Cells: Basic units of life Flashcards
Three parts of the cell wall.
- Middle lamella
- Thine membranous layer outside - Primary wall
- Formed inside of middle lamella
- Consists of cellulose - Secondary wall
- Found inside primary wall in certain specialized cells
- Made up of substances like suberin/lignin - Intercellular space
- Space between cells
Functions of cell wall
- Forms an outer protective layer in plant cells
- Provides a rigid framework and support for plants
- Walls are permeable meaning they allow most dissolved substances through
- Middle lamella binds cells together
What is protoplasm?
It refers to the living substance in cells. It is made up of cytoplasm and the nucleus
What is the plasma membrane?
It is the outer boundary of the cytoplasm. Its main function is to control the movement of substances in and out the cell as it is selectively-permeable.
What does the plasma membrane look like?
It is microscopic but there are theories as to what it looks like. One is the fluid-mosaic model, which says it it two sheets of phospholipids that are stuck together with pores at regular intervals. It has a hydrophilic head and a hydrophobic tail.
What substances go through the plasma membrane? And by what processes is it possible?
Water, gases, dissolves salts, glucose, amino acids
Diffusion, osmosis, active transport
What is diffusion?
It is a passive process meaning no energy is required. It is the movement of molecules from regions of high concentration to regions of low concentration. This is caused by kinetic energy, so if you increase that (by heating/stirring) the rate of diffusion also increases
What is osmosis?
It is a special kind of diffusion, it only transports water. It is the movement of water molecules from dilute solutions (more water - high water potential) to concentrated solutions (less water - low water potential) until dynamic equilibrium is reached
Explain water potential
Pure water has a water potential of 0. Adding a solute lowers the water potential. There is no way for it to get above 0. Adding a solute creates a water potential gradient and this will cause water molecules to move across the partially permeable membrane to try and create an equilibrium
What are the different stages called? (equal concentration / high / low water potential)
Equal concentration - Isotonic
More water in cell - Hypotonic / Turgid
Less water in cell - Hypertonic / Plasmolyzed
Why is osmosis important?
It carries out unwanted waste and carries in dissolved salts and minerals. The water it carries in is used for transport, making blood, provides shape or hydrostatic skeleton
What is active transport?
In some cases substances are absorbed against a concentration gradient, It requires energy
What are cytoplasmic organelles? Give examples
They are found in cytoplasm and are bound by membrane.
Examples: Mitochondria, nucleus, Golgi apparatus, endoplasmic reticulum, vacuoles, vesicles, chloroplasts
What is the mitochondria?
They vary in numbers and are found in the cytoplasm of most living cells. They are the centers of cellular respiration and give off energy
How are the mitochondria shaped?
They have a rod like shape and are hollow on the inside. They have 2 membranes (inner and outer). They inner one is folded (cristae). It has its own DNA + RNA for making protein and enzymes (ribosomes)
What is the endoplasmic reticulum (Smooth/Rough ER)
It is a system of tubes enclosed by membranes. It acts as a communication system. The rough ER has ribosomes attached to it
What is the Golgi apparatus?
It is the broken off ends of the ER. It has a secretory functions
What are ribosomes?
They are small, grain-like structures that are present in both animal and plant cells. They occur on ER, in cytoplasm, plastids and mitochondria. This is were proteins are made
What is a vacuole?
It is a fluid-filled organelle. It has a single membrane. It is filled with cell sap which creates pressure in the cell. They contain anthocyanins (pigments)
What are lysosomes?
They are round vesicles seen mainly in animals cells. They are bound by a single membrane and contain digestive enzymes. Help with intercellular digestion
What are the centrosomes?
They occur near the nucleus of animal cells. They are made up of microtubes and have centrioles in the centrosomes. They make spindle threads during mitosis
What is the nucleus? Describe it’s structure.
Largest organelle. Structure:
- It is bound by a double membrane with nuclear pores that control the entry/exit of things.
- There is nuclear sap that contains all the substances produces in the nucleus (protein, sugars, phosphates)
- The chromatin network is made up of entangled threads that becomes chromosomes during mitosis. It occurs in the nucleoplasm (nuclear sap)
- The nucleolus lines the nucleoplasm. Nucleoli break up during mitosis and reappear after
What is the function of the nucleus?
It controls all cell activity and enzyme production. Chromosomes are responsible for carrying DNA
What are plastids?
They are small disc shaped organelles and they are only found in plant cells (chloroplasts, chromoplasts, leucoplasts)
What are chloroplasts?
It is green because of chlorophyll and traps light for photosynthesis. It is enclosed by a double membrane and has thylakoids in the stroma. They are stacked in groups called granum
What are chromoplasts?
They are irregularly shaped and are various colours due to pigments such as carotenes or xanthophyll. Found in bright parts of the plant like petals.
What are leucoplasts?
They are colourless found in roots. They store food in different forms (proteins, starch, lipids)
