Plant Cells and Tissues Flashcards
2.11 Draw a typical plant cell
- Cell wall
- cell membrane
3.
2.12a Describe the structure and state the function of the ‘cell wall’
Description: cell wall separates one cell from another. It is a thick, rigid structure made from cellulose and sometimes contains lignin.
The cell wall firmly fixes the position & shape of the cell, it gives the cell protection and provides support
2.12b Describe the structure and state the function of the ‘cell membrane’
Descrption: Cell membrane is located on the inner surface of the cell wall. It is a selectively permeable barrier, controlling the movement of certain substances in and out of the cell
Function: The Cell membrane main function is to protect the cell from its surroundings
2.12c Describe the structure and state the function of the ‘nucleus’
Description: The nucleus is a membrane bound structure that contains the hereditary information (chromosones made from DNA) for the plant.
Function: The nucleus function is to coordinate the activities of the cell. It controls cell growth and cell division and via RNA production transmits instruction for the assembly of chemicals within the cell
2.12d Describe the structure and state the function of the ‘vacuole’
Description: Vaculole is a large space, bound by a membrance, within the centre of the cell. It starts off small in young cells and enlarges with age.
Function: Vacuole is the storage site of waste products
2.12e Describe the structure and state the function of the ‘cytoplasm’
Description: Cytoplasm enables substances disolved within it to move around the cell. Predominantly water, it is clear in color and has a gel-like appearance. Cytoplasm also contains enzymes, salts, organelles, and various organic molecules.
Function: Cytoplasm is where most chemical processes take place within the cell, controlled by enzymes.
2.12f Describe the structure and state the function of the ‘chloroplast’
Description: Chloroplast is a small body in plant cells containing chlorophyll (the green pigment in plant cells that makes photosynthesis possible)
Function: Chloroplast function as the site of photosynthesis, where plants convert sunlight into chemical energy that can be used by the plant.
2.12g Describe the structure and state the function of the ‘mitochondrion’
Description: Mitochondrion are small and plentiful organelles
Function: Mitochondrion release energy in a controlled way, via respiration. They produce energy through the oxidisation of sugars, fats and proteins. Mitochondria, therefore, are the main source of energy in the dark
2.13 Describe where cell division is located within the plant
Cell division is only located in certain regions of the plant:
1) apical meristems are the sites of primary lengthwise growth located at the tips of shoots and roots.
2) Lateral meristems are found in the cambium layer immediately below the bark in woody plants which allow stems and roots to increase in girth, known as secondary growth
2.14 Describe how plants increase in size cell division and enlargement (NO details of mitosis are required)
Plants increase in size by 2 methods:
- Cell division takes place at the tips of roots and shoots in areas of meristematic tissue. Located inside these sites are a tiny mass of small cells, which divide rapidly enlarging in three dimesions, thereby increasing the number of new undifferentiated cells.
- Cell enlargement takes place just behind the site of apical meristems. Cell enlaregment mostly occurs in one direction and soon becomes cell elongation. It is caused by water pressure (turgor pressure) within the cell pushing out on the cell membrane. Initially the the cell wall is elastic, enabling it to expand, but this is lost after the cell has differentiated into its final shape and can not expand further
2.21 State what is meant by the term ‘plant tissue’
Plant tissue is a group of cells, of the same type, having a common function
2.22a Describe the characteristics and function of ‘epidermis’
Description of characteristics: Epidermis a single layer of cells which form a boundary between the plant and the external environment. It includes differentiated cells including guard cells and epidermal hairs. May be covered by waxy layer called the cuticle
Function: Epidermis protects the plant. It protects against water loss, regulates gas exchange and damage / attack
2.22b Describe the characteristics and function of ‘cambium’
Description: Cambium is a layer of growing tissue that produces new cells, between the xylem & and phloem tissues.
Function: Cambium is meristematic tissue is where new cells are produced by cell division resulting in more xylem and phloem tissues thereby increasing the girth of the stem or root in dicotyledonous plants, known as secondary growth.
2.22c Describe the characteristics and function of ‘phloem’
Description: Phloem are long tube like cells (sieve tubes) They have cellulose walls and are living unlignified cells with no nucleus. The end walls are only partially broken down to leave sieve-like structures (sieve plates) at intervals along the sieve tubes. Each has a companion cell which regulates the movement of water through the sieve tube. Phloem is typically found to the outside of the xylem in most species
- pholem vessel have two way flow up and down
Function: Phloem allow the transport of food and plant hormones from the leaves to the rest of the plant
2.22d Describe the characteristics and function of ‘xylem’
Description: Xylem are the woody element of the vascular bundle. They are long wide open ended cells with very thick lignified walls, able to withstand the high pressures of water and solutes
- xylem vesel only have upwards flow
Function: Xylem support the transport of water, nutrients & plant hormones from the roots to the rest of the plant. Xylem tissue also provides physical support
