A2.2 Cell Structure Flashcards
1
Q
Function of Mitochondria
A
- Site of aerobic respiration (release energy)
2
Q
Function of ribosome
A
- Site of protein synthesis
3
Q
Function of cell membrane
A
- Controls movement of substances in and out of cell
4
Q
What is Cytology
A
Study of cells.
5
Q
Cell theory statements*
A
- All organisms are made up of one or more cells.
- Cells are the smallest unit of life.
- All cells come from pre-existing cells.
6
Q
How was cell theory made
A
Observation through microscope + inductive reasoning: pattern.
7
Q
Why are microscopes used?
A
Microscopes with high magnification and resolution helps make cells visible as they are very small.
8
Q
Define Magnification*
A
Number of times larger an image is than the object.
9
Q
Define Resolution*
A
Minimum distance between two points which they can still be distinguished.
10
Q
Difference between Light microscopes and Electron microscopes*
A
- Light: Inexpensive; specimen prep is simple; magnifies up to 2000; specimens can be dead or alive. Image can be in color.
- Electron: Expensive; preparation of specimens is very complex; magnifies up to 500000; specimens have to be dead. Image is produced in black and white.
11
Q
Explain fluorescent stains and immunofluorescence*
A
Fluorescent stains: absorbs light and re-emits it at different wavelength to brighten.
Immunofluorescence uses antibodies to bind to different structures. Different fluorescent stains bind to different antibodies which behind to specific proteins, creating different distinguishable colored images, allowing visualization of specific proteins in cells.
Used to identify structures or compounds in cells.
12
Q
Converting units*
A
μm = 1000 x mm
nm = 1000 x μm
13
Q
Magnification calculation*
A
Total magnification = Ocular x Objective
Magnification = Image size/ specimen size
14
Q
Example question: Object has been magnified x31000 and measures 43mm in length. What is its actual size in nm?
A
Object size = image / magnification
43/31000 = 0.001387
0.001387 x 1000 = 1.387μm
15
Q
Types of electron microscope
A
Transmission electron microscope (TEM): beam of electron is transmitted through a specimen and focused to produce an image. Similar to light microscopy. Has excellent resolution (resolving power of 0.5nm). Has magnification of up to 500,000.
Scanning electron microscope (SEM): a beam of electrons is sent across the surface of a specimen and the reflected electron are collected. Has good resolution (resolving power of 3-10nm). Has magnification of up to 100,000. Can produce 3D images.
16
Q
Explain what is meant by an Artefact
A
- Structures that are produced due to perpetration process, not actually a feature of the specimen.
- Can be found in light microscopy as well. Bubbles trapped under coverslip are artefacts.
- Artefacts are inevitable in electron microscopy. Experience allows scientists to distinguish between artefacts and actual structures.
17
Q
Explain Freeze-fracture microscopy*
A
- A process of preparing a sample for electron microscopy: Specimen is rapidly frozen then physically broken apart at weakest point.
- This reveals a plane through a sample: vital for understanding the structure of the cell membrane.
18
Q
Explain Cryogenic electron microscopy*
A
- Recent advancement in electron microscopy.
- Revolutionary in understanding structure of viruses and other cellular proteins. Protein structure.
- How it works: specimens are frozen in ice using very low temp and an image formed using computer enhancements that shows the 3D framework of proteins integral to cell functioning.
19
Q
Microscopy and technique used to study different structures within living organisms’ cells
A
- Light microscopy.
- Fluorescence: cells are stained with special dyes that bind to specific cellular components. When UV is shone on specimen, the parts that the dye bind to fluoresce.
- Immunofluorescence: antibodies combined with the dye are added to the specimen. The antibodies bind to their target. This allows specific parts of the cell to be visible when UV light is shone.
20
Q
Structures common to all cells
A
- DNA: as their genetic information
- Cytoplasm: water-based solution where metabolic reactions occur.
- Plasma membrane: Semi-permeable phospholipid bilayer on outside of cells.
21
Q
Prokaryote cell structure
A
- Believed to have been among first life forms on earth
- 10-100 microns in size (small)
- single-celled (unicellular) or Filamentous (strings of single cells)
- Lack a nucleus
- Have a cell wall
- No histones
- 70s ribosomes
- Non-compartmentalized
22
Q
How is DNA stored in Prokaryotes
A
Structure is same as Eukaryotes.
Different packaging:
Consists of one supercoiled chromosome
Genes grouped into operons (cluster of genes - switched on or off together)
Overall called a nucleoid DNA.
23
Q
Function and Composition of Cell Wall for Prokaryotes*
A
Made of peptidoglycan (murein): polymer formed from amino acids and sugars.
For structural support and protection for the cell. It acts as a rigid barrier that maintains the cell’s shape and prevents it from bursting due to osmotic pressure changes.
Many antibiotics work by targeting cell wall.
24
Q
Structure and Function of Capsule*
A
Some prokaryotes have a capsule that surround cell wall. Composed of monosaccharides joined together by glycosidic linkages in most bacteria.
Role: keep phagocytes from ingesting and destroying bacterial cell.
25
Function and Composition of Plasma membrane*
Semi-permeable membrane to control movement of substances in and out of cell. controls internal conditions of cell and regulates transport processes.
Composed of a phospholipid bilayer with embedded proteins.
26
Function and Composition of Cytoplasm*
The gel-like substance that fills the cell's interior. It provides a medium for the suspension of organelles and the occurrence of biochemical reactions.
Composed of water, enzymes, nutrients, and other cellular components.
27
Function of 70s Ribosome for Prokaryotes*
Site of Protein synthesis.
Two subunits (30s and 50s) composed of rRNA and proteins.
28
Flagella of Prokaryotes
Thinner than flagella of eukaryotes.
Consists of a filament attached to plasma membrane by a basal body.
A molecular motor causes hook to rotate, giving flagella whip like motion to propel cell.
29
How do Prokaryotes replicate?*
Binary fission. Chromosome is replicated semi-conservatively.
Beginning with point of origin, two copies of DNA moved to opposite ends of the cell.
Cell elongates.
Plasma membrane grows inward and pinches off to form two separate identical cells.
30
Eukaryote cell structure*
- Some have cell wall (fungi and plants)
- Compartmentalized
- Have a nucleus (DNA stored inside - histones)
- 80s ribosomes (larger than pro)
- Mitochondria: site of aerobic respiration.
31
Function and Composition of 80s Ribosome for Eukaryotes*
Site of protein synthesis.
Two subunits (40s and 60s) composed of rRNA and proteins.
32
Function and Composition of Nucleus for Eukaryotes*
Largest organelle in cell.
Contains nucleolus: produces ribosomes which move out of nucleus to latch onto outside of rough endoplasmic reticulum where they produce proteins.
Nuclear envelope: a dense spherical structure that surrounds the nucleolus - it is a structure made of two membranes (inner and outer) with fluid separating them. Nuclear envelope marked with nuclear poles to allow exchange of relatively large molecules.
Contains the DNA in the form of chromosomes.
The nucleus regulates gene expression, controls cell division, and produces ribosomes.
33
What is the role of Compartmentalization.*
All eukaryotes have compartmentalized cell structure - membranes used to separate certain parts of cell from rest to form separate organelles.
This allows:
- Internal conditions (E.g. pH) to be differentiated in a cell to maintain optimal conditions for different enzymes.
- Isolation of toxic substances away from cytoplasm.
- Flexibility of changing number and position of organelles within the cell based on requirements.
34
Function and Structure of Mitochondria for Eukaryotes*
Contain their own DNA
Have a double membrane: outer membrane is smooth, inner membrane is folded into cristae for bigger surface area when creating ATP.
Fluid inside inner membrane called the matrix.
Responsible for cellular respiration.
35
Function and Structure of Golgi Apparatus in Eukaryotes*
Stack of membrane-bound flattened sacs.
It modifies, sorts, and packages proteins and lipids synthesized by the ER. It also produces lysosomes.
Consists of cisternae (flattened sacs) and vesicles.
36
Function and Composition of Lysosomes for Eukaryotes (not in plants)*
Spherical sacs surrounded by a single membrane.
They are specialized vesicles.
Contain powerful hydrolytic digestive enzymes in order to break down materials.
37
Function and Composition of the Rough Endoplasmic Reticulum for Eukaryotes*
Consists of a series of flattened membrane-bound sacs called cisternae
Transports proteins that were made on attached ribosomes.
Some of the proteins secreted by the cell whilst others will be placed on surface of the cell membrane.
38
Function and Composition of the Smooth Endoplasmic Reticulum for Eukaryotes*
Same structure as RRE but does not have ribosomes.
Roles:
- Making phospholipids and cellular lipids.
- production of sex hormones (E.g. Estrogen)
- Detoxification of drugs in liver.
- Storage of calcium ions in the muscle, which are needed for muscular contraction.
- Help liver release glucose into blood when needed.
39
Function and Composition of Cytoskeleton (Centrioles) for Eukaryotes*
Self-replicating organelles made up of nine bundles of microtubules and are found only in animal cells.
Help in organizing cell division (but not required for process).
Role is to:
- provide mechanical strength to cells.
- Aid transport within cells.
- Enable cell movement.
40
Function and Composition of Vacuole for Eukaryotes*
Formed in Golgi apparatus.
Large, fluid-filled sacs that store water, nutrients, and waste products.
Occupy a large space in plant cells, but can be small and numerous in animal cells.
Roles:
- Storage of nutrition in plant cells.
- Metabolize toxins for removal.
- Uptake of water to provide rigidity
41
MR. SHENG*
life processes.
42
How are life processes done in unicellular organisms?*
Unicellular organisms: only one cell.
Different parts of the cell carry out different functions. All functions carried out by one cell.
E.g. Paramecium and Chlamydomonas
43
How are life processes done in multicellular organisms?*
More than one cell.
Different cells specialize and carry out different functions.
44
Characteristics of Paramecium that enable it to perform the life processes. (Unicellular organism)*
They have cilia outside for sensitivity and movement. Contractile vacuole removes water for homeostasis. Food vacuole holds food for ingestion. Nucleus to hold DNA for reproduction. Cytoplasm contains dissolved enzymes to catalyze metabolic reactions. Grows until reaches maximum surface area to volume ratio, at which point it will divide. Anal pore for excretion.
45
Characteristics of Chlamydomonas that enable it to perform the life processes. (Unicellular organism)*
Light sensitive 'eyespot' to sense light and move to it using its two flagella. Cytoplasm and chloroplast contain dissolved enzymes to catalyze metabolic reactions. Photosynthesis for nutrition. Grows until reaches maximum surface area to volume ratio, at which point it will divide. Nucleus divides to make another nuclei for reproduction. Oxygen diffuses out through cell membrane: excretion. Contractile vacuole to maintain homeostasis.
46
Differences between Eukaryotic and Prokaryotic cells*
Prokaryotic:
- DNA in a ring form without protein.
- DNA free in the cytoplasm (nucleoid region).
- No mitochondria.
- 70s ribosome.
- No internal compartmentalization to form organelles.
- Size less than 10 micrometers.
Eukaryotic:
- DNA with proteins as chromosomes.
- DNA enclosed within a nuclear envelope (nucleus).
- Mitochondria.
- 80s ribosome.
- Internal compartmentalization to form many types of organelles.
- Size more than 10 micrometers.
47
Eukaryotic cells are classified into what three types?
Animal cells.
Plant cells.
Fungal cells.
48
Compare and Contrast structures of plant, animal and fungal cells.*
Cell wall: Plant and Fungal.
Chloroplasts: Plant (for production of carbohydrates.)
Vacuoles: Plant - large centrally located vacuoles for storage of carbohydrates. Animal and Fungal - generally small and numerous with many unique functions.
Centrioles: Animal - both centrosome and centrioles.
Cilia and Flagella: Animal.
49
How do features of skeletal muscle fibers make them an atypical (abnormal) cell.*
Cells are supposed to have one nucleus but skeletal muscle fibers are long cells that have multiple nuclei.
50
How do features of aseptate fungal hyphae make them an atypical cell.*
Cells are supposed to have clear separation from neighbor cells but these lack a cell wall.
51
How do features of red blood cells make them an atypical cell.*
Cells are supposed to have one nucleus: red blood cells have none.
52
How do features of phloem sieve tube elements make them an atypical cell.*
Part of phloem.
Cytoplasm and nucleus removed: rely on companion cells to carry out necessary functions.
53
Distinguishing features of a prokaryotic cells (need to know when looking at image of electron microscopy)*
Shape: usually either a rod shape (column), a round shape or a spiral shape.
Size: less than 10 micrometers.
DNA: not in round structure, just spread out in middle.
Lack of membrane-bound organelles.
54
Distinguishing features of plant cells (image microscopy)*
Shape: more geometrical (not a blob) - from cell wall.
Vacuole: Large, in the center, white.
Chloroplasts: quite big, darkened disks inside.
55
Distinguishing features of animal cells.*
No cell wall: more of a blob sometimes. Animal cells have very different shapes.
Nucleus: larger part: specs inside.
56
What came first Prokaryotes or Eukaryotes*
A lot of evidence that suggest prokaryotes were the first cells.
Eukaryotes came much later.
57
Explain Endosymbiosis for the creation of Eukaryotic cells.*
Heterotrophic prokaryote (engulfing) and autotrophic prokaryote (making own food) engulfed by early Eukaryote and evolved to form the mitochondria and chloroplast. This means that the mitochondria and chloroplast were once prokaryotes
Evidence that this happened:
Mitochondria and chloroplasts are similar to prokaryotes in that they:
- Have their own circular DNA
- Have 70s ribosomes.
- Synthesize their own proteins.
- Reproduce independently by binary fission.
Mitochondria and chloroplasts also have a double membrane (their original membrane + from engulfing process).
58
Explain Cell differentiation as the process for developing specialized tissues in multicellular organisms.*
Multicellular organisms: many cells - specialized cells with different structures and functions that conduct different life processes.
During embryonic development: when we are embryos, the stem cells are undifferentiated; identical genes.
Variety of different cell types occur during embryonic development where some of those genes are expressed and some are not.
Some genes expressed in every cell: E.g. how to manufacture ribosomes, how to go through cell division.
59
Which organisms are multicellular?
All animals
All plants
Some fungi
Some algae
60
Advantages of Multicellularity*
Longer lifespan
Larger, so play different roles in ecosystems.
Can differentiate into cell types: greater efficiency.
61
Disadvantage of Multicellularity*
If one type of cell is removed, cannot survive as they all have specialized, necessary tasks.
