chp 4 Flashcards
cellular respiration
glucose+oxygen—>energy+co2+h2o
homeostasis
The maintenance of a constant internal environment of cells despite fluctuations in external environment
body systems work together to ensure a constant body temperature, correct level of molecules or ions maintained, fluid levels and body are correct
functions of a cell membrane
- it is a physical barrier: protect ourselves and separate cells cytoplasm from the extra cellular fluid. this is important because the composition of the cytoplasm and the extracellular fluid are very different
- regulates passage of materials: what enters and leaves, controls the movement of materials into and out of the cell. Achieves this through its semipermeable membrane
- sensitivity: protein receptors in membrane are sensitive to certain or particular molecules around it for example hormones. The cell membrane is the first part of the sale affected by any changes in the extracellular fluid
- support: inside part of membrane has microfilament’s attached, which is part of the cytoskeleton. there are also connections between the membranes of adjacent cells that give support to the whole tissue of which the cells are apart
cell membrane structure
membrane is the phospholipid bilayer, The main building blocks are phospholipids.
1. hydrophilic head made of an alcohol and glycerol group
2. hydrophobic tail made of chains of fatty acids
3. glycerol backbone
phospholipids can move sideways and allow water and other nonpolar molecules to pass through into or out of the cell
proteins and other molecules are in bedded in the membrane, it is called the fluid mosaic model.
fluid= proteins/molecules are constantly changing positions
mosaic=composed of many different types of molecules
A variety of proteins and cholesterol molecules are in bedded in the bilayer some past through the membrane others are only on the surface. Cholesterol makes the membrane more fluid.
membrane proteins
- channel proteins: form a central pole, allow small ions, water, and other small molecules to pass through by simple diffusion
- receptor proteins: receive information to provide a response (hormone, insulin)
- Carrier protein: are specific, allow certain materials to bind to it, For example only glucose, amino acids. allows facilitated diffusion for example glucose and active transport (specific membrane pumps)
- cell identity markers: identifies the sale as self to prevent attack by the bodies immune system. They have carbohydrate parts attached to it to help cells in recognising each other and certain molecules
membrane transport methods
- diffusion and osmosis
- Carrier mediated transport: facilitated diffusion (passive), active transport (active)
- vesicular transport: endo/exocytosis
active vs passive
passive: requires no energy or ATP
active: requires ATP and include specific membrane pumps
diffusion
occurs in gases and liquids
movement of molecules from areas of High concentration to low concentration, until evenly distributed. Because cell membrane is fatty, so most water soluble substances cannot diffuse through it except for oxygen and carbon dioxide
factors:
1. Concentration gradient: concentration and distance
2. surface area: larger surface area creates a larger rate of diffusion
3. barriers: thicker barriers slow diffusion rates, pores in a barrier in enhance diffusion
4. temperature: higher temperature leads to higher diffusion rates because particles have more energy
bring in water, oxygen, carbon dioxide, alcohol, fatty acids, ions, lipids, soluble drugs
concentration gradient
when the concentration of a substance is different at two places: the substance will diffuse along the concentration gradient until the concentration of the two areas become equal
x axis= distance
y axis= concentration
greater the difference in concentration, the steeper the gradient and the faster diffusion occurs
osmosis
diffusion of water across a semipermeable membrane. What are molecules move from high concentration to low concentration
solute=sugar(other),solvent=water
The higher the concentration of the solute increases the osmotic pressure.
water diffuses from the more watery to the less watery side of the membrane
osmotic pressure: The pressure due to differences in concentration on either side of a semipermeable membrane
carrier mediated
facilitated diffusion
diffusion with help, where molecules diffuse across cell membrane with assistance of carrier proteins. carrier protein changes shape and molecule is released on the other side of membrane
diffusion takes place from high concentration to low concentration does not require ATP for example amino acids or glucose
carrier proteins: specific, can become saturated, and can be regulated by hormones for example insulin have specific shape to glucose
bring in glucose and AA
carrier mediated
active transport
process of using ATP to pump molecules across membrane against the concentration gradient
they move from low concentration to high concentration
using active transport a cell can take in or pass out substances regardless of their concentration which is why energy is needed. For example membrane pumps sodium ions and potassium ions which are high in the nerve cells of the body
bring in glucose, certain ions, AA
endocytosis
vesicular transport
process that brings materials into the cell
involves the cell absorbing large particles such as proteins or even whole organisms such as bacteria, viruses, from outside by engulfing them with the cell membrane to form a vesicle like a bubble with in the cytosol
brings in cholesterol, iron ions
The cell membrane folds around a particle until the particle is completely enclosed, the vesicles so formed then pinches off and suspended in the cells cytoplasm
exocytosis
vesicular transport
release of molecules from the cell, things leaving the cell
contents of vesicle are emptied, vesicle formed inside cell then, membrane of vesicle fuses with the cell membrane and contents emptied into extracelluar fluid
empty secretions such as mucus or digestive juices
carrier proteins
specific: they will only buy to a particular molecule. for example the carrier that transports glucose can not transport any other molecules
saturated: once all the available carriers are occupied, any increase in the concentration of molecules to be transported cannot increase the rate of movement.
Regulated by hormones: they are important in coordinating the activities of carrier proteins
