomes
92
How do viruses reproduce
Invade a host cell
93
What are viruses composed of
A protein coat/capsid, which surrounds DNA, RNA or a few genes.
94
What does a virus exist as outside a living cell?
Exists as an inert viron
95
How are viruses viewed
Electron microscope since they’re so small
96
How does a virus invade a host cell?
Hijacks the cell’s metabolism and organelles to achieve protein synthesis and nucleic acid replication
97
Viruses are
Pathogenic
98
What does pathogenic mean
Cause a variety of infectious diseases in humans animals and plants
99
Describe molecules to systems
Atoms arranged into molecules,
Molecules form cells,
Similar cells work together to form tissues.
Tissues perform specific functions.
Different tissues come together to form organs.
Different organs work together in systems
100
What are tissues
Groups of similar specialised cells working together to perform a particular function
101
What are organs
Formed from two or more tissues and have a definite form and function
102
What is a system
Two or more organs working together to perform a specific function
103
What is an organism
Several systems performing numerous roles
104
What is histology?
The study of tissues
105
What is epithelium
A lining tissue.
106
Where do cells sit in epithelium?
Cells sit on a basement membrane and have a free surface on the other side
107
Cuboidal epithelium information
Lines the kidney tubules and ducts of salivary glands.
Cube shaped
108
Ciliated epithelium information
Composed of cells with Cilia.
Columnar shape
109
What does cilia do
Transport substances like mucus in the bronchi. Move and sweep substances along
110
Squamous epithelium information
Consists of flattened cells on a basement membrane.
Form the calls of the alveoli and line the Bowman’s capsule of the nephron in the kidney
111
Skeletal muscle tissue characteristics
- attaches and moves skeleton.
- long bands of cells or fibres which interweave.
- powerful contraction
- fatigues and tires easily
- voluntary
- striped pattern of fibres. Striped/striated
112
Smooth or unstriated muscle tissue characteristics
- spindle shaped cells.
- contract rhythmically.
- less powerful than striated.
- appear smooth : no stripes.
-found in the skin and digestive and respiratory systems.
- involuntary
- responsible for peristalsis
113
Heart muscle or cardiac muscle tissue characteristics
- highly specualised
- between striated and smooth.
- contract rhythmically
- never fatigues or tires
- myogenic: every cell beats rhythmically and continuously
114
What do connective tissues do?
Bind or separate tissues and organs
115
Areolar tissue characteristics
Found under the skin.
Connects organs and tissues together.
116
Collagen tissue characteristics
Forms tendons which connects muscles to bones
117
Elastic tissues characteristics
Ligaments which connect bones
118
Adipose tissue characteristics
Composed of fatty cells and is found just under the skin and around organs.
Functions as energy store, thermal insulator, and protects delicate organs. Provides buoyancy.
119
How is total magnification of image calcated
objective lens magnification X eyepiece lens magnification
120
Calibrating microscope meaning
Measure the actual size of structures on the slide
121
Calculating the true size of a structure from magnified image
1. Measure A-B in mm
2. Divide by magnification
3. Multiply by 1000 to convert mm to um (1mm=1000um)
122
Calculating the surface area of a cylindrical organelle
Surface area = 2 pi radius (length+radius)
123
Why are mitochondria cylindrical
Gives a larger surface area to volume ratio.
Shorter diffusion pathway so more oxygen can diffuse in and more carbon dioxide can diffuse out quickly. Aerobic respiration is more efficient so more ATP will be produced.
124
Calculating surface area of sphere
4 pi radius2
(2=squared)
