Specialised cells & tissues Flashcards
Erythrocytes properties (3)
- Flattened biconcave shape
- No nuclei or many other organelles
- Flexible
Why do erythrocytes have a flattened biconcave shape?
Increase surface area to volume ratio - transports oxygen around the body more efficiently
Why do erythrocytes have no nuclei or many other organelles?
Increases space available for haemoglobin
Why are erythrocytes flexible?
So they can fit through narrow capillaries
What are neutrophils?
A type of white blood cell
Neutrophils properties (2)
- Multi-lobed nucleus
- Granular cytoplasm containing many lysosomes
Why do neutrophils have a multi-lobed nucleus?
So they can squeeze through small gaps to reach the site of infection
Why do neutrophils have a granular cytoplasm containing many lysosomes?
Contains enzymes used to attack pathogens
Guard cells properties
- Cell wall thicker on one side than the other
- Change shape depending on water/K ion levels
What do guard cells control?
The entry of CO2 and the exit of water and O2
What are stomata?
The small opening between guard cells
How do guard cells become turgid?
When the concentration of K ions within guard cells are high, water diffuses into the cells by osmosis, causing the cells to become turgid and have a large stomatal opening for CO2 to enter
How do guard cells become flaccid?
When the concentration of K ions within guard cells are low, water diffuses out of the cells by osmosis, causing the cells to become flaccid and the stomatal opening to close
Why do stomata close/guard cells become flaccid?
To prevent water loss. This can happen when water levels are low and at night (as CO2 is not needed for photosynthesis)
What is the effect of the inner cell wall being thicker in guard cells?
When water enters, the thinner outer walls expand which cause the thicker inner walls to draw out causing opening of stomata
Where do you find squamous epithelium?
In areas where rapid diffusion across a surface is essential, such as the linings of the lungs
Why is squamous epithelium very thin?
Due to the flat cells that make it up, and because it is just one cell thick
What is the function of squamous epithelium in the lungs?
To allow for rapid diffusion of oxygen into the blood
What are cilia?
Hair like structures found on ciliated epithelial cells, that move in a rhythmic manner, sweeping mucus, dust and bacteria away (in the respiratory tract)
What two structures are found on ciliated epithelium?
Cilia and goblet cells
What do goblet cells do?
Release mucus, which traps and prevents any unwanted particles, which may be bacteria, from reaching the alveoli
What is the epidermis?
Single layer of closely packed cells covering the surface of plants. Stomata are present on the epidermis
What is the epidermis often covered by and why?
It is often covered by a waxy, waterproof cuticle, to reduce the loss of water
What is xylem tissue responsible for?
The transport of water and minerals throughout the plant
What is the xylem tissue made up of?
Elongated dead cells
What is the xylem tissue strengthened by?
A waterproof material called lignin, which provides structural support for plnats
What is phloem tissue responsible for?
The transport of organic nutrients from source to sink
What is phloem tissue made up of?
Sieve tube cells, separated by sieve plates
What are stem cells?
Undifferentiated cells that are not adapted to any particular function, and have the potential to differentiate to become a specialised cell
What happens once stem cells have become specialised?
They lose the ability to divide, and enter G0 of the cell cycle
What are the 3 different levels of stem cell potency?
Totipotent
Pluripotent
Multipotent
What are totipotent stem cells?
Can differentiate into any type of cell- for example zygotes are totipotent
What are pluripotent stem cells?
Can differentiate into any tissue type but not to form whole organisms- for example early embryos are pluripotent
What are multipotent stem cells?
Can only differentiate to form a certain range of cells- for example haematopoetic stem cells are multipotent as they can only produce various types of blood cells
Where are erythrocytes and neutrophils produced from?
Stem cells in bone marrow
Where do stem cells come from in plants?
Meristematic tissue
Where are xylem vessels and phloem
sieve tubes produced from?
Stem cells in meristems
