B1 - Cell Biology Flashcards

Question

What is the job of a root hair cell and how is it adapted to its function?

Answer 1

Their job is to absorb water and dissolved minerals. * It achieves this by **having a increased surface area.** * It **does not have chloroplasts as it is underground.** * It has **thin walls** so as not to restrict the movement of water.

Answer 2

They form **long tubes which carry water and dissolved minerals from the roots to the leaves.** They achieve this by: - **very thick walls containing lignin. This provides support to the plant**. But because the cell walls are sealed with lignin this causes the xylem cells to die. - **There are no top and bottom walls between xylem vessels, so there is a continuous column of water** running through them **flowing** **more easily.** - **They have no nucleus**, **cytoplasm, vacuole or chloroplasts** which makes it **easier for water and minerals to flow.**

Answer 3

Phloem tubes carry **dissolved sugars up and down the plant.** They have two different types of cells: * - **Phloem cells which have no nucleus and only limited cytoplasm**. The **end walls** of the vessel cells **have pores called sieve plates which allow dissolved sugars to move cell interior.** * - Each Phloem Vessel cell has a **companion cell connected by pores. Adjacent to the sieve tubes they provide energy required to transport substances in the phloem**

Answer 4

- They have a limited magnification. - They have a limited resolution which means we cannot see fine details.

Answer 5

the shortest distance between two points on a specimen that can still be seen as two different points by the observer.

Answer 6

Electron microscopes use a beam of electrons instead of light rays. There are two types of electron microscope: The scanning electron microscope (SEM) has a large field of view so can be used to examine the surface structure of specimens. SEMs are often used at lower magnifications. The transmission electron microscope (TEM) is used to examine thin slices or sections of cells or tissues. - Higher Magnification - Higher Resolution

Answer 7

A form of cell division used by prokaryotes to reproduce which is a simple form of cell division. The bacteria splits into two bacterial cells This level of replication will depend on the availability of nutrients and other suitable conditions such as temperature.

Answer 8

3 Hours = 180 minutes 180/20 = 9 rounds 2^9 = 512 = Number of Bacteria or 5.12\*10^2

Answer 9

We find Chromosomes that carry genetic information in a molecule called DNA.

Answer 10

**a small section of DNA on a chromosome, that codes for a particular sequence of amino acids , to make a specific protein .**

Answer 11

Each body cell contains two of each chromosome. They are paired Human body cells contain 23 pairs of Chromosome.

Answer 12

Each human body cell contains 46 chromosomes. These can be arranged into 23 pairs. Each chromosome in a pair carries the same types of genes. The 23rd pair are the sex chromosomes: In females, the two chromosomes are identical in shape. There are two X chromosomes. Females are referred to as XX. In males, one of the chromosomes is a different in shape. There is an X and also a Y chromosome. Males are referred to as XY

Answer 13

A growing and dividing cell goes through a series of stages called the cell cycle.

Answer 14

In the first stage(GROWTH STAGE) - , **the DNA replicates to form two copies of each Chromosome. The cell also grows and copies its internal structures such as mitochondria and ribosomes.** In the second Stage - **Mitosis takes place**. One set of **Chromosomes is pulled to each end of the cell.** The nucleus also divides. In the Final stage(Cytokinesis) of the cell cycle, **the cytoplasm and the cell membrane divide to form two identical cells.**

Answer 15

For a multicellular organism to grow, cells must divide by mitosis to produce two new identical daughter cells During mitosis, one chromosome from each set is pulled to each end of the cell, and a new nucleus forms around each group of chromosomes After this, the cytoplasm and cell membranes divide in a process known as cytokinesis. This results in the formation of two genetically identical daughter cells

Answer 16

So, if a human cell with 46 chromosomes in 23 pairs needs to divide by mitosis: Its 46 chromosomes are doubled, so that there are two copies of each of the 46 chromosomes (or 92 chromatids) in total in the cell The number of ribosomes and mitochondria subcellular structures also increases During mitosis, the chromatids are pulled apart, with a complete set of 46 chromosomes in 23 pairs moving to each end of the cell The cytoplasm and cell membrane divide, forming two new daughter cells

Answer 17

1. Mitosis is essential for Growth and Development for multicellular organisms. 2. Mitosis takes place when an organism repairs itself. 3. Mitosis happens during Asexual Reproduction.

Answer 18

Multicellular organisms are organisms made from more than one cell You (a human) are multicellular, being made from trillions of cells Specialised cells have a particular structure and composition that allow them to perform a specific function, and they form through a process known as differentiation There are about 250 specialised cell types in the human body (e.g. red blood cell, motor neurone cell etc.) If a specialised cell is able to divide by mitosis, the daughter cells produced will be the same type of specialised cell. These cells have lost their ability to differentiate into other types of cell

Answer 19

A stem cell is an undifferentiated cell of an organism which is capable of dividing (giving rise) to many more cells of the same type (undifferentiated stem cells) From these cells, other cells can arise through the process of differentiation

Answer 20

An embryo develops from a fertilised egg. Cells at the early stages in the development of the embryo are stem cells. If cells are removed from the embryo – called embryonic stem cells - they will differentiate into any cell type however they have to be taken from a embryo which can be seen as unethical.

Answer 21

A type of stem cell found in specific locations in adults. Adult stem cells can only differentiate into a limited number of related cell types. Adult stem cells can be found in several regions of the body, including the: brain eyes blood heart liver bone marrow skin muscles Adult stem cells can differentiate into related cell types only, for example, bone marrow cells can differentiate into blood cells and cells of the immune system but not other cell types.

Answer 22

Cell division in plants occurs in regions called meristems. Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant. The main meristems are close to the tip of the shoot, and the tip of the root. In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated – they enlarge and develop vacuoles

Answer 23

Transport substances, defend the body, regulate temperature

Answer 24

Remove waste products regulate the water content of the body.

Answer 25

Bring about movement

Answer 26

Respond to internal and external stimuli and conditions, carry messages for the body work as a coordinated whole

Answer 27

Deliver oxygen for respiration and remove waste

Answer 28

Bring about fertilisation to produce new offspring

Answer 29

To bring about movement, support and protect internal structures, produce blood cells, store and release calcium

Answer 30

Carry out photosynthesis

Answer 31

Allow gases to circulate for the exchange of gases between the leaf and the environment, carry out some photosynthesis

Answer 32

Open and close to control the exchange of gases – carbon dioxide, water vapour and oxygen

Answer 33

Transport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed

Answer 34

Provide the energy required for transporting substances in sieve tubes

Answer 35

Transport water and dissolved minerals from the roots, up the plant

Answer 36

Produce new cells as they divide

Answer 37

Cells from meristems can be cloned. Meristematic cells are removed from a plant and grown in tissue culture. The cells are grown in a culture medium that contains agar – to provide support and water for the growing cells – along with nutrients and plant hormones to stimulate growth and cell division.

Answer 38

Plants are cloned to produce identical plants quickly and economically. Producing new plants by cloning is quicker than allowing plants to reproduce and collecting and sowing seeds. It’s therefore an effective way of producing new individuals from rare and endangered plants, helping to preserve the species. Clones will be genetically identical to the original plant providing the meristem cells. This is useful to provide crop plants for large-scale cultivation that have desirable characteristics such as disease resistance. Unlike in animals, plant stem cells can be obtained easily, and without ethical objection, from meristems. They can then be used to produce clones of plants quickly and economically Plant clones can be produced in weeks at a relatively low cost for their potential value Rare species at risk of extinction as a result of human activity can be cloned to protect them and maintain biodiversity The plants produced are clones, so although numbers increase, genetic diversity within clones is low Cloning rare plants gives scientists more time to study them to see if they can produce any compounds of interest Crop plants with special features such as disease or pest resistance can be cloned to produce large numbers of identical plants for farmers This reduces the need to use chemicals such as pesticides, which has environmental benefits

Answer 39

Stem cells can divide to produce new cells, which can then divide into different cell types. They therefore have the potential to be transplanted into patients to treat medical conditions and disease. They could be used to replace cells that have been damaged or destroyed, eg: - type 1 diabetes - multiple sclerosis, which can lead to paralysis - spinal cord or brain injury, that have led to paralysis

Answer 40

As there is an inability on the pancreas to produce insulin to regulate blood sugar levels as a result Stem cells can differentiate into pancreatic cells and transported into the patient which produces insulin and as a result regulate blood sugar levels. They have to be sourced from Stem cell donors, embryos or through therapeutic cloning.

Answer 41

Adult stem cells will differentiate into a narrower range of cell types. Bone marrow transplants are an example of adult stem cell transplant. Bone marrow cells will differentiate into different types of blood cell. Bone marrow transplants are carried out: - in cases of blood cell cancer such as leukaemia and lymphoma - when blood cells have been destroyed by cancer treatment

Answer 42

Adult stem celltransplants use a patient's own stem cells. They are therefore genetically identical and **will not be rejected by the patient's immune system**. There are also fewer complications if the stem cells come from a close member of the family. Alternatively, donor cells can come from a person with closely-matched tissue types. Embryonic stem cells will always come from a donor – unless stem cells were collected from the patient as an embryo.

Answer 43

Therapeutic cloning could produce stem cells with the same genetic make-up as the patient. The technique involves the transfer of the nucleus from a cell of the patient, to an egg cell whose nucleus has been removed. Stem cells produced in this way could be transferred to the patient. Although human stem cells have been produced in this way, and used in research, there is no evidence that, as yet, they have been used to treat anyone.

Answer 44

- There is no guarantee how successful these therapies will be, for example the use of stem cells in replacing nerve cells lost in Parkinson’s disease patients. - **difficulty in finding donors**. - **difficulty in obtaining and storing a patient’s embryonic stem cells.** - **Mutations have been observed in stem cells** - **Cultured stem cells** could be c**ontaminated with viruses** which would be transferred to a patient.

Answer 45

- A source of embryonic stem cells is unused embryos produced by in vitro fertilisation (IVF) - For therapeutic cloning is it right to create embryos for therapy, and destroy them in the process? - Embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person. - At what stage of its development should an embryo be regarded as, and treated as a person?

Answer 46

- Educating the public about what stem cells can, and can't do, is important. - Whether the benefits of stem cell use outweigh the objections. - Much of the research is being carried out by commercial clinics, so reported successes are not subject to peer review. Patients could be exploited by paying for expensive treatments and being given false hope of a cure as stem cell therapies are only in their developmental stages.

Answer 47

- No need for Organ transplant - Could treat paralysis or Type 1 diabetes - There have been many successful trials

Answer 48

There are three transport processes that living organisms use for exchange: diffusion, osmosis and active transport

Answer 49

Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement of particles from an area of higher concentration to an area of lower concentration. It is a passive process as it requires no energy. This means: Particles in a solution or a gas are always moving about randomly If there happen to be more particles in one area/region, then there tends to be an overall (net) movement of particles from this region of higher concentration to a region where there are fewer particles (an area of lower concentration)

Answer 50

All cells are surrounded by a cell membrane which separates the inside of the cell from its outside environment Substances have to be able to diffuse through the cell membrane to enter or exit the cell unaided (there are other ways for substances to get in) Not all substances are able to diffuse across the cell membrane which is why it is described as being ‘partially permeable’; some substances are able to enter or leave the cell whilst others aren’t For example, oxygen and carbon dioxide can diffuse across the cell membrane during gas exchange whereas the carbohydrate starch cannot (it’s too big)

Answer 51

Examples of substances that enter cells by diffusion: -Oxygen must diffuse into cells for aerobic respiration -Carbon dioxide must diffuse into photosynthesising plant cells to be available for photosynthesis Examples of substances that leave cells by diffusion: -Liver cells break down excess amino acids into the waste product urea which is highly toxic and must diffuse out of cells to be excreted by the kidneys -Carbon dioxide produced by aerobic respiration must diffuse out of cells

Answer 52

A photosynthesising leaf cell will likely have a lower carbon dioxide concentration on a bright day compared to its environment, as carbon dioxide is used in photosynthesis faster than it is produced in aerobic respiration. At night, when the plant is not photosynthesising the carbon dioxide concentration inside the same leaf cell will be higher than the environment as the leaf cell is always respiring.

Answer 53

* Temperature * Surface Area * Concentration gradient

Answer 54

Role in the body: - Most absorption of digested food molecules into the bloodstream occurs across the wall of the small intestine. How it’s adapted to its role: - Huge surface area, produced by thousands of villi. - Only one layer of epithelial cells covers the surface of each villus – this decreases diffusion distance - Each villus has a good blood supply – this maintains a concentration gradient

Answer 55

The alveolus is the gas exchange surface in humans Role in the body: - Gas exchange between air in the alveoli and the blood, to supply cells with oxygen for aerobic respiration and to remove carbon dioxide How it’s adapted to its role: * Millions of alveoli (singular: alveolus) which collectively provide a huge surface area this increases SA * The wall of each alveolus is one cell thick, with a moist lining and excellent blood supply - this maintains a concentration gradient * Extensive blood supply - ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.

Answer 56

-Each **gill is made from lots of smaller plates called filaments**, which themselves are **covered in projections called lamellae – this increases SA** **-Dense capillary network ensures a good blood supply** which flows in the **opposite direction to water passing through the gills** – this **maintains a concentration gradient**

Answer 57

Role in the plant: - To absorb water and mineral ions (such as magnesium and nitrate ions) from the soil and anchor the plant How it’s adapted to its role: * **Mitochondria for active transport** of mineral ions * **The surface of the roots are covered in root hair cells** – this increases SA * **Thinner wall**s (due to shorter diffusion distance) * Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient * Remember that chloroplasts are not found in these cells – there’s no light for photosynthesis underground! * The root network is highly branched - this increases SA

Answer 58

Role in the plant: - The leaves contain most of a plant's photosynthetic cells - Photosynthesis requires efficient gas exchange between air surrounding the leaf and the photosynthetic cells, whilst minimising water loss How it’s adapted to its role: - Stomata are tiny openings that predominantly cover the lower side of the leaf, allowing air to circulate inside the leaf – this decreases diffusion distance for carbon dioxide and oxygen - The lower layer of the leaf is made from spongy mesophyll cells which allow air to circulate inside the leaf

Answer 59

Water moves from a **high water** to a **low water concentration** across a **partially permeable** **membrane** and down a **concentration gradient** Osmosis is a just a special type of diffusion, so water molecules move about randomly just like any other particle that can diffuse Water will always move from a more dilute solution to a more (solute) concentrated solution to even up the concentration of water molecules on each side of the membrane

Answer 60

The movement of water by osmosis can easily be observed by placing two similar pieces of plant tissue into solutions with differing concentrations If the plant tissue gains mass: * *- Water must have moved into the plant tissue from the solution surrounding it by osmosis - The solution surrounding the tissue is more dilute than the plant tissue (which is more concentrated)** If plant tissue loses mass: * *- Water must have moved out of the plant tissue into the solution surrounding it by osmosis - The solution surrounding the tissue is more concentrated than the plant tissue (which is more dilute)** If there is no overall change in mass: - There has been no net movement of water as the concentration in both the plant tissue and the solution surrounding it must be equal - Remember that water will still be moving into and out of the plant tissue, but there wouldn’t be any net movement in this case

Answer 61

Diffusion and osmosis rely upon the passive transport of substances down concentration gradients, relying on the random movement of particles However, cells also need to be able to transport substances across the cell membrane against a concentration gradient. This requires energy released by respiration The energy from respiration is used by protein transport molecules embedded in the cell membrane to move substances into or out of the cell Active transport moves substances from a more dilute solution to a more concentrated solution

Answer 62

Diffusion and osmosis rely upon the passive transport of substances down concentration gradients, relying on the random movement of particles However, cells also need to be able to transport substances across the cell membrane against a concentration gradient. This requires energy released by respiration The energy from respiration is used by protein transport molecules embedded in the cell membrane to move substances into or out of the cell Active transport moves substances from a more dilute solution to a more concentrated solution

Answer 63

Plants - Root hair cells lining the surface of plant roots need to move minerals such as magnesium ions from a region of lower concentration (the very dilute solution of minerals in the soil surrounding the roots) to a region of higher concentration (inside the cytoplasm of the cell) - Mineral ions are needed by plants to function healthily. - Magnesium ions are needed to make chlorophyll - Nitrate ions are needed to make amino acids and therefore for protein synthesis (and subsequently growth) Animals - Food molecules (such as the sugar glucose) can be absorbed across the wall of the small intestine by diffusion, but this is dependent on a concentration gradient existing between the lumen of the intestine and the bloodstream - Active transport allows sugar such as glucose to be transported into the bloodstream from the lumen of the small intestine (the gut) when the concentration of sugar molecules in the blood is higher Sugar molecules are used in respiration to release energy for cells to function

B1 - Cell Biology Flashcards

(91 cards)