B1: 1.1-1.4 Flashcards
1
Q
Three key ideas of Cell Theory:
A
- Cells are the structural building blocks of all living things.
- Smallest independent units of life.
3 Cells are formed from other pre-existing cells through mitosis/meiosis.
2
Q
Striated Muscle Cells
A
Irregular sizes- up to 30cm long, to stretch entire length of muscle.
Has between 2-150 nuclei.
3
Q
Aseptate Fungal Hyphae
A
not divided into cell sections- joins into one uninterrupted tube with many nuclei spread along it.
4
Q
Giant Algai
A
Unicellular organism 10cm in size.
5
Q
Two additional points to cell theory:
A
- Genetic material stores instructions for the cell’s functions.
- Cells are the sites of the chemical reactions for life.
6
Q
Functions of Life
A
Metabolism Response Sensitivity Growth Reproduction Excretion Nutrition
7
Q
Metabolism
A
The speed at which reactions take place within an organism.
8
Q
Response
A
How an organism reacts to stimuli.
9
Q
Sensitivity/Homeostasis
A
Maintaining an internal environment suitable for all of the processes necessary for survival.
10
Q
Growth
A
Multicellular= the whole organism grows larger. Unicellular= whole cell grows larger until it divides.
11
Q
Reproduction
A
sexual/asexual division.
12
Q
Excretion
A
Removal of poisonous waste.
13
Q
Nutrition
A
The absorption of nutrients from food in order to release energy necessary for bodily processes.
14
Q
Metabolism:
Paramecium + Chlamydomonas
A
Chemical reactions take place in the Cytoplasm, with enzymes in place to speed them up.
15
Q
Response:
Paramecium + Chlamydomonas
A
P: Cilia. Used to move the cell along.
C: The Flagella are used to propel the cell, and a light sensitive ‘eyespot’ allows them to sense the brightest light and move towards it.
16
Q
Sensitivity:
Paramecium + Chlamydomonas
A
P: Has a Contractile Vacuole that manages water content.
C: Contractile Vacuoles at the base of the Flagella store water.
17
Q
Growth:
Paramecium + Chlamydomonas
A
P: Consumes/ assimilates biomass until it is large enough to divide.
C: Photosynthesis occurs inside Chloroplasts in the Cytoplasm. Here CO2 can be converted into the compounds necessary for growth. However, in dark conditions carbon compounds are sometimes absorbed from other organisms.
18
Q
Reproduction:
Paramecium + Chlamydomonas
A
Divide by Mitosis.
19
Q
Excretion:
Paramecium + Chlamydomonas
A
P: Plasma Membrane controls what leaves the cell
C: Cell Wall is freely permeable, Membrane controls flow in and out of cell. Oxygen is excreted out after photosynthesis
20
Q
Nutrition:
Paramecium + Chlamydomonas
A
P: Nutrition: Food Vacuoles store the consumed organisms.
C: Carries out photosynthesis.
21
Q
Paramecium _ _, Chlorella has _, so does not.
A
Ingests food.
Chloroplasts.
22
Q
The rate of metabolism…
A
…is proportional to the volume of the cell.
23
Q
In metabolism, if the SA of a cell is too small…
A
> substances will not enter the cell quickly enough to keep up the pace of metabolism, and waste products will be produced more rapidly than they can be excreted.
the cell may overheat because the metabolism produces heat faster than it can be lost over the cell’s surface.
24
Q
Volvox Aureus
A
> Volvox Aureus colonies consist of a ball of protein gel with 500+ identical cells attached to its surface.
Daughter cells form inside them.
The cells cooperate, but are not fused together to form a single cell mass, so are not a single organism- therefore are unicellular.
25
Multicellular Organisms
Organisms consisting of a single mass of cells, fused together.
26
Caenorhabditis Elegans (C. Elegans)
> A type of worm with only 959 cells.
> Lives in decomposing organic matter.
> Feeds on the bacteria that cause decomposition.
> Has a mouth, pharynx, intestine and anus.
> Hermaphroditic.
> Cells are cooperative groups rather than having specific cells that organise the system.
27
Emergent Properties
> Characteristics of the whole organism, including the fact that it is alive.
> They arise from the interactions of the component parts of a complex structure, and can be summed up with the phrase ‘the whole is greater than the sum of its parts’.
28
Tissue
A layer of the same specialised cells that have come together. Form the ideal structure and contain all of the enzymes needed to carry out that cell's chemical reactions.
29
Differentiation
The development of cells in different ways to perform specific functions.
30
Properties of Stem Cells
> Can divide countless times to produce a large mass of tissue. > Useful for the replacement of damaged cells.
> They are not fully differentiated.
31
Possible Therapeutic uses of Stem Cells
> Produce regenerated tissue for burn sufferers.
> Healing Type 1 diabetes, where a specific cell has stopped functioning.
> Growing whole replacement organs.
32
Possible Non-Therapeutic use of Stem Cells
Production of large amounts of striated muscle fibres (meat) for human consumption.
33
Stargardt’s Macular Dystrophy
> genetic disease that develops in children aged between 6 and 12.
> Caused by recessive mutation of gene ABCA4. This causes a protein used for active transport in retina cells to malfunction. Photoreceptive cells in the retina disintegrate and vision is lost.
> By injecting embryonic stem cells into the eyes of humans and mice, vision was improved without any harmful side-effects.
34
Leukaemia
> form of cancer that develops in white blood cells in bone marrow.
> Unlike other cancers, this means it is not contained in one part of the body, and to cure it all of the white blood cells have to be destroyed. > This can not be done under normal circumstances as white blood cells are vital for survival.
35
Stem Cell Treatment for Leukaemia
1. A needle is inserted to a large bone (pelvis) and fluid is removed from the bone marrow.
2. Adult Stem Cells are extracted from this fluid and frozen. They are only capable of producing blood cells.
3. A high dose of chemotherapy is given to the patient in order to kill the cancer cells in the bone marrow. Loses its ability to produce blood cells.
The frozen stem cells are then returned to the body. They re-establish themselves and start to produce red and white blood cells.
36
Embryonic Stem Cells
> Almost unlimited growth potential.
> Can differentiate into any cell type in the body.
> More risk of becoming tumour cells than with adult stem cells, including teratomas that contain different tissue types.
> Less chance of genetic damage due to the accumulation of mutations than with adult cells.
> Likely to be genetically different from an adult patient receiving the tissue.
> Removal of cells from the embryo kills it, unless only one or two cells are taken.
37
Umbilical Cord Blood Stem Cells
> Easily obtained and stored.
> Commercial collection and storage services already available.
> Fully compatible with the tissues of the adult that grows from the baby, so no rejection problems occur.
> Limited capacity to differentiate into different cell types- only naturally develop into blood cells, but research may lead to the production of other types.
> Limited quantities of stem cells from each cord.
> The umbilical cord is discarded whether or not stem cells are taken from it.
38
Adult Stem Cells
> Difficult to obtain as there are very few of them and they are deep in tissues.
> Less growth potential than embryonic stem cells.
> Less chance of malignant tumours developing than from embryonic stem cells.
> Limited capacity to differentiate.
> Fully compatible with the tissues of the adult that grows from the baby, so no rejection problems occur.
> Removal of stem cells does not kill the adult from which they are taken.
39
Light Microscope
> Maximum resolution is 0.2µm (micrometres)
> Limited by the wavelength of light (400-700nm)
> Any smaller than this and the image will be blurred.
> Max magnification x400.
40
What is the smallest resolution captured by the human eye?
0.1mm
41
Resolution
Making the separate parts of an object distinguishable by eye.
42
Why do electron microscopes have a higher resolution?
Because they have a shorter wavelength.
43
Electron Microscope
> Max resolution 0.001 micrometers- 200x greater than light Microscope.
44
Light Microscopes reveal the _ of cells,
| Electron Microscope reveal the _ of cells.
Structure
| Ultrastructure.
45
Eukaryotes
Have a compartment within the cell that contains the chromosomes (the nucleus).
Bound by a nuclear envelope consisting of a double layer of membrane.
46
Prokaryotes
> Do not have a nucleus.
> Earlest organisms.
> Simples cell structure- small in size and found everywhere.
> Have cell walls containing peptidoglycan.
> Extracellular.
47
What is inside a Prokaryote?
> Cytoplasm- no membrane or nucleus.
> No cytoplasmic organelles except for ribosomes.
> Enzymes contained in cytoplasm.
> Nucleoid
48
Nucleoid
Area of a Prokaryote containing the DNA, but not an actual nucleus.
49
Alternative name for Bacteria
Prokaryote
50
How do Prokaryotes divide?
Binary Fission
51
Binary Fission
(Asexual Reproduction)
1. Single circular chromosome is replicated and the two copies of the chromosome move to opposite ends of the cell,
2. Division of the cytoplasm of the cell.
3. Each daughter cell contains one copt of the chromosome, so they are genetically identical.
52
How are Eukaryotic Cells different from Prokaryotic Cells?
Eukaryotic cells are compartmentalised by either single or double membranes
53
Organelles
Compartments in the cytoplasm of Eukaryotes
54
Advantages of the compartmentalisation of Eukaryotic cells
1. Specific enzymes and substrates are much more concentrated- faster reactions
2. Substances that could be potentially damaging to the cell are kept inside the membrane of an organelle.
3. Condition (e.g. pH) can be maintained at different levels at different parts of the cell,
4. Organelles, with their contents, can be moved around within the cell.
55
Nucleus
> Double nuclear membrane
> Contains chromosomes (DNA associated with histone proteins).
> Uncoiled chromosomes spread through nucleus called chromatins.
> Densely satining areas of chromatin around edge.
> Site of DNA replication into mRNA, which is exported via nuclear pores to cytoplasm.
56
Rough Endoplasmic Reticulum
> rER.
> Consist of flattened membrane sacs called cisternae, with ribosomes attached to them.
> Synthesize protein for secretion from the cell.
> Protein synthesised is passed into cisternae- then carried by vesicles- these bud off- moved to the Golgi Apparatus.
57
Golgi Apparatus
> Organell consisting of flattened membrane sacs, like rER.
> Not as long, often curved, do not have ribosomes attached, vesicles nearby.
> Processes proteins, which are then carried by vesicles to the plasma membrane for secretion.
58
Lysosome
> Approx. spherical.
> Single membrane.
> Formed from Golgi vesicles.
> Contain high concentrations of protein, making them densely staining in electron micrographs.
> Contain digestive enzymes which can be used to break down ingested food in vesicles or break down organelles in the cell or even the whole cell.
59
Mitochondrion
> Double membrane.
> Inner membrane is invaginated to form cristae.
> Fluid inside it called the matrix.
> Produce ATP for the cell by aerobic cell respiration.
> Fat is digested here if it is being used as an enemy source in the cell.
60
Free Ribosomes
> Dark granules in the cytoplasm, no membrane.
> Synthesise proteins and release them into the cytoplasm.
> Constructed in a region of the nucleus called the nucleolus.
61
Chloroplast
> Double membrane.
> inside are thylakoids- flattened sacs of membrane.
> Produce glucose and other organic compounds through photosynthesis.
> Some also contain starch grains from rapid photosynthesis.
62
Vacuoles and Vesicles
> Single membraned organelles with fluid inside.
> Some animals absorb foods and digest them inside the vacuole.
> Some unicellular organisms use them to expel excess water.
> Vesicles are very small vacuoles used to transport materials inside the cell.
63
Microtubules and Centrioles
> Small cylindrical fibres found in the cytoplasm.
> Move chromosomes during cell division.
> Animal cells have centrioles, which are two groups of nine microtubules.
> Centrioles form an anchor point for microtubules during cell division.
64
Cilia and Flagella
> Whip like structure projecting from the cell's surface.
> contain a ring of nine double microtubules plus two central ones.
> Flagella are larger and usually there is only one.
> Cilia are smaller and many are present.
> Used for locomotion.
> Cilia can be used to create a current in the fluid to the next cell.
65
Function of Gland Cells
To secrete substances.
| released through plasma membrane
66
Types of gland cells in the pancreas.
> Endocrine Cells: Secrete hormones into the bloodstream.
| > Exocrine Gland Cells: Secrete digestive enzymes into a duct to the small intestine where they digest foods.
67
What are enzymes?
Proteins
68
What do Exocrine Gland Cells Contain?
> Organelles needed to synthesise protein on large scales.
69
Organelles of Exocrine Gland Cells (7)
```
Plasma Membrane
Mitochondrion
Nucleus
rER
Golgi Apparatus
Vesicles
Lyosomes
```
70
Organelles of Palisade Mesophyll Cells (6)
```
Cell wall
Plasma Membrane
Chloroplasts
Mitochondrion
Vacuole
Nucleus
```
71
Function of Palisade Mesophyll Cells
To carry out photosynthesis.
72
Hydrophilic
Substances attracted to water.
73
Hydrophobic
Substances not attracted to water.
74
Amphipathic
Substances that are in part both hydrophilic and hydrophobic.
75
Hydrophilic part of a Phospholipid
the Phosphate Group.
76
Hydrophobic part of a Phospholipid
2 Hydrocarbon Chains
77
Simple representation of a phospholipid
Circle for the phosphate group and two lines for the hydrocarbon chains.
78
Phospholipid reactions to water.
> Phosphate heads are attracted to water, hydrocarbon tails are attracted to each other.
> Arrange themselves into phospholipid bilayers, with tails facing inwards.
> Stable structures that are the base of all cell membranes.
79
Functions of Membrane Proteins
> Hormone binding sites/hormone receptors.
> Immobilised enzymes with the active site on the outside.
> Cell adhesion to form tight junctions between groups of cells in tissues and organs.
> Cell to cell communication
> Channels for passive transport.
> Pumps for active transport.
80
Integral Proteins
> Hydrophobic on at least part of their surface, so embedded in the hydrocarbon chains in the centre of the membrane.
> Many are transmembrane- extend across the membrane, with hydrophilic parts reaching the extending phosphate heads.
81
Peripheral Proteins
> Hydrophilic on their surface, so not embedded in the membrane.
> Most attached to the surfaces of integral proteins.
> Some have a hydrocarbon chain anchoring them protein to the membrane, keeping it attached.
82
the more active a membrane...
... the higher its protein content.
83
Membrane Structure:
:
84
Main components of cell membranes
Phospholipids
| Proteins.
85
Extra structure in animal cell membranes
Cholesterol
86
Cholesterol
> Type of lipid- a steroid.
> Mostly hydrophobic, so is attracted to the hydrocarbon tails of the phospholipid bilayer.
> One end of the cholesterol has an OH group, which is attracted to the phosphate heads (hydrophilic).
> Cholesterol molecules are therefore positioned between phospholipids.
87
Hydrocarbon tails state of matter
liquid (ish)
88
Phosphate heads state of matter
solid (ish)
89
Overall state of matter of mammalian membranes
Fluid and free to move
90
How does cholesterol help to control the fluidity of membranes?
> Disrupts the regular packing of hydrocarbon tails, so prevents crystallisation and their ability to behave like a solid
> Restricts molecular motion.
> reduces the permeability to hydrophilic particles.
> Due to its shape it can help membranes curve into a concave shape, which helps in the formation of vesicles (endocytosis).
91
why are vesicles able to happen?
Because of the fluidity of membranes
92
What is endocytosis?
The process of the formation of Vesicles
93
The process of endocytosis
A small piece of plasma membrane of a cell is pinched off, trapping substances from outside the cell and bringing them into it inside the newly formed Vesicle
94
What do Vesicles do?
Move materials inside cells
95
An example of moving vesicle contents
The Secretory Cells
96
.
.
97
Exocytosis
The process of a vesicle fusing with the plasma membrane and expelling its contents from the cell.
98
Other name for a vesicle
Contractile Vacuole
99
Methods of particles moving across a membrane
simple diffusion
facilitated diffusion
osmosis
active transport
100
Diffusion
The spreading out of particles in liquids or gases that happens because the particles are in continuous random motion.
Movement down a concentration gradient.
101
In diffusion, particles move from an area of _ concentration to an area of _ concentration
high
| low
102
How much energy is needed to allow diffusion?
None
103
What must the phospholipid bilayer be to allow diffusion across it?
Permeable to the particles.
104
What sort of particles can diffuse through the phospholipid bilayer easily?
non-polar molecules.
Polar molecules find it difficult because the centre of the bilayer is hydrophobic.
Small polar particles find it easier to pass through.
105
Facilitated Diffusion
The use of channels through the plasma membrane to allow particles that would otherwise not be able to to pass through a membrane to move from an area of high conc. to an area of low conc.
106
What do the walls of facilitated diffusion channels consist of?
Protein
107
What sort of different facilitated diffusion channels are there?
A different one for each substance that has to pass through.
108
Osmosis
The movement of water particles from an area of low solute concentration to an area of high solute concentration through a partially permeable membrane.
109
Are water cells small enough to pass through the phospholipid bilayer?
Yes :)
110
Aquaporins
> Water channels which greatly increase the permeability of membranes to water.
> (kidney cells, root hair cells)
> Channels are only slightly wider than the water molecules, meaning they have to pass through in single file.
> +ve charges in the channel prevent protons from passing through.
111
How do substances dissolve?
By forming intermolecular bonds with water- these restrict the movement of water molecules.
112
Active Transport
Movement of particles against the concentration gradient, fuelled by ATP.
113
What carries out Active Transport?
Globular proteins in membranes called Pump Proteins.
114
Process of Active Transport
1. Molecule/ion reaches central chamber.
2. Conformational change to the protein takes place using energy from the ATP.
3. The ion/molecule can pass to the opposite side of the membrane.
4. the pump protein returns to its original conformation.
115
Axon
Part of a neuron cell.
Consists of a tubular membrane with cytoplasm inside.
Function is to convey messages through a communicated nerve impulse.
116
What substances does a nerve impulse include?
Sodium and Potassium through movements that occur through facilitated diffusion.
