B2.3 Cell Specialisation

Zygote

Fertilised egg cell

Morula

Solid ball of cells formed from divisions.

The cell continues to divide and after 5-6 days, it will start to differentiate into a hallow ball of cells called _______ . This contains an outer layer of cells called ________

blastocyst, trophoblast

Alleles

A variant/version of a gene

Differentiation

Cells are specialised to carry out specific functions

Morphogens

Chemical in the cell governing the pattern of tissue development

Totipotent Cells

Cells that can divide and generate an entire organism

Pluripotent

Cells that can generate multiple types of cells of an organism.

Multipotent

Cells that can generate many cells of an organism.

Stem Cell Niche

Microenvironment in which the stem cells exist and receive instructions.

Haemoglobin

Iron-containing proteins within red blood cells (helps give blood the red pigment as well)

Types of muscles

• Skeletal

• Cardiac

• Smooth

Compare and Contrast toti, multi and pluripotent

	Toti.	Multi.	Pluri.
Similarities	unspecialised cell	unspecialised cell	unspecialised cell
Differences	can give rise to both embryonic and extraembryonic tissues	typically found in adult tissues	differentiated in only embryonic tissues

Feature of surfactant

(is a lipoprotein complex) reduces surface tension in alveoli

Size of sperm

3–5 μm length

Size of female egg

0.12 mm in diameter

Size of red and white blood cells

• Red: 7.5 µm diametre, 2 µm thick

• White: 10 to 20 µm

Size of neurons and striated muscle fibres

• Neuron: <1mm

• Striated muscle fibres: 1-40mm long, 10-100 µm in diametre

Length of sciatic nerve

> 1m

Explain the adaptations of flattening of cells to increase SA:V ratios in cells

• Squamous epithelial cells are thin, flat, and horizontal or elliptical in shape

• Found in locations such as alveoli of the lungs, kidney tubules, and capillaries

• Facilitate diffusion of molecules, including gas exchange and nutrient transfer

Explain the adaptations of invaginations to increase SA:V ratios in cells

• Mitochondria, generate ATP

• They contain numerous invaginations of the inner membrane (cristae) enabling increased metabolic reactions to take place

Invagination

Process of folding in on itself to form a cavity, pouch or tube

Explain the adaptations of chloroplasts to increase SA:V ratios in cells

Have multiple membranes, enabling more reactions to occur

Explain the adaptations of microvilli to increase SA:V ratios in cells

• Columnar cell has these

• Forms a brush border of the small intestine

• Facilitate max absorption possible in intestine

Explain the adaptations of proximal convuluted tubule to increase SA:V ratios in cells

• Lining has cuboidal-shaped cells with microvilli to increase absorption of substances

Type I pneumocytes

Extreme thinness of cells in lungs to reduce distances for diffusion for gas exchange

Type II pneumocytes

Presence of many lamellar bodies (secretory vesicles) in cytoplasm

• Cuboidal cells of the lung that secrete surfactant

Alveolar epithelieum

A tissue that has more than one cell type because different adaptaitions are required for the overall function of tissue

Sacromeres

Unit of a muscle containing actin and myosin

Striated

Shapes that are long, thin streaks

Cardiac cells

• Form the contractile walls in the heart

• Have a single nucleus, contain many mitochondria and have branched fibres

Skeletal cells

• up to 12cm

• Attached to bones, and is responsible for moving the skeleton as the muscle contracts and relaxes

Branches of the muscle types

• Skeletal: UNbranch

• Cardiac: Branched

Compare and contrast cardiac and striated muscles

SIMILARITIES

• both contain myofibrils

DIFFERENCES

• cardiac muscle cells are branched whereas striated muscle cells unbranched

• cardiac muscle cells are shorter than striated muscle cells;

• cardiac muscle cells have one nucleus but striated muscle cells have many nuclei/ are multinucleated;

Adaptations of sperm and egg cells

SPERM

• Being motile

• Contain mitochondria for energy

EGG

• Has several specialised layers of cells covering the outside, prevents polyspermy

State why cell length and volume ratios are not constant for all cell types

• Cell shape is not constant

• Cell shape is related to function

Role of stem cells

• Retain the ability to divide

• Divide by mitosis

• Division produces new tissue

• Can replace stem cells