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Human Physiology 1 > Unit 2a: Cells and Tissues > Flashcards

Unit 2a: Cells and Tissues Flashcards

1
Q

List and describe the general functions of the Cell membrane

A

i. Acts as a physical barrier separating the ECF from the
ICF.

ii. Regulates exchange of molecules between the ECF
and ICF.
- Semipermeable (or selectively permeable)
membrane controls what molecules (solutes) can
move into or out of the cell.

iii. Communication between cell and environment
–receptors on outer surface of membrane detect and
respond to signals (chemical and physical) in the
environment (e.g. levels of regulated variables – like
temperature, ion concentration, CO2, etc.; some
hormones, neurotransmitters, etc).

iv. Structural support for the cell
– cytoskeleton attaches
to membrane proteins and gives cell shape. Some
have protein junctions that help connect the
membranes of adjacent cells

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2
Q

What is the cell membrane composed of?

A

Composed mostly of lipids and
proteins

Ratio of lipids & proteins
varies with more metabolically
active structures/cells having more
protein in their membranes

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3
Q

Describe why the membrane is called a Fluid Mosaic Model

A

proteins appear
floating around in a sea of lipids
(like boats in a harbour). Fluid
because the proteins/lipids can
move two dimensionally within the
membrane (i.e. they are not fixed
in space)

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4
Q

List the parts of a cell membrane

A
  1. phospholipid bilayer
  2. cholesterol
    3.sphingolipids
  3. membrane proteins
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5
Q

describe the role of the phospholipid bilayer

A
  • Creates hydrophobic barrier between ECF and ICF
  • Phosphate heads (polar & hydrophilic) orient
    towards ECF or ICF; fatty acid tails (non-polar &
    hydrophobic) orient towards each other and form the
    hydrophobic barrier
  • 3 main types of phospholipids in the membrane. They
    differ in their R group and the degree of saturation of their
    fatty acids, and are asymmetrically distributed between the
    outer and inner parts of the bilayer. Asymmetric
    distribution provides mechanical stability to the membrane
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6
Q

List the main types of phospholipids

A
  1. Phosphatidylethanolamine – inner layer
    2) Phosphatidylserine – inner layer, -ve charged head.
    3) Phosphatidylcholine – mostly outer laye
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7
Q

: Which phospholipid
is most abundant in the
membrane?

A

Phosphatidylcholine

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8
Q

describe the role of Cholesterol in a cell membrane

A

Located between fatty acid chains of adjacent
phospholipids

  • Slows diffusion of molecules across membrane; can
    block small water soluble molecules.
  • Determines membrane fluidity
  • Prevents membranes from becoming too rigid at cold
    temperatures or too fluid at high temperatures by
    interfering with movement of fatty acid chains.
  • Keeps fatty acids together at high temps, (prevents
    bilayer from breaking apart) and keeps them apart at
    low temps (prevents bilayer from freezing).
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9
Q

Describe the role of Sphingolipids in the membrane

A

Ø E.g. sphingomyelin
Ø Have longer fatty acid tails than phospholipids.
Ø Form lipid rafts

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10
Q

lipid rafts

A

aggregation of sphingolipids
with a higher density of cholesterol than other
areas of the membrane.

  • Some membrane proteins can only be found in
    lipid rafts, for example some G-protein coupled
    receptors (common receptor for detecting
    peptide or protein neurotransmitters, and
    hormones, as well as odours, light, etc.).
  • Studies have associated lipid rafts with
    numerous diseases including Alzheimer’s,
    Parkinson’s, and recently COVID-19
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11
Q

List the types of membrane proteins

A
  1. integral; lipid anchored and transmembrane
  2. peripheral
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12
Q

Integral Proteins

A

Permanently attached to cell membrane

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13
Q

Transmembrane Proteins

A
  • type of integral membrane protein
  • Cross the entire membrane.
  • Have one (bitopic) or more (polytopic)
    membrane spanning regions.

-The protein’s non-polar (hydrophobic)
regions (made up of 20-25 non-polar amino
acids) are embedded in the hydrophobic
regions of the phospholipid bilayer.

  • The polar (hydrophilic) regions interact with
    either the ECF or ICF
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14
Q

Lipid-Anchored Proteins

A

Ø Monotopic = permanently attached to one
surface of the membrane (i.e. do not cross
entire membrane)

Ø Many are attached to lipid portion of
phospholipid bilayer by covalent bonds.

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15
Q

Peripheral proteins

A

Attached to integral proteins or to polar heads of
phospholipids by non-covalent interactions
(weaker bonds and therefore not permanent)

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16
Q

Membrane carbohydrates

A

Ø Found only on membrane surface
facing the ECF

Ø Attached to lipids (forming glycolipids)
or to proteins (forming glycoproteins

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17
Q

glycocalyx

A
  • formed from membrane carbs
  • protective layer around cell
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18
Q

cytoplasm

A

spans area between the cell membrane and the nucleus

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19
Q

List the components of the cytoplasm of a typical cell

A
  • cytosol
  • membranous organelles
  • inclusions
  • protein fibres
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20
Q

Cytosol

A

intracellular fluid made of of
H2O, dissolved (soluble) nutrients, proteins,
ions and waste products

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21
Q

Membranous organelles

A

compartments
in cell separated from the cytosol by a
phospholipid membrane

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22
Q

Inclusion

A

insoluble material in direct
contact with the cytosol

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23
Q

Protein fibers

A

involved in structural
support for the cell and/or movement

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24
Q

List the membranous organelles

A
  • mitochondria
  • ER
  • Golgi apparatus
  • lysosomes
  • peroxisomes
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25
Q

Mitochondria

A

double membrane; site of most ATP
synthesis

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26
Q

Endoplasmic reticulum (ER)

A
  • network of membranous tubes connected to nuclear membrane.
    Two types:
  • rough and smooth
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27
Q

Rough ER

A

covered in ribosomes, so involved in
protein synthesis and in transporting and
modifying proteins assembled by the ribosomes

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28
Q

Smooth ER

A

– no ribosomes; synthesizes lipids (e.g.
phospholipids for membranes; fatty acids;
steroids; sebum in skin oil gland cells, etc

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29
Q

Golgi apparatus

A

– stacks of membranous tubes
(cisternae) that modifies proteins and packages them
into vesicles for delivery to different areas (e.g. to the
cell membrane, to the outside of the cell, to other
membranous organelles, etc)

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30
Q

Peroxisomes

A

contain enzymes that breakdown fatty
acids and amino acids

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31
Q

Lysosomes

A

contain digestive enzymes that breakdown
worn out cell parts and can be used by some cells to
destroy viruses and bacteria

  • Can also trigger apoptosis
    (programmed cell death) if the cell is damaged
  • like the digestive system of the cell
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32
Q

Nucleus

A

Control center of cell
- nuclear envelope
- nucleolus
- Contains chromatin (DNA + histone proteins)

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33
Q

Nuclear envelope

A

double membrane with nuclear
pores (allow molecules to be passed back and forth
between cytosol/rough ER and inside of nucleus (e.g.
messenger RNA)

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34
Q

Nucleolus

A

dense region of DNA and RNA in nucleus
responsible for synthesis of ribosomal RNA units that
become the ribosome

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35
Q

List the inclusions

A

ribosomes
glycogen granules
lipid droplets
pigment proteins

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36
Q

Ribosomes

A

protein subunits that synthesize
proteins (translation).
Can be:
fixed or free (can alternate between the 2)

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37
Q

Fixed ribosomes

A

e.g. attached to ER (proteins made here
will go to the Golgi apparatus and be packed
into vesicles that will deliver them to the ECF,
to the cell membrane or to lysosomes)

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38
Q

Free ribsomes

A

– suspended in cytosol (proteins made
here destined for cytosol or mitochondria, or
persoxisomes

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39
Q

Glycogen granules

A

storage form of glucose in
liver cells and muscle cells

40
Q

Lipid droplets

A

– storage of triglycerides in fat
(adipose) cells and liver cells.

41
Q

Pigment proteins

A

– e.g. hemoglobin in red blood
cells; melanin in skin and hair cells

42
Q

List the different types of protein fibres

A

a. cytoskeleton
- microfilaments
-IF
-microtubules

b. cilia and flagella
c. centrosomes and centrioles

43
Q

describe the composition and function of microfilaments

A

mall diameter (7 nm) protein
fibers made of the protein actin

Functions:
structural; movement (acts with motor proteins,
to produce movement e.g. movement of white
blood cells through tissues; cytokinesis during
cell division; contraction of skeletal muscles)

44
Q

describe the composition and function of intermediate filaments

A

intermediate diameter
filaments (8-10 nm) made of different proteins
depending on tissue type, e.g. in skin, hair and
nails the protein is keratin

45
Q

Microtubules

A

large diameter fibres (~25 nm)
made of protein tubulin

  • Act as a track for
    some motor proteins to move structures
    around the cell
  • Also important to cell division
    (moves chromosomes and pulls them apart)
46
Q

Describe the functions of the cytoskeleton:

A

i. Give cell shape (like scaffolding.).

ii. Internal organization of cells – stabilizes position of
organelles.

iii. Intracellular transport – facilitates transport into
the cell and within the cell (acts as a track for
motor proteins that can move organelles).

iv. Assembly of cells into tissues – interaction of
cytoskeleton with membrane proteins and
secreted proteins found on the extracellular
surface of cells helps provide physical strength.

v. Movement – of the cell itself or parts of the cell
(cilia/flagella have microtubules in their structure

47
Q

Centrosome & Centrioles

A

assembles tubulin into
microtubules that direct DNA movement during cell
division (mitosis & meiosis).

*MTOC

48
Q

Cilia and Flagella

A

Ø Both have microtubules in their structure.

Ø Cilia project into the ECF and wave back and forth to
move fluid across the surface of cells.

Ø In humans, only sperm cells have flagella, which propel
sperm through fluid

49
Q

motor proteins

A

convert stored energy into direct movement

50
Q

list the 3 types of motor proteins

A
  1. myosins
  2. kinesins
  3. dyneins
  • all use ATP to propel themselves
51
Q

myosins

A

bind to actin
involved in muscle contractions

52
Q

kinesins and dyneins

A

assist in movement of vesicles along MTs

53
Q

describe the 3 parts of a motor protein

A

2 heads that bind to cytoskeletal fibre
a neck and tail that binds organelles

54
Q

Describe protein synthesis

A
  1. RNA for protein synthesis is made from DNA templates in the nucleus
  2. then transported to the cytoplasm through the nuclear pores
  3. Inthe cytoplasm, proteins are synthesized on ribosomes that may be
  4. free inclusions
  5. or attached to the rough endoplasmic reticulum
  6. The newly made protein is compartmentalized in the lumen of the rough ER 5
  7. where it is modified before being packaged into a vesicle
  8. The vesicles fuse with the Golgi apparatus, allowing additional modification of the protein in the Golgi lumen.
  9. The modified proteins leave the Golgi packaged in either storage vesicles
    or secretory vesicles whose contents will be released into the extracellular fluid 10.
55
Q

List all the different compartments involved in protein synthesis

A

nucleus
cytoplasm
ribosomes
er
golgi apparatus
vesicles

56
Q

What are the 3 major types of cell junctions?

A
  1. communicating junctions (gap junctions)
  2. occluding junctions (tight junctions)
  3. anchoring junctions (desmosomes)
57
Q

Communicating junctions (e.g. Gap junctions

A

protein clusters called connexins form pores between
adjacent cells

Allow molecules to pass directly from
one cell to another

Common in cardiac and smooth
muscle so that multiple cells can contract as a uni

58
Q

Occluding junctions (e.g. Tight junctions)

A

regions of
membranes from two adjacent cells fuse together
preventing material from passing in between the two
cells

Common in intestinal cells (enterocytes) lining
the gut – blocks potentially harmful substances from
moving between cells and crossing into the blood.

59
Q

Anchoring junctions (e.g. desmososmes)

A

connects
cells to each other and to extracellular proteins (acts
like a staple or a rivet holding cells together)

60
Q

List the 4 major types of tissue

A
  1. epithelial
  2. connective
  3. nervous
  4. muscle
61
Q

Describe the basic structure of an epithelium

A
  • Structure: one or more cells stacked on a
    basement membrane (basal lamina) with a free
    surface (the apical surface) that faces a
    cavity/lumen
  • named according to how many layers of cells and cell shape
62
Q

List some characteristics of epithelial tissue

A
  • Avascular (no blood supply)
  • Closely packed cells
  • line the cavities and surfaces of the body
    Ø E.g. lining of the digestive tract; lining of the
    thoracic cavity; lining of the bladder, lining of the
    chambers of the heart and blood vessels (called
    endothelium).
  • Makes up secretory portions of exocrine and
    endocrine glands (e.g. much of the pancreas,
    sweat glands, salivary glands, etc).
  • any substance that enters or leaves the internal envir. of the body must cross an epithelium
63
Q

What are the 5 function categories of epithelial tissue?

A
  1. exchange
  2. transport
    3.secretory
  3. protective
  4. ciliated
64
Q

Exchange Epithelia

A

Ø Cell shape: Thin flattened (squished cells)

Ø Allow gas exchange

Ø Line the blood vessels and lungs

Ø Classified as simple squamous epithelia – simple
because there is one layer of cells, squamous
meaning “flat”)

65
Q

Transporting Epithelia

A

Ø Cell shape: cuboidal or columnar (cubes or
rectangles)

Ø Apical membrane faces lumen/cavity

Ø Selectively move substances between the ECF
and ICF

Ø Simple epithelia such as those found lining the
stomach/intestines/kidney tubules.)

66
Q

Ciliated epithelia

A

Ø Cell shape: square (cuboidal) or rectangular
(columnar)

Ø Cilia on surface beat back and forth and move fluids
across the outer surface of the cells.

Ø Found in nose, in trachea, uterine tubes, etc

67
Q

Protective Epithelia

A

Ø Stratified epithelium – many layers of cells to protect
against abrasion. Cells close to surface are flat
(squamous) but are cuboidal close to the basement
membrane.

Ø Blocks movement of molecules between ECF and ICF

Ø Includes epidermis of skin, lining of the mouth, parts
of the pharynx, esophagus, urethra, vagina, etc.

68
Q

Secretory epithelia

A

Ø Cell shape: varies depending on gland, but typically cuboidal or columnar.

Ø Produce and secrete a substance into the extracellular space

Ø Two types
- exocrine and endocrine glands

69
Q

Exocrine glands

A

Ø Secretions often travel through ducts to the reach the external
environment

Ø E.g. sweat glands, salivary glands, digestive enzymes from
pancreas; goblet cells that secrete mucou

70
Q

Endocrine glands

A

Secrete hormones into the ECF (first into ISF, then into blood plasma).

Ø No ducts required

Ø E.g. thyroid gland, Islets of Langerhans in pancreas

71
Q

Extracellular matrix

A

extracellular material that is synthesized and secreted by the cells of a tissue

2 components:
proteoglycans and insoluble protein fibres

72
Q

List some of the major characteristics of connective tissue

A

Ø Cells separated by a non-living extracellular matrix
(ECM). Exact composition of ECM determines the
type of connective tissue and its properties

Ø Cells can be fixed in place (as in bone), or can be
mobile (as in blood)

Ø 3 cell types:
a. -blasts (build ECM);
b. -cytes (maintain ECM);
c. -clasts (break down ECM)
Ø E.g. in bone – osteoblasts, osteocytes, osteoclasts

72
Q

List some of the major characteristics of connective tissue

A

Ø Cells separated by a non-living extracellular matrix
(ECM). Exact composition of ECM determines the
type of connective tissue and its properties

Ø Cells can be fixed in place (as in bone), or can be
mobile (as in blood)

Ø 3 cell types:
a. -blasts (build ECM);
b. -cytes (maintain ECM);
c. -clasts (break down ECM)
Ø E.g. in bone – osteoblasts, osteocytes, osteoclasts

73
Q

List the components of ECM

A

Protein fibers
ground substance

74
Q

Protein fibres of ECM

A

i. Collagen – gives tissues strength and flexibility

ii. Elastin – gives tissues stretch and recoil

iii. Fibronectin – connects cells to matrix

75
Q

Ground substance

A

Ø Mixture of proteoglycans and water and other
soluble or insoluble molecules

Ø Highly variable – can be mineralized with
hydroxyapatite as in bone, or can be a watery
fluid as in blood plasma

76
Q

List the different types of Connective tissue

A

Loose CT; areolar CT

Desne CT; irregular or regular

blood

bone

cartilage

adipose

77
Q

Loose CT (areolar CT)

A

lots of ground
substance with collagen and elastin

  • cells are
    fibroblasts

Ø Often the glue holding 2 tissues types together.
For example the epidermis of skin is attached to
the layers below by areolar CT

78
Q

Dense regular CT

A

ECM with lots of collagen
fibers all oriented parallel to one another.

Provides tensile strength as in tendons and
ligaments

79
Q

Dense irregular CT

A

ECM with lots of collagen
that randomly arranged

80
Q

Adipose CT

A

very little ground substance;

no fibers;

cells are adipocytes that contain a
large storage area for triglycerides (cell is
mostly a droplet of fat with cell organelles
pushed out towards the cell membrane

81
Q

Bone

A

mineralized ground substance due to
hydroxyapatite (calcium) salts gives bone their
strength;

fiber = collagen;

cells are
osteoblasts, osteocytes and osteoclasts

82
Q

Cartilage

A

semi-rigid but flexible ground
substance contains hyaluronic acid;

fibers are
collagen;

cells are chondroblasts,
chondrocytes and chondroclasts.

Found
covering ends of bones at joint surfaces; also
cartilage of ear, nose, larynx (voice-box), etc

83
Q

Blood

A

fluid matrix (blood
plasma/intravascular fluid); contains soluble
protein fibers involved in blood clotting
(fibrinogen)

Cells include red blood cells
(RBCs = erythrocytes) and white blood cells
(WBCs = leukocytes)

RBCs transport gases
(O2 and CO2) while WBCs support immune
function

RBCs are located in blood vessels
while WBCs are found in blood vessels and
lymphatic vessels/tissues

84
Q

Explain what an excitable tissue is

A

nervous and muscle tissue are excitable (have very little ECM)

  • called this bc of their ability to generate and propagate action potentials
85
Q

Muscle Tissue

A

Has the ability to generate electrical signals in response
to stimuli that will cause contraction and shortening

86
Q

List the 3 major types of muscle tissue

A
  1. skeletal
  2. cardiac
  3. smooth
87
Q

Skeletal muscle tissue

A

long multinucleate cells; voluntary contraction
produces force that can move the skeleton and produces
facial expressions.

E.g. your deltoid (shoulder muscle)
contains skeletal muscle tissue. When it contracts, it moves
your humerus (whole arm).

88
Q

Cardiac muscle tissue

A

branched uninucleate cells; produces involuntary
rhythmic contractions of heart in order to pump blood
throughout the cardiovascular system

89
Q

Smooth

A

involuntary muscle that forms part of the wall of
most internal organs (e.g. stomach, intestines, bladder, uterus,
blood vessels, etc.)

Also forms muscles of the iris of the eye,
which contract to control pupil size and muscles in the skin
(arrector pili muscles that make our hair stand on end)

90
Q

List the 2 types of neural tissue

A

Neurons
glilal cells

91
Q

Neurons

A

– generate chemical and electrical
signals in response to stimuli that can be
propagated over long distances

Located in
the brain, spinal cord and nerves that go to
all structures in the body.

92
Q

Glial cells (neuroglia)

A

– support cells for
neurons that have various functions (we will
look at these more closely when we study
the nervous system)

93
Q

Explain what an organ is and describe how the skin fits this definition

A

Organs are made of 2 or more tissue types.

ØSkin contains all 4 of the major tissue types.

94
Q

Describe what tissue type each layer of the skin is composed of

A
  1. Epithelial Tissue is present in :
    a. Epidermis = stratified squamous epithelial tissue protects
    b. Sweat glands and sebaceous (oil) glands
  2. Connective Tissue is present in:
    a. Dermis = dense irregular CT and areolar CT, gives skin strength,
    but also flexibility
    b. Hypodermis – adipose CT
  3. Muscle Tissue is present in:
    a. Arrector pilli muscle – contraction causes hairs in skin to stand
    straight up causing “goosebumps” . In other mammals with more
    hair, this helps to trap a warm layer of air against the skin in cold
    weather.
  4. Nervous Tissue is present in:
    a. Sensory receptors for touch, temperature, pain, and pressure,
    which are all parts of neurons.

Human Physiology 1 (16 decks)

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