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Cell biology Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Eukaryotic cells

A

Eukaryotic cells are found in plants, animals, fungi and protists (single-celled organisms that don’t fit other categories).
They are 10 - 100 micrometres in size.
A eukaryote is an organism made up of eukaryotic cells.

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2
Q

Prokaryotic cells

A

Prokaryotic cells are 0.1 - 5.0 micrometres in size.
A prokaryote is an organism made up of prokaryotic cells.
Bacteria are prokaryotes.

Prokaryotic cells do not have a nucleus (where DNA is stored).
Instead, most of their genetic material is stored in a single DNA loop in the cytoplasm (watery jelly that fills the cell).
Prokaryotic cells do NOT contain mitochondria (where respiration takes place) or chloroplasts (where photosynthesis takes place).
Some prokaryotic cells contain small rings of DNA called plasmids.
These plasmids can replicate and move between cells so that genetic information can be shared.

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3
Q

Cell membrane

A

The cell membrane holds the cell together, separating the inside of the cell from the environment outside, controlling what can and cannot enter and exit the cell. It is selectively permeable.

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4
Q

Cytoplasm

A

Cytoplasm is a solvent in which chemical reactions take place and surrounds the sub-cellular structures. It also supports internal cell structures.

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5
Q

Scale and size of cells

A

Cells are very small and require a microscope to be seen.
Scientists measure the size of a cell to be approximately 0.003mm in diameter.

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6
Q

Nucleus

A

It contains the genetic material (DNA) which control the activities of the cell.

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7
Q

Ribosomes

A

Ribosomes are found in the cytoplasm and are the site of protein synthesis.

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8
Q

Mitochondria

A

Mitochondria is the site of aerobic respiration.
Cells with high rates of metabolism (carrying out many different cell reactions) have significantly higher numbers of mitochondria than cells with fewer reactions taking place.

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9
Q

Vacuole

A

A permanent vacuole is a fluid-filled sac that stores water.
It is enclosed in a membrane (a wall that substances can pass through).
It can make up as much as 90% of a plant cell’s volume.

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10
Q

Chloroplast

A

Chloroplast is an organelle that contains green pigment called chlorophyll, which absorbs light energy for photosynthesis.

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11
Q

Cellulose cell wall

A

Cellulose cell wall is a tough outer coating made of cellulose that helps support the plant and gives the cell a rigid structure.

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12
Q

Fat cells

A

Function – acts as an energy store

Contains a fat store which can be broken down to release energy.
Can increase in size too store more fat when needed.
Contains very little cytoplasm to allow more space for fat storage.
Excess fat is stored in lipocytes, which expand in size until fat is used for fuel.

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13
Q

Specialised cells

A

A specialised cell is a cell that has a structure that aids its specific function.
This could relate to cell shape, or the combination of cellular structures present within the cell.

Cells specialise by undergoing a process known as differentiation

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14
Q

Muscle cells

A

Function - Contraction for movement

Muscle cells have many mitochondria to release energy for contraction.
All muscle cells contain protein filaments that can slide over each other to allow muscle contraction.

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15
Q

Ciliated epithelial cell

A

Function – line the airways to protect from pathogens

Mucus is made by goblet cells. Mucus trap pathogens.
Ciliated epithelial cells contain cilia (like tiny hairs) that waft mucus.
Contain many mitochondria as energy is needed for cilia to waft mucus.

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16
Q

Sperm cells

A

Function - Transfer of genetic material to an egg cell for fertilisation

The mid-piece is packed with mitochondria to release energy (via respiration) for the tail.
The tail rotates, propelling the sperm cell forward and allowing it to move.
The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus.
The head contains a nucleus with half the normal number of chromosomes, allowing the sperm cell to fuse with an egg cell to restore the normal chromosome number.

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17
Q

Egg cells

A

Function – it is a gamete used in sexual reproduction to pass on the mothers genes

Contains a nucleus which contains half the normal number of chromosomes. Therefore, when the egg and the sperm fuse, the embryo will have the full amount.
Cell membrane changes after fertilisation so only one sperm can enter.
Cytoplasm contains lots of nutrients needed for growth of an early embryo.

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18
Q

Nerve cell

A

Function - Conduction of electrical impulses

Nerve cells are long, meaning that they can conduct nerve impulses between different areas of the body
Extensions of the cytoplasm known as dendrites allowing nerve cells to communicate with other nerve cells, muscles and glands
The axon is covered with a fatty sheath which speeds up nerve impulse transmission

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19
Q

Cone cell

A

Function – allows colour vision

Contains visual pigment to allow colour vision.
One end usually links up to a nerve cell so our body can respond to visual stimuli.
Contains lots of mitochondria to release energy.

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20
Q

Differentiation

A

Structural differences between different types of cells enables them to perform specific functions within the organism.
Cell differentiation is an important process by which a cell changes to become specialised.
Cells that have not differentiated are therefore unspecialised. As an organism develops, cells differentiate to form different types of cells.
Almost all of the cells in a multicellular organism will contain the same genetic information (the same genes or alleles), but depending on what role one particular cell needs to have, only some of the total sum of genes in a particular cell are used to control its development.
When a cell differentiates, it develops a structure and composition of subcellular structures which enables it to carry out a certain function.

21
Q

Differentiation and development

A

As a multicellular organism develops, its cells differentiate to form specialised cells.
In an animal, most cells differentiate at an early stage of its development. Cell division is mainly restricted to repair and replacement in mature animals.
Animal cells therefore lose their ability to differentiate after they have become specialised early in the life of the animal.
Some cells in various locations throughout the body of an animal retain the ability to differentiate throughout the life of the animal.
These cells are called adult stem cells and are mainly involved in replacing and repairing cells (such as blood or skin cells).
Plants differ from animals in that many types of plant cell retain the ability to fully differentiate throughout the life of a plant, not just in the early stages of development.

22
Q

Light microscopes

A

Advantages
They are relatively cheap from £200 – £2000
You can see colour
They don’t require special training to use
They are portable
You can see living specimens

Disadvantages
They have low magnification meaning you can’t see organelles such as mitochondria
They have a low resolution

23
Q

Electron microscopes

A

There are two types of electron microscopes
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)

Advantages
The SEM has a large depth of field which allows more of a specimen to be in focus at one time
Has 1,000,000 to 2,000,000 times magnification

Disadvantages
They are very expensive £2,000,000 +
They are not portable
They can’t see live organisms
They don’t show image in colour

24
Q

Binary fission

A

Bacteria multiply by a type of simple cell division known as binary fission
In the right conditions, a bacterial cell prepares to divide by replicating its. genetic material before it increases in size.
A copy of each piece of circular DNA moves to each end of the cell before the cytoplasm divides, and new cell walls form around each daughter cell.

25
Q

Growing bacterial cultures

A

The effect of disinfectants and antibiotics on microorganisms can be investigated using cultures of bacteria grown in the lab.
In the right conditions, some species of bacteria (such as coli) can multiply as much as once every 20 minutes. This is ideal as large cultures of bacteria for study can be grown in relatively short periods of time.
To multiply this quickly, bacteria require an adequate supply of nutrients (carbohydrates, proteins, minerals and vitamins) and an appropriate temperature (which varies depending on the species being grown).
Bacteria can be grown in a nutrient broth solution or as colonies on an agar gel plate.

26
Q

Uncontaminated cultures

A

It is vital that uncontaminated cultures of microorganisms are grown in the lab.
The presence of competing species can affect the growth of cultures, as well as the validity of any study performed on them.

27
Q

Calculating inhibition zone area

A

Inhibition zone is an area which no bacterial growth has occurred. The larger the zone the more effective the substance tested is against the bacteria.
The effectiveness of different antibiotics, antiseptics or disinfectants can be determined by calculating the area of an inhibition zone around a disc of the substance being tested.

28
Q

Calculating bacteria in a population

A

The average amount of time it takes for a bacter cell in a population to divide is the mean division time.
The number of times a cell has divided and how many cells it produces can be determined if you know the mean division time and how long division has been occurring.

29
Q

Chromosomes

A

In eukaryotic cells, the nucleus contains thread-like structures called chromosomes.
Chromosomes are made from highly coiled strands of relatively long DNA.
Each chromosome is made from one
DNA molecule.
In the body cells of diploid organisms, chromosomes are normally found in pairs.
One chromosome from each pair is inherited from the mother, the other from the father.
Different species of organisms have different numbers of chromosomes in their nuclei.
Humans have 46 chromosomes in the nucleus of all their body cells, found in 23 pairs.
Before a cell can divide, its genetic material needs to be doubled. This results in the characteristic x shaped chromosome.

30
Q

Cell cycle

A

G1 – sub-cellular structures duplicate. Structures include mitochondria and ribosomes
S – DNA replicates to form 2 copies of each chromosome
G2 – DNA is checked for errors made during replication. Done using enzymes, and any errors can be fixed
Mitosis – the chromosomes move to opposite poles of the cell and 2 nuclei form
Cytokinesis – cytoplasm divides and cell membrane separates creating 2 new cells
G0 – Temporary cell resting. Some cells will never divide again, e.g. nerve cells

31
Q

Mitoses

A

Mitosis is cell division that results in genetically identical diploid cells.
The main purpose of mitosis is to create 2 identical daughter cells from 1 parent cell. Daughter cells are identical to one another and to the parent cell.
The 4 stages of mitosis are prophase, metaphase, anaphase, telophase.

32
Q

Prophase

A

Prophase is the first stage of mitosis
Chromosomes condense and become visible
Spindle fibres emerge from centrosomes
Nuclear envelope breaks down
Nucleus disappears

33
Q

Metaphase

A

Mitotic spindle is fully developed, centrosomes are at opposite poles of the cell
Chromosomes are lined up at the metaphase plate
Each sister chromatid is attached to a spindle fibre originating from opposite poles

34
Q

Anaphase

A

Cohesion protein binding the sister chromatids break down
Sister chromatids (now called chromosomes) are pulled towards opposite poles
Non-kinetochore spindle fibres lengthen, elongating the cell

35
Q

Telophase

A

Chromosomes arrive at opposite poles and begin to decondense
Nuclear envelope material surrounds each set of chromosomes
The mitotic spindle breaks down

36
Q

Cytokinesis

A

Plant cell - a cell plate separates the daughter cells
Animal cell – a cleavage furrow separates the daughter cells

37
Q

Stem Cells

A

Stem cell is an undifferentiated cell which is capable of self-renewal to produce more stem cells or differentiate into specific specialised cells.

38
Q

Plant stem cells

A

Many plant cells retain the ability to differentiate throughout their lives and have a layer of unspecialised stem cells (meristem) in the roots and shoots. They can become any type of plant cell.
They are often used to save species that are at risk of extinction.

39
Q

Adult stem cells

A

Some stem cells remain in the bodies of adults as adult stem cells. Adult stem cells are rare and found at certain locations. They can only differentiate into cells from the type of tissue where they are found. Their role is to replace body cells that die through injury and disease. For example, bone narrow cells can differentiate into blood cells and cells of the immune system, but not other cell types

40
Q

Embryonic stem cells

A

Embryos contain stem cells that can grow into any type of cell found in the body and are not specialised. Stem cells can be removed from human embryos that are 3-5 days old to cure diseases however, as the new cells are used to treat a different individual, immunosuppressants are required.

41
Q

Umbilical cord stem cells

A

After a baby is born, stem cells may be collected from the umbilical cord. This is a rich source of stem cells that are formed from the placenta. These can be frozen and stored for possible use in the future by that child. These stem cells have been used to treat a variety of blood disorders as they can differentiate into different blood cells.

42
Q

Therapeutic stem cells

A

In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.

The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections.

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.

Rare species can be cloned to protect from extinction.
Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.

43
Q

Stem cells in medicine

A

Stem cells can be used to treat a wide variety of diseases including diabetes and paralysis.
Organs developed from a patients own stem cells reduces the risk of rejection and the need to wait for an organ donation.
However stem cells cultured in the lab could become infected and potentially be transmitted to the patient. There is also a risk of stem cells mutating which can lead to them developing into cancer cells.

44
Q

Diffusion

A

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient. It is a passive process which means that no energy is needed. It occurs until an equilibrium is reached. There will be a faster rate of diffusion when…

A greater difference in concentration
A higher temperature as the particles will have more kinetic energy and move faster
A larger surface area of membrane for particle to diffuse across
A shorter diffusion distance

45
Q

Osmosis

A

Osmosis is the net movement of water molecules from a dilute region to a concentrated region, down a concentration gradient across a partially permeable membrane. It is a passive movement

46
Q

Hypotonic solution

A

The outside of the cell is more dilute than the inside of the cell (more water outside)
In animal cells, too much water may enter, and the cell will swell until it bursts (lysis)
In plant cells, when too much water enters, it fills the vacuole, and this pushes it against the cell wall making it turgid. They will not burst as the have a rigid cell wall

47
Q

Hypertonic solution

A

The outside of the cell is more concentrate than the inside of the cell (less water outside)
In animal cells, too much water may leave, and the cell will shrink and shrivel (crenation)
In plant cells, when to much water leaves, the vacuole shrinks, and the cell becomes flaccid. they will not shrivel up because they have a rigid cell wall

48
Q

Active transport

A

The movement of particles from an area of low concentration to an area of high concentration through a partially permeable membrane and it requires energy.

Active transport takes place in many situations including:
Plant roots – minerals are absorbed from the soil into the roots
The gut – villi absorb glucose and amino acids into the blood
The kidney – kidney cells absorb sodium ions back into the blood

49
Q

Plasmolysis

A

Plasmolysis is shrinking of the cytoplasm away from the cell wall of a living cell due to water loss by osmosis

Biology (8 decks)

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