CELLS AND TISSUES

Question 1

CELLS

Answer 1

• smallest functioning unit
• group together to form tissues (specialised function)
• different types of tissues form different organs
• systems = formed organs, set of related functions that maintain homeostasis and contribute to the health of the individual

Question 2

CELLS: STRUCTURE AND FUNCTION

Answer 2

• The human body developed = zygote (fertilized egg) = fusion of ovum (female egg cell)
• spermatozoon (male sex cell) = cell division = fetus grows
• cells are too small to be seen by the naked eyes

Question 3

PLASMA MEMBRANE (phospholipids & hydrophilic )

Answer 3

PHOSPHOLIPIDS (have a head):
- protein and sugars embedded
- lipids cholesterol
- electrically charged &hydrophilic (water-loving)
- tails = no electrical charge = hydrophobic (water-hating)

HYDROPHILIC:
- head on the outer surface of membrane = hydrophobic tails = water repellent layer

Question 4

MEMBRANE PROTEIN

Answer 4

• carbs molecules attached to the outer surface, cells’ immunology identity
• acts as receptors = hormones and chemical receptors
• enzymes
• transmembrane protein channels filled with H20, H20 soluble ions cross the membrane
• pumps that transport substances across the membrane

Question 5

TRANSPORT OF SUBSTANCES ACROSS CELL MEMBRANES

Answer 5

• cells = enclosed by plasma membrane = barriers for the substance entering or leaving = selective permeability
• plasma membrane controls entry/exit of substances and regulation of the internal environment
• small molecules
• freely around the membrane = simple diffusion
• diffusion studied with specialised pumps imports/exports specific substances
• selective permeability together: passive & active transport mechanism, chemical composition
• The chemical composition of fluid inside cells is different from the interstitial fluid that bathes them

Question 6

PASSIVE TRANSPORT

Answer 6

• substances cross the semipermeable plasma and organelle membranes `
• down the concentration gradient without using energy

Question 7

DIFFUSION

Answer 7

• down contration gradeient
• Lipid-soluble materials e.g. O2 cross by dissolving in the lipids part of the membrane
• water-soluble materials cross the membrane through water-filled channels

Question 8

FACILITATED DIFFUSION

Answer 8

• cant diffuse through a semipermeable membrane
• specialised protein = specialised sites that attack and bind substances to be transferred (lock and key mechanisms)
• carrier changes (only used by one shape) shape on the other side of the membrane
• infinite number of carriers limited amount of substances transported at anytime

Question 9

OSMOSIS

Answer 9

• passive movement, water down its concentration gradient across a semipermeable membrane towards equilibrium

Question 10

ACTIVE TRANSPORT(AT)

Answer 10

• transport of a substance up a concentration gradient from a lower to a higher concentration.
• chemical energy from ATP (protein carrier)
• transport across the membrane
• substance is transferred depending on the number of sites available
• active transport mechanisms include the sodium/potassium pump and bulk transport

Question 11

SODUIM-POTASSIUM PUMP

Answer 11

• cell membrane possesses the pump
• other transport mechanisms, e.g. glucose uptake
• generate an action plan for nerve and muscles
• AT maintains unequal concentrations of NA+ and K+
• each side membrane used up 30% of cellular ATP requirements
• K+ levels higher inside cells = intracellular cations.
• NA+ levels = higher outside the cell than inside = extracellular
• diffuse down concentration K+ to NA+ into the cell

Question 12

BULK TRANSPORT

Answer 12

• transfer to particles = too big to cross cell membrane = occurs by PINCOYTOSIS (cell-drinking) / PHAGOCYTISIS (cell-eating) = extention of the cytoplasm
• LYSOSMONES = vacuole membrane = release enzymes that digest food.
• release of extra materials = reverse process exocytosis