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AS LEVEL BIOLOGY > Cell stucture > Flashcards

Cell stucture Flashcards

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1
Q

Magnification and calculation

A

Magnification: how bigger the image is when compared to the object
Object: material put under the microscope
Image: appearance of material
magnification = size of image/ size of real object
size of real object = size of image/ magnification

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2
Q

Resolution

A

definition: minimum distance apart that two objects can be in order for them to appear as separate items
- resolving power depends on the wavelength
- increasing the magnification increases the size of the image but doesn’t always increase the resolution

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3
Q

cell fractionation

A

a process where the cells are broken up and the different organelles they contain are separated out.
Before cell fractionation can occur, the tissue is placed in a cold, buffered solution of the same water as the tissue. The solution is:
- Cold: to reduce enzyme activity that may break down the organelles
- is of the same WP of the tissue: to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
- buffered: so the pH doesn’t fluctuate, any change in pH could alter the structure of the organelles

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4
Q

Two stages of cell fractionation

A

Homogenation: cells are broken up by a homeogeniser which releases organelles from cells, the fluid made as a result known as homogenate is filtered to remove any complete cells and large pieces of debris
Ultracentrifugation: the fragments in the filtered homogenate are separated in a centrifuge. This spins at a very high speed to create a centrifugal force

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5
Q

Light microscopes

A
  • they have poor resolution as a result of the long wavelength of light
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6
Q

Electron microscope

A
  • this microscope uses a beam of electrons instead of light
    ADVANTAGES:
  • short wavelength so it can resolve objects well and it has a high resolving power
  • they electrons are negatively charged so the beam can be focused using electromagnets
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7
Q

two types of electron microscope

A
  • transmission electron microscope

- scanning electron microscope

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8
Q

TEM

A
  • parts of the specimen absorb electrons and appear dark
  • other parts allow electrons through so appear light
    LIMITATIONS:
  • staining process is required and even then the image isn’t in colour
  • the specimen must be extremely thin
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9
Q

SEM

A
  • limitations of the TEM apply to SEM
  • We can build a 3-D image by computer analysis of the pattern pf scattered electrons
  • The basic SEM has a lower resolving power than a TEM
    ADVANTAGE:
  • specimens don’t need to be extremely thin as electrons don’t penetrate
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10
Q

The nucleus

A
  • The nuclear envelope: double membrane surrounding the nucleus. The outer membrane is continuous with endoplasmic reticulum and has ribosomes on it’s surface and it controls the entry and exit of materials and controls the reactions inside
  • Nuclear pores: allow passage of large molecules such as mRNA out of the nucleus
  • Nucleoplasm: jelly like material that makes up the bulk of the nucleus
  • chromosomes: consists of protein bound, linear DNA
  • Nucleolus: manifactures ribosomal RNA and assembles the ribosomes
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11
Q

Functions of Nucleus

A
  • act as a control centre of the cell through the production of mRNA and tRNA and protein synthesis
  • retain genetic material of the cell in the form of DNA and chromosomes
  • manufacture ribsomal RNA and ribosomes
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12
Q

Mitochondrion

A
  • double membrane: that controls the entry and exit of material
  • cristae: extensions of inner membrane which provide a large surface area for attachment of enzymes and other proteins involved in respiration.
  • Matrix: contains protein, lipids, ribosomes and DNA that allows the mitochondrion to control the production of own proteins
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13
Q

Function of Mitochondria

A
  • sites of aerobic stages in respiration (krebs cycle and OP)
  • responsible for the production ATP and other respiratory substrates like glucose
  • examples of metabolically active cells include muscle and epithelial cells
  • epithelial cells require a lot of ATP in the process of absorbing substances from the intestines by active transport
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14
Q

Chloroplasts

A
  • chloroplast envelope: double plasma membrane that surrounds the organelle. its selective to what can leave or enter
  • Grana: are stacks of 100 disc like structures called thylakoids. in the thylakoids is a photosynthetic pigment called chloropyll. some thylakoids have tubular extensions that join up with thylakoids in the adjacent grana. The grana is where light absorption takes place
  • Stroma: fluid filled matrix where the second stage of photosynthesis occurs. Starch grains are also present in the stroma
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15
Q

Function of structures in chloroplasts

A
  • GRANAL MEMBRANES: provide a large surface area for attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis
  • The fluid of the stroma holds all the enzymes needed to make sugars in the second stage of photosynthesis
  • Chloroplasts contain both DNA and ribosomes so they can quickly and easily manifacture some of the proteins needed for photosynthesis
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16
Q

Endoplasmic reticulum

A
  • 3-Dimensional system of sheet like membranes, spreading through the cytoplasm. its continuous within the outer nuclear membrane. The membranes enclose a network of tubules and flattered sac called cisternae
  • cells that manufacture and store large quantities of carbohydrates, proteins and lipids have a very extensive ER, cells such as liver and secretory cells e.g the epthelial cells that line the intestines
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17
Q

Rough endoplasmic reticulum

A

> the ribosomes present on outer surfaces of the membranes. Its functions are to:

  • provide a large surface area for the synthesis of proteins and glycoproteins
  • provide a pathway for the transport of materials, especially proteins throughout the cell
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18
Q

Smooth endoplasmic reticulum

A

> lacks ribosomes on its surface and is often tubular in apperance. its functions are to:

  • synthesise, store and transport lipids
  • synthesise, store and transport carbohydrates
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19
Q

Golgi apparatus

A

> GA is especially well developed in secretory cells, such as the epithelial cells that line the intestines

  • it consists with stacks of membranes that make up flattened sacs or cisternae with vesicles
  • the proteins and lipids produced by the ER are passed through the GA
  • GA modifies these proteins by adding non proteins such as carbohydrates.
  • these vesicles may move to the cell surface where they fuse with the membrane and release their contents to the outside
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20
Q

Golgi apparatus functions

A
  • add carbohydrate to proteins to form glycoproteins
  • produce secretory enzymes such as those secreted by the pancreas
  • secrete carbohydrates, such as those used in making cell walls in plants
  • transport, modify, and store lipids
  • form lysosomes
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21
Q

Lysosomes

A
  • they’re formed when the vesicles produced by the GA contain enzymes such as proteases and lipases
  • they also contain lysozymes, enzymes that hydrolyse the cell walls of certain bacteria
  • lysosomes are abudant in secretory cells such as epithelial cells and in phagocytic cells
22
Q

Functions of lysosomes:

A
  • hydrolyse material ingested by phagocytic cells such as white blood cells and bacteria
  • release enzymes to the outside of the cell in order to destroy material around the cell
  • break down cells after they’ve died
23
Q

Ribosomes

A
  • ribosomes are small cytoplasmic granules found in all cells. They may occur in the cytoplasm or be associated with the RER. There are two types
  • 80S found in eukaryotic cells and around 25nm in diameter
  • 70S found in prokaryotic cells, mitochondria and chloroplasts is slightly smaller
24
Q

Cell wall

A
  • the cell wall consists of microfibrils of the polysaccharide cellulose, embedded in the matrix
  • cellulose microfibrils have considerable strength and so contribute to the overall strength of the cell wall.
    features of cell wall:
  • they consist of a number of polysaccharides such as cellulose
  • there is a thin layer called middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together
  • cell walls of algae are made up of either cellulose or glycoproteins or both
  • the cell walls of fungi don’t contain cellulose but a mixture of a nitrogen containing polysaccharide called chitin a polysaccharide called glycan and glycoproteins
25
Q

functions of the cellulose cell wall

A
  • provide mechanical strength in order to prevent the cell bursting under pressure created by the osmotic entry of water
  • give mechanical strength to the plant
  • allow water to pass along it and so contribute to the movement of the water through the plant
26
Q

Vacuoles

A
  • fluid filled sac bounded by a single membrane may be termed a vacuole.
  • The single membrane is called the tonoplast
  • A plant vacuole contains a solution of mineral salts, sugars, amino acids, wastes and sometimes pigments such as anthocyanins
27
Q

Vacuole functions

A
  • they support herbaceous plants, and herbaceous parts of woody plant by making cells turgid
  • the sugars and amino acids may act as a temporary food store
  • the pigments may colour petals to attract pollinating insects
28
Q

Tissues

A

definition: cells that are aggregated together to perform a specific function
- Epithelial cells: found in animals and consist of sheets of cells. They line the surfaces of organs and have a secretory function

29
Q

Tissues

A

definition: cells that are aggregated together to perform a specific function
- Epithelial cells: found in animals and consist of sheets of cells. They line the surfaces of organs and have a secretory function.
e. g the cilitated epithelium that lines a duct such as the trachea. The cilia are used to move mucus over the epithelial surface
- Xylem: which occurs in plants and is made up of similar number cell types. it is used to transport water and mineral ions throughout the plant and also give mechanical support

30
Q

Organs

A

an organ is a combination of tissues that are coordinated to perform a variety of functions.
The stomach is an organ that is involved in the digestion of certain types of food, it’s made up of tissues such as:
- muscle

31
Q

Organs

A

an organ is a combination of tissues that are coordinated to perform a variety of functions.

32
Q

Stomach as an organ

A

The stomach is an organ that is involved in the digestion of certain types of food, it’s made up of tissues such as:

  • muscle to churn and mix the stomach contents
  • epithelium to protect the stomach wall and produce secretions
  • connective tissue to hold together the other tissues
33
Q

Leaf as an organ

A

its made up of tissues such as:

  • palisade mesopyll made up of leaf palisade cells that carry out photosynthesis
  • spongy mesophyll adapted for gaserous diffusion
  • epidermis to protect the leaf and allow gaseous diffusion
  • phloem to transport organic materials away from the leaf
  • xylem to transport water and ions into the leaf
34
Q

determining which structures are organs

A
  • blood capillaries are not organs
  • artieries and veins are both organs.
  • all 3 structures have the same major function which is the transport of blood
  • capillaries are made up of epithelium whereas arteries and veins are made up of many tissues e.g epithelial, muscle
35
Q

Organ systems

A
  • DIGESTIVE SYSTEM: digests and processes food. it is made up of organs that include the salivary glands, oseophagus, stomach, duodenum, ileum, pancreas and liver
  • RESPIRATORY SYSTEM: used for breathing and gas exchange. it is made up of organs that include the trachea, bronchi and lungs
  • CIRCULATORY SYSTEM: pumps and circulates blood. it is made up of organs that include the heart,arteries and veins.
36
Q

two types of cells

A
  • eukaryotic cells: are larger and have a nucleus bounded by nuclear membranes
  • prokaryotic cells: are smaller and have no nucleus or nuclear envelope
37
Q

Structures and roles of a bacterial cell

A
  • A CELL WALL: barrier made up of murein that excludes certain substance and protects against damage
  • CAPSULE: protects bacterium from other cells and helps bacteria to stick together
  • CELL SURFACE MEMBRANE: contains 70S ribosomes and acts as a permeable later which controls the entry and exit of chemicals
  • CIRCULAR DNA: holds all genetic info for replication of bacterial cells
  • PLASMID: possess genes that may aid the survival of bacteria in adverse conditions e.g producing enzymes that break down antibiotics
38
Q

Viruses

A
  • they’re non living, acellular particles
  • They contain nucleic acids such as DNA or RNA but can only multiply inside living host cells
  • nucleic acid enclosed with a protein coat called capsid
  • Some viruses like HIV are surrounded by a lipid envelope
  • if the lipid isn’t present then the capsid has attachment proteins which are essential for the virus to identify and attach to a host cell
39
Q

Two types of cell division

A
  • Mitosis: produces two daughter cells that have the same number of chromosomes as the parent cell
  • Meiosis: produces four daughter cells, each with half the number of chromosomes of the parent cell
40
Q

Telophase (MITOSIS)

A

Interphase: cell copies its DNA in prep for mitosis

41
Q

Prophase (MITOSIS)

A

Prophase: chromosomes become visible, spindle fibres develop (spindle apparatus), nuclear envelope breaks down leaving chromosomes free and they’re drawn to the equator by the spidle fibres attached to centromere

42
Q

Metaphase (MITOSIS)

A

Metaphase: chromosomes are seen to be made up of two chromatids and are joined by the centromere. chromatids are pulled along spindle fibres and arrange themselves across equator

43
Q

Anaphase (MITOSIS)

A

Anaphase: centromeres divide into two and spindle fibres pull the individual chromatids making up the chromosome apart, chromatids move to opposite poles and are now chromosomes

44
Q

Telophase and Cytokinesis (MITOSIS)

A
  • Telophase and cytokinesis: chromosomes reach poles and become longer and thinner, disappearing and leaving chromatin, spindle fibres disintergrate and nucelar envelope and nuceleolus re form. finally cytoplasm divides in a process called cytokinesis
45
Q

stages of mitosis (in order)

A
  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase and Cytokinesis
46
Q

Cell division in prokaryotic cells

A

Cell division in prokaryotic cells take place by binary fission

  • circular DNA molecule replicates and both copies attach to the cell membranes
  • plasmids also replicate
  • cell membrane begins to grow between the two DNA molecules and begins to pinch inward, dividing the cytoplasm into 2
  • a new cell wall forms between the two molecules of DNA, dividing the orginal cell into 2 identical daughter cells, each with a single copy of circular DNA and copies of plasmids
47
Q

Replication of viruses

A
  • viruses are non living therefore they cannot replicate unless they attach to a living host cell with attachment proteins on their surface
  • they inject their nucleic acid into the host cell. the genetic into on the inject viral nucleic acid then provides the instructions for the host cell’s metabolic processes to start producing nucleic acid, enzymes and structural proteins which are assembled into new viruses
48
Q

3 stages of the cell cycle

A
  • interphase: occupies most of the cell cycle and is also known as the resting phase
  • nuclear division: when the nucleus divides into two (mitosis) or four (meiosis)
  • division of cytoplasm: which follows nuclear division and is the process by which the cytoplasm divides to produce the two new cells (mitosis) or four new cells (meiosis)
  • the cell cycle in a mammalian cell takes about 24 hours and 90% is interphase
49
Q

Cancer and control of mitosis

A
  • cancer is caused by a growth disorder of cells. it’s the result of damage to the genes that regulate mitosis and the cell cycle
  • this leads to uncontrolled growth and division of cells and as a result a group of abnormal cells called a tumour develops and expands
  • tumours can develop in any organ of the body but are mostly found in the lungs, prostate gland (male), breast and ovaries (female), stomach, oeseophagus and pancreas
  • a tumour becomes cancerous if it changes from benign to malignant
50
Q

Cancer and control of mitosis cont

A
  • the rate of mitosis can be affected by the environment of the cell and growth factors. its also controlled by two types of genes.
  • a mutation to one of these genes in controlled mitosis. the mutant cells formed are usually structurally and functionally different from normal cells.
  • most mutated cells die
  • malignant tumours grow rapidly
51
Q

Treatment of cancer

A

> treatment of cancer involves dividing cells by blocking a part of the cell cycle is disrupted and cell division
Drugs used to treat cancer usually disrupt the cell cycle by:
- preventing DNA from replicating
- inhibiting the metaphase stage by interfering with spindle formation

AS LEVEL BIOLOGY (9 decks)

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