2.5 The Ultrastructure of Plant Cells (2.1.1) Flashcards
1
Q
What are 11 things that are found in both animal and plant cells? (11)
A
- Nucleus
- Nucleolus
- Mitochondria
- Vesicles and lysosomes
- Cytoskeleton
- Centrioles
- Flagella and cilia
- Endoplasmic reticulum
- Ribosomes
- Golgi apparatus
- Protein production
2
Q
What are plant cell walls made of?
A
Cellulose, a complex carbohydrate
3
Q
Why are plant cell walls so rigid? (2)
A
- Cellulose is a polysaccharide, meaning it’s made up of many glucose chains arranged in parallel. This arrangement gives cellulose a fibrous nature, similar to rope.
- The contents of the cell press against the cell wall making it rigid.
4
Q
Describe the structure of the plant cell wall (4)
A
- Cellulose is a polysaccharide, meaning it’s made up of many glucose chains arranged in parallel. This arrangement gives cellulose a fibrous nature, similar to rope.
- The cell wall of plants is on the outside of the plasma membrane.
- The wall is freely permeable so substances can pass into and out of the cell.
- The contents of the cell press against the cell wall making it rigid. This supports both the individual cell and the plant as a whole.
5
Q
Describe the function of the plant cell wall (2)
A
- The cell wall is strong and can prevent plant cells from bursting when turgid (swollen).
- The cell wall of plant cells maintains the cell’s shape, contributes to the strength and supports the whole plant, is permeable and allow solutions (solute and solvent) to pass through.
6
Q
Describe the structure of vacuoles (2)
A
- The vacuole is surrounded by a membrane called the tonoplast, and contains fluid.
- It is selectively permeable.
7
Q
Describe the function of vacuoles (4)
A
- Only plant cells have a large permanent vacuole.
- It is filled with water and solutes and maintains cell stability which is very important in the maintenance of turgor, so that the contents of the cell push against the cell wall and maintain a rigid framework for the cell.
- If all the plant cells are turgid then this helps to support the plant, especially in non-woody plants.
- It is selectively permeable, which means that some small molecules can pass through it but others cannot. If vacuoles appear in animal cells, they are small and transient (not permanent).
8
Q
Where in plants are chloroplasts found?
A
They are found in the cells in the green parts of plants such as the leaves and the stems but not in the roots.
9
Q
Describe the structure of chloroplasts (5)
A
- These are large organelles, 4-10 micrometres long.
- They are surrounded by a double membrane or envelope.
- The inner membrane is continuous with stacks of flattened membrane sacs called thylakoids (resembling piles of plates), which contain chlorophyll. Each stack or pile of thylakoids is called a granum (plural: grana). The grana are joined by membranes called lamellae.
- The fluid-filled matrix is called the stroma.
- Chloroplasts contain loops of DNA, ribosomes and starch grains.
10
Q
Describe the function of chloroplasts (6)
A
- Chloroplasts are the site of photosynthesis. The internal membranes provide the large surface area needed for the enzymes, proteins and pigment molecules necessary in the process of photosynthesis.
- The first stage of photosynthesis, when light energy is trapped by chlorophyll and used to make ATP, occurs in the grana. Water is also split to supply hydrogen ions.
- The second stage, when hydrogen reduces carbon dioxide, using energy from ATP, to make carbohydrates, occurs in the stroma.
- Starch produced by photosynthesis is present as starch grains.
- Like mitochondria, chloroplasts also contain DNA and ribosomes. Chloroplasts are therefore able to make their own proteins.
- Chloroplasts are abundant in leaf cells, particularly the palisade mesophyll layer.
11
Q
Prokaryotes can be classed into two evolutionary domains. What are these?
A
Archaea and Bacteria
12
Q
What type of cells are chloroplasts found in?
A
They are found only in plant cells and in some protoctists.
