B3 - Growth & Development and Stem Cells Flashcards
What are some cell features and their functions that both plants and animals have?
Cell membrane - it controls the movement of substances into and out of the cell.
Nucleus - It contains chromosomes made of DNA. The nucleus controls the activities of the cell, and how it develops.
Cytoplasm - most of the chemical reactions of the cell occur here.
Mitochondria - small rod - shaped structures that release energy during aerobic respiration.
What are some cell features and their functions that only plants have?
Cell wall - made of cellulose, which is throng and supports the cell.
Permanent vacuole - contains cell sap. The Sao helps support the cell.
Chloroplasts - contain chlorophyll that traps light energy for photosynthesis. Found in cells of leaves and seems ( not roots / flowers )
Describe the cell of a bacteria.
- Bacteria is one cell.
- no nucleus or mitochondria or chloroplasts
- contains DNA in the form of a singular circular strand ( chromosome ) floating around in the cell
How do organisms grow? What is differentiation?
- plants and animals start as one cell ( fertilised egg)
- this is an undifferentiated stem cell
- it divides by mitosis to give cells which can become specialised
- this process of becoming specialised is differentiation
- stem cells can develop into any of the different cell types and form tissues and organs
What are the four main human growth stages?
• Infancy – growth is rapid following birth.
• Childhood – growth slows to a steady rate.
• Adolescence – puberty causes rapid growth.
• Adulthood – growth rate falls to zero.
How do plants grow and form where? What can it be measured in?
- they grow and gain height throughout their lives by means of cell enlargement.
- it can be measured by increase in length, wet mass, or dry mass
- they only grow at specific parts, called meristems, at root tips, shoot tips, stem nodes, and buds.
Describe the stem cells in meristems.
• are undifferentiated • have very small vacuoles
• have very thin walls • are packed very closely together
• are small and do not contain chloroplasts
• can divide, making new cells that differentiate.
Why can differentiated stem cells not divide?
Due to their thick rigid cell wall. They also have chloroplasts and a large vacuole
What grows at different rates during infancy and adolescence?
- Babies have undeveloped brains when born, otherwise their heads would be too large to pass along the birth canal. Just after birth the child’s brain is growing faster than the whole body.
- During adolescence your reproductive organs grow a lot as you become an adult.
What are the advantages and disadvantages of different methods of measuring plant growth?
- Measuring increase in dry mass is best, because wet mass varies according to how much water is present in the tissues.
- However, organisms must be killed to calculate their dry mass.
- Using length as a measure of growth is simple, but won’t account for the variable growth rates of different parts of an organism.
How do scientists get stem cells and what are they exploring with them?
From spare very early embryos created during IVF treatment. Embryonic stem cells are still able to differentiate into any type of cell. Medical research is developing ways of using stem cells to
• treat Parkinson’s disease • repair spinal cord injuries
• grow tissues or organs • treat type 1 diabetes.
What are the issues with embryonic stem cells? What’s the issue with its alternative?
- Use of embryonic stem cells raises ethical issues as the spare embryos used could have developed into people. However, without stem cell research these embryos would still be discarded.
- Scientists can obtain adult stem cells from bone marrow or umbilical cord blood, which is less controversial than using embryonic stem cells. However, these stem cells cannot differentiate into as many different types of cells as embryonic stem cells.
