2.6 Foundations in biology Flashcards
(117 cards)
1
Q
Define cytokinesis.
A
cytoplasmic division following nuclear division, resulting in two new daughter cells.
2
Q
Define interphase.
A
Phase of the cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phase.
3
Q
Define mitosis.
A
Type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell.
4
Q
What happens during mitosis overall?
A
Cell division.
5
Q
What happens between each M phase during mitosis?
A
Interphase.
6
Q
Where are the checkpoints in mitosis?
A
The two main checkpoints, the G1/S checkpoint, also called the restriction point, and the G2/M checkpoint.
There are other checkpoints, for example, there is one half way through mitosis and one in early G1.
7
Q
What is the purpose of checkpoints during mitosis?
A
- To prevent uncontrolled division that would lead to tumors (cancer).
- To detect and repair damage to the DNA (for example damages caused to UV light).
- The cell cycle can not be reversed.
- The DNA is only duplicated once during each cell cycle.
8
Q
What is the Hayflick constant?
A
Cells should normally only undergo a certain number of cycles or divisions. The number is about 50 and is known as the Hayflick constant.
9
Q
What are the stages of the cell cycle starting the mitosis?
A
- M phase
- G0 (gap 0) phase
- G1 (gap 1) phase -also called the growth phase
- S (synthesis) phase of interphase]
- G2 (gap2) phase of interphase
10
Q
What occur in the cell during M phase of mitosis?
A
- Cell growth stops.
- Nuclear division (mitosis) consisting of stages: prophase, metaphase, anaphase, telophase.
- Cytokinesis
11
Q
What occur in the cell during G0 phase of mitosis?
A
- Cells may undergo apoptosis, differentiation or senescence.
- Some types of cells remain in this phase for a long time or indefinitely.
12
Q
What is apoptosis?
A
Apoptosis- programmed cell cycle
13
Q
What occur in the cell during G1 phase of mitosis?
A
- cell grows and increases in size.
- Transcription of genes to make RNA occurs.
- Organelles duplicate.
- Biosynthesis. e.g. protein synthesis, including making enzymes needed for DNA replication in the S phase.
- The p53 (tumor suppressor) gene helps control this phase.
14
Q
What occur in the cell during S phase of mitosis?
A
- Once the cell has entered this phases, it is committed to completing the cell cycle.
- DNA replicates.
- When all the chromosomes have been duplicated, each one consists of a pair of identical sister chromatids.
- This phase is rapid, and because the exposed DNA base pairs are more susceptible to mutagenetic agents, this reduces the chances of spontaneous mutations happening.
15
Q
What occur in the cell during G2 phase of mitosis?
A
Cell grows.
16
Q
What is M phase?
A
- A checkpoint hat chemical triggers condensation of chromatin.
- Halfway through the cycle, the metaphase checkpoint ensures that the cycle is ready to complete mitosis.
17
Q
What is G0 phase?
A
- A resting phase triggered during early G1 at the restriction point, by a checkpoint chemical.
- Some cells,e.g epithelial cells lining the gut, do not have this phase.
18
Q
What is G1 phase?
A
- A G1 checkpoint controls mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis.
19
Q
What is S phase?
A
Because the chromosomes are unwound and the DNA id diffuse, every molecule of DNA is replicated.
Housekeeping genes- those which are active in all types of cells, are duplicated first. Genes that are normally inactive in specific types of cells are replicated last.
20
Q
What is G2 phase?
A
Special chemicals ensuring that the cells is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and formation of the spindle.
21
Q
What does prophase look like in mitosis?
A
22
Q
What does Metaphase look like in mitosis?
A
23
Q
What does anaphase look like in mitosis?
A
24
Q
What does prophase look like in mitosis?
A
25
What acronym is used to remember the stages of mitosis?
PMAT
26
What us a chromotid?
One of two identical halves of a replicated chromosome.
27
Define mitosis.
A type of **nuclear division** that **maintains the chromosome number**; in each new daughter cell contains the same genetic information as the parent cell. They're **genetically identical** and is a product of **asexual reproduction**.
28
What is the significance of mitosis in the life cycle?
* **Asexual reproduction**-e.g. strawberries forming new plantlets at the end of runners and protoctists dividing to form new individuals.
* **Growth**- all multicellular organisms by producing more cells that are genetically identical to each other which occurs by mitosis.
* **Tissue repair**
29
What has happened during the synthesis that must have occurred before prophase?
The chromosomes have replicated.
30
What happens during prophase in mitoisis?
* **Nuclear envelope** breaks down
* **Centriole divides** and these two new daughter centrioles move to **opposite poles** of the cell.
* **Tubulin** (cytoskeleton protein) threads from a **spindle between these new centrioles**.
31
What happens during metaphase in mitosis?
* Pairs of chromatids attach to the spindle threads at the equator region of the cell.
* The chromosomes attach by there centromeres.
32
What happens during anaphase in mitosis?
* The **centromere** of each pair of chromatids **splits.**
* **Motor proteins**, walking along the tubulin threads, **pull each sister chromatid of a pair, in opposite directions**, towards opposite poles.
* Because these centromere goes first, the chromatid, now called chromosomes, assume a **V shape**.
33
What happens during telophase in mitosis?
* The separated **chromosomes reach the poles.**
* A **new nuclear envelope** forms around each set of chromosomes.
* The **cell now has two nuclei** each **genetically identical** to each other and to the parent cell which they arose.
34
What happens after mitosis?
Cytokinesis- once mitosis is complete, the cell splits in two, so that each new cell contains a nucleus.
35
What happens during cytokinesis in animal cells?
The plasma membrane folds inwards and ‘nips in’ the cytoplasm.
36
What happens during cytokinesis in plants cells?
An end plate forms where the equator of the spindle was, and new plasma membrane and cellulose cell-wall material are laid down on either side along this end plate.
37
Define differentiation.
Process by which stem cells become specialised into different types of cell.
38
What are epithelial cells? And where are they found? Give some examples?
Cells that are lining tissue. They're found on the inside and the outside of your body. e.g. makes up the walls of the alveoli and capillaries; and line your intestines.
39
What is an erythrocyte?
Red blood cell.
40
What is a neutrophil?
Type of white blood cell that is phagocytic (can ingest microbes and small particles).
41
What is a stem cell?
Unspecialised cell able to express all of its genes and divide by mitosis.
42
What is a zygote?
Multicelluar organisms start life as a undifferentiated cell, called a zygote.
43
How does a zygote form?
A zygote results when an **ovum** (egg cell) is fertilized by a **spermatozoon** and the **two haploid** **nuclei** fuse to give a cell with a **diploid nucleus**.
44
Are zygotes specialised?
No. It is a stem cell. All the genes in its genome are able to be expressed.
45
What happens to a zygote after several mitotic divisions?
After several mitotic divisions, an embryo forms, containing many undifferentiated embryonic cells.
46
What happens as an embryo continues to develop after it is no longer a zygote?
The embryonic cells differentiate as certain genes are switched off and other genes may be expressed more so that:
* The proportions of different organelles differ from those of other cells.
* The shape of the cell changes.
* Some of the contents of the cell changes.
Also to this differentiation, each cell type is specialised for a particular function.
47
Where do neutrophils and erythrocytes derive from?
From stem cells in the bone marrow/
48
How are erythrocytes adapted to carry out their function?
* They're small so have a large SA/V ratio, meaning oxygen can diffuse across there membranes and can easily reach all religions inside the cell.
* They can a biconcave shape which also increase there SA/V ration.
* They're flexible- A well developed cytoskeleton allows them to change shape so the
* at they can twist an turn, as they travel through narrow capillaries.
* Most of their organelles are lost at differentiation, so they have no nucleus, mitochondria or endoplasmic reticulum, and very little cytoplasm. This provides more space for the many haemoglobin molecules housed inside them.
49
How are neutrophils adapted for their jobs?
* They make up about 50% of white blood cells in your body.
* They're about twice the size of erythrocytes, and each neutrophil contains a multilobed nucleus.
* They're attracted to and travel towards infection sites by chemotaxis.
* Their function is to ingest bacteria and some fungi by phagocytosis.
50
How are spermatozoa specialised?
* **Many mitochondria** carry out aerobic respiration. The ATP provides **energy** for the **undulipodium** to **move** and propel the cell towards and ovum.
* **Small but long and thin**, they can move easily.
* Once it reaches the ovum, **enzymes** are released from the **acrosome** (a specialised lysosome). The enzyme **digests the outer protective covering** of the ovum, allowing the sperm head to **enter the ovum**.
* The **head** of the cell contains the **haploid** male gamete nucleus and **very little cytoplasm.**
51
What is a acrosome?
A specialised lysosome found in the head of a spermatozoa cell in which enzymes are released to digest the outer protective covering of the ovum.
52
How are epithelial cells adapted to their purpose?
* Squamous epithelial cells are flattened in shape.
* Many of the cells in epithelium have cilia.
53
What is a guard cell?
in leaf epidermis, cells that surround stoma within the lower epidermis.
54
What are palisade cells?
Closely-packed photosynthetic cells within leaves.
55
What are root-hair cells?
Epidermal cells of young roots with long hair-like projections.
56
How are palisade cells adapted for photosynthesis?
* They are **long and cyclical**, so that they **pack together** quite closely but with **little space** between them for **air to circulate**; carbon dioxide in these air spaces diffuse into the cells.
* They have a **large vacuole** so that the **chloroplasts are positioned nearer the periphery of the cell**, reducing the distance for carbon dioxide.
* Contain **many chloroplasts**.
* They contain **cytoskeleton threads** and **motor proteins** to **move the chloroplasts**- nearer to the upper surface of the leaf when sunlight intensity is low, but further down when it is high.
57
How are guard cells specialised for its role?
* **Light energy** is used to produce **ATP.**
* The ATP **actively transports potassium ions** from surrounding epidermal cells into the guard cells, **lowering their water potential.**
* **Water now enters** the guard cell from neighboring epidermal cells, by osmosis.
* The **guard cells swell**, but at the tip of the cellulose wall is more flexible, and is more rigid where it is thicker. The **tips bulge**, and the gap between the, **the stoma enlarges.**
* As the stoma opens, **air can enter** the spaces within the layer of cells beneath the palisade cells.
* **Gaseous exchange** can occur, and carbon dioxide will diffuse into the palisade cells. As they use it for photosynthesis, this will maintain a steep concentration gradient.
* Oxygen produced during photosynthesis can diffuse out of the palisade cells into the air spaces and out of the open stoma.
58
How are root hair cells specialised?
* The **hair-like projection** greatly **increase the surface area** for absorption of water and mineral ions, such as nitrates, from the soil.
* **Mineral ions** are **actively transported** into the cells, **lowering the water potential**, causing **water to follow** by osmosis.
* The cells have **special carrier proteins** in the plasma membranes in order to **actively transport the mineral ions in**.
* These cells will also **produces ATP,** as this is needed for active transport.
59
Define tissue.
Group of cells that work together to perform a specific function/ set of functions.
60
What are the four main tissue types?
* Epithelial
* Connective tissue
* Muscle tissue
* Nervous tissue
61
How are epithelial tissue specialised?
* Epithelial tissue is made up **almost entirely of cells.**
* These cells are **very close to each other** and form continuous sheets. Adjacent cells are bound together by lateral contacts such as tight junctions and desmosomes.
* There is **no blood vessels** within epithelial tissue; cells receive **nutrients by diffusion from the tissue fluid** in the underlying connective tissue.
* Some epithelial cells have **smooth** surfaces, but some have **projections**, either cilia or microvilli
* Epithelial cells have **short cell cycles** and **divide up to two or three times a day** to replace worn or damaged tissues.
* Epithelial tissue is specialised to carry out its functions of **protection, absorption, filtration, excretion and secretion**.
62
What is the function of epithelial tissue?
* Protection
* filtration
* Excretion
* Secretion
63
What are microvilli?
Extensions of the plasma membrane to increase it's surface area.
64
What are cilia?
Hair-like organelles, which beat and propel substances along epithelial surfaces.
In some cases, a single cilium cell acts as an antenna. It has receptors on it to receive chemical signals from its surroundings.
65
What is connective tissue? What does in consist of?
Connective tissue **holds structures together** and **provides support**.
It consists of a **non-living extra-cellular matrix** containing **proteins** (collagen and elastin) and **polysaccharides** (such as hyaluronic acid, which traps water). This matrix separates the living cells within the tissue and enables it to withstand forces on it such as weight.
Examples of connective tissue includes: blood, bone, cartilage, tendons, ligaments and skin.
66
What are immature cells in cartilage called?
Chondroblasts.
67
What are the three types of cartilage?
* Hyaline
* Fibrous
* Elastic
68
What is hyaline cartilage?
Hyaline cartilage forms the embryonic skeleton, covers the ends of long bones in adults, joins the ribs the the sternum, and is found in the nose, trachea and larynx.
69
What is fibrous cartilage?
Fibrous cartilage occurs in disks between vertebrae in the backbone and in the knee joint.
70
What is elastic cartilage?
Elastic cartilage makes up the outer ear and the epiglottis ( flap that closes over the larynx when you swallow).
71
What are muscle cells called?
Fibres
72
What is muscle tissue made up of?
Muscle cells are **well vascularised** (has many blood vessels). Fibres are **elongated** and contain special organelles called **myofilaments** which allow the muscle tissue to contact.
73
What does muscle tissue do?
Allows movement.
74
What are the three types of muscle cells?
* Skeletal muscle
* Cardiac muscle
* Smooth muscle
75
What is skeletal muscles?
Skeletal muscles, packaged by connective tissue sheets, joined to bones by tendons; these muscles, when they contact, **cause bones to move.**
76
What is cardiac muscle?
Cardiac muscle **makes up the walls of the heart** and **allows the heart to pump blood**.
77
What is smooth muscle?
Smooth muscle occurs in the walls of intestine, blood vessels, uterus and urinary tract, and **it propels substances along these tracts**.
78
What a meristem?
Area of unspecialised cells within a plant that can divide and differentiate into different cell types.
79
What is an organ?
Collection of tissues working together to perform a function.
80
What is a ploem?
Tissue that carries products of photosynthesis, in solution, within plants.
81
What is a xylem?
Tissues that carry water and mineral ions from the roots to all parts of the plant.
82
What is epidermal tissue?
This is **equivalent to epithelial tissue in animals**. It consists of **flattened cells** that, apart from guard cells, **lack chloroplasts** and **form a protective covering** over leaves, stems and roots.
Some epidermal cells also have walls impregnated with a waxy substance, forming a cuticle. This is particularly important to plants that live in dry places, as the cuticle reduces water loss.
83
What is vascular tissue? How many types are there and name them?
Vascular tissue is concerned with **transport**.
There are two sorts, **xylem** and **phloem**, each present in **vascular bundles**.
84
What is the function of the xylem?
Xylem vessels carry water and minerals from roots to all parts of the plant.
85
What is the function of the phloem?
Phloem sieve tubes **transfer** the **products** of **photosynthesis** (mainly sucrose sugar), in solution, from leaves to parts of the plant that do not photosynthesise, such as roots, flowers and growing shoots.
86
What is meristematic tissue?
Meristematic tissues **contain stem cells**. It is from this tissue that all other plant tissues are derived by cell differentiation. It is found at **root and shoot tips**, and in the **cambium** of vascular bundles. These areas are called **meristems**.
87
What do the cells in meristems contain?
* Have thin walls containing very little cellulose.
* Do not have chloroplasts.
* Do not have a large vacuole.
* Can divide by mitosis and differentiate into other types of cells.
88
What is cambium cells?
In plants, is a tissue layer that provides partially undifferentiated cells for plant growth. It is found in the area between xylem and phloem.
A cambium can also be defined as a cellular plant tissue from which phloem or xylem grows by mitosis.
89
How do xylems derive from meristems?
Some cambium cells differentiate into xylem cells:
* **Lignin** (a woody substance) is **deposited in their cells** to **reinforce** and **waterproofs** them; however, this also **kills the cells**.
* The **ends of the cells break down** so that the xylem forms **contentious columns** with **wide lumens** (inner open area inside the xylem) to carry **water** and dissolved **minerals**.
90
What is the lumens of a xylem cell?
Inner open space or a central hollow cavity present inside the xylem.
91
How do phloem sieve tubes derive from meristems?
Some cambium cells differentiate into **phloem sieve tubes** or **companion cells**:
* Sieve tubes **lose most of their organelles**, and sieve plates between them.
* Companion cells **retain their organelles** and continue **metabolic functions** to **provide ATP** for active loading of sugars into the sieve tubes.
92
Name 4 plant organs.
* Leaf
* Root
* Stem
* Flower
93
What is the function of a leaf.
Photosynthesis
94
What is the function of a root?
* Anchorage in soil
* Absorption of mineral ions in water
* Storage, e.g. carrot, parsnip roots store carbohydrates.
95
what is the function of a stem?
* Support
* Holds leaves up so they're exposed to more sunlight
* Transportation of water and minerals
* Transportation of products of photosynthesis
* Storage of products of photosynthesis, e.g. potato tubers store starch; rhubarb stems store sugars and polysaccharides
96
What is the function of a flower?
Sexual reproduction
97
What are some examples of animal organs?
* Heart
* Kidney
* Liver
* Brain
* Optic nerve
* Biceps muscle
* Lungs
* Eye
98
Define organ system.
A number of organs working together to carry out an overall life function.
99
What are some examples of organ systems in animals?
* Digestive system
* Circulatory system
* Respiratory system
* Urinary system
* Integumentary system
* Musculo-skeletal system
* Immune system
* Nervous system
* Endocrine system
* Reproductive system
* Lymph system
100
What does the digestive system do and what organs and tissues are involved?
It provides **nutrition** to provide **ATP** and materials for **growth and repair**.
Organs and tissues involved include: stomach, intestines plus associated glands; the liver and the pancreas.
101
What does the circulatory system do and what organs and tissues are involved?
It provides transport of blood to and from cells.
Organs and tissues involved incudes: the heart and blood vessels.
102
What does the respiratory system do and what organs and tissues are involved?
It provides breathing and gaseous exchange excretion.
Organs and tissues involved: airways and lungs, plus diaphragm and intercostal muscles.
103
What does the urinary system do and what organs and tissues are involved?
It provides excretion and osmoregulation (process of maintaining salt and water balance).
Organs and tissues involved: kidneys, ureters and bladder.
104
What does the integumtary system do and what organs and tissues are involved?
It provides waterproofing, protection and temperature regulations.
Organs and tissues involved include: skin, hair and nails.
105
What does the musco-skeletal system do and what organs and tissues are involved?
It provides support, protection and movement.
Organs and tissues involved, include: skeleton and skeletal muscles.
106
What does the immune system do and what organs and tissues are involved?
It provides protection against pathogens.
Organs and tissues involved, include: bone marrow, thymus gland, skin, stomach acid and blood.
107
What does the nervous system do and what organs and tissues are involved?
It provides communication, control and coordination.
Organs and tissues involved, include: brain, spinal cord and nerves.
108
What does the endoctrine system do and what organs and tissues are involved?
It provides communication, control and coordination.
Organs and tissues involved include: glands that make hormones.
109
What does the reproductive system do and what organs and tissues are involved?
It provides reproduction.
Organs and tissues involved include: testes, penis, ovaries, uterus and vagina.
110
What does the lymph system do and what organs and tissues are involved?
It provides transport fluid back to the circulatory system and is also important is resisting infections.
Organs and tissues involved include: lymph nodes and vessels.
111
What are stem cells?
Unspecialised cells able to express all of it's genes and divide via mitosis. They're described as pluripotent (capable of developing into any type of cell). They can differentiate into specialised cells, for growth and repair.
112
What are the sources of stem cells?
* **Embryonic stem cells**- present in an early embryo formed when a zygote begins to divide.
* **Stem cells in the umbilical-cord blood**
* **Adult stem cells**- (also in children) are found in developed tissues, such as blood, brain, muscle, bone and skin, among the differentiated cells; they act like a repair system because the are renewing source of undifferentiated cells.
* **Induced pluripotent stem cells**- developed in laboratories by reprogramming differentiated cells to switch on certain key genes and becoming undifferentiated.
113
How is stem cells from bone marrow used in treatments?
Stem cells from bone marrow and extensively used in **bone-marrow transplants** to **treat diseases of the blood and immune system**. They're also used to **restore the patient's blood** system after treatment for specific types of **cancer**, where the patient's bone-marrow cells can be **obtained** before treatment, **stored**, and then **put back** inside after treatment.
114
How can stem cells be used for drug research?
If **stem cells** can be made to **develop** into particular **types of human tissue**, then new **drugs** can be **tested** first on these tissues, rather than on animal tissue.
115
How are stem cells used in developmental biology?
Scientists can make use of stem cells, in many ways, to research **developmental biology** and enable **understanding** of how **multicellular** organisms **develop, grow and mature**.
* They can study **how** these **cells develop** to make cell types and can **learn how each cell type functions** and see **what goes wrong when they're diseased**.
* They are trying to find out if they can extend the capacity that embryos have for growth and tissue repair, into later life.
116
Give some examples of how stem cells have been used to repair damaged tissues or replace those lost.
* Bone-marrow stem cells can be made to develop into liver cells and could be used to treat liver disease.
* Stem cells directed to becoming nerve tissue could be used to treat Alzheimer and Parkinson diseases or repair spinal tissue.
117
What is regenerative tissue?
Stem cells maybe used to populate a **bioscaffold** (artificial structure, implanted in the body, on which tissue grows in the form of a missing or damaged organ) of an organ, and then directed to develop and grow into specific organs for transplanting.
