1.1: Cell structure and function Flashcards
1
Q
What is the structure of cell surface membranes?
A
- 7nm thick
- 3 layers
2
Q
what is the function of cell surface membranes?
A
- partially permeable membranes which controls exchange between the cell and its environment
3
Q
What is the structure of a nucleus?
A
- surrounded by 2 membranes known as the nuclear envelope
- contains chromosomes which are usually in loosely coiled state known as chromatin
- nucleus contains a darker staining area, the nucleolus
4
Q
what is the nuclear envelope?
A
2 membranes with small holes or pores
5
Q
What is chromatin?
A
chromosomes which are usually in loosely coiled state known
6
Q
what is the function of a nucleus?
A
- controls the cells activities (contains genetic information to make polypeptides).
- chromosomes contain DNA
- nucleolus manufactures ribosomes
- nuclear pores allow mRNA and ribosomes to leave the nucleus and hormones to enter the nucleus.
7
Q
What is the structure of an endoplasmic reticulum?
A
- extensive system of membranes
- forms a system of flattened sacs called cisternae
- small organelles can be attached to the membranes: rough ER
- with no ribosomes: smooth ER
8
Q
What is the function of rough Endoplasmic reticulum?
A
rough:
- transports proteins which have been made on the ribosomes around the cell
- makes the Golgi apparatus
9
Q
What is the function of the smooth Endoplasmic reticulum?
A
- makes lipids and steroids (e.g. cholesterol and reproductive hormones
10
Q
What is the structure of ribosomes?
A
- can be found free in the cytoplasm or attached to the Endoplasmic reticulum
- 22nm in diameter
- made of RNA and protein
11
Q
what is the function of ribosomes?
A
site of protein synthesis
12
Q
What is the structure of Golgi apparatus?
A
- stack of flattened sac called cistemae
- formed from vesicles which off the rough ER
- broken down at the other end to form Golgi vesicles
13
Q
What is the function of Golgi apparatus?
A
- molecules are collected, processed and sorted
- taken from the rough ER and packaged into Golgi vesicles for transport around and out of the cell
- Golgi vesicles are used to make lysosomes
14
Q
what is the structure of lysosomes?
A
- have a single membrane
- size 0.1-0.5 micrometers
- contain hydrolytic enzymes
15
Q
What is the function of lysosomes?
A
- breakdown of old cell organelles or whole cells (e.g. white blood cells digest bacteria)
16
Q
What is the structure of mitochondrion?
A
- surrounded by 2 membranes called an envelope
- inner membrane is folded to form projections called cristae
- interior solution - the matrix
17
Q
What is the function of mitochondrion?
A
- the later stages of aerobic respiration
- they make ATP and are involved in the synthesis of lipids
18
Q
What is the structure of centrioles?
A
- small hollow cylinder
- 0.4 micrometers in length
- found next to the nucleus
- contains a ring of microtubules
ONLY IN ANIMAL CELLS
19
Q
what is the function of centrioles?
A
- help to form the spindle in nuclear division
20
Q
what is the structure of the cytoskeleton?
A
- cytoskeleton is a network of protein fibres
21
Q
what are the 2 types of cytoskeleton?
A
- actin filaments
- microtubules made of tublin which are about 25 nanometers in diameter
22
Q
What do Microtubules have?
A
other proteins called microtubule motors which use ATP
- made of protein tublin that follows narrow hollow tubes throughout the cell
23
Q
What is the structure of cellulose cell wall?
A
- made of cellulose
- plant cells are linked together by plasmodesmata
- these are fine strands of cytoplasm which pass through pore like structures in the cell wall
24
Q
What is the function of cellulose cell wall?
A
- cellulose is rigid
- gives a definite shape and prevents it from bursting when water enters by osmosis
25
What is the structure of large central vacuole?
- surrounded by a membrane called a tonoplast
- vacuole is fluid filled
- contains e.g. minerals, salts, sugars, oxygen, carbon dioxide, pigments
26
What is the function of large central vacuole?
- tonoplasts controls the exchange of materials between the vacuole and the cytoplasm
- gives shape and support
- keeps the cell turgid
27
What is the structure of chloroplasts?
- surrounded by 2 layers of membranes
- inside there is a jelly-like substance - the stroma
- there are membranes forming flattened sacs called thylakoid membranes
- stacks of thylakoid membranes = grana
- small starch grains and lipid droplets are present in the stroma
28
What is the function of chloroplasts?
photosynthesis
29
What is a cell?
A cell is a basic unit of structure and function of an organism. Arises from pre-existing cells by cell division
30
What is an organelle?
a structurally and functionally distinct part of a cell
31
What is contained in a nucleus?
- chromatin
- nuclear pore
- nucleolus
- nuclear envelope
32
What is the cytoplasm and function?
The cytoplasm is fluid that contains in the cell.
it is where all the chemical reactions take place
33
What is the plasmodesmata and function?
Is where transport and communication can occur between the adjacent cells.
34
using cell structure booklet label each structure on the animal and plant cells
use the booklet for answers
35
What is the definition of magnification (MUST BE WORD FOR WORD)
The degree to which the size of an image is larger than the object itself
36
What is the definition of resolution (MUST BE WORD FOR WORD)
The degree to which it's possible to distinguish between two objects
37
What cell structures can be found in animals only?
centrioles
38
What cell structures can be found in plants only?
- chloroplasts
- cellulose cell wall
- large central vacuole
- plasmodelmata
39
What structures are in both plant and animal cells?
- mitochondria
- ribosomes
- SER/RER
- nucleus (nucleolus, nucleotide, nuclear envelope)
- cytoplasm
- Golgi apparatus/vesicles
- lysosomes
40
What cells structures have a single membrane surrounding it?
- cell surface membrane
- LCV
- RER
- SER
- lysosomes
- Golgi apparatus/vesicles
41
What cell structures have a double membrane surrounding it?
- nucleus
- mitochondria
- chloroplasts
42
What cell structures have no membranes surrounding it?
- ribosomes
- centrioles
43
What is the maximum resolution equal to light?
half wavelength
44
what is wavelength described to be compared to resolution?
inversely proportional (as one goes up, the other goes down)
For example: as wavelength decreases, the resolution increases.
45
long wavelength equals
low resolution
46
short wavelength equals
high resolution
47
what is the max magnification and resolution of a light microscope?
mag - x1500
res - 200nm
48
what is the max magnification and resolution of a scanning electron microscope?
mag - x100000
res - 20nm
49
what is the max magnification and resolution of a transmission electron microscope?
mag - x500000
res - 0.2nm
50
How do electron microscopes work?
They use a beam of electrons - shorter wave length than light.
51
What is an electron micrograph?
not visible to the eye. Image projected onto a screen of photographic paper
52
What are the two types of electron microscopes?
- Transmission electron microscope
- Scanning electron microscope
53
How does a Transmission electron microscope work?
Electron beams pass through the sample and the image is in 2D and black/white
54
How does a scanning electron microscope work?
Electron beam does not pass through the Sample - it is a reflected image of the cell surface
The image is 3D and black/white
55
What are the advantages of electron microscopes?
- higher (not better) resolution - more detailed images produced of organelles
- can see prokaryotes cell structure that is too small to see under microscope
- SEM produces 3D images
56
What are the limitations of electron microscopes?
- samples have to be in a vacuum
- expensive
- needs a high degree of skill and training
57
What is an eyepiece graticule?
An eyepiece lens with a scale etched on the glass
58
What is a stage micrometer?
A glass slide with a scale of known dimensions on it
59
What is the measurement of one division on the stage micrometer?
100 micrometers
60
What are the units for the eyepiece graticule?
eye piece units (epu)
61
How do you use a stage micrometer and an eyepiece graticule to measure the length of a cell?
- put micrometer on the microscope stage
- put graticule in eyepiece
- focus on the micrometer
- calibrate the graticule against the micrometer
- replace the micrometer with the specimen used
- using the SAME objective lens
- Measure the length of the cell using the calibrated graticule in epu
- show the calibration
62
What is staining?
Refers to any process that helps to reveal or distinguish different textures
63
What are the stain colours in light microscopy?
May be colours or fluorescent dyes, coloured stains are chemicals that bind to chemicals in or on the specimen.
64
What structures do chemicals bind to?
actin orcein stains (DNA dark red)
Gentian violet stains (Bacterial cell walls)
65
What are the stains in electron microscopy?
- metal particles or metal salts (heavy metals)
66
How can colours be added to electron micrographs?
By adding computer software are called false-colour
67
What cell structures can be seen with a good light microscope?
- nucleus
- centrioles
- cellulose cell wall
- mitochondrion
- chloroplast
- large central vacuole
- starch granules
68
How electrons in microscopes focused onto the specimen?
electromagnets
69
What does the specimens affect? (microscopes)
direction of electrons
70
How are the electrons projected (in microscopes)?
onto a screen of photographic paper to produce an electron micrograph
71
How do you prepare a specimen for TEM? (STEP 1 - vaporise)
- the high energy electron beam can cause temps of up to 150 degrees which would vaporise the sample immediately so all the water must be removed from a sample first.
72
How do you prepare a specimen for TEM? (STEP 2 - vacuum)
The specimen must be placed in a vacuum or the air particles would scatter the electrons
73
How thin must the specimen be for a TEM?
30-60nm
74
How do you prepare a specimen for TEM? (STEP 4 - prepping sample)
A sample is foxed in glutaraldehyde (keeps structure set in place), dehydrated in alcohol and embedded in resin then cut into thin slices using an ultramicrotome and the thin slice mounted onto copper grid to allow electrons to penetrate the sample
75
Why can metal particles or heavy metal salts can be added to specimen? (TEM)
to increase the contrast, colours can also be added by computer software and are called false-colour electron micrographs
76
What are the two types of hair-like extensions that move?
- flagella
- cilia
77
What is the difference between flagella and cilia?
- flagella (few and longer in length)
- cilia: many and shorter in length (less than 10mm)
78
What is the name of flagella in eukaryotes?
undulipodium
79
What motion does cilia move in?
sweeping motion
80
How do cilia and flagella move?
using energy from ATP
The microtubules slide past each other
81
What is the structure of cilia and flagella in eukaryotes?
Both contain microtubules. 9 pairs of these are arranged in a circle. 2 form a central bundle, which is called the 9 + 2 arrangement
82
What is the movement pattern of flagella?
movement of the whole cell, associated with locomotion.
For example: sperm cells
83
What is the movement pattern of cilia?
also associated with locomotion but the sweeping motion of the cilia move substances such as mucus across the cell surface. THIS CAN BE SEEN IN CILIATED EPETHELIAL CELLS
84
what are actin filaments (from actin)?
can be extended or shortened by adding/removing extra actin subunits
85
What is the function of a cell wall in prokaryotes?
Made of murein (petidoglycan).
Physical barrier which prevents mechanical and osmotic damage to cell
86
What is the function of the capsule in prokaryotes?
protection against drying out and helps bacteria stick together
87
What is the function of a mesosome for prokaryotes?
Helps form new cell walls and site of attachment of respiratory enzymes
88
What is the function of the flagellum in prokaryotes?
aids cell movement
89
What is the function of pili in prokaryotes?
attachment to cells and involved in "sexual reproduction"
90
What is the function of circular DNA in prokaryotes?
contains genetic information of the cell
91
What is the function of plasmids in prokaryotes?
Small circle of DNA which contains genes which help bacteria survive adverse conditions
92
What is the function of glycogen granules in prokaryotes?
store carbohydrates for breakdown during respiration
93
What is the function of lipid droplets in prokaryotes?
lipid storage. May be converted to carbohydrate and used in respiration
94
What is the function of photosynthetic lamellae in prokaryotes?
contains Chlorophyll. site of photosynthesis
95
What structures are always present in prokaryotes?
- plasma membrane
- nucleus
- cytoplasm
- ribosomes
- murein cell wall
96
What structures are sometimes present in prokaryotes?
- pili
- capsule
- plasmid
- mesosome
- flagellum
- infolding of plasma membrane
97
Prokaryote vs Eukaryote : average diameter
p: 1-5 micrometers
E: Upto 40 micrometers
98
Prokaryote vs Eukaryote : dna organisation
p: Circular DNA, Naked DNA
E: Linear DNA, histones
99
Prokaryote vs Eukaryote : DNA location
P: either as circular DNA in the cytoplasm or as plasmids
E: in the nucleus
100
Prokaryote vs Eukaryote : Ribosomes
P: Free in the cytoplasm (70s)
E: Connected to rough endoplasmic reticulum or free in cytoplasm (80s)
101
Prokaryote vs Eukaryote : Organelles
P: no membrane-bound
E: Membrane bound
102
Prokaryote vs Eukaryote : similarities
- both structures contain DNA
- have cell surface membranes
- have ribosomes
- have cytoplasm
103
Division of labour: protein synthesis
STEP 1
DNA in nucleus contains instructions to make proteins
104
Division of labour: protein synthesis
STEP 2
Protein is synthesised in ribosomes
105
Division of labour: protein synthesis
STEP 3
Protein is transported through RER
106
Division of labour: protein synthesis
STEP 4
Protein molecules are pinched off in vesicles and travel towards Golgi apparatus
107
Division of labour: protein synthesis
STEP 5
Vesicle fuses with Golgi apparatus (cis face to trans face)
108
Division of labour: protein synthesis
STEP 6
Golgi apparatus processes and packages protein molecules ready for release
109
Division of labour: protein synthesis
STEP 7
Packaged protein molecules are pinched off in vesicles. From Golgi apparatus and move towards cell surface membrane
110
Division of labour: protein synthesis
STEP 8
protein leaves cell by exocytosis
111
protein synthesis: What happens when a vesicle joins from the Golgi body?
releases it's contents/protein into the Golgi body cisternae
112
protein synthesis: what happens to the protein in the Golgi body?
modified & tagged (carbs added)
113
protein synthesis: What two things happen to vesicles leaving the Golgi body?
- travel to cell surface membrane (leaves cells by exocytosis)
- form lysosomes
114
protein synthesis: What happens to proteins from vesicles that join the cell membrane?
Become integral/ intrinsic/ extrinsic/ peripheral/ channel/ transport membrane proteins
