Topic 2- Cells Flashcards
1
Q
Describe the cell theory
A
- All living organisms consist of one or more cells
- All cells come from pre-existing cells via cell division
- The cell is the fundamental building block of life
2
Q
Function of cell membrane
A
Control the exchange of materials between the cell and its environment
NOTE - large molecules are unable to pass through the cell membrane
3
Q
Describe the structure of the cell membrane
A
- Phospholipid bilayer
- Hydrophobic tails and Hydrophilic heads
- Proteins embedded
- Cholesterol embedded
4
Q
Function of cholesterol molecules
A
to stabilise the phospholipid bilayer at high temperatures
5
Q
State 3 key differences between plant and animal cells
A
- Plant cells have a cell wall
- Plant cells have chloroplasts
- Plant cells have central vacuole
6
Q
State 3 key differences between prokaryotes and eukaryotes
A
- Eukaryotes contain membrane-bound organelles
- Eukaryotes have a nucleus whereas prokaryotes do not have a well-defined nucleus
- Eukaryotes are structurally complex
- chromosomes are circular and unbound in prokaryotes whereas they are linear and bound with histones in eukaryotes
7
Q
What is the capsule
A
- In a prokaryote- layer of sticky material that covers the cell wall
8
Q
What is the pilus
A
- hair like structures that project from the cell wall
- allows bacterium to sense and stick to surfaces
9
Q
What is the flagellum
A
(tail) attached to cell wall that allows the cell to move
10
Q
What are plasmids
A
small circles of DNA in cytoplasm separate from the chromosome
11
Q
Explain the theory of endosymbiosis
A
Suggests that the engulfing of a whole prokaryotic organism into the larger prokaryote, the ancestral eukaryote led to the development of eukaryotic cells. Mitochondria and chloroplast are believed to be incorporated in this way.
12
Q
State the evidence for endosymbiotic theory
A
- Chloroplasts and mitochondria have a double membrane
- presence of ribosomes allows mitcochondria to be able to make their own proteins
- mDNA is circular and unbound and is therefore evidence that mitochondria are prokaryotic in origin
- mitochondria can divide
13
Q
Which organelles are not membrane bound
A
Nucleolus
Ribosome
Cytoskeleton
14
Q
Structure of the nucleus
A
- Membrane bound organelle
- often spherical in shape
- contains DNA
15
Q
Functions of nucleus
A
Protects and stores genetic information
16
Q
Structure of nucleolous
A
- Round body
- located inside nucleus
17
Q
Function of nucleolous
A
- makes ribosomal subunits from ribosomal proteins and ribosomal RNA
- it then sends the subunits to the cytoplasm for translation
18
Q
Structure of mitochondria
A
- double membrane bound
- inner membrane is convoluted forming folds called cristae
- cristae are location of ATP synthase
- outer membrane smooth
19
Q
Structure of chloroplasts
A
double surrounding membrane with internal stacked plate like structures. contains chlorophyll
20
Q
Function of chloroplast
A
Trap energy from sunlight. Site of photosynthesis
21
Q
Structure of vacuoles
A
- simple membrane-bound fluid-filled sac
22
Q
Function of vacuole
A
animal cells
membrane-bound sacs for storage, digestion and waste removal
plant cells
vacuole maintains the cell’s shape and stores water and ions
23
Q
structure of Golgi body
A
stack of membranes. molecules transported to and from the Golgi body by means of vesicles which are small membrane-bound sacs
24
Q
Function of Golgi body
A
- processing and packaging of proteins into small membrane-bound vesicles (exocytosis)
25
Structure of Smooth ER
a series of folded membrane that form sacs or tubes connected to nucleur membrane
26
Function of smooth ER
the site of lipid, phospholipid and fat synthesis
27
Structure of ribosomes
- made of ribosomal proteins and rRNA.
| - They may be free or attached to form the rough ER
28
Function of ribosomes
- the site of translation in protein synthesis
29
what are the two types of ribosomes and how do they differ
FREE RIBOSOMES - located in the cytosol and produce proteins for the cell.
BOUND RIBOSOMES - found attached to the rough ER and produce proteins that are packaged into vesicles
30
structure of lysosomes
Usually spherical in shape and found near Golgi bodies as they bud off from it
31
Function of lysosomes
A type of vesicle/vacuole that contain digestive enzymes to digest unwanted particles and recycle defective organelles. Help white blood cells to destroy bacteria.
32
Structure of cytoskeleton
The cytoskeleton is made up of microtubules, actin filaments and intermediate filaments which help give the cell its shape and help organise the cells parts
33
functions of cytoskeleton
1. movement of organelles such as vesicles from the golgi body within the cell
2. mechanical support to change a cells shape
3. cell to cell adhesions. intermediate filaments function to attach cells together
34
Describe the spacial relationship with the nucleus, rough ER, smooth ER and the Golgi body
- mRNA leaves nucleus and travels to ribosomes on the rough ER
- proteins made at the ribosomes are packaged in the smooth ER into membrane-bound structures called transport vesicles which fuse with the Golgi body
- vesicles that contain enzymes are called lysosomes. they fuse with the surface membrane of a food vacuole to digest the contents.
- some vesicles contain proteins destined for export. these vesicles fuse with the cell membrane to release the proteins to the extracellular environment (exocytosis)
35
What are autotrophs
provide energy to first order consumers who in turm provide energy for the next trophic level
36
Two types of producers/autotrophs and what they do
PHOTOSYNTHETIC organisms
make their food by taking sunlight and using the energy to form sugar (glucose)
CHEMOSYNTHETIC organisms
use energy from oxidising inorganic compounds to making organic compounds
37
What are heterotrophs/consumers
any organism that cannot make its own food. consumers have to feed on producers or other consumers to survive
38
definition of photosynthesis
a set of enzymatic processes that convert light energy into chemical energy
39
Photosynthesis formula
Carbon dioxide + Water gives (light energy over chlorophyll) glucose + oxygen
40
What are photosynthetic pigments
In photosynthesis, light-trapping pigments are used to capture sunlight. In photosynthetic eukaryotes, chlorophyll is the light-trapping pigment found in specialised organelles called chloroplasts in the thylakoid membranes.
41
Where are photosynthetic pigments found
The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments
42
What is chlorophyll's role in photosynthesis
absorb light energy
It absorbs all the wavelengths except those that make the green light. These are transmitted or reflected.
43
Photosynthesis is a complex...
Set of reactions simplified into a single chemical equation.
The Calvin cycle (dark reactions) makes sugar from carbon dioxide.
The Light reactions covert solar energy to chemical energy.
44
Chromosomes special functions
- control protein synthesis
| - cellular activity
45
Prokaryotes do not contain a nucleus, mitochondria, or an endoplasmic reticulum. Given the importance of these organelles, describe how it is possible for them to divide, transform energy and carry out essential metabolic processes.
They possess the chemical such as DNA, proteins and enzymes to allow for normal metabolic processes, pathways and synthesis to occur, it is just not in membrane-bound organelles.
46
Identify from the following list, structures that are not membrane-bound organelles: lysosome, cell wall, cell membrane, vesicle, Golgi body, endoplasmic reticulum, ribosomes, cytoskeleton
- Cell wall
- Cell membrane
- Cytoskeleton
- Ribosomes
47
What is respiration
When chemical energy (glucose) is converted to chemical energy stored in ATP
48
What 2 cycles make up the carbon cycle
Photosynthesis and aerobic respiration
49
What does photosynthesis do
converts sunlight into chemical energy within the glucose molecule
50
What does aerobic respiration do
releases the chemical energy trapped within the glucose molecule and converts it into chemical energy trapped within the ATP molecule
51
What is the formula for aerobic respiration
glucose + 6O2 gives 6CO2 + 6H2O
52
What two organelles does aerobic respiration occur in?
Cytoplasm and mitochondria
53
What processes occur in the cytoplasm and mitochondria during aerobic respiration?
In the Cytoplasm:
Glycolysis occurs converting glucose into 2 pyruvic acids (2 ATP molecules made)
In the mitochondria:
Pyruvic acid converted into 6CO2 + 6H2O (34-36 ATP molecules made)
54
What happens in photosynthesis in regards to carbon molecules?
The plant takes one carbon molecule (CO2) and uses the energy from sunlight to join 6 carbon molecules into glucose. The energy is used to form the carbon bonds.
55
Briefly describe how ATP is generated in aerobic respiration
Aerobic respiration begins with glycolysis in the cytoplasm where glucose is converted to pyruvic acid with a net of 2 ATP. The pyruvate then enters the mitochondria and in the presence of oxygen it is converted to CO2 and H2O with the release of energy which is captured in producing 36 ATP.
56
Describe the key differences between aerobic respiration and fermentation (anaerobic respiration) including the amount of energy released
Aerobic respiration occurs in the cytoplasm and mitochondria and involves the complete breakdown of glucose in the presence of oxygen to produce CO2 and H2O with a net production of about 36 ATP. Anaerobic respiration occurs in the cytoplasm and involves the incomplete breakdown of glucose into lactic acid in animals or ethanol and CO2 in plants and yeast with a net worth of only 2 ATP.
57
Describe the relationship between cell size and surface area to volume ratio
As a cell gets larger its surface area to volume ratio decreases which means it is less readily able to exchange materials with its environment. e.g. a growing cell. Molecules that enter larger cells have further to diffuse than in smaller cells.
58
Define active transport
The movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration
59
Describe the process of anaerobic respiration
- An alternative to aerobic respiration that lacks the presence of oxygen
- Glucose is the only reactant
- Occurs in the cytoplasm
- Incomplete breakdown of glucose
- 2 ATP made
60
Formula for fermentation in plants and yeast
Glucose gives ethanol + carbon dioxide
61
Formula for ethanol
2 C2 H5 OH
62
Formula for fermentation in animals
Glucose gives lactic acid
2 C3 H6 O3
63
Describe the formation of ATP from ADP to Pi
- glucose made during photosynthesis contains trapped chemical energy
- During aerobic respiration, the glucose molecules is broken down by many different enzymes to gradually release the energy
- released energy from glucose is then used to convert ADP and Pi to ATP
64
IGNORE
- some metabolic processes and transport require energy to proceed. ATP functions as the source of energy for these processes.
- The conversion of ATP to ADP and Pi released energy for metabolic processes to occur
65
What is Pi
Free phosphate ions
66
List examples of processes that move substances in and out of cells
- diffusion
- facilitated diffusion
- osmosis
- active transport
- endocytosis
- exocytosis
67
Which molecules can pass through the semi-permeable cell membrane?
- carbon dioxide
- oxygen
- steroid hormones such as oestrogen and testosterone
68
Define diffusion
A passive process which molecules move from a high concentration of that molecule to a low concentration of that molecule
69
Explain the role of carrier proteins
They recognise and accept a specific molecule and when the carrier protein changes shape, the molecule is released inside the cell. The process is called facilitated diffusion, glucose enters by this process
70
Which process does glucose enter a cell through?
Facilitated diffusion
71
Define the process of facilitated diffusion
The movement of molecules from high to low concentration with the help of carrier proteins
e.g. glucose
72
Define the process of osmosis
The movement of water (solvent) through a permeable membrane into a region of higher solute concentration.
Aquaporins provide the specific channel which makes biological membranes semi-permeable
73
What are aquaporins?
Membrane proteins that act as water channels
74
What is a hypertonic solution?
A hypertonic solution has a higher solute concentration (lower water concentration)
75
What is a hypotonic solution?
A hypotonic solution has a lower solute concentration (higher water concentration)
76
What happens when cells are placed in an isotonic solution?
When placed in an isotonic solution water molecules move at the same rate in both directions and the cells do not lose or gain water.
77
What is an isotonic solution?
Where the concentration on both sides of the membrane is the same
78
What happens when red blood cells are placed in a hypertonic solution?
Water molecules move from inside to outside as determined by the water gradient set-up. The cells lose water and consequently shrink in size.
If water concentration is larger inside the cell membrane then a water concentration gradient is set up and the water molecules move out of the cell (it will shrink in size)
79
What happens when red blood cells are placed in a hypotonic solution?
Water molecules move by osmosis from outside to inside and the cells swell in size and burst. This does not happen with plant cells as they have a cell wall.
If the water concentration is larger outside the cell membrane, then a water concentration gradient is set up and the water molecules appear to move into the cell (swells and bursts)
80
Which organelle determines all movement within the cell?
Cytoplasm
81
Describe endocytosis and exocytosis
Endocytosis is the movement of substances into the cell and exocytosis is the movement of substances out of the cell. Both processes required energy in the form of ATP.
82
IGNORE
- Phagocytosis involves the uptake of food or particles
- Pinocytosis involves the uptake of solutions
- Receptor-mediated endocytosis refers to a target molecule binding to a receptor protein where something must bind to a receptor to be taken up
83
When does exocytosis occur?
When a vesicle containing material for export fuses with the cell membrane to release its contents to the exterior of the cell
84
describe the process that proteins are exported out of cell with
Proteins to be exported out of the cells are synthesised in ribosomes attached to the rough ER. They are packaged into vesicles which move to the Golgi body where they are processed and packaged into secretory vesicles. These vesicles move through the cytosol to the membrane with the aid of the cytoskeleton. They then fuse with the membrane releasing their contents to the outside.
85
Why is a larger surface area to volume ratio an advantage?
The larger the surface area compared to the smaller volume means that there is more surface area available for the movement of substances across the membrane.
86
Which factors affect a substances ability to cross the membrane?
- Size
- Hydrophobic molecules pass readily through the membrane
- Hydrophilic molecules such as sugars and amino acids require specific channels
87
What are metabolic pathways
A series of reactions leading to the formation of an end product
88
What does the statement "cells are compartmentalised" mean
The organisation of cellular structures including organelles and membranes helps bring order to metabolic pathways. Having the enzymes needed for a specific process all in the same place makes the process more efficient
89
Explain how the structure of internal membranes in the mitochondria carry out biomechanical processes
The internal membrane of the mitochondria is a highly folded structure greatly increasing its surface area. These form structures called cristae. This membrane is the location of ATP synthase and so greatly increases the capacity of ATP synthesis; more ATP synthase leads to more ATP.
90
Explain how the structure of the internal membrane of chloroplasts carry out biomechanical processes
the membrane of the thylakoids is an inter-connected series of membranes inside the chloroplast and is arranged in stacks. The light-trapping pigment (chlorophyll) is found in the thylakoid membranes, and so this highly folded structure increases the ability of the chloroplast to trap light energy in photosynthesis.
91
What happens in a metabolic pathway to the enzyme and substrate at each stage of the pathway?
The product formed from each step in the metabolic pathway becomes the substrate for the enzymes that catalyses the next step in the pathway. (changing shape so enzymes with different active sites)
92
Each step as a metabolic pathway loses some energy as...
HEAT
Otherwise this heat would denature the enzyme if released in one large step in the metabolic pathway. The heat lost is used to maintain body temperature in mammals.
93
Each step of a metabolic requires... what?
ACTIVATION ENERGY
Although the same amount of energy is required, the enzymes at each step require less activation energy for the reaction to proceed. This makes it easier for each step to occur.
94
A metabolic pathway is controlled by.....at each step
A metabolic pathway is controlled by a specific enzyme at each step. The product formed from each step of the pathway becomes the substrate for the enzyme that catalyses the next step in the pathway. Enzymes at various points in the pathway can be inhibited from working by negative feedback. This enables the speed of the metabolic pathway to be slowed down and thus controlled.
95
Describe two structural features of the chloroplast that would suit its function in a plant cell
- Stacks of grana to increase the surface area for reactions like photosynthesis.
- Chlorophyll to trap light for photosynthesis
96
Explain why photosynthesis is said to be a form of autotrophic nutrition
In a reaction inorganic molecules (carbon dioxide and water) are converted into organic molecules (glucose)
97
Show your understanding of the following statement 'fermentation is an anaerobic alternative to aerobic respiration'
When oxygen is in short supply, cells switch over to fermentation which can still release energy however at a much slower rate
98
Explain the importance of crossing over and independent assortment in meiosis
Crossing over at prophase I, occurs between non-sister chromatids of homologous pairs to produce new combinations of parental alleles. Independent assortment at metaphase I is the random assortment of homologous chromosomes resulting in new combinations of parental chromosomes. Together these processes ensure that all the gametes produced will be genetically different leading to increased genetic diversity in offspring.
99
Explain why all the products of meiosis are genetically different
At prophase I, crossing over between non-sister chromatids of homologous pairs produces new combinations of the parental alleles. In addition, at metaphase I, there is an independent assortment of the homologous chromosomes resulting in new combinations of parental chromosomes. As a result at the end of meiosis, all the gametes formed will be genetically different.
100
State the meaning of haploid. Explain why the products of meiosis are haploid cells and contain a single set of chromosomes
A haploid cell has only one copy of each chromosome and thus only one copy of each gene or one genome (the set of all the different genes of an individual). Meiosis begins with a diploid cell in which the chromosomes are replicated. After meiosis I, the homologous chromosomes have separated producing two haploid cells. No DNA replication occurs before meiosis II where the sister chromatids are then separated. Thus, producing 4 haploid cells. (i.e. they contain a single set of chromosomes)
101
What are somatic cells
Body cells
102
What is a diploid cell
A cell with 2 copies of each chromosome
103
What is the name of the replication in prokaryotes
Binary fission
104
Explain why the amount of DNA in a cell doubles before division
The DNA is duplicated so that each daughter cell can receive an identical, and complete set of genetic information.
105
Describe the process of binary fission
1. Cell elongates and DNA is replicated
2. Cell wall and plasma membrane begin to divide
3. Cell wall begins forming with one chromosome on each side
4. Cell separates
106
Describe prophase
- Nucleur envelope dissolves
- Centrioles move towards poles of cell and the spindle fibres form
- Chromatin condenses forming chromosome pairs consisting of two chromatids joined by centromere
107
Describe metaphase
- Contraction of spindle fibres draws the replicated chromosomes to the equator of the cell
108
Describe anaphase
Centromere splits and the chromatids, now daughter chromosomes, are drawn to the poles of the cell via the centromere.
109
Describe telophase
- Spindle fibres disappear
- New nuclear membrane forms around the chromosomes
- Cytokinesis begins
- Cleavage furrow forms
110
How does cytokinesis differ in plant cells than animal cells
Requires the release of vesicles from the golgi body containing new cell wall material
111
Name 1 similarity between binary fission and mitosis
Both require DNA replication to occur before the process begins
112
Name 1 difference between binary fission and mitosis
Binary fission is fast whereas mitosis takes longer
113
What is meiosis
Cell division produces genetically different cells with half the normal number of chromosomes. Cells with half the normal number of chromosomes are gametes/haploid cells/sex cells
114
What are homologous chromosomes
Chromosomes from different parents but similar in size and shape and the genes they contain
115
Describe the process of Meiosis I in eukaryotes
PROPHASE I - the chromosomes condense and the nuclear envelope breaks down. Crossing over occurs
METAPHASE I - pairs of homologous chromosomes move to the equator
ANAPHASE I - homologous chromosomes move to opposite poles of cell
TELOPHASE I - chromosomes gather at the poles of cells. Cytoplasm divides
116
Describe the process of Meiosis II in eukaryotes
PROPHASE II
a new spindle fibre forms around the chromosomes
METAPHASE II
chromosomes line up at the equator
ANAPHASE II
Centromere divide. Chromatids move to the opposite poles of cells
TELOPHASE II
Nuclear envelope forms around each set of chromosomes. The cytoplasm divides.
117
What is the significance of crossing over
Creates genetic variation by producing new combination alleles
118
Significance of independent assortment
Produces new combinations of chromosomes
119
What is an allele
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
120
Compare the products of mitotic and meiotic cell division
The products of mitosis are 2 genetically identical daughter cells each containing the same full set of genes as the parent cell. The products of meiosis are 4 haploid cells and genetically different
121
State the importance of fertilisation
to restore the diploid number
122
describe exocytosis
- proteins synthesised on ribosomes attached to the rough ER
- proteins packaged into vesicles that bud off and move to the golgi body
- the vesicle fuses with the golgi body and the proteins enter where they are processed and then packaged into secretory vesicles
- the vesicle moves through cytoplasmic and fuses with the plasma membrane releasing its contents to the outside of the cell.
123
How can growth factors/hormones stimulate the cell cycle
They can bind to their receptors and trigger signal transduction pathways that can lead to gene expression that stimulates the cell cycle
124
What is the cell cycle comprised of?
```
G0 = cells not replicating but still functioning
G1 = cell growth
S = DNA synthesis
G2 = growth and preparation for mitosis
```
125
What is the importance of each of the checkpoints in the cell cycle?
G1 checkpoint - Ensures DNA is damage-free and ready to be replicated
G2 checkpoint - Checks if DNA has been replicated properly
M - the attachment of the chromosome to the spindle fibre is assessed
126
Where are the checkpoints located?
G1 - end of G1
G2 - end of G2
M - midway through m phase
127
What are cyclins?
Cell signalling molecules that regulate the cell cycle
128
What are carcinogens?
Mutagens that cause cancer
129
How do mutations relate to cancer?
- Cancer is the result of an accumulation of several mutations affecting key regulatory proteins in the cell cycle.
- Multiple mutations to certain genes that control the cell cycle can cause normal cells to become cancer cells.
- Cancer cells ignore the cell cycle checkpoints and therefore exhibit accelerating cell division and do not perform apoptosis
130
Mutations to what two types of genes can disturb the cell cycle?
- Tumour-suppressor genes
| - proto-oncogenes
131
Describe the steps of cancer progression
- Cell requires a mutation for repeated cell division
- New mutations arise and one cell has the ability to start a tumour
- The tumour is at its place of origin and one cell mutates further
- Cells have gained the ability to invade underlying tissues by producing a proteinase enzyme.
- Once metastasis (growth elsewhere) occurs, treatment options become limited
132
Describe the effect of a mutation on proto-oncogenes
Proto-oncogenes stimulate the cell to grow, divide and move through each cell cycle checkpoint. When mutated, they become oncogenes and lead to uncontrolled cell division due to the overproduction of the protein (signal transduction proteins) that stimulates the cell cycle.
133
Describe the effect of mutations to tumour-suppressor genes/DNA repair genes
DNA repair genes code for proteins that correct errors in duplicated DNA before cell division. DNA repair genes are active throughout the cell cycle. Mutations of tumour suppressor genes can lead to failure in repair, which in turn allows more mutations to accumulate.
134
Explain the effect of concentration levels on tumour suppressor genes
Proteins produced by tumour suppressor genes detect DNA damage. In low concentrations, these will pause the cell cycle and active DNA repair mechanisms and in high concentrations, they stop the cell cycle or cause apoptosis.
135
What is cell culturing?
Growing cells in a laboratory
136
Describe techniques of eukaryotic animal cell culture
Animal cells are grown and maintained at an appropriate temperature and gas mixture in a cell incubator. To grow eukaryotic cells, growth factors and antibiotics (to kill bacteria) need to be added to the nutrient medium
137
What are Hela cells
Cancer cells have been cultured and used in genetic engineering since the 1950s for research
138
What is an ethical issue
when a given decision, scenario or activity creates a conflict with a society's moral principles
139
What is a social issue
An issue that affects many individuals in society
140
What is an economic issue
An issue that creates new or increased financial liability
141
Describe application and limitation SHE concept
The impact and effect the processes have on society
142
Describe the development SHE concept
What scientific developments have taken place to get to this point
scientific knowledge and understanding can enable scientists to develop solutions
143
What is an example of contemporary cell culturing
- Skin cells are grown on a layer of collagen gel to prevent skincare companies from using animals to test their products before selling them.
- IVF
