Cell Structure Flashcards
Define
Protoplasm
The living contents of the cell
Nucleus and cytoplasm- surrounded by plasma membrane
Define
Nucleus of the cell
A membrane bound structure that contains the cell’s hereditary material and controls the cell’s growth and reproduction. Separates the contents of the nucleus from the cytoplasm
What are nuclear pores?
Pores in the nucleus that enables and control movement of substances between the nucleus and cytoplasm
Describe
The function of the mitochondria
Breaks down glucose molecules to release energy in cellular respiration
Describe
The features of the mitochondria
4 features
- Rod shaped
- Double membraned
- Inner membrane is highly folded (Cristae)
- High surface area to volume ratio–> More proteins to release energy as part of the electron transport chain (ETC) - Contain its own DNA
- Enables it to replicate when more are needed in a cell
Describe
The general functions of the endoplasmic reticulum
- Transporting material within a cell
- Site of biochemical reations within a cell
Differences between the smooth and rough endoplasmic reticulums
Rough ER: Dotted with ribosomes which manufacture polypeptides and inserts them in the ER to transport to the Golgi apparatus
Smooth ER: Not dotted with ribosomes. Involved in the synthesis of lipids and steriods, as well as the detoxification of drugs
Describe
The function of ribosomes
Attached and free
Attached ribosomes manufacture polypeptides to be sent to Golgi apparatus and sent out of the cell.
Free ribosomes (suspended in cytosol) manufacture polypeptides for internal use (cell repair etc.)
Describe
The function of the Golgi apparatus
Modifies proteins for specific functions and prepares them for transport to other parts of the cell by packaging them into membrane bound sacs (secretory vesicles). These membrane bound sacs that contain the modified protein pinch off the margins of the Golgi apparatus.
Features of the Golgi Apparatus
Consists of a curved stack of flattened sacs that are not connected.
Describe the process of protein secretion out of a cell
- Vesicles containing substances made in the ER pinch off from the ER
- Transport vesicle fuses with the Golgi apparatus
- Substances released into the Golgi apparatus and are modified
- Secretory vesicles containing the modified proteins pinch off from the Golgi apparatus and move towards the cell surface membrane
- Secretory vesicle fuses with the cell surface membrane and releases contents to the exterior of the cell
Describe
The function of chloroplasts
Carry out the process of photosynthesis
Light energy converted to chemical energy
Features of chloroplasts
6 features
- Double membraned
- Found mainly in autotrophs (organisms that make their own food)
- Contain chlorophyll found in grana (stack of thylakoids–> disc like structures)
- Plentiful starch grains
- Contains its own DNA (can replicate when needed)
- Ovoid shaped
Types of membrane-bound sacs
Vacuoles: In plants (known as tonoplasts), large and centrally located cavities containing cell sap. In animals. smaller and temporary that are used for the storage of chemicals.
Vesicles: Vacuoles that pinch off the ERs and Golgi bodies. Usually involved in the transport of chemicals within the cell
Lysosomes: Specialised vacuoles that contain a mixture of hydrolytic enzymes that help in intracellular digestion and cell death
Describe
The functions of the cell wall
3 functions
- Protect the plant cell from outside particles, invading or otherwise
- Maintain the turgidity of the cell as it is rigid
- Hold the plant up against the force of gravity
Describe
The function of the cell surface membrane
- Separates the interior of the cell from the outside environment
- Controls movement of substances in and out of the cell
Describe
The features of the cell surface membrane
- Partially permeable
- Consists of the phospolipid bilayer and different embedded proteins
Describe
The features of the phosholipid bilayer
- Phospholipids are the main lipids that make up the layer
- All phospholipids have a hydrophobic and a hydrophilic end
- They have a hydrophilic head (phosphate group) and two hydrophobic tails (fatty acids)
- When they are exposed to water, they will arrange themselves in a two-layered sheet with all their tails pointing towards the centre of the sheet
State and explain
The types and functions of proteins in the cell surface membrane
Peripheral proteins (on the outside) and integral proteins (penetrate partially or fully into the membrane)
Examples are:
1. Transmembrane proteins (eg of integral proteins): Required for movement of substances past the cell membrane
2. Proteins that function of enzymes
3. Proteins that function as receptor sites for the bonding of hormones that trigger reactions within a cell
State the structure and function of glycolipids and glycoproteins
- Carbohydrates are bonded to lipids and proteins in the surface membrane
- They participate in cell-cell recognition and cell-cell adhesion
State
The function of cholesterol in the cell surface membrane
- Found in between phopholipid molecules
- Maintain the fluidity of the membrane
Give
4 examples of cell differentiation
- Red blood cells
- Xylem vessels
- Root hair cells
- Muscle cells
Define
Cell differentiation
The process by which a cell becomes specialised for a specific function
State
The adaptation of root hair cells
- Elongated in shape: Higher SA:V ratio–> Higher absorption of water and mineral salts
- Numerous mitochondria: More energy–> more absorption by active transport
- Cell sap is very concentrated: Lower water potential of cell–> more absorption by osmosis
- Very large central vacuole: Higher storage of substances
