Cells (Chapter 2)

Question 1

Cell theory

Answer 1

• All living organisms are composed of one or more cells.
• The cell is the basic unit of structure and organization in organisms.
• Cells arise from pre-existing cells

Question 2

Endoplasmic reticulum

Answer 2

• Provide a surface on which chemical reactions can occur
• The channels between the paired membranes are used for storage and transport of materials
• Rough endoplasmic reticulum has ribosomes attached to it
• Smooth endoplasmic reticulum has no ribosomes

Question 3

Ribosomes

Answer 3

• Site of protein synthesis

Question 4

Lysosomes

Answer 4

• Small spheres that contain enzymes able to break down proteins, lipids, nucleic acids
• Formed from golgi body

Question 5

Vesicle

Answer 5

membrane-bound sac that transports materials into, out of, or within the cell

Question 6

Nucleus

Answer 6

Contains the genetic material of a cell

Question 7

Mitochondria

Answer 7

• Where cellular respiration takes place (energy production)
• The folding of its inner membrane produces a large surface area for these chemical reactions to take place
• Called ‘powerhouses’ of cell

Question 8

Golgi body

Answer 8

• Modifies and packages proteins for their secretion from the cell

Question 9

Why do cells prefer a high surface area to volume ratio?

Answer 9

Becasue if the volume of a cell is too big compared to the surface area the cell can’t exchange material efficiently enough to stay alive.

Question 10

Homeostasis

Answer 10

The maintenance of the balanced environment a cell needs to operate

Question 11

Phospholipid bilayer

Answer 11

• The basic ‘part’ of the cell membrane
• Phospholipids contain a head and a tail
• The head contains a phosphate group and likes water (hydrophilic)
• The tail is made of lipids (fats) and dislikes water (hydrophobic)
• Contains carrier proteins which act as a tunnel for substances to move in and out at will
• Contains channel proteins which bind to a particular substance to carry them through the membrane in and out of the cell
• Contains cholesterol molecules which sit within the bilayer, acting as velcro the keep the phospolipids joined
• Also cell identity markers which are nametags for the cell, letting the immune system know that the cell is not a foreign invader

Question 12

Functions of the cell membrane

Answer 12

• Physical barrier between cytoplasm and extracellular fluid
• Regulation of passage of materials
• Support
• Sensitivity - uses receptors to detect changes in the environment

Question 13

Transport across membrane

Answer 13

The membrane is selectively permeable. Permeable meaning it allows liquids and gases to pass through and selectively referring to having control over what goes in and out. There are 3 basic forms of transporting material across the membrane:
Diffusion
Carrier-mediated transport
Vesicular transport

Question 14

Diffusion

Answer 14

• The movement of small molecules such as oxygen and carbon dioxide directly across the cell membrane along a concentration gradient (from areas of high concentration to low concentration)
• The greater the differential between high and low the steeper the concentration gradient. The steeper the concentration gradient the quicker diffusion happens.
• A passive process

Question 15

Osmosis

Answer 15

the diffusion of a water from high to low concentration through a selectively permeable membrane in order to balance the concentration of another substance.

Question 16

Two types of carrier-mediated transport

Answer 16

• Facilitated diffusion:
  Passive (doesn’t require ATP)
  Moves with the concentration gradient
• Active transport:
  Active (requires ATP)
  Moves against the concentration gradient

Question 17

Endocytosis and Exocytosis

Answer 17

• Endocytosis – entering the cell. The cell membrane engulfs the solid or liquid until it’s completely enclosed. The vesicle is then engulfed in the cytoplasm.
• When the cell engulfs solids it is called phagocytosis. When it engulfs liquids it is called pinocytosis.
• Exocytosis - exiting the cell. A vesicle is formed around contents in the cytoplasm, and migrates to the membrane. It then fuses with the membrane and pushes the contents outside.

Question 18

4 types of tissues

Answer 18

• Muscular, contains muscle fibres which contract becoming shorter to contract the muscle
• Epithelial, lines body surfaces, cavities, glands, cells close together
• Connective, provides support and structure, cells separated by material called matrix
• Nervous, composed of neurons that receive and transmit information around the body as electrical impulses

Question 19

3 types of muscle tissue

Answer 19

• Skeletal muscle
  -Muscles that are attached to our skeleton.
  -Striated appearance
  -Controlled voluntarily.
• Smooth / Involuntary muscle
  -Muscles that make up our organs.
  -No striations so referred to as smooth or non-striated
  -Can not be controlled voluntarily
• Cardiac muscle
  -Muscle of the heart.
  -Faint striations.
  -Can not be controlled voluntarily.