Cells - Compleate Flashcards
(102 cards)
0
Q
What is resolution?
A
The degree to which it is possible to tell two different objects apart that are very close together.
1
Q
what is magnification?
A
how much larger a image size is compared to the size of the object itself.
2
Q
What is staining?
A
Coloured stains are chemicals that bind to chemicals on the specimen so the specimen can be see. some bind to specific cell surfaces, so if a certain colour is present, then the object or organelle can be named.
3
Q
what colour does acetic orcein stain DNA?
A
Dark Red.
4
Q
What stains bacterial cell walls in particular?
A
Gentian Violet.
5
Q
What is sectioning?
A
When specimens are embedded In wax, so they can then be cut out it hour distorting the specimen’s structure (often used in soft tissue, I.e. Brain)
6
Q
How does a decimetre relate to a metre?
A
A decimetre is one tenth of a metre and is equivalent to 0.1 m
(Dm)
7
Q
How does a centimetre relate to metres?
A
A centimetre is one hundredth of a metre, and is equivalent to 0.01 of a metre. (Cm)
8
Q
How does a millimetre relate to a metre?
A
A millimetre is one thousandth of a metre and is equal to 0.001 of a metre. (Mm)
9
Q
How is a micrometer related to a metre?
A
It is a one millionth of a metre and is equivalent to 0.000 001 of a metre.
10
Q
How is a nanometer related to a micrometer?
A
It is one thousandth of a micrometer
11
Q
What is the resolution for the human eye?
A
100um (micrometers)
12
Q
What is the resolution for a light microscope?
A
200 nm
13
Q
What is the resolution for an electron microscope?
A
0.2 nm
14
Q
What is the sum triangle for magnification?
A
Image size
_________________________
Actual size x magnification
15
Q
What are the characteristics of living organisms?
A
M movement
R respiration
S sensitivity
N nutrition
E excretion
R reproductiob
G growth
16
Q
What is a cell’s ultrastructure?
A
The detail of the inside of a cell, as revealed by an electron microscope.
17
Q
How do electron microscopes work?
A
- generate a beam of electrons (with wavelength of 0.004nm)
- use magnets to focus beams
- electrons are not visible to human eye so image is projected onto screen
- resolution is 0.2 nm (500 000 more than human eye)
18
Q
what is a greyscale image?
A
An image projected onto a screen or photographic paper because we cannot see electrons with the human eye.
19
Q
Describe the TEM
A
The transmittion electron microscope:
- electron beam passes through thin sample
- pass through less dense parts more easily (so give contrast)
- 2D image with magnification of 500 000
20
Q
what is the SEM?
A
- electrons hit specimen and ‘bounce off’ to produce a 3D image with magnification of x100 000
21
Q
What are the advantages of using an electron microscope?
A
- resolution in 0.1nm (better than light)
- can produce detailed images (of organelles)
- SEM can produce 3D image
22
Q
What are the limitations of an electron microscope?
A
- specimens have to be placed i a vacuum so electron don’t bouce off air
- v. expensive
- require high skill and training
23
Q
What is division of labour?
A
Where each type of organelle has a specific role in the cell. They work together to ensure the survival of the cell.
24
what is the cytoskeleton?
a internal framework made up of a network of fibres made of protein that keep the cell's shape
25
What are actin filaments?
Some of the fibres in the cytoskeleton are called actin filaments which are able to move against each other. They cause movement of organelles inside cells and cause movement of white blood cells?
26
What are microtubules?
Some fibres that make up the cytoskeleton. They are made out of the protein tubulin. they can be used to waft a microorganism through a liquid, or waft a liquid through a cell. This is how chromosomes and vesicles move.
27
What are undulipodia and cilia?
hair like extensions that stick out from the surface of the cell. made up of a cylinder that contains 9 microtubules arranged in a circle with two in the middle.
28
What is the difference between the undulipodia and cilia?
Undulipodium has a long whip like structure which can be used to move the whole cell (e.g. sperm cells). cilia use sweeping movements to move substances across the surface of cells.
29
What are vesicles and vacuoles?
vesicles are membrane bound secs found in cells that are used to carry substances around cells. In plants, the vacuole maintains cell stabikity as it is filled with water to provide turgidity.
30
What are cell walls?
Found in plant cells, these are on the outside of the cell membrane. they are made of cellulose (carbohydrate monomer made up of glucose subunits) which provide sieve like strands to make the wall strong. it is held rigid by the pressure on the inside of cell.
31
Describe the structure of the nucleus.
- the largest organelle
- when stained, there are dark patches called chromatin
- surrounded by nuclear envelope (two membranes with fluid inside)
- many nuclear pores going through nuclear envelope
- dense spherical nucleolus inside
32
What is the function of the Nucleus?
- Contains the cells genetic material
- Chromatin is DNA and proteins, some of which regulate cell activities
- when cells divide, chromatin has condenses into chromosomes
- The nucleolus contains RNA and ribosomes which pass into the cytoplasm and assemble proteins
33
Describe the structure of the Endoplasmic Recticulum
- Consists of cisternae (fattened, membrane bound sacs)
- Continuous with the outer nuclear membrane
- Rough ER is studded with ribosomes
- Smooth ER is not
34
What is the function of the ER?
- Rough ER transports proteins made on the attached ribosomes (some may be secreted by cell or placed on the cell surface)
- the Smooth ER makes lipids
35
Describe the structure of the Golgi apparatus
A stack of membrane bound, flattened sacs
36
What is the function of the Golgi apparatus?
It modifies a proteins from the ER (e.g. by adding sugar molecules)
It packages proteins in vesicles
some of these proteins may be secreted at the cell surface
37
Describe the structure of mitochondria
May be spherical or sausage shape
| Two membranes filled with fluid - inner membrane folds to make cristae. the central part is called the matrix
38
What is the function of mitochondria?
- the site where ATPis made as all activities that use energy need ATP
39
Describe the structure of choloroplasts
- only in plant cells
- two membranes filled with fluid
- inner membrane is continuous, with and elaborate network of thylakoids (membrane bound sacs) a pile of which is called a granum
- Chlorophyll is present in thylakoid and intergranal membranes
40
what is the function of chloroplasts?
They are the site of photosynthesis light energy fuels the reaction where carbohydrates make carbon dioxide and water
41
describe the structure of lysosomes
Spherical sacs surrounded by a single membrane
42
What is the function of lysosomes?
They contain powerful digestive enzymes and their role is to break down materials. Whit blood cells break down invading microorganisms; acrosome no the the head of a sperm cell braks down the material of the egg
43
What is the function of Ribosomes?
They are the site of protein synthesis; they act as an assembly line where mRNA is used to assemble proteins from amino acids.
44
Describe the structure of Ribosomes
tiny organelles in cytoplasm or bound to ER each one consisting of two subunits
45
Describe the structure of centrioles
Small tubes of protein fibres (microtubules). There is a pair next to the nucleus in animal cells.
46
What is the function of centrioles?
They form spindle which moves chromosomes in cel division.
47
Describe how a cell works together when making a protein:
1. genetic info (gene) is stored in the nucleus and a copy carried out by mRNA through the nuclear pores
2. This is taken to a ribosomes or Rough ER where protein synthesis occurs
3. It is pinched off in a vesicle and transported to the Golgi body
4. The Golgi body modifies the protein and then packages it in a vesicle
5. the vesicle moves to the cell membrane and they fuse together, releasing the protein
48
What is a Eukaryotic cell?
A cell that contains a 'True' nucleus
49
What are the features of a prokaryotic cell?
- Only have one membrane (cell surface membrane)
- Surrounded by a cell wall (usually made of peptidoglycan)
- Smaller ribosomes than eukaryotic cells
- Free DNA in cytoplasm as one loop unlike liner DNA of eukaryotic cell
- General area of DNA called nuleoid
- ATP takes place in specialised in folded region of cell membrane (mesosomes)
- Some have flagella
50
What are some useful prokaryotic cells?
- Use of bacteria in cheese and yoghurt
- Bacteria helps vitamin K production an digestion of some food
- Skin has normal flora bacteria to prevent harmful microorganisms from getting into the body
- sewage treatment and natural recycling involve bacteria
51
What are the roles of membranes?
- Separate cell content from outside world
- Separate cell components from cytoplasm
- Cell recognition and signalling
- Holding components of metabolic pathways in place
- Regulate transport of materials in / out of cells
52
Expain the nature of phospholipids.
The phosphate head is hydrophilic and the two fatty acid tails are hydrophobic. This is due to the way that charges are distributed throughout the molecule. if phospholipids are mixed with water, they form a layer on top with the hydrophobic tails out of the water and the hydrophilic heads in the water.
53
Explain how a bilayer forms with phospholipids.
when the phosphate hydrophilic heads stick to the water while the hydrophobic fatty acid heads point towards each other so it looks like a reflection and the tails are held away from the water. The hydrophilic head cannot pass through the hydrophobic region easily so the bilayer is given some stability.
54
Name some specialised cell membranes and their functions
- Plasma membrane of cells in a growing shoot contain receptors that allow them to detect the growth regulation molecules.
- muscle cell membrane contain many channels to allow rapid uptake of glucose
- internal membranes of chloroplasts contain chloroplast for photosynthesis
- white blood cell plasma membrane contain proteins to allow the cell to recognise self and foreign bodies
55
What are the main features of a fluid mosaic model ?
- a bilayer of phospholipids to form the molecules to form the basic structure
- various proteins floating in the bilayer, some freely, some bound to other components or structures in the cell
- some extrinsic proteins partially embedded in bilayer on outside of cell
- some intrinsic proteins spanning across the bilayer
56
what are glycoproteins and glycolipids?
Glycolipids are where phospholipid molecules hve a carbohydrate part attached and a Glycoprotein is a protein with a carbohydrate part attached.
57
What does cholesterol do in the fluid mosaic model?
It give the membranes in some eukaryotic cells mechanical stability by sitting between fatty acids ad making it more compleate so water cannot get through.
58
what do channel proteins do in the fluid mosaic odel?
Allow the movement of large and hydrophilic molecules to pass directy through the bilayer.
59
What do carrier proteins do in the fluid mosaic model?
They actively transport molecules through the membrane. i.e. against the concentration gradient.
60
Explain how recognition and communication happens withe the fluid mosaic model.
Receptor site allow specific hormones to bind with the cell so that the cell can react to the hormone. They also import drugs to bind with and affect the cell metabolism.
glycoproteins and glycolipids signal that the cel is 'self' to allow recognition by the immune system. they may also be hormone receptors.
61
Explain how temperature effects membranes:
- increasing temp increases KE so molecules move faster
- makes membranes leaky so increases permeability
- organisms live in hot conditions will need more cholesterol to reduce permeability
- organisms in cold conditions will need less cholesterol
62
What is a target cell?
A cell with a receptor for the specific hormone
63
Explain how the insulin receptor works:
- insulin is released by special cells in islets of Langerhans in the pancreas
- insulin is a protein that attaches to receptor molecules of many cells, including in muscle and liver cells
- hen insulin attaches to receptor, internal responses in the cell mean more protein channels are present in the plasma membrane so the cell can take up more glucose and the blood sugar drops
64
How do medical drugs interfere with receptors?
- some drugs are a complementary shape to a specific receptor
- such drugs block receptors
- beta blockers is used to prevent heart muscle from increasing heart rate
- drugs to treat schizophrenia work in this way.
65
Explain how viruses hijack receptors:
- viruses enter cells by binding with receptors on membrane
- HIV can infect humans as it can enter cells in the immune system
- once etering the cell it may reproduce and destroy it
66
What is the rate of diffusion affected by?
```
Temp - more KE
conc. gradient
stirring/moving - increases movement
SA - larger SA
distance/thickness
sizeof molecule - smaller molecules diffuse faster
```
67
Give two examples of when active transport is needed:
Mg ions are in short supply soil by still need to be taken up by roots
Helps to absorb glucose from intestines
68
Explain how carrier molecules work:
They act as pumps ad have a complementary fit to the molecule they carry. They carry specific large or charges molecules through membranes against their conc. gradient. They use ATP so carry molecules much faster than just diffusion. The energy used changes the shape of the carrier protein and this means that the molecule cannot go out the way it came back.
69
Explain what endocytosis and exocytosis are:
The bulk transport of materials inside (endocytosis) or outside the cell(exocytosis). This is achieved by membranes fusing, separating and being 'pinched off'. it needs energy from ATP which it uses to move the vesicles.
70
What is water potential?
A measure of the tendency of water molecules to diffuse from one place to another. Water moves from high water potential to low water potential.
71
What is osmosis?
The diffusion of water molecules across a partially permeable membrane.
72
What will happen if the water potential outside a cell was higher than the cell contents?
Water molecules will move down the water potential gradient through osmosis and they will enter the cell.The cell will swell, in animals, the cell will eventually burst but in plant cells, the cell will just become turgid due to the cell wall.
73
Explain how water potential is measured:
- Measured in KiloPascals (kPa)
- Pure water has the highest water potential, but is 0 kPa
- Goes from 0 to negative figures (as thee becomes less water molecles)
74
Explain Chromosomes and instructions:
- Chromosomes are in the nucleus of eukaryotic cells
- Each one contains one molecule of DNA which contains genes
- Chromosomes there fore hold the instructions for making a new cell
- A daughter cell must contain a full set of chromosomes so it has a full set of the instructions
75
Why do all cells need to be able to produce genetically identical daughter cells?
- Asexual reproduction
- Growth, multicellular organisms grow by crating by cells
- Repair, damaged cells need to be replaced
- Replacement
76
What are the four stages of mitosis in order?
PROPHASE - replicated chromosomes supercoil (shorten/thicken)
METAPHASE - replicated chromosomes line up in the middle of cell
ANAPHASE - replicas of chromosomes are pulled apart
TELOPHASE - two new nuclei are formed
77
What happens in prophase?
- Each chromosome has already replicated in interphase
- Chromosomes supercoil (shorten and thicken) - you can see them and sister chromatids with a light microscope
- Nuclear envelope breaks down and disappears
- The centriole divides into two and each daughter centriole move to opposite poles to form the spindle
78
What happens in metaphase?
Chromosomes move into the centre of the spindle (at the equator) each becomes attached to the spindle thread by its centromere
79
What happens in metaphase?
replicated sister chromatids that make up chromosomes are separated as the centromere holding them together splits. Each sister chromosome effectively becomes an individual chromosome and each one is identical. The spindle fibres shorten, pulling the sister chromatids further to the poles.
80
What happens in telophase?
As the sister chromatids/chromosomes reach the poles new nuclear envelopes form around them.
The spindle breaks down and disappears The chromosomes uncoil so you can no longer see them under the light microscope.
81
What is Cytokinesis?
When the whole cell splits to make two new ones each containing a full set of chromosomes.
82
What are meristem cells?
Special cells in plants that are capable of mitosis and cytokinesis.
83
Explain what happens when Amoeba undergoes mitosis?
The daughter cell is a clone of the original cell and they are genetically identical. Both cells can reproduce and survive. They are created by binary fission when they divide.
84
Explain clones in plants?
many plants undergo asexual reproduction using specialised parts of the plants that are derived from adult plant cells. These parts produce new, individual organisms that are genetically identical to the rigioal parent, and they are called clones.
85
Explain how artificial cloning has been used in growing plants:
Cuttings are taken from plants and grown into adult plants. These plants will be genetically identical to the plant so they are clones
86
What are stem cells?
Mitosis produces daughter cells that are genetically identical to the parent cells. they are potentially capable of becoming any one of the cells found in the organism. e.g. they are omnipotent or totipotent. They only appear in small numbers in an adult mammal. it is found in the bone marrow as cells divide to produce blood cells or bone cells.
87
Why can animals repair damaged organs?
They are capable of mitosis and cytokinesis so they can create more cells to replace damaged ones.
88
What are meristems?
Meristem is found at the in the growing regions (root tip and shoot tip) and it is only meristem cels that can divide like this.
89
What is meiosis?
This is sexual reproduction so involves two nuclei , normally from different individuals to produce offspring. Each cell would provide half of the adult chromosomes so the are a gamete. The fusion of two of these Gametes creates a zygote that can then reproduce by mitosis. one member of each homogenous pair will go into each cell.
90
how meiosis different from mitosis?
Meiosis produces cells that are genetically different.
| Meiosis produces cells with half of the number of chromosomes.
91
Why is there a physical size limit to cells?
Because they need to be able to support internal structures of the cell and a larger cell will have a lower SA to volume ratio so will get less O2 in. `
92
What is differentiation?
The change that occur in multicellular organisms so that each cell becomes specialised to be a special role
93
Explain how Erythrocytes and Neutrophils are different (and why)
Both are produced in the bone marrow
- RBC (erythrocytes) loose their nucleus, mitochondria, Golgi body, and RER to become biconcave.
- RBC become packed with Haemoglobin and proteins
- WBC (neutrophils) contain many lysosomes-cytoplasm seems grainy
-
94
What is tissue?
A collection of cells that are similar to each other and preform a similar function. (MAY be attached to each other). (E.g. includes Xylem/Phloem)
95
What are organs?
A collection of tissues working together to preform a particular function.
96
What is an organ system?
A number of organisms working together to produce an overall life function. E.g. reproductive system.
97
What are the four main categories of tissue?
```
Epithelial tissue (layers an linings)
Connective tissue (Holds together structure, provides support)
Muscle tissue (Specialised cells to contract and move body parts)
Nervous tissue (Convert stimuli to electric impulse and conducts this)
```
98
What is Squamous Epithelial Tissue?
made up of thin, flattened cells to make thin, smooth surface. Ideal for lining blood vessels as liquid can pass through easily. Also makes thin walls (e.g. alveoli)
Held in place by basement membrane (produced by epithelial tissue)
99
What is Ciliated Epithelial tissue?
- made up of column shapes
- often inner surface of tubes (e.g. lung airways, uterus and oviducts
- exposed lumen as cilia, Some produce mucus and cilia can move mucus
100
What are the requirements for photosynthesis?
- light
- CO2
- Water
- Chlorophyll
101
What are the adaptations / structure of a leaf?
- Upper epidermis is transparent to let light through
- Long, thin, tightly packed cells of palisade layer contain many chloroplasts that contain chlorophyll
- Spongy mesophyll allows gasses to circulate
- lower epidermis contains stomata with guard cells to allow gaseous exchange
- Vein system with Xylem/Phloem provide support and give O2 to the leaf, and takes products of photosynthesis out.
