Topic 2 - cell specialisation Flashcards
Egg Cells
Egg cells or ova are the female GAMETES in animals
It is one of the largest cells in the human body (approx. 0.12mm in diameter)
It contains a nucleus which houses the genetic material
ZONA PELLUCIDA is the outer protective layer/membrane of the egg
Attached to this is the CORONA RADIATA which consists of two or three layers, its function is to supply proteins needed by the fertilised egg
Gamete
Gamete – one set of chromosomes compared to two sets in the parent cells
Sperm Cells
Sperm cells are male GAMETES
They have a tail like structure called a UNDULIPODIUM so they can move
They contain many MITOCHONDRIA to supply the energy they need to move
In a human sperm the mid piece of the tail is 7µm long and the end is approx. 40µm in length
The sperm head is 3µm wide and 4µm long
It is made up of an acrosome which contains digestive enzymes.
When the sperm meets the egg the enzymes are released to digest the protective layer and allow the sperm to enter.
The sperm’s function is to deliver genetic information to the ovum
This is fertilisation
Root Hair Cell
These cells are found at a plant’s roots, near the growing tip
They have long hair-like extensions called root hairs
They increase the surface area of the cell to maximise the movement of water and minerals from the soil into the plant root.
The cells have thin cellulose walls and a vacuole containing cell sap with a low water potential.
This encourages the movement of water into the cell
Water potential definition
Water potential: a measure of the ability of water molecules to move in a solution
Palisade Mesophyll Cell
Palisade cells found in leaves, they are rectangular box-shaped cells that contain chloroplasts
Chloroplasts are able to absorb a large amount of light for photosynthesis
They can move around the cytoplasm to maximise the amount of light absorbed
These cells are closely packed together and form a continuous layer in the leaf
Palisade cells are surrounded by a plasma membrane and a cell wall made of cellulose, this helps to protect the cell and keep it rigid
They have a large vacuole to maintain a turgor pressure (the plasma membrane pushes against the cell wall of the plant to maintain its rigid structure)
Turgor
Turgor – rigidity of plant cells due to pressure of cell contents on the cell wall
Red Blood Cells
Erythrocytes (RBC) are a biconcave shape.
This increases the surface area to volume ratio of an erythrocytes
They are flexible so that they can squeeze through narrow blood vessels (capillaries)
Their function is to transport oxygen around the body
They do not have a nucleus or other organelles
This increases space for haemoglobin molecules inside the cell that carry oxygen
Haemoglobin
Haemoglobin – protein molecule in RBC. It carries oxygen from the lungs to other parts of the body and carbon dioxide back to the lungs.
White Blood Cells
Neutrophils are a type of WBC and they play an important role in the immune system
They have multi-lobed nuclei, which enables them to squeeze through small gaps when travelling to the site of infection
The cytoplasm holds lysosomes that contain enzymes that are used to digest pathogens that are ingested by the neutrophil
Pathogen
Pathogen – a micro-organism that can cause disease
Osmosis
Diffusion of water molecules that are free to move from an area of high water potential to a low water potential through a partially permeable membrane
Water Potential
Measured in Kilopascals (kPa).
Pure-0 kPa.
Cell cytoplasm contains dissolved sugars, salts etc so water potential is more negative
A solution with a high water potential has a large number of water molecules that are free to move.
