2.6.8 The Organisation of Cells

Question 1

What is a tissue?

Answer 1

Group of cells working together with similar structural features to carry out a particular function

Eg. epithelial cells forming epithelial tissue, or muscle cells forming muscle tissue

Question 2

What are organs?

Answer 2

Different tissues working together

Question 3

How is xylem specialised?

Answer 3

Function - transports water and dissolved mineral ions up plant

No top and bottom walls - Continuous column through which water is drawn by transpiration, maintains water tension

Cells are dead - No organelles or cytoplasm, so less resistance as water flows up column

Outer walls thickened with lignin - Supports the plant

Question 4

How is phloem specialised?

Answer 4

Living ells - Supported by companion cells

Sieve plates - Contain perforations allowing sugars and amino acids to flow easily by translocation

Companion Cells - Contain lots of mitochondria for the loading of sucrose into the sieve tube elements

Question 5

How are muscle cells specialised?

Answer 5

Contain layers of protein filaments - can slide over each other causing muscle contraction

Muscle cells have lots of mitochondria - Provides sufficient energy for aerobic respiration

Skeletal muscles fuse together - Form multinucleated cells contracting in unison