Unit 1: Cells Flashcards
(140 cards)
1
Q
Define magnification
A
the number of times larger an image is compared to the real size of an object
2
Q
Define Resolution
A
the ability to distinguish two objects close together (clear) rather than see them as a single object (blurred)
3
Q
Equation for magnification?
A
Magnification= size of image/actual size of specimen
4
Q
Resolution levels of human eye, light microscope and electron microscope?
A
Eye=100 micrometres
Light m-s=200 nanometres
Electron m-s=0.2 nanometres
5
Q
Average size of a plant cell? animal cell?
A
Plant cell= 100 micrometres
Animal cell= 10 micrometres
6
Q
How does a light microscope work?
A
Lightbulb/mirror turned on at base of microscope which emits light.
Light passes through condenser, under stage then to specimen.
Objective lens focuses light into eyepiece and then our eyes.
7
Q
Adv. and Disadv. of Light microscopes?
A
Adv:
- Cheap (£100-£500) and only uses a lightbulb
- Small and easily transported
- Simple sample prep
- Distortion only slight
- Vacuum not required
- Image is in colour
- Can use living cells or dead cells
Disadv:
- Limited resolution
- Samples still need preparation
8
Q
Preparing specimens for a light microscope?
A
1) Specimen is stained as most tissue isn’t coloured. Acetic orcein stains DNA dark red, Gentrian violet stains bacterial cell walls
2) Specimen is set in wax an then cut (to avoid the specimen getting distorted) and placed on glass slide
9
Q
Why do we use stains on specimens?
A
Most tissue cut thin enough for a light microscope is clear so can’t distinguish parts of cell
- Stains create a CONTRAST
- Nuclei tend to absorb a lot of stain
10
Q
How do TEM work? Describe the image produced
A
Electron beam passes through vr. thin prepared sample, focused by magnets
Electrons pass less easily through denser parts of sample-creates some contrast
Vacuum used to prevent electrons interacting with particles in air
Final image=2D
Magnification= x500,000
11
Q
How do SEM work? Describe the image produced
A
Electron beam directed onto sample-doesn’t pass through it
Electrons bounce off sample
Vacuum prevents electrons interacting with particles in air
Final image=3D
Magnification= x500,000
12
Q
How are specimens prepared for an electron microscope?
A
Specimen has to be one cell thick
Specimen stained with heavy metals eg Osmium/lead/gold=help absorbs elctrons as metals positively charged
13
Q
Adv. and Disadv. of electron microscopes?
A
Adv:
- Greater magnification
- Can form 3D images
Disadv:
- Expensive (£100,000+) and to produce electron beam
- Large+require special rooms
- Lengthy complex sample prep
- Process distorts material
- Vacuum required
- Specimens dead
- Beam can damage specimens
14
Q
How is colour added to electron micrographs?
A
Using specialized computer software which takes signals from backscattered elctron detectors assigned to different colours which can be transferred to image
15
Q
What is a prokaryotic cell?
A
a primitive cell which doesn’t have a true nucleus
16
Q
What is a eukaryotic cell?
A
a cell that has a true nucleus and membrane bound organelles eg mitochondria
17
Q
Compare Cell diameter of E+P cells
A
P= 0.5-5 micrometres
E=Less than 40 micrometres
18
Q
Compare DNA in E+P cells
A
P=Naked, Circular DNA (plasmids for antibiotic resistence) but no nucleus
E=DNA found in nuclues, associated with chromosomes and histones
19
Q
Compare Ribosome diameter of E+P cells
A
P=18 nanometres
E=22 nanometres
20
Q
Compare Organelles present in E+P cells
A
P: = No ER =Few cell organelles =Cell wall made of peptidoglycan =only 1 membrance (cell surface membrane) so no mitochondria
E: =ER present =Many cell organelles =Sometimes cell wall eg plant cell cellulose walls =Multiple membranes
21
Q
Compare ATP production in E+P cells
A
P=Takes place in mesosomes
E=Takes place in mitochondria
22
Q
How can Prokaryotes cause disease?
A
Some bacterial cells are resistant to anti-biotics like MRSA
Resistance is coded on plasmid DNA-bacteria can share plasmids and pass on resistence during binary fission.
23
Q
How are prokaryotes helpful to humans?
A
Making cheese and yogurt Help with vitamin K production Help digest food in mammalian intestines Part of 'natural flora' of skin=can prevent harmful microorganisms getting into the body Sewage treatment and natural recycling
24
Q
What are the roles of the cytoskeleton?
A
1) To main structure and stability
2) Allow movement in the cells
25
What are microfilaments made of and what is their function?
Microfilaments are made from the protein Actin.
| They are used to move some organelles around inside a cell and some white blood cells
26
What are microtubles made of and what is their function?
Microtubles are made of the protein Tublin.
| They are used to move a microorganism through a liquid or waft a liquid past a cell.
27
Describe the structure and movement of flagella and cilia
9+2 structure - 9 pairs of microtuble around the outside and a pair of two microtubles in the centre.
They cause movement when the microtuble pairs try and slide past each other. They are anchored at their base so they 'lean' to one side and back again.
28
Structure of nucleus?
Structure= dense,round nucleolus surrounded by 2 membranes with fluid between (nuclear envelope) + chromatin (DNA and protein)
29
Function of nucleus?
Holds nearly all genetic material of cell, nucleolus makes RNA and ribosomes where cytoplasm and proteins are formed
30
Structure of smooth ER and Rough ER?
Smooth ER= flattened, membrane bound sacs (cisternae)
| Rough ER= studded with ribosomes
31
Function of smooth ER and rough ER?
Smooth ER= making lipids for cell
| Rough ER= transports proteins made on attached ribosomes, it's an extension of the nuclear envelope
32
Structure of Golgi apparatus?
Stack of membrane bound, flattened sacs (like pitta)
33
Function of Golgi apparatus?
Modifies proteins received from ER (may add sugar), packages proteins into vesicles to be transported
34
Structure of mitochondrion?
2 membranes separated by fluid filled space
- Inner membrane= highly folded (cristae)
- Central part is the matrix
35
Function of mitochondrion?
ATP (adenosinic triphosphate) produced during respiration
36
Structure of chloroplasts?
2 membranes separated by fluid filled space, inner network of flattened sacs (thylakoids) in stacks (grana) with chlorophyll molecules in thylakoid membranes
37
Function of chloroplasts?
Site of photosynthesis in plants-carbohydrates made from carbon dioxide and water
38
Structure of lysosomes?
Spherical sacs surrounded by a single membrane
39
Function of lysosomes?
Contains digestive enzymes-break down materials (eg acrosomes in sperm cells) to replace parts of cell
40
Structure of ribosomes?
Tiny organelles, each consisting of 2 subunits
41
Function of ribosomes?
Site of protein synthesis, coded information (messenger RNA) from nucleus used to assemble proteins from amino acids
42
Structure of centrioles?
Small tubes of protein fibres (microfibres), a pair of centrioles are found next to nucleus in animal cell
43
Function of centrioles?
Take part in cell division, form fibres (spindles) which move chromosomes during nuclear division
44
Structure of vesicles?
Membrane bound sacs
45
Function of vesicles?
Used to carry different substances around cell
46
Structure of vacuoles?
Filled with water and solutes
47
Function of vacuoles?
Maintains cell stability-pushes cytoplasm against cell wall making cell turgid
Helps support plant, especially important in non-woody plants
48
Structure of plant cell walls?
Cellulose structure
49
Function of plant cell walls?
Cellulose forms a sieve-like network of strands=strong wall
Held rigid by pressure of fluid inside cell
= supports cell so supports whole plant and prevents cell from bursting
50
Function of Tonoplast?
Surrounds the vacuole, controls what goes in/out of cell
51
Why does DNA use mRNA to transport genes in division of labour?
DNA itself big to fit through nuclear pores
52
Function of cell surface membranes?
1) isolates cell from surroundings
2) permits control over substances entering and leaving cell
3) cell signalling and communication
4) recognition e.g. anti-gens
- don't want to be broken down by WBC
53
Function of membranes within cells?
1) Compartmentalisation- separates areas in cells eg reaction pathways separate/respiration in mitochondria
2) Site of reaction eg enzymes within membrane
3) Prevents disruption to cell (lysosomes)
4) Formation of vesicles
5) Allow exocytosis
54
How are membranes of a growing shoot adapted?
Cell surface membranes contain receptors which allow them to detect molecule that regulates growth
55
How are muscle cell membranes adapted?
Contain large number of channels
| -> allows rapid uptake of glucose to provide energy for muscle contraction
56
How are chloroplast membranes adapted?
Internal membrane contains chlorophyll and other molecules for photosynthesis
57
What is the approximate width of the cell surface membrane in a typical animal cell?
7.5-10 nanometres
58
What is the difference between bacterial and eukaryotic flagella?
Bacterial flagella= a spiral attached to a disc, it uses ATP enregy to make the disc rotate which spins the flagellum.
Eukaryotic flagella= 9+2 structure which uses sweeping movements from the microtubles.
59
How are WBC membranes adapted?
Plasma membranes contain special protein that enable cells to recognise foreign cells and parasites
64
What is the difference between an intrinsic and an extrinsic protein?
```
Intrinsic= goes through whole membrane
Extrinsic= partially embedded in bilayer
```
65
What is the name of the model of the phospholipid bilayer?
The fluid mosaic model
66
Why is the membrane partially permeable?
To allow substances like water molecules and some solutes to pass through
67
Structure of phospholipid molecules?
```
Hydrophilic head (water loving) =phosphate
Hydrophobic tail (water hating) =fatty acid
```
68
Function of cholesterol in phospholipid bilayer?
Creates stability so bigger/charged substances can't pass straight through
69
Function and structure of glycoprotein?
Carbohydrate part attached to protein
Involved in cell signalling and binding cells together in tissues
70
Function of structure of glycolipids?
Carbohydrate part attached to bilayer
Involved in cell signalling
71
Function of channel protein?
Allows movement of larger molecules (eg glucose) to enter/leave cell
72
Function of carrier protein?
Uses active transport to move substances across a membrane
73
Feature of phospholipid bilayer?
Molecules can move freely in this state
| Some will 'flip-flop' from one layer to another
74
How does cell signalling happen?
Cell has to stay in contact with environment to survive so pick up signals at surface to respond
Signals arrive at plasma cells membrane from outside cell
Receptor in plasma cell membrane picks up signals and brings about action in cell
75
What is a target cell?
Any cell that has a receptor for a hormone molecule e.g liver-has receptor cells for hormone insulin
76
Define diffusion
The net movement of molecules (or ions) from a region of high concentration to a region of low concentration (down a concentration gradient)
77
What factors can increase the rate of diffusion?
Steeper concentration gradient
Higher temperature
Larger SA
Smaller/non-charged particles diffuse quicker
Shorter distance
Stirring (similar to effect of draught/breeze)
78
Which substances can diffuse through the phospholipid bilayer and why?
Oxygen as non-charged
Carbon dioxide as small even though charged
Water as small even though charged
Lipids as membranes also made of lipids
79
Which substances can't diffuse through the phospholipid bilayer?
Glucose, Amino acids, Proteins (hormones)- too big
| Ions- polar/charged particles
80
Why does facilitated diffusion occur across channel proteins and not active transport?
Substances move down a concentration gradient and do not use energy=PASSIVE PROCESS
81
How does a carrier protein work?
Shaped so a specific molecule can fit eg glucose
When molecule is in the protein, it 'flip flops' so molecule can enter other side
-can travel via diffusion OR active transport
82
Why would a membrane be broken down in the wrong pH?
Wrong pH could alter shape of receptors and cause cell to denature
83
What is active transport?
The movement of particles from an area of low concentration to an area of high concentration (against a concentration gradient). It always has to occur across a membrane and uses ATP energy
84
Why do muscles need calcium ions to function?
Muscle fibres can only contract if calcium ions are present.
>Muscle stimulated to contract, calcium ions released from specialised ER=increased concentration
>When muscle needs to relax, calcium ions pumped back into stores by calcium ion pumps at membrane of specialised ER
85
What does 'bulk transport' refer to?
Exo/endocytosis
86
What is a vesicle made of and how does it move?
Made of phospholipids and moves using cytoskelton
87
What is exocytosis?
| How does it work?
It's the releasing/ removing of materials
Vesicles move to membrane using cytoskeleton, fuses with membrane and releases materials
88
What is endocytosis?
| How does it work?
It's the bringing in/engulfing of materials
Membrane folds inwards to form a vesicle, engulfs materials, gets 'pinched off' into cell
89
What is phagocytosis?
Cell feeding (uptake of solid material)
Only occurs in a few specialised cells eg WBC
90
What is pinocytosis?
```
Cell drinking (intake of
Liquids)
```
Similar to phagocytosis but on a smaller scale
91
Examples of Bulk transport?
Hormones: insulin packaged into vesicles by Golgi apparatus+fuse with outer membrane to release insulin into blood
Plant cells: materials required to build cell walls carried out in vesicles
WBC: engulf invading microorganisms by forming vesicle around them
92
How does temperature affect membrane permeability?
Higher temperature: phospholipids have more kinetic energy so they vibrate a lot; carrier proteins denature and lose their shape
Hence permeability increases
93
What is water potential?
A measurement of how much water a solution contains in relation to other substances and pressure applied to it
Highest water potential=0 (pure water) and gets more negative
94
What does hypotonic mean?
There is a higher water potential outside a cell that inside
95
What does isotonic mean?
The water potential inside and outside a cell are the same
96
What does hypertonic mean?
The water potential outside a cell is lower than inside
97
What happens when an animal cell is haemolysed?
Cell swells and bursts as water enters cell
98
What happens when an animal cell becomes crenated?
Cell shrivels up as water leaves cell
99
What happens when a plant cell becomes turgid?
Membrane of cell expands and contents is held rigid by plant cell wall as water enters cell
100
What happens in a plant during incipient plasmolysis and full plasmolysis?
Incipient plasmolysis: membrane of cell starts to shrink away from cell wall as water leaves cell
Plasmolysis: membrane of cell completely loses contact with cell wall
101
How do cells reproduce?
Divide by mitosis-nucleus divides first
| Genes passed onto daughter cells
102
How many chromosomes are in our cells?
46 chromosomes in ordinary cells
| 23 in gametes
103
What is mitosis for?
Growth
Replacement of cells
Asexual reproduction
104
What stages occur in the interphase cycle of mitosis?
Growth 1: biosynthesis-protein synthesis and replication of organelles
S phase: DNA replicates to form pairs of sister chromatids
Growth 2: normal growth, ATP generated
Mitosis completed
105
How do sister chromatids form in the S phase of interphase?
```
Homologus chromatids (alleles of each other with F and M versions) join together by a centromere to form a pair of sister chromatids
=one chromosome
```
106
Why do chromosomes supercoil before mitosis?
So they are sturdier and shorter and can be moved more easily
107
Why does an enzyme check replicated DNA after supercoiling?
To ensure copying has been done correctly and there are no mutations
108
How does mitosis occur?
| Hint: IPMAT
Interphase: chromosomes replicate
Prophase: chromosomes supercoil; nuclear envelope breaks down, centrioles divide into 2 and move to poles to form spindles (protein threads)
Metaphase: chromosomes move to centre of spindle and line up along equator (central region); attach to spindles by centromeres
Anaphase: centromere splits and pulls sister chromatids apart; spindle fibres shorten to pull sister chromatids towards poles, led by centromeres
Telophase: separated sister chromatids (now individual chromosomes) reach poles new nuclear envelope forms around each set; spindle breaks down and disappears; chromosomes uncoil; splitting is called cytokinesis
109
How does cytokinesis occur in plant and animal cells?
Animal: starts from outside 'nipping in' to cell membrane
Plant: formation of cell plates where spindle equator was+new material laid down along plate
110
What is a model?
A simplified representation of something to aid understanding
111
How do cells produced from meiosis differ from those produced by mitosis?
Meiosis produces 4 cells
| Cells produced by meiosis are haploid (have half the number of chromosomes)
112
What is a clone?
An organism made up of genetically identical cells
113
What is the name for cell division in bacteria?
Binary fission
114
What is the name for asexual production done by plants?
Vegetative propagation
115
How are animals cloned?
Tissue biopsy taken from donor
Donor cells grown in tissue culture
Donor cell nucleus transferred to recipient egg
Cloned egg is transferred to surrogate mother
Pregnancy monitored by ultrasound
Clone is born
116
Why does a target cell only respond to the correct chemical?
The receptor and the hormone have complimentary shapes, any other hormone wouldn't fit the receptor
117
How do beta-blockers work?
Prevent hormones sending signals by blocking appropriate receptor, so hormone doesn't trigger a response
Useful for people with heart conditions-helps stop adrenaline acting on heart to prevent raised heart beat
119
Where is insulin made and how does it affect the body?
In the pancreas, from special beta-cells
Insulin triggers more glucose channels in plasma membrane to open and allow greater uptake of glucose
120
How do HIV and Botox poisons work?
HIV: virus binds with receptors on cells plasma membrane and enters cell (due to complimentary shape of virus with receptors at cell surface like helper T lymphocytes).
Virus then reproduces in cell after period of inactivity eventually destroying it
Botox: toxins from clostridium botulinium bacteria bind with receptors in muscle fibres, causing paralysis
Paralyse small muscles in face to reduce wrinkling
121
How does a hormone trigger a response?
It enters a receptor and forms a hormone-receptor complex which activates internal signals in cell, telling it what to do
122
What are omni/totipotent stem cells?
Stem cells which can become any kind of cell
123
Where can mitosis occur in animals and plants?
Animals: most cells can do mitosis and cytokinesis
Plants: only in meristem cells e.g. Roots, cambium and shoot tips
124
What is budding?
The process of cell division in yeast
Yeast cells produce a small bud that 'nips off' the cell in cytokinesis
125
When in our life cycle does meiosis occur?
In the production of gametes which are haploid cells
126
What are tissues? Give an example
A collection of cells that are similar to each other and perform a common function. May be attached to each other but not always
E.g xylem+phloem in plants, epithelial and nervous tissues in animals
127
What are organs? Give an example
Collection of tissues working together to perform a particular function
E.g. Leaves in plants, liver in animals
128
What are organ systems? Give an example
They are made up of a number of organs working together to perform an overall life function
E.g. Excretory system, reproductive system
129
How are organisms organised? Give them in the order smallest to largest
```
Organelles
Cells
Tissues
Organs
Organ systems
Organism
```
130
What is differentiation?
When a cell becomes specialised to carry out a particular role
131
What changes can occur in a cell during differentiation?
The number of a particular organelle can change
The shape of a cell can change
The contents of a cell can change
(In some cases, differentiation can involve all 3 types of change)
132
Why might a mitochondrion have a different shape than normal when observed under a microscope?
Could be a younger cell
Cell could've been distorted in sample prep
Cell could be at a different angle
133
How are erythrocytes and neutrophils similar?
Both human cells
Both begin with the same set of chromosomes
Both produced from undifferentiated cells in the bone marrow
134
What happens when a cell differentiates into a erythrocyte (RBC)?
What function do erythrocytes perform?
They lose their nucleus, Golgi apparatus and rough ER
Packed full of haemoglobin
Shape becomes bioconcave disc so cell now capable of transporting oxygen from lungs to tissues
135
What happens when a cell differentiates into a neutrophil?
| What function do neutrophils perform?
Cell keeps it's nucleus
Cytoplasm appears granular due to large amounts of lysosomes produced
Neutrophils use potent enzymes in lysosomes to ingest and kill invading microorganisms
136
What is xylem tissue made up of?
Xylem vessels with parenchyma cells and fibres, strengthened by lignin deposits
137
How is xylem adapted for water and mineral uptake?
Lignin deposits reinforce and waterproof vessel walls for high pressure of flowing water
Cell contents of wall are dead so no water is lost in cells
138
What is phloem tissue made up of?
Companion cells and sieve tube elements
139
How do the roles of the companion cells and sieve tube elements differ?
Sieve tube elements: pathway for movement of sugars
Companion cells: helps move products in and out of the sieve
140
What are the 4 main types of animal tissue?
Epithelial-involved in layers and lignin
Connective-holds structures together and provides support e.g. Cartilage, bone, blood
Muscle-specialised cells contract and move parts of body
Nervous-cells that can convert stimuli to electrical impulses and conduct these impulses
141
What is squamous epithelial tissue?
The flattened epithelial tissue lining the insides of tubes like blood vessels
142
What are the 4 requirements of a plant?
Light
Carbon dioxide
Water
Presence of chlorophyll
143
How is a plant adapted to fulfil its needs?
Transparent upper surface to let light in
Chlorophyll found in chloroplasts
Spongy mesophyll with air spaces allow gas exchange
Stomata on lower epidermis control gas exchange with outside environment
144
How is movement an example of our different organ systems working together?
Muscular and skeletal systems work to move
Movement can only happen if nervous systems instruct muscles to move
Circulatory system ensures supply of nutrients and oxygen to provide energy to muscle and nervous system
Circulatory system gets chemicals from digestive and ventilation systems
145
What is the magnification of the eyepiece and the different objective lenses for a light microscope?
Eyepiece mag.=x15
| Objective lens mag.=x4, x10, x40
