B1 - Cell Structure And Organisation Flashcards
E. Magnification
Magnification= image size / size of real object
Function of cytoplasm?
Liquid gel where organisms are suspended and most chemical reactions for life take place.
Function of ribosomes?
Site of protein synthesis
Function of mitochondria?
Site of aerobic respiration
Function of cell membrane?
Controls the passage of substances in and out of the cell.
Function of chlorophyll?
Absorbs light so plant can make food by photosynthesis
Give a feature of a eukaryotic cell
Genetic material is enclosed in a nucleus
Give a feature of a prokaryotic cell
similar to the eukaryotic cell feature
Genetic material is not enclosed in a nucleus (free floating in the cytoplasm).
What are plasmids?
Small rings of DNA that code for specific features such as antibiotic resistances
Bacteria are….
Prokaryotic cells
Examples of specialised cells?
Nerve cells, muscle cells, sperm cells, red blood cells, ciliated epithelial cells, root hair cells etc etc
How are nerve cells specialised? (3)
- Lots of dendrites that make connections to other cells
- Axons that carry the impulse from one place to another
- Synapses are adapted to pass the impulse to another cell or between a nerve cell and a muscle cell
How are muscle cells specialised? (3)
- Contain proteins that slide over each other and make the fibres contract
- Contain many mitochondria to provide the energy needed for chemical reactions to take place
- Store glycogen, which can be broken down and used in cellular respiration by the mitochondria to provide energy needed for the fibres to contract.
How are sperm cells specialised?
4
- Long tail helps it to move
- Middle section is full of mitochondria, which provide energy for the tail
- Large nucleus contains genetic information to be passed on
- Acrosome stores digestive enzymes to break down the outer layers of the egg
Specialised plant cells?
Root hair cells, photosynthetic cells, xylem cells and phloem cells
How are root hair cells specialised? (3)
- Long and narrow, which increases the surface area for water to move into the cell
- Permanent vacuole that speeds up movement of water by osmosis from the soil across the root hair cell
- Many mitochondria to transfer energy needed for active transport of mineral ions into the cells
How are photosynthetic cells specialised? (3)
- Contain specialised chloroplasts containing chlorophyll which absorbs the sunlight needed for photosynthesis
- Usually positioned in continuous layers in the leaves and outer layers of the stem so they absorb as much light as possible
- Large perm vacuole that keeps the cell rigid as a result of osmosis when lots of these rigid cells are arranged together, they help support the stem.
How are xylem cells specialised? (2)
- Alive at first but die and form long hollow tubes to allow water and mineral ions to move easily through them
- Spirals and rings of lignin make them very strong and help them to withstand pressure of water.
How are phloem cells specialised? (2)
- Call walls between the cells break down to form special sieve plates. Allow water carrying dissolved food to move freely
- Supported by companion cells which transfer energy and support them.
D. Diffusion
The spreading out of the particles of gas of any substance in a solution ( a solute)
Net movement of diffusion ?
From high to low concentration, down the conc gradient
What effects the rate of diffusion?
Difference in concentrations, the temperature and the available surface area
How do substances such as urea and glucose and gases such as oxygen and carbon dioxide move out and into cells?
Diffusion
D. Osmosis?
The movement of water to dilute a solution across a partially permeable membrane, Down the conc gradient
D. Isotonic?
The concentration of the solution is the same inside and outside the cell
D. Hypertonic?
Solution conc is higher OUTSIDE the cell
D. Hypotonic
Conc of solution is higher INSIDE the cell
Why is osmosis important in plants?
To maintain turgor ( turgidity )
Plasmolysis?
When the vacuole and cytoplasm shrink and the cell membrane is pulled away from cell wall
D. Active transport?
The movement of substances from a dilute solution to a more concentrated solution against the concentration gradient
Where does active transport occur? (2)
- Small intestine - uptake of sugar
* In the roots (root hair cells)
As the object gets bigger…
The surface area:volume ration decreases
Why do most exchange surfaces usually have a large SA and thin walls?
To give a short diffusion distance.
Differences between prokaryotes and eukaryotes? (3)
pro’s are….
- smaller
- don’t have a nucleus
- may have plasmids
