B1 - Cell Structure and Transport Flashcards
What organelles are found in a plant cell?
Ribosomes, Cell membrane, Cellulose cell wall, Mitochondria, Cytoplasm, Permanent vacuole, Chloroplasts, Nucleus
What organelles are found in an animal cell?
Cell membrane, Ribosomes, Mitochondria, Cytoplasm, Nucleus
What is a nucleus?
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)
What is a cytoplasm?
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
What is a cell membrane?
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.
What are mitochondria?
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
What are ribosomes?
Ribosomes is where protein synthesis takes place, making all the proteins needed in the cell
What are chloroplasts?
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
What is a permanent vacuole?
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
What is a Cellulose cell wall?
A cellulose cell wall is a cell wall made of cellulose that strengthens the cell and gives is support
What are examples of eukaryotic cells?
Animal and plant cells
What are examples of prokaryotic cells?
bacteria
Are eukaryotic cells unicellular or multicellular?
unicellular or multicellular
How large are eukaryotic cells?
10-100μm long
Where is DNA stored in a eukaryotic cell?
In the nucleus
Do eukaryotic cells contain membrane bound organelles?
yes, they have membrane bound organelles
Are prokaryotic cells unicellular or multicellular?
unicellular
How large are prokaryotic cells?
0.2-2.0μm long
Where is DNA stored in a prokaryotic cell?
it is free floating
Do prokaryotic cells contain membrane bound organelles?
no, they do not have membrane bound organelles
Do eukaryotic cells have a nucleus?
yes
Do prokaryotic cells have a nucleus?
no
How large is an average animal cell?
10-30μm long
How large is an average plant cell?
10-100μm long
What is active transport?
the movement of substances from a dilute solution to a more concentrated solution against a concentration
gradient, requiring energy from respiration
What is algae?
simple aquatic organisms (protista) that make their own food by photosynthesis
What is an alveoli?
tiny air sacs in the lungs that increase the surface area for gaseous exchange
What is bacteria?
single-celled prokaryotic organisms
What is cellulose?
the complex carbohydrate that makes up plant and algal cell walls and gives them strength
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
What are eukaryotic cells?
cells from eukaryotes that have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus
What is hypertonic (osmosis)?
a solution that is more concentrated than the cell contents
What is hypotonic (osmosis)?
a solution that is less concentrated than the cell contents (more water outside cell)
What is isotonic (osmosis)?
a solution that is the same concentration as the cell contents
What is osmosis?
the diffusion of water through a partially permeable membrane from a dilute solution (which has a high
concentration of water) to a concentrated solution (with a low concentration of water|) down a concentration gradient
What is a partially permeable membrane?
a membrane that allows only certain substances to pass through
What is phloem?
the living transport tissue in plants that carries dissolved food (sugars) around the plant
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
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
What is resolving power?
a measure of the ability to distinguish between two separate points that are very close together
What is sperm?
the male sex cells or gametes that carry the genetic material from the male parent
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
What is turgor?
the pressure inside a plant cell exerted by the cell contents pressing on the cell wall
What is ventilated?
movement of air or water into and out of the gas exchange organ, for example lungs or gills
What is xylem?
the non-living transport tissue in plants that transports water from the roots to the leaves and shoots
What type of cells contain plasmids?
Prokaryotic cells
What are plasmids?
plasmids are small rings of DNA that code for very specific features such as antibiotic resistance
What is a flagellum?
a long protein strand that lashes about to help bacteria move themselves around
What is a slime capsule?
A protective capsule that is around the outside of the cell wall on a bacteria cell
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.
Can bacteria colonies be seen with the naked eye?
yes
What does it mean if an object is 1 order of magnitude larger than another object?
it is 10x larger than the other object
Describe the method for looking at cells
1) Collect a sample of the cell you want to observe
2) Remove the inner layer of onion skin using forceps
3) Place the thin slice onto a clean glass slide. Use your forceps to keep the onion skin flat on the glass slide
4) Using a pipette, add 1 or 2 drops of dilute iodine solution on the top of the onion skin
5) Hold the coverslip by its side and lay one edge of the cover slip onto the microscope slide near the specimen
6) Lower the cover slip slowly so that the liquid spreads out.
7) Move the microscope stage to its lowest position
8) 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 magnification
10) 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 viewed
16) Calculate the new width of the field of view at this magnification, using the formula: FoV = (original magnification / new magnification) x original FoV
17) Count the number of cells visible across the field of view
18) Calculate the length of a single cell using the following formula: Length of cell = FoV / No. Cells
What is magnification?
the number of times bigger something appears
What is resolution?
the ability to distinguish between 2 separate points
What is the maximum resolution of a light microscope?
200 nm
What is the maximum resolution of an electron microscope?
0.2 nm
What is the maximum magnification of a light microscope?
2000x
What is the maximum magnification of an electron microscope?
2,000,000x
How does a light microscope form an image?
using a beam of light
How does an electron microscope form an image?
using a beam of electrons
Can a light microscope view living objects?
yes
Can an electron microscope view living objects?
no
What are the 2 types of electron microscopes?
1) Transmission electron microscope
2) Scanning electron microscope
What type of images does a Transmission electron microscope produce?
2D images but a higher magnification than a Scanning microscope
What type of images does a Scanning electron microscope produce?
3D images but a lower magnification than a Transmission microscope
What is 1km in m?
1km = 1000m
What is 1m in cm?
1m = 100cm
What is 1cm in mm?
1cm = 10mm
What is 1mm in μm?
1mm = 1000μm
What is 1μm in nm?
1μm = 1000nm
What is pico- in standard form?
x10⁻¹²
What is nano- in standard form?
x10⁻⁹
What is micro- in standard form?
x10⁻⁶
What is milli- in standard form?
x10⁻³
What is centi- in standard form?
x10⁻²
What is kilo- in standard form?
x10³
What is mega- in standard form?
x10⁶
What is giga- in standard form?
x10⁹
What is tera- in standard form?
x10¹²
What is the equation for magnification?
magnification = image size / actual size
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.
What are the adaptations of a nerve cell?
- Lots of different dendrites to make connections to other nerve cells
- An axon that carries the nerve impulse from one place to another. They can be very long - the axon of a nerve cell in a blue whale can be up to 25m long! the largest axon in your body runs from the base of your spine to your big toe
- The nerve endings or synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle cell in the body using special transmitter chemicals. They contain a lot of mitochondria to provide the energy needed to make the transmitter chemicals
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
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
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
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
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
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
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.
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
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.
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
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
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
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
Where do particles move to and from in diffusion?
From a high concentration to a lower concentration of the particle
What is net movement?
Net movement = particles moving in - particles moving out
What are 2 things that change the rate of diffusion?
1) Concentration gradient
2) Temperature
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
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.
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
What is a dilute solution of sugar?
It has a low concentration of sugar and a high concentration of water
What is a concentrated sugar solution?
It has a high concentration of sugar and a low concentration of water
What is osmosis?
Osmosis is the diffusion of water across a partially permeable membrane.
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)
What is an example of a partially permeable membrane?
The Cell Membrane
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
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
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
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
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
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
When does turgor pressure occur?
Turgor pressure occurs when no more water can enter the cell due to the pressure inside
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
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
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
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/dm³
4) 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/table
9) If you have time repeat the experiment and get a mean average for more accurate results
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
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
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)
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
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
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
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
As an organism gets bigger, its SA:V ratio …………
gets smaller
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
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
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
