B2.3 Cell specialization

Question 1

In plants, which cell remain unspecialized? 1 example

Answer 1

meristematic tissue is found in buds and stems. This tissue can differentiate into any of the many types of tissue that plants need to grow.

Question 2

What are the steps of development for humans?

Answer 2

gametes -> zygote-> embryo -> foetus-> infant. Multicellular organisms usually start their existence as a single cell called a zygote.

Question 3

How is the zygote formed?

Answer 3

this is a result of fertilization, which is part of sexual reproduction. This is the result of 2 gametes that fuse in sexual reproduction.

Question 4

Info about a zygote:

Answer 4

can divide at a rapid rate. Initially the cells that are being produced are unspecialized, however, the cells of the zygote rapidly start to differentiate, a process that results in the formation of specialized cells.

Question 5

What is the cell signalling process?

Answer 5

is the process by which information is transferred from the cell surface to the nucleus of a cell. This process is essential in controlling gene expression and therefore differentiation

Question 6

What are morphogens?

Answer 6

they are signal molecules that control cell differentiation. These signal molecules occur in gradients (areas of concentration differences) in different regions of the early embryo. The concentration of the signal molecules controls the regional development of the first cells into head and tail structures. The gradient of the signalling molecule results in different genes being expressed in different parts of the embryo, with the result that different parts of the embryo develop different features. As the embryo develops, other signalling molecules become factors in differentiation

Question 7

Which cells have a greatly diminished ability to reproduce once they become specialized, or lose ability all together?

Answer 7

Nerve and muscle cells.

Question 8

Which cells retain their ability to reproduce once specialized?

Answer 8

This includes epithelial cells, retain the ability to reproduce rapidly throughout their life. The cells formed from these rapidly reproducing cells will be the same cell type as the original cell

Question 9

What are stem cells?

Answer 9

populations of cells within organisms that retain their ability to divide and differentiate into various cell types. Stem cells retain the ability to divide indefinitely and can differentiate along different pathways, resulting in all the cell types an organism possesses.

Question 10

Where do plants contain stem cells?

Answer 10

Plants contain stem cells if regions of meristematic tissue. These are found near root and stem tips. The tissues are composed of rapidly reproducing cells that can become various types of tissue with the root or stem.

Question 11

Why do gardeners take advantage of these stem cells?

Answer 11

They use plant stem cells to grow new plants, repair damage, and improve crop production. they take cuttings, which use stem cells to grow new roots and shoots, or practice grafting, where stem cells help fuse different plants together

Question 12

What happens when stem cells divide?

Answer 12

when they divide to form a specific type of tissue, they also produce some daughter cells that remain as stem cells.

Question 13

What is the process of self-renewal in stem cells?

Answer 13

where stem cells divide to produce identical copies of themselves, maintaining the stem cell population while also generating specialized cells. This ensures continuous growth, repair, and regeneration in tissues throughout an organism’s life.

Question 14

What are the two unique properties that stem cells have?

Answer 14

1. They can self-renew. When a stem cell divides, there are several possible outcomes; both daughter cells remain stem cells, or a stem cell and a differentiated cell. Whatever outcome stem cells are maintained.
2. They can recreate functional tissues. Cells become differentiated when cell signalling ensures that specific genes are expressed as the cell develops.

Question 15

What is a stem cell niche

Answer 15

for stem cell research, scientists examine certain locations or stem cell niches in humans. This is where stem cells are present in high numbers as a result of regular proliferation, but they also demonstrated differentiation

Question 16

What are 2 examples of stem cell niches?

Answer 16

Bone marrow and Hair follicles

Question 17

More info about bone marrow as stem cell niche

Answer 17

In the bone marrow, the stem cells that produce blood cells are found alongside self-renewing stem cells. As the blood cells are produced, the differentiated cells are transported away via a large array of supporting blood vessels. The renewal process ensures a constant supply of stem cells to continue differentiation

Question 18

More info about hair follicles as stem cell niche

Answer 18

They exist in the skin, and large numbers of epithelial stem cells are found in the bottom, rounded area of a hair follicle. These stem cells are multipotent. They are involved with hair growth, skin and hair follicle regeneration and the production of sebaceous glands associated with hair follicles.

Question 19

What is one feature that all these stem cell niches have in common?

Answer 19

Something all of them have is the presence of signalling factors that bring about both self-renewal and cell differentiation.

Question 20

What are the four types of stem cells in embryo stage?

Answer 20

1. totipotent
2. pluripotent
3. multipotent
4. unipotent

Question 21

What are totipotent stem cells?

Answer 21

These are capable of continued division and possesses the ability to produce any tissue in the organism. Very low numbers of cells are totipotent. Only exist in the very early stages of embryo development. They may form a complete organism

Question 22

What are pluripotent stem cells?

Answer 22

only exist in early embryonic stage. They can mature into almost all the different cell types that exist in an organism. Unlike totipotent cells, they cannot produce a complete organism

Question 23

What are multipotent stem cells?

Answer 23

Only forms a limited number of cell types. Bone marrow tissues that produces different types of blood cell is multipotent. They occur later in the development of the embryo and are present during the remainder of an organism’s life

Question 24

What are Unipotent stem cells?

Answer 24

Only forms a single cell type, such as sperm cells in mammals. They usually form late in the embryonic stage and exist in the functioning organism

Question 25

What problem was discovered early on in stem cell research?

Answer 25

Stem cells cannot be distinguished by their appearance. They can only be isolated from other cells based on their behaviour.

Question 26

What is current research doing to help injuries/diseases?

Answer 26

Research has been directed towards growing large numbers of embryonic stem cells in culture so that they can be used to replace differentiated cells lost because of injury and disease. This involves therapeutic cloning. EX. parkinsons + alzheimers are cause by the loss of proper functioning brain cells, and it is hoped that implanted stem cells could replace many of these lost or defective brain cells, thus relieving the symptoms of the disease.

Question 27

Order of cell types, largest to smallest..

Answer 27

skeletal muscle cell, neuron cell, fat cell, egg cell, sperm cell, white blood cell, red blood cell

Question 28

What does the development of a zygote->infant involve?

Answer 28

It involves a tremendous increase in the number of cells present as well as the differentiation of cells in various regions to become specialized tissues.

Question 29

Why are sperm cells small?

Answer 29

They are relatively small because they only carry out the function of transporting genetic material so that a viable zygote can be formed

Question 30

What adaptations do red blood cells have?

Answer 30

- They contain haemoglobin that can combine with and release oxygen - They have a biconcave disc shape that allows more surface area for oxygen absorption - They lack mitochondria as well as a nucleus - They are flexible and size limited because they need to move through narrow blood capillaries

Question 31

Why are white blood cells larger than red blood cells?

Answer 31

Their main function is defence against infections. They retain their nucleus throughout their lifetime. Many possess vesicles with enzymes that can kill microorganisms. The enzymes present are also used in the breakdown of harmful cellular debris brought into the cell by phagocytosis. Their increased size is because of the necessary presence of the nucleus, granules, and organelles such as mitochondria

Question 32

What is the motor neuron + its function

Answer 32

it is a nerve cell that carries impulses from the brain or spinal cord to muscles allowing movement. This nerve cell has long fibres called axons that can carry impulses up and down the body over long distances

Question 33

How are motor neurons adapted to their function?

Answer 33

They have long axons (up to 1 meter) to transmit impulses quickly over long distances, enabling fast muscle responses

Question 34

What are striated muscle cells?

Answer 34

These are specialized muscle cells found in skeletal muscle. Each muscle fibre is a single muscle cell. The fibres are cylindrical and surrounded by membranes capable of impulse propagation. They can be up to 12cm long and are longer than the muscle fibres found in smooth or cardiac muscle.

Question 35

What is cell size dictated by? What are the two major factors?

Answer 35

1. Basic processes of cell physiology, such as the need for materials to move in and out of the cell. This usually involves the surface-area-to-volume ratio 2. Cell division apparatus. If cells are too large or too small the mitotic spindle will not function properly

Question 36

When is cell size set?

Answer 36

Cell size is set as the cell goes through its differentiation process to become a particular type of cell within an organism. All the adaptations come together to produce the most efficient cell possible for the specific function it has

Question 37

What limits the size of a cell

Answer 37

The surface-area-to-volume ratio of a cell limits the size a cell can reach.

Question 38

What is the surface area to volume ratio? and why is it important for cells?

Answer 38

It determines how efficiently a cell can exchange materials (nutrients, waste, heat). A higher ratio allows for faster exchange, while a lower ratio limits cell function

Question 39

Why don't cells grow larger instead of multiplying?

Answer 39

As a cell gets larger, its volume increases faster than its surface area, making it harder to absorb nutrients and remove waste efficiently

Question 40

How does surface area and volume change with increasing cell size?

Answer 40

Surface area increases with the square of the radius, while volume increases with the cube of the radius. This causes the surface area to volume ratio to decrease as cells grow larger.

Question 41

Why do large animals have more cells instead of larger cells?

Answer 41

Larger organisms maintain efficiency by having more small cells, which retain a higher surface area to volume ration for effective material exchange.

Question 42

What are modifications that give more favorable surface-area-to-volume ratios in cells?

Answer 42

- changes in cell shape - cellular projections, both inwards and outwards - location relative to sources of nutrients and means of transporting away wastes - how the cells fit together at a specific location

Question 43

What adaptations do the proximal convoluted tubule (cells that line the part of the human kidney) that increase their ability to reabsorb fluids and secrete ions?

Answer 43

-the cube-shaped cells are closely packed together in order to use space efficiently - cells have tiny projections called microvilli pointing outwards into the lumen of the tubule in which fluids flows, and this brush border increases the surface are of the cell - Large numbers of mitochondria are found in the cells, allowing active transport of ions + other substances - channels on the opposite side of the cell to the lumen increase the surface area of the cell to help transporte

Question 44

What is the functional unit of the lungs?

Answer 44

It is the alveolus/alveoli. The alveoli increase the surface area of the lung to maximise gas exchange. The alveoli must be able to function as the lungs expand and contract during the breathing process. They are at the very end of the respiratory tract and can be though of as empty sacs lined by a wall mades up of a layer of single cells

Question 45

What is each alveolus covered with (3 active cell types)

Answer 45

- type 1 pneumocytes - type 11 pneumocytes - alveolar macrophages

Question 46

What are type 1 pneumocytes?

Answer 46

They cover 95% of the alveolar surface. Their major function is to allow gas exchange between the alveoli and the capillaries.

Question 47

What are the adaptations of type 1 pneumocytes?

Answer 47

- They are thin and flat in shape to increase the surface area and minimize diffusion distance - a shared basement membrane with the endothelium (lining) of lung capillaries, which minimizes diffusion distances for respiratory gases - they are tightly joined to eachother so that fluids cannot enter the alveoli from the capillaries

Question 48

What are type 11 pneumocytes?

Answer 48

these make up less than 5% of alveolar surface. They are found between type 1. Their role is to produce pulmonary surfactant, which reduces surface tension and prevents the alveoli from collapsing and sticking to eachother during the breathing process

Question 49

Adaptations of type 11 pneumocytes

Answer 49

- A cube shape, providing a larger cytoplasmic area for the organelles producing the surfactant - microvilli oriented towards the alveolar sac, increasing the surface area and allowing more surfactant secretion - a cytoplasm that contains many organelles involves with surfactant productions and its secretion, including secretory vesicles - the ability to transform into type 1 when needed

Question 50

What are some adaptations of striated skeletal muscle?

Answer 50

- a long, cylindrical shape - a membrane capable of impulse propagation - multiple nuclei - visible bands capable of shortening to produce voluntary movement

Question 51

What are cardiac muscle fibres?

Answer 51

These fibres occur in the heart, and they have banded cells like the striated skeletal muscle cell

Question 52

What are adaptations of the cardiac muscle fibres?

Answer 52

- Are composed of branching, striated cells - have a single nucleus per fibre/cell - are connected at the ends by intercalated discs. - Cardiac muscles are shorter than skeletal muscle fibres and have branchin connections, allowing coordinated contractions to pump blood efficiently throughout the body

Question 53

Why don't skeletal muscle fibers divide like other cells?

Answer 53

Skeletal muscle fibres do not undergo normal cell division. Instead, they grow by fusing with satellite cells. When damaged, they do not follow the usual apoptosis process for cell replacement

Question 54

adaptations of sperm + egg cell adaptations (compare style)

Answer 54

SC: one of the smallest human cells, EC; one of the largest human cells. SC:3 micrometer width, and 50 in length, EC: 120 micrometers. SC: flagellum present, EC: no flagellum present. SC: shape includes a head + tail region and is streamlined, EC: shape is non-streamlined. SC; very few cytoplasmic organelles, EC: most cytoplasmic organelles are present plus specialized storage, SC: Continually produced in vast numbers, EC: no new egg-forming cells are produced after birth, SC + EC contain a haploid nucleus