B1 - Cell structure and transport Flashcards
1
Q
What organelles are found in a plant cell?
A
Ribosomes, Cell membrane, Cellulose cell wall, Mitochondria, Cytoplasm, Permanent vacuole, Chloroplasts, Nucleus
2
Q
What organelles are found in an animal cell?
A
Cell membrane, Ribosomes, Mitochondria, Cytoplasm, Nucleus
3
Q
What is a nucleus?
A
The nucleus controls all the activities of the cell and is surrounded by the nuclear membrane. It contains the genes on the chromosomes that carry the instructions for making the proteins needed to build new cells or organisms. The average diameter is around 10 micrometres (10 μm)
4
Q
What is a cytoplasm?
A
The cytoplasm is a liquid gel in which the organelles are suspended and where most of the chemical reactions take place that are needed for life
5
Q
What is a cell membrane?
A
The cell membrane controls the passage of substances such as glucose and mineral ions into the cell. It also controls the movement of substances such as urea or hormones out of the cell.
6
Q
What are mitochondria?
A
The mitochondria are structures in the cytoplasm where aerobic respiration takes place, releasing energy for the cell. They are very small:1-2 μm in length and only 0.2-0.7 μm in diameter
7
Q
What are ribosomes?
A
Ribosomes is where protein synthesis takes place, making all the proteins needed in the cell
8
Q
What are chloroplasts?
A
Chloroplasts are found in all the green parts of a plant. They are green because they contain the green substance chlorophyll. Chlorophyll absorbs light so the plant can make food by photosynthesis. Each chloroplast is around 3-5 μm long. Root hair cells do not have chloroplasts because they are underground and do not photosynthesise
9
Q
What is a permanent vacuole?
A
The permanent vacuole is a space in the cytoplasm filled with cell sap. This is important for keeping the cells rigid to support the plant
10
Q
What is a Cellulose cell wall?
A
A cellulose cell wall is a cell wall made of cellulose that strengthens the cell and gives is support
11
Q
What are examples of eukaryotic cells?
A
Animal and plant cells
12
Q
What are examples of prokaryotic cells?
A
bacteria
13
Q
Are eukaryotic cells unicellular or multicellular?
A
unicellular or multicellular
14
Q
Where is DNA stored in a eukaryotic cell?
A
In the nucleus
15
Q
Do eukaryotic cells contain membrane bound organelles?
A
yes, they have membrane bound organelles
16
Q
Are prokaryotic cells unicellular or multicellular?
A
unicellular
17
Q
Where is DNA stored in a prokaryotic cell?
A
it is free floating
18
Q
Do prokaryotic cells contain membrane bound organelles?
A
no, they do not have membrane bound organelles
19
Q
Do eukaryotic cells have a nucleus?
A
yes
20
Q
Do prokaryotic cells have a nucleus?
A
no
21
Q
What is active transport?
A
the movement of substances from a dilute solution to a more concentrated solution against a concentrationgradient, requiring energy from respiration
22
Q
What is algae?
A
simple aquatic organisms (protista) that make their own food by photosynthesis
23
Q
What is an alveoli?
A
tiny air sacs in the lungs that increase the surface area for gaseous exchange
24
Q
What is bacteria?
A
single-celled prokaryotic organisms
25
What is cellulose?
the complex carbohydrate that makes up plant and algal cell walls and gives them strength
26
What is diffusion?
the spreading out of the particles of any substance in a solution, or particles in a gas, resulting in a net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient
27
What are eukaryotic cells?
cells from eukaryotes that have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus
28
What is hypertonic (osmosis)?
a solution that is more concentrated than the cell contents
29
What is hypotonic (osmosis)?
a solution that is less concentrated than the cell contents (more water outside cell)
30
What is isotonic (osmosis)?
a solution that is the same concentration as the cell contents
31
What is osmosis?
the diffusion of water through a partially permeable membrane from a dilute solution (which has a highconcentration of water) to a concentrated solution (with a low concentration of water|) down a concentration gradient
32
What is a partially permeable membrane?
a membrane that allows only certain substances to pass through
33
What is phloem?
the living transport tissue in plants that carries dissolved food (sugars) around the plant
34
What is plasmolysis?
the state of plant cells when so much water is lost from the cell by osmosis that the vacuole and cytoplasm shrink and the cell membrane pulls away from the cell wall
35
What are prokaryotic cells?
from prokaryotic organisms have a cytoplasm surrounded by a cell membrane, and a cell wall that does not contain cellulose. The genetic material is a DNA loop that is free in the cytoplasm and not enclosed by a nucleus. Sometimes there are one or more small rings of DNA called plasmids
36
What is resolving power?
a measure of the ability to distinguish between two separate points that are very close together
37
What is sperm?
the male sex cells or gametes that carry the genetic material from the male parent
38
What is stomata?
openings in the leaves of plants, particularly on the underside and opened and closed by guard cells, allowing gases to enter and leave the leaf
39
What is turgor?
the pressure inside a plant cell exerted by the cell contents pressing on the cell wall
40
What is ventilated?
movement of air or water into and out of the gas exchange organ, for example lungs or gills
41
What is xylem?
the non-living transport tissue in plants that transports water from the roots to the leaves and shoots
42
What type of cells contain plasmids?
Prokaryotic cells
43
What are plasmids?
plasmids are small rings of DNA that code for very specific features such as antibiotic resistance
44
What is a flagellum?
a long protein strand that lashes about to help bacteria move themselves around
45
What is a slime capsule?
A protective capsule that is around the outside of the cell wall on a bacteria cell
46
Describe the structure of a bacteria cell
Bacteria have cytoplasm and a cell membrane surrounded by a cell wall, but the cell wall does not contain cellulose like in plant cells.
47
Can bacteria colonies be seen with the naked eye?
yes
48
What does it mean if an object is 1 order of magnitude larger than another object?
it is 10x larger than the other object
49
Describe the method for looking at cells
1) Collect a sample of the cell you want to observe2) Remove the inner layer of onion skin using forceps3) Place the thin slice onto a clean glass slide. Use your forceps to keep the onion skin flat on the glass slide4) Using a pipette, add 1 or 2 drops of dilute iodine solution on the top of the onion skin5) Hold the coverslip by its side and lay one edge of the cover slip onto the microscope slide near the specimen6) Lower the cover slip slowly so that the liquid spreads out.7) Move the microscope stage to its lowest position8) Place a prepared slide on the centre of the stage and fix it in place using the clips.9) Select the objective lens with the lowest magnification10) Look through the eyepiece and turn the coarse focus adjustment until the cells on the slide come into view.11) Turn the fine focus adjustment to sharpen the focus so the cells can be clearly seen.12) If you wish to view the object at greater magnification to see more detail, repeat the above steps using a higher magnification lens.13) At a low magnification, place a transparent ruler across the microscope stage.14) Measure the width of the field of view using the ruler markings.15) Place the slide to be viewed into position. Increase the magnification until individual cells can be viewed16) Calculate the new width of the field of view at this magnification, using the formula: FoV = (original magnification / new magnification) x original FoV17) Count the number of cells visible across the field of view18) Calculate the length of a single cell using the following formula: Length of cell = FoV / No. Cells
50
What is magnification?
the number of times bigger something appears
51
What is resolution?
the ability to distinguish between 2 separate points
52
What is the maximum resolution of a light microscope?
200 nm
53
What is the maximum resolution of an electron microscope?
0.2 nm
54
What is the maximum magnification of a light microscope?
2000x
55
What is the maximum magnification of an electron microscope?
2,000,000x
56
How does a light microscope form an image?
using a beam of light
57
How does an electron microscope form an image?
using a beam of electrons
58
Can a light microscope view living objects?
yes
59
Can an electron microscope view living objects?
no
60
What are the 2 types of electron microscopes?
1) Transmission electron microscope2) Scanning electron microscope
61
What type of images does a Transmission electron microscope produce?
2D images but a higher magnification than a Scanning microscope
62
What type of images does a Scanning electron microscope produce?
3D images but a lower magnification than a Transmission microscope
63
What is 1km in m?
1km = 1000m
64
What is 1m in cm?
1m = 100cm
65
What is 1cm in mm?
1cm = 10mm
66
What is 1mm in μm?
1mm = 1000μm
67
What is 1μm in nm?
1μm = 1000nm
68
What is pico- in standard form?
x10⁻¹²
69
What is nano- in standard form?
x10⁻⁹
70
What is micro- in standard form?
x10⁻⁶
71
What is milli- in standard form?
x10⁻³
72
What is centi- in standard form?
x10⁻²
73
What is kilo- in standard form?
x10³
74
What is mega- in standard form?
x10⁶
75
What is giga- in standard form?
x10⁹
76
What is tera- in standard form?
x10¹²
77
What is the equation for magnification?
magnification = image size / actual size
78
What is a nerve cell?
Nerve cells are specialised to carry electrical impulses around the body of an animal. They provide a rapid communication system between different parts of the body.
79
What are the adaptations of a nerve cell?
*An axon that carries the nerve impulse from one place to another.
*Myelin sheath is an insulating layer around the axon which allows the electrical impulses to travel quickly and efficiently along the axon
* Lots of different dendrites to make connections to other nerve cells and receive electrical impulses
* They contain a lot of mitochondria to provide the energy needed to make the transmitter chemicals in the nerve endings
80
What is a muscle cell?
Muscle cells are specialised cells that can contract and relax. Striated (striped) muscle cells work together in tissues called muscles. Muscles contract and relax in pairs to move the bones of the skeleton, so vertebrates can move on land and in water, and in some cases fly. Smooth muscle cells from one of the layers of tissue in your digestive system and they contract to squeeze the food through your gut
81
What are the adaptations of a muscle cell?
*They contain special proteins that slide over each other making the fibres contract
*They contain mitochondria to transfer the energy needed for the chemical reactions to take place as the cells contract and relax
*They can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the fibres to contract
82
What is a sperm cell?
Sperm cells are released a long way from the egg that they are going to fertilise. They contain the genetic information from the male parent. Depending on the type of animal, sperm cells need to move through water or the female reproductive system to reach the egg. Then they have to break into the egg
83
What are the adaptations of a sperm cell?
*A long tail that whips from side to side to help move the sperm through the water or the female reproductive system
* The middle section is full of mitochondria, which transfers the energy needed for the tail to work.
*The acrosome stores digestive enzymes for breaking down the outer layers of the egg
*A large nucleus contains the genetic information to be passed on
84
What is a root hair cell?
You find root hair cells close to the tips of growing roots. Plants need to take in a lot of water (and dissolved mineral ions). The root hair cells help them take up water and mineral ions more effectively. Root hair cells are always relatively close to the xylem tissue. The xylem tissue carries the water and mineral ions up into the rest of the plant. Mineral ions are moved into the root hair cell by active transport
85
What are the adaptations of a root hair cell?
*They greatly increase the surface area available for water to move into the cell*They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell*They have many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells
86
What is a photosynthetic cell?
One of the ways plant cells differ from animals is that they can make their own food by photosynthesis. There are lots of plant cells that can carry out photosynthesis - and lots that cannot.
87
What are the adaptations of a photosynthetic cell?
*They contain specialised green structures called chloroplasts containing chlorophyll that trap the light needed for photosynthesis
*They are usually positioned in continuous layers in the leaves and outer layers of the stem of a plant so that they absorb as much light as possible
*They have a large permanent vacuole that helps keep the cell rigid as a result of osmosis. When these rigid cells are arranged together to form photosynthetic tissue they help support the stem. They also keep the leaf spread out so it can capture as much light as possible
88
What is a xylem cell?
Xylem is the transport tissue in plants that carries water and mineral ions from the roots to the highest leaves and shoots. The xylem is also important in supporting the plant.
89
What are the adaptations of a xylem cell?
*The xylem cells are alive when they are first formed but a special chemical called lignin builds up in spirals in the cell walls. The cells die and form long hollow tubes that allows water and mineral ions to move easily through them, from 1 end of the plant to another
*The spirals and rings of lignin in the xylem cells make them very strong and help them withstand the pressure of water moving up the plant. They also help support the plant stem
90
What is a phloem cell?
Phloem is the specialised transport tissue that carries the food made by photosynthesis around the body of the plant. It is made up of phloem cells that form tubes like xylem cells, however phloem cells do not become lignified and die. The dissolved food can move up and down the phloem tubes to where it is needed
91
What are the adaptations of a phloem cell?
*The cell wall between the cells break down to form special sieve plates. These allow water carrying dissolved food to move freely up and down the tubes to where it is needed*Phloem cells lose a lot of their internal structure but they are supported by companion cells that help keep them alive. The mitochondria of the companion cells transfer the energy needed to move dissolved food up and down the plant in phloem
92
Describe the process of diffusion
When particles are added to another group of particles they are not mixed at all. As the particles move randomly they begin to mix. As the particles move and spread out, they bump into each other, this helps them to keep spreading randomly. Eventually, the particles are completely mixed and diffusion is complete, although they do continue to move randomly. They are in equilibrium
93
Where do particles move to and from in diffusion?
From a high concentration to a lower concentration of the particle
94
What is net movement?
Net movement = particles moving in - particles moving out
95
What are 2 things that change the rate of diffusion?
1) Concentration gradient2) Temperature
96
How does concentration gradient effect the rate of diffusion?
If there is a steeper concentration gradient, diffusion will speed up. This is because diffusion occurs down a concentration gradient
97
How does Temperature effect the rate of diffusion?
An increase in temperature means that means that the particles have more kinetic energy and are moving faster. This speeds up diffusion as the random movement of particles is sped up.
98
What are examples of diffusion in a living organism?
*The diffusion of oxygen and glucose into the cells of the body from the bloodstream for respiration
*The diffusion of carbon dioxide into actively photosynthesising plant cells
*The diffusion of oxygen and carbon dioxide in opposite directions in the lungs, known as gas exchange
*The diffusion of simple sugars and amino acids from the gut through cell membranes
99
What is a dilute solution of sugar?
It has a low concentration of sugar and a high concentration of water
100
What is a concentrated sugar solution?
It has a high concentration of sugar and a low concentration of water
101
What is osmosis?
Osmosis is the diffusion of water across a partially permeable membrane.
102
Where does water move to and from during osmosis?
Water moves from a dilute solution (high water concentration) to a concentrated solution (low water concentration)
103
What is an example of a partially permeable membrane?
The Cell Membrane
104
What is a hypotonic solution?
If the concentration of solutes in the solution outside the cell is lower than the internal concentration (dilute solution), the solution is hypotonic to the cell
105
What is a isotonic solution?
If the concentration of solutes in the solution outside the cell is the same as the internal concentration, the solution is isotonic to the cell
106
What is a hypertonic solution?
If the concentration of solutes in the solution outside the cell is higher than the internal concentration (concentrated solution), the solution is hypertonic to the cell
107
What is the effect of a hypotonic solution on an animal cell?
The animal cell will swell and possibly burst as there is more water moving into the cell than out of the cell
108
What is the effect of a isotonic solution on an animal cell?
The animal cell will remain as normal as there is the same amount of water moving into the cell as there is moving out of the cell
109
What is the effect of a hypertonic solution on an animal cell?
The animal cell will shrink and shrivel up as there is more water moving out of the cell than there is moving into the cell
110
When does turgor pressure occur?
Turgor pressure occurs when no more water can enter the cell due to the pressure inside
111
What is the effect of a hypotonic solution on a plant cell?
A hypotonic solution causes cells to become turgid (rigid) which supports the plant. This is because there is more water moving into the cell than out of the cell
112
What is the effect of an isotonic solution on a plant cell?
The cell will remain in its current state, eg if it is turgid it will remain turgid and if it is flaccid it will remain flaccid. This is because the same amount of water is moving into the cell as there is moving out of the cell
113
What is the effect of a hypertonic solution on a plant cell?
The cell will become flaccid and the plant will wilt. This is because there is more water moving out of the cell than into it and there is no longer any pressure on the cell wall. If even more water is lost through osmosis, the vacuole and cytoplasm shrink, and eventually the cell membrane pulls away from the cell wall. This is called plasmolysis. Plasmolysis is usually only seen in laboratory experiments. Plasmolysed cells will die quickly unless the osmotic balance is restored
114
Describe the method for investigating osmosis in plant cells
1) Measure the mass of two pieces of skinned potato using a balance. Cut the pieces of potato so that they are all the same mass and length. Record the mass of each of the pieces of potato.2) Measure 15 cm³ of distilled water using a measuring cylinder. Put the water into a boiling tube.3) Measure 15 cm³ of 0.1 mol/dm³ concentration of the sugary solution. Put the solution into a boiling tube. Repeat this for all solution from 0.2-0.5 mol/dm³4) Put a piece of vegetable in each boiling tube and press start on the stop-watch.5) After 10 minutes, use tweezers to remove the pieces of vegetable from the boiling tubes and place on some filter paper.6) Dab the pieces of vegetable to remove any excess liquid.7) Measure the mass of the pieces of vegetable using a balance. Record the new mass.8) Record data in appropriate graph/table9) If you have time repeat the experiment and get a mean average for more accurate results
115
What are 2 examples of passive transport systems and what does it mean?
Diffusion and Osmosis, a passive transport system means that no energy is expended during the process
116
What is an examples of an active transport system and what does it mean?
Active Transport, energy from respiration is required for the process to take place
117
In which direction do substances move during active transport?
From an area of low concentration to an area of high concentration (against the concentration gradient)
118
What is an example of when active transport is used?
Cells use active transport to absorb substances across a partially permeable membrane against the concentration gradient
119
What does active transport allow cells to do?
It allows cells to absorb ions from very dilute solutions. It also enables cells to move substances, such as sugar and ions, from one place to another through the cell membrane
120
How are the rate of active transport and the rate of respiration related?
As the rate of respiration increases, the rate of active transport increases. This is because as the rate of respiration increases, more energy is released. This allows more active transport to be carried out
121
Describe how active transport takes place
On the edge of the cell there is a transport protein. If there is a useful molecule outside the cell this transport protein will grab it. The transport protein will then rotate so it is facing inside the cell and release the molecule inside the cell (using energy). It will then rotate back to face outside the cell (using energy) to wait for other useful molecules
122
As an organism gets bigger, its SA:V ratio ............
gets smaller
123
What difficulties can a lower SA:V ratio in an organisms cause?
*Gases and food molecules cannot reach every cell in the organism by simple diffusion*Metabolic waste cannot be removed fast enough to avoid poisoning the cells
124
How can the effectiveness of an exchange surface be increased?
*Having a large surface area
*Having a thin membrane or being thin to provide a short diffusion path
*Maintaining a steep concentration gradient by being ventilated and having an efficient blood supply
125
What are examples of adaptations to make the exchange of materials more efficient?
*Alveoli - they have a large surface area and a good blood supply to maintain a good concentration gradient so they can perform rapid gas exchange*Villi - Large surface area, thin diffusion path, and a good blood supply to absorb soluble food molecules*Roots - Long thin roots increase the surface area for water absorption, root hair cells further increase the surface area *Stomata - Stomata allow gases in and out of the leaf
126
How can you make the results of a practical MORE VALID?
*Repeat and calculate a mean
* Ensure any control variables are controlled
127
How can you improve a practical?
*Repeat the experiment more times
*Add more intervals
128
Why will there be no NET movement of water in the cell when the solution is isotonic to the cell?
There is no net movement as the concentration of the solution is the same as the concentration inside the cell. Therefore, the volume of water which diffuses into the cell through a partially permeable membrane is equal to the volume of water which diffuses out of the cell through a partially permeable membrane. Therefore there is no net movement.
129
What is net movement?
Movement in - movement out
130
What causes water to move up the xylem?
The transpiration pull
131
Why is having few stomata on the upper epidermis an advantage of leaves?
Prevents uncontrolled water loss meaning the plant does not wilt
