lab exam 2 Flashcards
Plasma membrane
Each cell receives raw materials for various cellular functions through the plasma membrane. There are different processes involved in plasma membrane transport, diffusion being one of them.
diffusion
Diffusion is defined as movement of particles from an area of higher concentration to an area of lower concentration due to random mixing because of inherent kinetic energy of molecules.
Fick’s Law
Fick’s Law of diffusion states that, rate of diffusion depends on the following:
- Concentration gradient
- Molecular weight
- Diffusion distance
- Temperature of the diffusion media
Homeostasis
For the cells to maintain their own homeostasis, they require several types of intracellular biochemical molecules referred to as enzymes. To maintain overall homeostasis, many of these enzymes are
secreted out of the cell to facilitate several types of chemical reactions.
enzyme
An enzyme is a biological
catalyst that can increase the rate of chemical reactions without structurally altering themselves. As a result, a handful of enzymatic molecules can be used repeatedly.
Holoenzyme
A holoenzyme (whole enzyme) is
composed of a protein component known as apo-enzyme and a co-factor or co-enzyme. Since a large part of enzyme is a protein, it is likely to denature when exposed to high heat, large deviations in pH, excess salt etc.
enzyme activation
Enzymes are substrate-specific and can only act on their specific target substrates because their interaction depends on relative shapes of the enzymes and substrates.
effect of temperature on enzymes
Enzymes are biological catalysts that speed up the rates of chemical reactions that take place within or without cells. Being proteins, enzymes are affected by temperature and pH. Human enzymes work best at human body temperature (37°C or 98.6°F). Many human enzymes no longer function when heated beyond 60°C because their molecular structure is denatured at this higher temperature. Conversely, as enzymes are cooled, their activity slows as the temperature decreases and activity ceases at 0°C
amylase
Human saliva contains the enzyme salivary amylase. Amylase splits starch to maltose and dextrin, which are combination of sugars or disaccharides.
effect of PH on enzymes
Enzyme activity is also affected by pH. Various enzymes have an optimal pH at which they catalyze reactions at the fastest rate. If the pH is higher or lower than optimal, the rate of reaction decreases. For example, the inactive enzyme pepsinogen, which is produced by “Chief cells” in the stomach, requires gastric acid containing HCl to convert it to the active enzyme pepsin, which works fastest at pH 2.0 to
break down proteins into short chain peptides. If the gastric juice pH increases (it becomes more alkaline) because a person ingests an antacid such as Tums, Rolaids etc., the ability of an enzyme to
hydrolyze proteins ceases.
General Characteristics of Muscle Tissue
- Muscle tissue is contractile – cells shorten when stimulated
– Contraction causes movement - Anatomical classification:
– Striated (striped) OR Non-striated (not striped) - Physiological classification:
– Voluntary (consciously controlled) OR Involuntary (unconsciously controlled)
Unique characteristics of muscle tissue
– Excitability: Muscles can be stimulated (electrical/chemical stimulus)
– Contractility: Muscles can shorten
– Extensibility: Muscles can be stretched
– Elasticity: When relaxed, a stretched muscle will return to its original position
skeletal muscle location
Usually attached to bones by tendons.
skeletal muscle
Consists of long, cylindrical, striated fibers. Vary greatly in length, from a few centimeters in short muscles to 30-40 cm in the longest muscles. A muscle fiber is roughly cylindrical, multinucleated
cell with nuclei at the periphery. It is voluntary because it can be made to contract or relax by conscious control.
skeletal muscle function
Motion, posture, heat production, protection
cardiac muscle location
Heart wall.
cardiac muscle
Consists of branched, striated fibers with usually only one centrally located nucleus. Attach end to end by transverse thickenings of plasma membrane called intercalated discs, which contain desmosomes
and gap junctions. Desmosomes strengthen tissue and hold fibers together during vigorous contractions. Gap junctions provide route for quick conduction of electrical signals throughout heart.
Involuntary control.
smooth muscle
Consists of nonstriated fibers (lacking striations, hence the term smooth). Smooth muscle fiber is a small spindle-shaped cell thickest in the middle, tapering at each end, and containing a single,ncentrally located nucleus. Gap junctions connect many individual fibers in some smooth muscle
tissue. Usually involuntary; can product powerful contractions as many muscle fibers contract inunison. Where gap junctions are absent, such as iris of eye, smooth muscle fibers contract
individually, like skeletal muscle fibers.
smooth muscle location
iris of eyes; walls of hollow internal structures such as blood vessels, airways to lungs, stomach,intestines, gallbladder, urinary bladder, and uterus
smooth muscle function
Motion (constriction of blood vessels and airways, propulsion of foods through gastrointestinal tract, contraction of urinary bladder and gallbladder).
Interaction of Skeletal Muscles
- Most skeletal muscle function in groups. Roles of muscles in
performing certain actions: - Agonist/Prime Mover
– muscle that causes an action - Synergists
– muscles that assist agonist / prime mover - Antagonist
– muscles whose contraction causes movement in the opposite direction of the
prime mover
origin and insertion
- One end of a skeletal muscle is
more fixed, and the other end is
more movable - Origin: less movable end
- Insertion: more movable end
- When a muscle contracts, the
insertion is pulled toward the origin
Frontal belly of
Occipitofrontalis
origin is Epicranial aponeurosis
insertion is Frontal bone
Elevates eyebrow
Occipital belly of
Occipitofrontalis
Origin is occipital bone and temporal
bone
insertion is Epicranial aponeurosis
Draws scalp posteriorly
