B2.3 Cell Specialisation

Question 1

What is a zygote

Answer 1

An unspecialized cell produced from fertilization

Question 2

Impact of chemical gradients on gene expression within an early stage embryo

Question 3

Two properties of stem cells

Answer 3

Undifferentiated cell that can:

Divide indefinitely to create more stem cells.

Differentiate to become a specialized cell type.

Question 4

Define Stem cell niche

Answer 4

Locations within tissues where stem cells reside and receive signals that integrate to influence fate of stem cell.

Question 5

Location and function of two multipotent stem cells in adult human body

Answer 5

Hematopoietic stem cell: located in hematopoietic stem cell niche in bone marrow. Produces many different human blood cells.

Hair follicle stem cell: located in hair follicle stem cell niche in bulge region of hair follicle. Produces different epithelial skin cells.

Question 6

Define Totipotent and example

Answer 6

Can become any body cell.

Zygote.

Question 7

Define Pluripotent and example

Answer 7

Can become any body cell EXCEPT for placenta.

Inner cell mass of blastocyst.

Question 8

Define Multipotent and example

Answer 8

Can become multiple related cell types.

Adult stem cells.

Question 9

Relate cell size to the cell’s specialized function: sperm cell

Answer 9

Long and narrow cells with flagellum for propulsion.

Function is to deliver DNA to egg cell. DNA is tightly packed so volume is minimized for transport. Many mitochondria to power movement of flagellum. Flagellum for movement and burrow through egg’s coat.

Question 10

Relate cell size to the cell’s specialized function: egg cell

Answer 10

Large and spherical.

Egg stores all materials and nutritional reserves for initial development of embryo.

Question 11

Relate cell size to the cell’s specialized function: red blood cell

Answer 11

Biconcave shape with small width.

Small and flexible to fit through capillary vessels. Biconcave shape maximises SA to V ratio for loading and unloading oxygen.

Question 12

Relate cell size to the cell’s specialized function: white blood cell

Answer 12

Small when inactive but increase in size when active.

Increase size as RER and golgi increases for secreting antibody proteins.

Question 13

Relate cell size to the cell’s specialized function: cerebellum neuron cell

Answer 13

Small cell body with long, narrow axons.

Small volume allows neurons to be densely packed.

Question 14

Relate cell size to the cell’s specialized function: striated muscle fibre cell

Answer 14

Long, narrow and cylindrical.

Allows for greater length of contraction.

Question 15

Outline the activities occurring in the volume and at the surface of the cell

Answer 15

Surface: movement of materials in and out of cell via cell membrane.

Volume: internal regions of cell; metabolic reactions.

Question 16

SA: V ratio calculation

Answer 16

SA/V

Question 17

Relationship between cell size and SA:V ratio

Answer 17

Smaller cell has larger ratio.

Larger cell has smaller ratio.

Question 18

Define Alveoli

Answer 18

Tiny air sacs in lungs where gas exchange occurs between air and blood.

Question 19

Define Alveolar Epithelium

Answer 19

Cells that form the boundary between air outside the body and the blood capillaries.

Act as a barrier protecting body from inhaled foreign particles.

Question 20

Structure and function of Type I pneumocytes

Answer 20

Thin, flat cells of alveolar epithelium.

Responsible for gas exchange between blood and alveoli.

Thin shape maximizes gas exchange by increase SA:V ratio and minimizing diffusion distance.

Question 21

Structure and function of Type II pneumocytes

Answer 21

Rounded cells of alveolar endothelium.

Responsible for synthesizing and secreting surfactant into alveolar lumen.

Question 22

Function of surfactant

Answer 22

Reduces surface tension in alveoli, preventing collapse.

Facilitates gas exchange by being a liquid in which CO2 and O2 can dissolve before diffusing.

Question 23

Function and structure of Basement membrane

Answer 23

Thin, extracellular matrix that separates alveolar epithelium from capillary endothelium.

Thin to minimize diffusion distance between alveoli and capillaries.

Contains adhesion proteins to help anchor cell in place.

Question 24

Three types of muscle tissue found in human body

Answer 24

Skeletal muscles

Cardiac muscles

Smooth muscles

Question 25

Structure of a muscle fibre

Answer 25

Sarcolemma: cell membrane of a muscle fibre. Sarcoplasm: cytoplasm in muscle fibre. Myofibrils: strands of contractile protein running parallel within cell. Nucleus: contains DNA; muscle fibres contain multiple nuclei. Sarcoplasmic reticulum: specialized ER that pumps in and store CA+. Mitochondria: many mitochondria for making ATP required for muscle contraction.

Question 26

Compare Skeletal vs. Cardiac muscle fibre

Answer 26

Both striated Function: Skeletal attach to bones to cause movement. Cardiac for pumping blood throughout body. Skeletal is voluntary or involuntary. Cardiac is only involuntary. Skeletal is atypical: fusion of multiple cells. Cardiac muscles are shorter, have a single nucleus, are branched and connect to adjacent cells via intercalated discs.

Question 27

How does branching and intercalated discs of cardiac muscle cells allow for propagation of the stimulus to contract

Answer 27

Branching and intercalated discs enable rapid transmission of electrical impulses between cells, enabling coordinated contraction of heart. Intercalated discs contain proteins for strong adhesion between cells, preventing separation during contraction.

Question 28

Function of gamete cells

Answer 28

Contain haploid nucleus used to pass on genetic information from parents to offspring.

Question 29

State the function of each sperm structure (head, acrosome, plasma membrane receptors, binding proteins in the acrosome, haploid nucleus, midpiece, and tail)

Answer 29

Head: small, streamlined to reduce resistance. Contains tightly packed haploid nucleus and cytoplasm. Acrosome: sac of digestive enzyme in head of sperm to digest zona pellucida. Plasma membrane receptors: at head; bind to proteins of zona pellucida. Binding proteins: in acrosome; bind to egg cell plasma membrane during fusion. Haploid nucleus: delivers paternal DNA to ovum where it combines with ovum's DNA to create 2n. Midpiece: multiple mitochondria wound around microtubules at base of tail to perform cellular respiration for ATP production to power movement of tail. Tail: long flagellum with microtubules that generate force to propel sperm forward.

Question 30

State the function of each egg structure (haploid nucleus, binding proteins, zona pellucida, cortical granules, yolk and mitochondria)

Answer 30

Haploid nucleus: contains 23 chromosomes to combine with sperms 23. Binding proteins: on plasma membrane to bind binding proteins of sperm cell during fusion. Zona pellucida: layer of glycoproteins to be digested by acrosome. Cortical granule: Vesicles full of enzymes along inner edge of cell. Released by exocytosis to make zona pellucida impenetrable to more than one sperm after fertilization. Corona radiata: layer of follicle cells that form around egg. Yolk: large volume of cytoplasm that contains nutrients for early embryonic development. Mitochondria: produces ATP to fuel cell division.