B1 Cell structure and transport Flashcards
Nucleus
Controls all activities of the cell, contains genetic information
Cytoplasm
Where most of the chemical reactions needed for life take place
Cell membrane
Controls what substances go in and out of the cell
Mitochondria
Site of aerobic respiration, releasing energy
Ribsomes
Where protein synthesis takes place
Cell wall
Strengthens plant cells and provides support
Permanent vacuole
Contains cell sap to keep plant cells rigid, provide support
Chloroplasts
- Where photosynthesis takes place
- Contains chlorophyll, absorbs light for photosynthesis
Compare eukaryotic and prokaryotic cells
Eukaryote
- genetic material enclosed in nucleus
- membrane-bound organelles e.g. chloroplasts, mitochondria
- animals, plants, fungi, protists
Prokaryote
- genetic material not enclosed in a nucleus
- no membrane- bound organelles
- much smaller than eukaryotes
- bacteria
What is one benefit of having DNA contained in a nucleus?
Protects the DNA
Define resolution
The ability to distinguish between two separate points that are very close together
Magnification equation
magnification = image size / actual size
Where does the genetic material of a prokaryotic cell exist?
In the cytoplasm
What is haemoglobin?
Protein which carries the oxygen molecule
Function of red blood cells
Transport oxygen around the body in the blood
Adaptions of red blood cells
- No nucleus, more space for haemoglobin (which carries oxygen)
- Bi-concave shape, increases surface area so more oxygen can diffuse into the cell
Function of ciliated cells
Keeps dust and bacteria out of the lungs
Adaptions of ciliated cells
- Cilia (hair like structures), beat rhythmically to sweep mucus containing bacteria and dust out of the lungs
- Lots of mitochondria, provide energy for movement of cilia
Adaptations of nerve cell
- Lots of dendrites, to make connections to other nerve cells
- Long axon, carries impulses from one place to another, allows it to be carried long distances
- Lots of mitochondria, to release the energy needed to make the transmitter chemicals that diffuse across the synapses
Adaptation of muscle cell
- Special proteins, slide over each other to make the fibres contract
- Lots of mitochondria, transfers energy needed for the chemical reactions to take place as the cells contract and relax
- Can store glycogen, can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the fibres to contract
Adaptations of sperm cells
- Long tail, helps sperm move through the female reproductive system
- Middle-section containing lots of mitochondria, transfers the energy needed for the tail to work
- Acrosome, stores digestive enzymes for breaking down the outer layers of the egg
- Large nucleus, contains the genetic information to be passed on
Adaptations of root hair cell
- Has lots of root hairs which increase the surface area available for water to move into the cell
- Large permanent vacuole, speeds up the movement of water by osmosis from the soil across the root hair cell
- Lots of mitochondria, transfers energy needed for active transport of mineral ions into the root hair cells
Explain the difference between magnification and resolution
Magnification describes how many times larger the image is compared to the original, whereas resolution describes the clarity of the image being viewed.
Most animal cells have the following parts…
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribsomes
In addition to the parts found in animal cells, plant cells often have:
- Chloroplasts
- Permanent vacuole
- Cell wall
Explain the difference of differentiation in animal and plant cells
- Most types of animal cell differentiate at an early stage
- Many types of plant cells retain the ability to differentiate throughout life
What is diffusion?
The net movement of particles from an area of higher concentration to an area of lower concentration, down a concentration gradient
Factors that affect the rate of diffusion
- Difference in concentrations
- Temperature
- Surface area
How does the difference in concentrations affect the rate of diffusion?
The greater the difference in concentration/the steeper the concentration gradient between two areas, the faster the rate of diffusion
How does the temperature affect the rate of diffusion?
- The higher the temperature, the more kinetic energy the particles in a gas or solution will have, so they move around quicker
- Diffusion takes place more rapidly as the random movement of particles speeds up
How does surface area affect the rate of diffusion?
A membrane with a greater surface area will have a greater rate of diffusion across it
What is osmosis?
The movement of water from a dilute to a more concentrated solution across a partially membrane
What is an 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, the solution is hypertonic to the cell
What is a hypotonic solution
If the concentration of solutes in the solution outside the cell is lower than the internal concentration, the solution is hypotonic to the cell
What is active transport
The movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient, with the use of energy from respiration
Adaptations for exchanging materials
The effectiveness of an exchange surface can be increased by:
- having a large surface area over which exchange can take place
- having a thin membrane or being thin to provide a short diffusion path
- in animals, having an efficient blood supply moves the diffusing substances away from the exchange surfaces and maintains a steep concentration gradient
- in animals, being ventilated makes gas exchange more efficient by maintaining steep concentration gradients
What is cell differentiation
The process where a cell becomes specialised to its function
What is a concentration gradient
The difference in concentration between two areas
What are plasmids?
- Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA
- Carry genes that provide genetic advantages, for example, antibiotic resistance
How do we calculate the total magnification of a microscope?
eyepiece lens x objective lens magnifying power
Which focus knob should be used during low and medium power magnification?
Coarse focus knob
Which focus knob should be used during high power magnification?
Fine focus knob
Why does the tissue sample need to be stained before looking at it under the microscope?
To visualise/see structures clearly
What is the function of the flagella?
To allow the cell to swim and move around
Adaptations of xylem cells
- Lignin builds up spirals in the cell walls and causes the cells to die. These dead cells form long, continuous, hollow tubes that allow water and mineral ions to move easily through them, from one end of the plant to the other
- Spirals and rings of lignin make the very strong and help them withstand the pressure of water moving up the plant. They also help support the plant stem
Adaptations of phloem cells
- The cell walls between the cells break down to form sieve plates. These allow water carrying dissolved food to move freely up and down the tubes to where it is needed
- Phloem cels lose a lot of their internal structures but they are supported by companion cells that help to keep them alive. The mitochondria of the companion cells transfer energy needed to move dissolved food up and down the plant in phloem
Differences in structure between xylem and phloem
Xylem:
- dead
- hollow tube
- has lignin
Phloem:
- living
- has sieve plates
- no lignin
Substances that diffuse into our cells for use
Oxygen and glucose
Substances that diffuse out of our cells to be removed
Carbon dioxide and urea
Why is osmosis so important in plant cells?
Osmosis is important to maintain turgor in plant cells. Turgor pressure makes the cells hard and rigid, which in turn keeps the leaves and stems of the plant hard and rigid.
Explain the importance of active transport in animals
Cells in the gut lining do active transport to absorb glucose effectively from the bloodstream
Explain the importance of active transport in plants
Root hair cells carry out active transport to absorb mineral ions, required for healthy growth, effectively in dilute soil
Adaptations for exchanging materials
- Having a large surface area over which exchange can take place
- Having a thin membrane or being thin to provide a short diffusion path
- In animals, having an efficient blood supply moves the diffusing substances away from the exchange surfaces and maintains a steep concentration gradient
- In animals, being ventilated makes gas exchange more efficient by maintaining steep concentration gradients
How are alveoli adapted for efficient gaseous exchange?
- Large surface area over which exchange can take place
- Thin membrane for short diffusion distance
- Rich blood supply maintains a steep concentration gradient
How are plant roots adapted for efficient water and mineral absorption?
- Root hairs provide a large surface area
- Water constantly moves away from the roots in the transpiration stream, maintaining a steep concentration gradient in the cells
How does stomata help maintain efficient gas exchange in leaves?
- Provide a big surface area
- Allows gases to move in and out of the cell, maintaining a steep concentration gradient for diffusion
What two differences does an image produced by an electron microscope have compared to one with a light microscope?
- Electron microscopes differ from light microscopes in that they produce an image of a specimen by using a beam of electrons rather than a beam of light.
- Electrons have much a shorter wavelength than visible light, and this allows electron microscopes to produce higher-resolution images than standard light microscopes.
Describe the trend between the size of the organism and the surface area to volume ratio
The ratio of surface area to volume falls as objects or organisms get bigger
How are alveoli and villi adapted to their use?
- Alveoli have an enormous surface area over which diffusion can take place
- Both alveoli and villi have a very rich blood supply which maintains a steep concentration gradient, for effective gas exchange
- Villi of the small intestine also provide a large surface area
- Villi have thin walls which provides short diffusion paths
Explain how electron microscopy has increased understanding of sub-cellular structures
- An electron microscope has much higher magnification and resolving power than a light microscope
- This means that it can be used to study cells in finer detail
- This has enabled biologists to see and understand many more sub-cellular structures
