B1: Cell Structure And Organisation Flashcards
How do you find out what the magnification of an object is?
Magnification = size of image/size of real object
What is the function of the cytoplasm?
- Liquid gel where organisms are suspended
- Where most chemical reactions for life take place.
What is the function of ribosomes?
- Where protein synthesis takes place (the process of making all proteins for the cell)
What is the function of mitochondria?
- Realease energy for the cell by aerobic respiration.
What is the function of the cell membrane?
- To control the passage of substances in and out of the cell.
What is the function of chlorophyll?
- To absorb light so that the plant can make food by photosynthesis.
How are eukaryotes and prokaryotes different?
Genetic Material:
- In Eukaryotic cells the genetic material is enclosed in a nucleus.
- In Prokaryotic cells the genetic material is not enclosed in the nucleus.
Mitochondria:
- Eukaryotes have mitochondria
- Prokaryotes do not have mitochondria.
Prokaryotic Cells are also always smaller than Eukaryotic Cells.
What are plasmids?
- Small rings of DNA.
- Code for specific features such as antiobiotic resistance.
Is bacteria prokaryotic or eukaryotic?
Prokaryotic.
Examples of specialised cells in animals?
- Nerve cells
- Muscle cells
- Sperm cells
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.
- Myelin Sheath for insulation and it speeds up the electrical impulses
How are muscle cells specialised? (3)
- Contain proteins that slide over each other and make the fibres contract
- Contain many mitochondria to transfer 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
Give examples of specialised plant cells?
Root hair cells, photosynthetic calls’ xylem cells and phloem cells
How are root hair cells specialised? (3)
- Increased 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
How are photosynthetic cells specialised? (3)
- Contain specialised chloroplasts
- 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 them rigid as a result of osmosis - keep the lead spread out to absorb as much light as possible.
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 is lignin make them very strong and help them to withstand pressure of water.
- Also help support phloem.
How are phloem cells specialised? (2)
- Cell 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.
What is diffusion?
- The spreading out of the particles of gas of any substance in a solution (a solute).
What is the net movement of diffusion ?
- From high to low concentration, down the concentration gradient.
What affects the rate of diffusion?
- Difference in concentrations
- The temperature
- The available surface area
What substances diffuse in out body?
- Glucose
- Urea
- Gases (such as oxygen and carbon dioxide) move out and into cells
What is osmosis?
- A dilute solution to a concentrated solution.
- The movement of water particles from an area of high water concentration to an area of low water concentration across a partially permeable membrane.
- Down the concentration gradient.
Why is osmosis important in plants?
To maintain turgor (rigidity)
What is isotonic?
- When the concentration of the solution is the same inside and outside the cell
What is hypertonic?
- When the concentration of a solution is higher outside the cell.
What is hypotonic?
- When the concentration of a solution is higher inside the cell.
What is plasmolysis?
- When the vacuole and cytoplasm shrink and the cell membrane is pulled away from cell wall
Where does active transport occur? (2)
- Small intestine - uptake of sugar
- In the roots (root hair cells)
What is active transport?
- The movement of substances from a dilute solution to a more concentrated solution.
- Against the concentration gradient.
- The movement of particles from an area of low concentration to an area of high concentration against a concentration gradient using energy from respiration.
What is the surface area to volume ratio?
As an object gets bigger, the ratio of the surface area to volume falls.
Why do most exchange surfaces usually have a large surface area and thin walls?
To give a shorter diffusion distance
What is the importance of diffusion in animal and plant cells?
Why do animal cells burst in a hypotonic solution?
They do not have a cell wall.
Which organism has a higher surface area: volume ratio? A whale or a fly?
A fly. They have more surface area per unit of volume.
State one adaptation cells may need if they need to carry out active transport.
Lots of mitochondria – to allow a lot of energy to be released for active transport.
Explain how SA:V ratio of an organism affects the way it exchanges materials with the environment.
- It affects how quickly an organism can exchange the materials with the outside world.
- Smaller ratio means diffusion alone cannot provide sufficient gas and food molecules to cells and metabolic waste cannot be removed quickly enough.
