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Biology: Core Concepts > Cell Structure and Organisation > Flashcards

Cell Structure and Organisation Flashcards

1
Q

What are cells?

A

the fundamental unit of structure, function, and organisation in all living organisms

can only arise from pre-existing cells

  • basic unit of life
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2
Q

What are the structures in an animal cell?

A
  • nucleolus
  • chromatin
  • nuclear pore
  • nuclear envelope
  • smooth endoplasmic reticulum (SER)
  • rough endoplasmic reticulum (RER)
  • 80s ribosomes
  • cell membrane
  • cytoplasm
  • mitochondrion
  • centrioles
  • lysosome
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3
Q

What are the additional structures in a plant cell?

A
  • chloroplast
  • vacuole
  • plasmodesmata
  • cell wall
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4
Q

What are the components of a microscope?

A
  • eyepiece lens (x10)
  • stage
  • diaphragm
  • course focus
  • fine focus
  • objective power lens
  • light source
  • stage clips
  • arm
  • power chord
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5
Q

How do you calculate magnification?

A

eyepiece lens x objective lens

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6
Q

How do you calculate actual size?

A

image size/magnification

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7
Q

What is the nucleus?

A

the largest organelle in the cell
contains
- nuclear envelope
- nucleoplasm
- chromatin
- nucleolus

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8
Q

What is the function of the nucleus and its substructures?

A

the nucleus retains the genetic information (DNA) that codes for protein synthesis

nuclear envelope - a double membrane with pores to allow the transport of mRNA and ribosomes out of the nucleus to the cytoplasm

nucleoplasm - cytoplasm-like material with the nucleus which contains chromatin

chromatin - coils of DNA bound to histone protein - condenses during cell division to form visible chromosomes

nucleolus - within the nucleus, small spherical bodies that synthesise rRNA (vital to protein synthesis)

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9
Q

What is the function of the mitochondira?

A

to release energy in the form of ATP during aerobic respiration

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10
Q

What are the structures of mitochondria?

A

cristae - inner membrane folded inwards to form these extensions, increases the surface area for ATP synthesis to occur

organic matrix - contains many chemical compounds (lipids, proteins, 70s ribosomes) and a small circle of DNA for self replication

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11
Q

Where does aerobic respiration occur on the mitochondrial membrane?

A

matrix and inner membrane

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12
Q

Where are mitochondria found in the highest concentrations?

A

liver and muscle cells

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13
Q

Why are mitochondria sometimes seen as round and sometimes seen as elongated in electron micrographs?

A

the mitochondria were cut at different angles (when thin slices made for the electron microscope)

round = cut through the middle
elongated = cut along the length

the mitochondria are in different stages of cell replication

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14
Q

What are ribosomes and where are they found?

A
  • small subunit and large subunit are made of rRNA and proteins
  • found free in the cytoplasm or associated with the RER
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15
Q

What is the function of ribosomes?

A

protein synthesis (translation) occurs at the ribosomes as mRNA from the nucleus fits into the groove between the two subunits to provide the code for amino acids

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16
Q

What is the RER and what is its function?

A
  • internal system of cisternae (membrane sacks) which are continuous with the nuclear membrane
  • covered in ribosomes

FUNCTION: protein synthesis and transport of proteins

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17
Q

What is the SER and what is its function?

A
  • internal system of cisternae but unlike RER has no ribosomes

FUNCTION: involved in the synthesis and transport of lipids

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18
Q

What is the Golgi body?

A

-interconnected flattened membranes
- vesicles pinch off of the RER and fuse with the cis face of the Golgi body, are modified and packaged into vesicles
- vesicles containing the modified proteins pinch off on the trans face

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19
Q

What is the function of the Golgi body?

A
  • modifying and packaging proteins into secretory vesicles for secretion from the cell
  • producing glycoproteins
  • forming lysosomes

have a role in:
- transporting and storing lipids
- secreting carbohydrates for the formation of plant walls

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20
Q

What are lysosomes?

A
  • single, membrane bound vesicles that contain hydrolytic enzymes
  • produced by the Golgi body and isolate the potentially harmful digestive enzymes from the remainder of the cell
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21
Q

What is the function of the lysosome?

A
  • release hydrolytic enzymes when the cell needs to break down worn down organelles
  • digest material that have been taken into the cell
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22
Q

How are proteins synthesised and secreted by the cell?

A
  • nucleus contains the DNA which is copied during transcription to produce mRNA
  • nuclear pore in the nuclear envelope allow mRNA molecules to leave the nucleus and attach to ribosomes in the cytoplasm or on the RER
  • protein synthesis occurs on ribosomes to produce polypeptide chains
  • polypeptide chains are moved through the cisternae of the RER and are packaged into vesicles, which bud off the RER and are carried to the Golgi body
  • the vesicle fuses with the Golgi body membrane and sheds its contents into the Golgi bogy, where the protein is modified and packaged into vesicles
  • vesicles bud off the Golgi body and either fuse with the cell membrane for exocytosis or are used within the cell if lysosomes
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23
Q

What is the cell membrane?

A
  • surrounds the cell
  • made up of phospholipids and protein molecules
  • arranged as a bilayer with one sheet of phospholipid molecules opposite another
  • width is 7-8nm
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24
Q

What do phospholipids in the bilayer do?

A
  • form the bilayer by the hydrophilic heads pointing outwards and interacting with the tissue fluid and blood plasma surrounding the cell whilst the hydrophobic tails point towards the inside of the membrane
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25
What do proteins do in the phospholipid membrane?
- found on the surface of the bilayer or partially embedded (extrinsic) or extending completely across both phospholipid layers
26
Describe and explain the position of the charged or hydrophilic parts of the protein in relation to the phospholipids
charged -hydrophilic- R groups of proteins are attracted to the phosphate polar heads and fluid/cytoplasm uncharged -hydrophobic- R groups of proteins associate with non-polar fatty acid tails of phospholipids
27
What do carbohydrates do in the phospholipid bilayer?
are attached to either proteins (glycoproteins) or the phospholipids (glycolipids) are formed through glycosylation and are known as the glycocalyx
28
What does cholesterol do in the phospholipid bilayer?
makes the membrane less fluid and less permeable inserts in the hydrophobic fatty acid tail layer
29
Why is the phospholipid bilayer is called the fluid mosaic model?
the individual phospholipid molecules can move around relative to one another, and the proteins embedded in the bilayer can vary in shape and size and are arranged in a random pattern
30
What is the function of extrinsic and intrinsic proteins?
EXTRINSIC: act as receptors to hormones INTRINSIC: act as carriers or channels to allow the passage of charged/polar molecules through the bilayer
31
What is the function of the glycocalyx
acts as cell to cell recognition (e.g. white blood cells in an immune response) important in cell adhesion and acting as receptors
32
What are centrioles and what is their function?
- found in the cells of all animals and most protoctists, but not in the cells of higher plants - located just outside of the nucleus at right angles to one another FUNCTION: during cell division they migrate to opposite poles of the cell and form the spindle
33
In plant cells, what are vacuoles and what do they do?
- large + permanent fluid filled sac bound by the tonoplast - contain cell sap that stores glucose, amino acids, minerals, vitamins FUNCTION: support soft plant tissues
34
In animal cells, what are vacuoles?
- small, temporary vesicle formed by phagocytosis - may occur in large numbers
35
What is the cell wall?
- cellulose microfibrils embedded in a polysaccharide matrix called pectin FUNCTIONS: provides strength and support, permits movement of water from cell to cell
36
What is the plasmodesmata?
- cell wall is interrupted at intervals by narrow pores carrying fine strands of cytoplasm, joining the living cells to one another - contains ER - the ER is therefore continuous from cell to cell and facilitates the movement of materials between cells
37
What are chloroplasts?
THE SITE OF PHOTOSYNTHESIS found only in plant cells and contain a double membrane
38
What are the structures in a chloroplast?
stroma - colourless, gelatinous matric that contains 70s ribosomes, circular DNA (for self replication), lipids, starch grains thylakoids - stacked to form grana and connected by lamellae, contains chlorophyll and other photosynthetic pigments
39
What is the endosymbiotic theory?
- organelles such as chloroplasts and mitochondria were originally free-living prokaryotic cells - theory states they were engulfed by a cell through endocytosis to form the double membrane for mitochondria - cell gained ATP energy - mitochondria gained a glucose source and protection
40
What is a eukaryote?
organisms made of cells that have membrane bound organelles and have DNA within the nucleus in the form of chromosomes
41
What is a prokaryote?
single celled organism lacking membrane bound organelles, such as nuclei, free in the cytoplasm
42
What are the structures in a prokaryote?
- peptidoglycan cell wall - circular DNA (not enclosed by nuclear membrane) - mesosome (infolding of cell membrane where respiration occurs) - plasmid DNA - flagellum (propels the prokaryote) - photosynthetic membrane (only present in blue-green algae) - caspule/slime layer (present in some bacteria for protection) - cytoplasm - cell membrane - pill (short hairs that may have a protective or signalling function) - 70s ribosomes
43
What are viruses?
- not made of cells (acellular) - cannot be seen through a light microscope - do not have organelles, enzymes, chromosomes, cytoplasm so cannot carry out protein synthesis
44
How do viruses reproduce?
can only reproduce inside a host cell, hijack the hosts metabolism using the host cells organelles and enzymes
45
What is a virus made of?
- nucleic acid surrounded by a protein coat (capsid) - some have DNA that attack another viruses RNA
46
How can viruses be transmitted?
- aerosol - insect vectors - exchange of bodily fluids - bites - close personal contact
47
What is an organism?
all the systems in the body working together to make an organism which is a discrete individual
48
What are the specialised animal cells?
- red blood cells (contain no nucleus so more space for Hb) - ovum (large with some food reserves, haploid gamete) - neurone (long axon for nerve transmission) - sperm cell (small motile with flagellum for swimming) - intestinal epithelial cells (microvilli on surface to increase surface area)
49
What is a tissue?
an aggregation of specialised cells carrying out a specific function
50
What is epithelial tissue?
forms a continuous layer, covering or lining the internal and external surfaces of the body - squamous epithelium - cuboidal epithelium - columnar epithelium - ciliated columnar epithelium
51
What is squamous epithelium?
- form a single layer attached to basement membranes - cells are closely packed together and flattened to provide a smoother surface e.g. cells lining the alveoli
52
What is cuboidal epithelium?
- found lining the ducts of glands that secrete hormones and in the lining of the kidney tubules
53
What is columnar epithelium?
- elongated column like cells - found lining the insides of the hollow organs such as the stomach and intestines
54
What is ciliated columnar epithelium?
found lining the trachea, bronchi, and bronchioles (as well as lining the oviducts)
55
What is connective tissue?
connects and anchors structures and gives strength and support to the body and its organs
56
What does collagen protein do?
forms extracellular fibres that gives strength to dense connective tissues such as the tendons and ligaments also found in the tough outer layer of large blood vessels
57
What is smooth muscle tissue?
- found in the walls of hollow organs like the intestines and the stomach - contractions of smooth muscle constrict the vessels they surround - peristalsis
58
What is skeletal muscle?
- covers the skeleton and gives the body its shape - all body movement from walking to nodding is caused by skeletal muscle contraction - called 'striated' as its appearance consists of light and dark bands visible using a light microscope
59
What is nervous tissue?
- allows electrical signals to be conducted through the animal - responsible for sensing stimuli and transmitted signals to and from different parts of the organism
60
What is an organ?
an aggregation of several tissues that carry out a function for the whole organism e.g. heart, liver, kidney, bladder, stomach, pancreas
61
What is an organ system?
two or more organisms working together to provide a common function e.g. endocrine system (glands) performing homeostasis
62
What are specialised plant tissues?
- palisade mesophyll - guard cells - root hair cells
63
What are plant tissues?
- xylem - phloem - palisade mesophyll - spongy mesophyll - epidermis
64
What are plant organs?
- flower - leaf - stem - roots

Biology: Core Concepts (6 decks)

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