Topic 2: Cells and Control

Question 1

Define Growth

2.2

Answer 1

Permanent increase in size or mass. This happens as a result of increase in number of cells or size of cells. Number of cells can increase by cell division by mitosis.

2.2

Question 2

Describe cell differentiation

2.1

Answer 2

Unspecialised stem cells differentiate to form specialised cells

2.1

Question 3

What is mitosis

2.3

Answer 3

the division of a cell by mitosis is the production of
two daughter cells, each with identical sets of chromosomes in
the nucleus to the parent cell, and this results in the
formation of two genetically identical diploid body cells

2.3

Question 4

Adaptations of a sperm cell

2.6 - Importance of cell differentiation

Answer 4

• Flagellum - movement
• Midpiece packed with mitochondria - releases energy for swimming
• Acrosome in the head - Enzymes digest the cell membrane of the egg cell
• Haploid nucleus in the head - Contains half the chromosomes (23) needed to form a zygote

2.6

Question 5

Adaptations of an egg cell

2.6 - importance of cell differentiation

Answer 5

Jelly coat and cell membrane - hardens after one sperm cell enters so no more can.
Haploid nucleus - contains half the chromosomes (23) needed to form a zygote.
Contains lots of cytoplasm - for the growth of an early embryo.

2.6

Question 6

Growth in animals

2.5 A

Answer 6

Cell division (mitosis) and cell differentiation. Measured based on head circumference, mass and length.

2.5 A

Question 7

How do percentile growth charts work?

2.7

Answer 7

Based on head circumference, mass and length.
Shows if a baby is growing well compared to others their age. Chart is divided into 100 groups (percentiles).
Different health issues (like down syndrome) have seperate charts.
Changes in percentile could mean: disability, manutrition, obesity, health problems, inconsistencies across measurements.

2.7

Question 8

Advantages and disadvantages of percentile growth charts

2.7

Answer 8

Advantages: compares baby to other ages and shows expected growth; can quickly catch on to health problems.
Disadvantages: does not indicate problems with internal organs; only takes 3 measurements, growth fluctuation does not necessarily mean the baby is unhealthy.

2.7

Question 9

Growth in Plants

2.5 B

Answer 9

Includes cell division, elongation and differentiation. Measured based on height, leaf circumference and mass.

2.5 B

Question 10

What is elongation in plants?

2.5 B

Answer 10

• Process by which plants become longer when growing
• Occurs throughout plants, not just meristems.
• Occurs only in plants
• Auxin (hormone) promotes cell elongation

2.5 B

Question 11

How do you calculate percentage change?

Answer 11

((final value - starting value) / starting value) x 100

Question 12

What are meristem cells?

2.6

Answer 12

• Plant stem cells found in meristems.
• A group of cells near the end of each shoot and root that allows plants to continue growing throughout their lives.
• Includes: root tips, buds and shoots.
• Increase in length and differentiate into specialised cells with different funtions and features.

2.6

Question 13

Give examples of specialised cells in plants

Answer 13

Xylem cells, phloem cells, root hair cells, palisade cells and guard cells

Question 14

Describe xylem vessels (plant)

Answer 14

• Where: runs from the roots through the stems, to the leaves, flowers and buds.
• Functions: carry water and dissolved nutrients from the roots to other parts of the plant.
• Adaptations: thick, strong walls stiffened with lignin (polymer) - for water pressure; dead cells/ no cytoplasm - so water water moves quickly; no end walls between cells - water moves quickly

Question 15

Describe root hair cells (plant)

Answer 15

• Where: surface of roots, behind the root tip.
• Function: Absorb water and dissolved nutrients from the soil.
• Adaptations: Large surface area - increase rate of absorption.

Question 16

Describe guard cells (plant)

Answer 16

• Where: either sides of pores (stomata), usually on the under side of leaves.
• Function: control opening and closing of pores at different times of day/ in different conditions.
• Adaptation: changes shape - pores can open and close.

Question 17

Function of stem cells

2.8

Answer 17

• Stem cells are undifferentiated cells that have the potential to undergo cell differentiation and self-renewal by mitosis.
• Self renewal by mitosis is so that the body continually has a bank of stem cells that can differentiate to replace dead cells.
• Stem cells in animals include embyonic stem cells and adult stem cells

2.8

Question 18

Describe embryonic stem cells

2.8

Answer 18

• Found in the early stages of embry development.
• Have the potential to differentiate into a wide range of specialised cells.
• Used to make all different tissues and organs needed during development.

2.8

Question 19

Describe adult stem cells

2.8

Answer 19

• Limited in number and places:
• Limited to: nose, eyes, brain, liver, blood, heart, skin, bone marrow (needs to continually produce blood cells throughout life) and muscles.
• Found only in tissues containing specialised cells.
• Have the potential to** produce only a few different cell types.**
• Lose their ability to form other kinds of specialised cells.
• Used to replace old cells and damaged cells.
• Produce new cells for growth.
• Includes partially specialised blood stem cells (platelets, red blood cells and white blood cells) and partially speciallised immune cells (white blood cells).

2.8

Question 20

What are the 4 components of blood and their functions?

Answer 20

• Red blood cell - carry oxygen
• Plasma - carry dissolved substances
• White blood cell - remove foreign cells
• Platelets - clotting

Question 21

Describe embryonic stem cells in medicine

2.9

Answer 21

• Can be sourced from stem cell donors or through therapeutic cloning.
• Human embryos can be grown in the lab.
• Embryonic stem cells extracted from these embryos.
• These cells are stimulated to differenciate into most types of specialised cells.
• Then they’re injected into the places they’re needed.
• Can treat certain diseases and repair damaged organs (effective).

2.9

Question 22

Describe adult stem cells in medicine

2.9

Answer 22

• Can be sourced from stem cell donors or through therapeutic cloning.
• Can be cultured in a lab.
• Made to differentiate into specialised cells, mostly blood cells.
• Used to treat some diseases (like Leukemia), but have the potential to cure more in the future (e.g. diabetes and paralysis).

2.9

Question 23

What are plant stem cells used for?

2.8

Answer 23

Have the ability to differentiate into any type of plant cell. Used to close plants with desired characteristics (e.g. resistance from certain diseases).

2.8

Question 24

Plant stem cells in medicine

2.9

Answer 24

Two methods for this:
-Cuttings:
* Cutt a part of the plant stem, leaf or root cut.
* Plant in deep compost.
* Add plant hormones.
* Add a clear plastic bag to keep in moisture and warmth.
* After a few weeks, new roots develop and plant grows.
-Tissue culture:
* Take an explant - small piece from a plant.
* Grow in vitro - using glassware like petri dishes.
* Add sterile agar jelly to the petri dish - provides ideal growth conditions.
* Samples develop and are planted in compost.

2.9

Question 25

What is the purpose of mitosis?

2.2

Answer 25

• Growth - cell division produces new cells, so increases number of cells.
• Repair - Cell division produces new cells, so the dead or damaged cells can be replaced.
• Asexual reproduction - Cell division produces offspring that are genetically identical to the parent.

2.2

Question 26

What are the 3 parts of the cell cycle?

2.1

Answer 26

1. Interphase
2. Mitosis
3. Cytokinesis

2.1

Question 27

Describe the interphase stage

2.1

Answer 27

• Preparation for mitosis.
• The longest phase in the cell’s life.
• Cell make extra sub-cellular structures.
• DNA replication occurs in the nucleus (chromosomes duplicate to form x-shaped chromosomes).

2.1

Question 28

Describe the mitosis stage

2.1

Answer 28

* Definition: nuclear division that gives rise to two genetically identical, diploid daughter cells.
* Consists of 4 stages: prophase, metaphase, anaphase and telophase.
* Chromosomes line up along the centre of the cell.
* Cell fibres pull the chromosomes apart.

2.1

Question 29

Stage 1 of mitosis: Prophase

2.1

Answer 29

• DNA condenses
• Chromosomes become visible
• Nuclear membrane breaks down
• Spindle fibres appear

2.1

Question 30

Stage 2 of mitosis: Metaphase

2.1

Answer 30

• Chromosomes line up in the centre of the cell
• Spindle fibres attach to chromosome

2.1

Question 31

Stage 3 of mitosis: Anaphase

2.1

Answer 31

• Spindle fibres split the chromosomes down the centre.
• The pull one chromatid to either side of the cell.

2.1

Question 32

Stage 4 of mitosis: Telophase

2.1

Answer 32

• new membrance forms around each set of chromosomes at either end of the cell.
• This forms the nuclei.

2.1

Question 33

Describe the cytokinesis stage

2.1

Answer 33

• Cell cytoplasm and membrane divides to produce two genetically identical diploid daughter cells.
• If it is a plant, a cell wall also forms.

2.1

Question 34

What is cancer?

2.4

Answer 34

The result of change in cells that leads to uncontrollable cell division.

2.4

Question 35

What are the 4 sections of the brain?

2.10B

Answer 35

1. Frontal lobe
2. Temporal Lobe
3. Parietal Lobe
4. Occipital Lobe

Question 36

Describe the Cerebral Cortex/ Cerebrum

2.10B

Answer 36

• Where:
• Description:
• Function: