6.4 Organisation and specialisation of cells Flashcards
Differentiation
process by which an unspecialised cell develops and specialised to become more distinct in form and function
Erythrocytes (red blood cells)
- flattened biconcave shape (increases their surface area to volume ratio)
- enucleated (no nucleus= increases spaces available for haemoglobin)
- flexible (they are able to squeeze through narrow capillaries
- 2 micrometers side view / 7.5 micrometers top view
Neutrophils (type of white blood cell)
- essential role in immune system
- characteristic multi-lobed nucleus (easier for them to squeeze throguh small gaps to get to the site of infections)
- granular cytoplasm contains many lysosomes (contains enzymes used to attack pathogens
-10-14 micrometers
Sperm cells
male gametes (made to deliver genetic information to female gamete, the ovum)
- tail/ flagellum (capable of movement & contain many mitochondria to supply energy needed to swim)
- acrosome on head of sperm (contains digestive enzymes, which are released to digest the protective layers around ovum/ allow sperm to penetrate, leading to fertilisation
Sperm cell (structure)
head is 4 micrometers long
- centriole connects tail to head
mid piece is 7 micrometers long
- helical mitochondria in mid piece
tail is 40 micrometers long
- made of 9+2 microtubule arrangement
Palisade cells
-present in mesophyll
- contains chloroplasts to absorb large amounts of light for photosynthesis
- rectangular box shapes (can be more closely packed to form a continuous layer)
- thin cell walls (increase rate of diffusion of CO2)
- large vacuole to maintain turgor pressure
- Chloroplasts can move within cytoplasm to absorb more light)
Root hair cells
-present at surfaces of roots near growing tips
long extensions called root hairs (increase surface area of cell)
This maximises uptake of water and minerals from soil
- vacuole containing cell sap (solution of ions and sugars= lower water potential
Pair of Guard cells
- forms small openings called stomata
- allow carbon dioxide to enter for photosynthesis
-water lost= less swollen due to osmotic forces, they change shape and stoma close (prevents further water loss) - water gained= swollen guard cells= stoma open for exchange
- cell wall of inner guard cell is thicker on one side= cell does not change shape symmetrically as volume changes)
What is a tissue
a collection of differentiated cells that have a specialised function or functions
4 categories of tissues
nervous tissue
epithelial tissue
muscle tissue
connective tissue
Squamous epithelium
made up of specialised squamous epithelial cells (flat structure)
- very thin due to squat or flat cells and only one cell thick
- present when rapid diffusion is essential
-forms the lining of lungs and allows rapid diffusion of oxygen into blood
ciliated epithelium + goblet cells
-cells with hair-like structures (cilia) that move in a rhythmic manner
- line trachea, causing mucus to be swept away from lungs
- goblet cells release mucus to trap any unwanted particles e.g. bacteria (prevents them from reaching alveoli once inside lungs
Cartilage
connective tissue found in outer ear, nose & ends of bones
- contains fibres of proteins elastin and collagen
- firm, flexible connective tissue composed of chondrocyte cells embedded in extracellular matrix
- prevents end of bones from rubbing together and causing damage
Muscle
tissue that needs to be able to contract in order to move bones
- different types of muscle fibres
1. Skeletal muscle fibres contain myofibrils (dark pink bands on the micrograph) which contains contractile proteins
- several individual muscle fibres (pink) separated by connective tissue (thin white strips)
Epidermis
- single layer of closely packed cells covering the surface of plants
- covered by a waxy, waterproof cuticle (reduce water loss)
- Stoma are present for gas diffusion
