Organisation and specialisation of cells

Question 1

Levels of organisation in multicellular cells?

Answer 1

Specialised cells –> tissues –> organs –> organ systems –> whole organism

Question 2

Erythrocytes (red blood cells)

Answer 2

• Bioconcave shape –> increase surface area to volume ratio.
• Essential for role of transporting oxygen around the body.
• In mammals RBCs do not have nuclei or many other organelles. –> increases space available for haemoglobin.
• Flexible –> can squeeze through narrow capillaries.

Question 3

Neutrophils (type of white blood cell)

Answer 3

• Essential role in immune system.
• Multi-lobed nucleus. –> easier for them to squeeze through small gaps to get to site of infection.
• Granular cytoplasm contains many lysosomes –> contain enzymes used to attack pathogens.

Question 4

Width of a haemoglobin molecule?

Answer 4

2.0 micrometers

Question 5

Diameter of a red blood cell

Answer 5

7.5 micrometers

Question 6

Sperm cells:

Answer 6

• Male gametes
• Deliver genetic information to the female gamete (ovum)
• Have tail or flagellum –> capable of movement and contain many mitochondria to supply energy needed to swim.
• Acrosome on the head of the sperm contains digestive enzymes –> released to digest the productive layers around the ovum and allow the sperm to penetrate leading to fertilisation.

Question 7

Anatomical features of sperm cells?

Answer 7

• Haploid nucleus
• Acrosome
• Plasma membrane
• Centriole
• Mid-piece (7 micrometers long)
• Microtubules in a 9+2 arrangement in tail
• Protein fibres to strengthen the tail
• Tail ( 40 micrometers long)
• Head ( 3 micrometers wide and 4 long)

Question 8

Palisade cells

Answer 8

• Present in mesophyll
• Contain chloroplasts to absorb large amounts of light for photosynthesis.
• Cells are rectangular box shapes –> closely packed to form a continuous layer.
• Thin cell walls –> increasing the rate of diffusion.
• Large vacuole to maintain turgor pressure.
• Chloroplasts more within cytoplasm to absorb more light.

Question 9

Size of palisade cells:

Answer 9

• 25-75 micrometers

Question 10

Root hair cells:

Answer 10

• Present at surfaces of roots near growing tips
• Have long extensions called root hairs –> increase the surface area of the cell
• Maximises the uptake of water and minerals from the soil.

Question 11

Guard cells:

Answer 11

• On surfaces of the leaf to form small openings called stomata.
• CO2 enter plants for photosynthesis.
• When guard cells lose water and become less swollen (osmatic forces) they change shape and stomata closes to prevent further water loss from the plant.
• Guard cell thicker on one side of cell so does not change shape symmetrically as volume changes.

Question 12

Size of root hair cells:

Answer 12

20 - 150 micrometers

Question 13

Size of guard cells:

Answer 13

15-20 micrometers

Question 14

Tissues

Answer 14

• Made up of a collection of differentiated cells that have a specialised function / functions.
• Each tissue is adapted for a particular function within the organism.

Question 15

Categories of tissues:

Answer 15

• Nervous tissue –> adapted to support the transmission of electrical impulses.
• Epithelial tissue –> adapted to cover body surfaces (internal and external)
• Muscle tissue –> adapted to contract
• Connective tissue –> adapted to either hold other tissues together or as a transport medium.

Question 16

Squamous epithelium:

Answer 16

• Made up of specialised squamous epithelial cells
• Thin (one cell thick) –> rapid diffusion across surface is essential.
• Forms lining of lungs and allows for rapid diffusion of oxygen into the blood.

Question 17

Ciliated epithelium:

Answer 17

• Made of ciliated epithelium cells
• Hair-like structures called cilia on surface –> move in a rhythmic manner.
• Ciliated epithelium lines the trachea –> causes mucus to be swept away from the lungs.
• Goblet cells also present –> release mucus to trap any unwanted particles present in the air.
• Prevents particles (bacteria) from reaching the alveoli once inside the lungs.

Question 18

Cartilage

Answer 18

• Connective tissue found in the outer ear, nose and at the ends of (and between) bones.
• Contains fibres of elastin and collagen.
• Cartilage is a firm, flexible connective tissue composed of chondrocyte cells embedded in an extracellular matrix.
• Cartilage prevents bone ends from rubbing together and causing damage. –> many fish have whole skeletons made of cartilage and not bone.

Question 19

Muscle:

Answer 19

• Shorten in length (contract) in order to move bones, which move different parts of the body.
• Different types of muscle fibres. Skeletal muscle fibres (muscles which are attached to bone) and myofibrils (dark pink bands) which contain contractile proteins.

Question 20

Epidermis:

Answer 20

• Single layer of closely packed cells coving surface of plants.
• Covered in waxy, waterproof cuticle to reduce the loss of water.
• Stomata, formed by a paid of guard cells that can open and close are present in epidermis.
• Allow CO2 in and water vapour and oxygen out.

Question 21

Xylem tissue

Answer 21

• Vascular tissue responsible for the transport of water and minerals throughout plants.
• Tissue is composed of vessel elements –> elongated dead cells.
• Walls strengthened by waterproof lignin

Question 22

Phloem tissue

Answer 22

• Vascular tissue –> responsible for the transport of organic nutrients (sucrose) from leaves to stems.
• Composed of columns of sieve tube cells separated by perforated walls called sieve plates.

Question 23

Organs:

Answer 23

Collection of tissues that are adapted to form a particular function for the organism.

Question 24

Organ systems:

Answer 24

• Digestive system –> takes in, breaks down large insoluble molecules into small soluble ones, absorbs nutrients into the blood, retains water needed by the body and removes any undigested material from the body.
• Cardiovascular system –> moves blood around the body
• Gaseous exchange system –> brings air into the body for respiration / CO2 expelled