Unit 1: Homeostasis, Cell structure

Question 1

Describe Prokaryotic Cells

Answer 1

No nucleus, few organelles, lack of internal membranes
Simple, primitive cells
(i.e., Bacteria)

Question 2

Describe Eukaryotic Cells

Answer 2

Complex cells

• Has nucleus, with many organelles and an internal membrane.
• Each organelle has a specific function.
• More efficient than prokaryotic cells as chemical reactions occur in the specialized areas, not all over the cytoplasm.
  (i. e., Animals, Plants, fungi, etc)

Question 3

Plant cells vs Animal cells

Answer 3

Plant: Cell wall, one central vacuole, chloroplasts, no centrosome nor lysosome

Animal: No cell wall, many small vacuoles, no chloroplasts, centrosome and lysosome both exist

Question 4

Structure & Function: Nucleus

Answer 4

Structure: Largest organelle, surrounded by double-layered membrane called the nuclear envelope, membrane has pores where molecules pass through called the nuclear pores

Function: The Control Center, governs all cellular activities

Question 5

Function of Nucleolus

Answer 5

Where ribosomal RNA (rRNA) is produced/stored.

rRNA joins with protein to form ribosomal subunits, eventually forming ribosomes

Question 6

Chromatin & Chromosomes

Answer 6

Chromatin is the hereditary material found in nucleus
Provides instruction to the organelles
Chromatin coils up into short rods to form chromosomes during cell division

Question 7

Cytoplasm function and structure

Answer 7

Colloidal (small particles mixed evenly with another substance) substance that changes from liquid to solid

Contains and supports organelles

Question 8

Cell membrane basic structure and function

Answer 8

Made up of proteins and phospholipids

The Barrier

• Controls movement of specific materials in and out of cell
• Provides rigidity and structure to cell

Question 9

Cell wall

Answer 9

Only plant cells, additional protection with the cell membrane

Question 10

Endoplasmic reticulum (Smooth vs Rough, function & structure)

Answer 10

System of flattened tubes, sacs, or canals. Sections of ER can break off vesicles in the process of blebbing.

Smooth ER: No ribosomes, manufactures lipids and contains enzymes to detoxify toxins

Rough ER: Has ribosomes which are sites of protein synthesis

Question 11

Golgi Body function

Answer 11

The center of modification, storage, sorting and shipping of materials

• Receives protein or lipid filled vesicles from the ER
• Modifies and packages the vesicles
• From here they transport to different locations in and out of the cell

Question 12

Vacuoles and Vesicles function

Answer 12

Vacuoles: More prominent in plant cells, storing water, nutrients, and wastes

Vesicles: Small vacuoles; transport vesicles move materials from organelle to organelle while secretory vesicles move materials from Golgi Body - cell membrane

Question 13

Lysosomes function

Answer 13

Double membrane, special vacuoles formed by Golgi Body

Contains hydrolytic enzymes for digesting various materials in the cells. Fuses with vesicles entering the cell while also recycling old cell parts in a process called auto-digestion

Question 14

Mitochondria function and structure (also the cellular respiration equation)

Answer 14

Double membrane organelle
-Inner membrane loops back and forth to increase its surface area. The inner space is called the matrix while the folds of the membrane are called the cristae.

• Uses carbohydrate and oxygen to from ATP, energy needed for cellular processes, while giving off carbon dioxide and water. This is called cellular respiration, described by the formula: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
• The matrix contains the DNA, ribosomes, and enzymes that break down the carbs, while the cristae accommodates all the participants that are necessary for cellular respiration

Question 15

Chloroplasts function (photosynthesis equation)

Answer 15

Found only in plant cells
Uses solar energy along with water & CO2 to produce glucose (carb)

Has a mutualistic relationship with the mitochondria. Uses CO2 and water produced by mitochondria to in turn produce carbs and oxygen that the mitochondria uses

The process is called photosynthesis, by the equation: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2

Question 16

Cytoskeleton function

Answer 16

Maintains cell shape, anchors the organelles and allows them to move when appropriate

Also allows cell movement, due to an interconnected system of microfilaments and microtubules

Question 17

Cilia & Flagella function

Answer 17

Microtubules that project out of cells but bounded by the cell membrane

• Cilia: short and hair-like, used for movement by unicellular organisms
• Flagella: Longer than cilia, also for movement

Question 18

Centrioles function

Answer 18

Found only in animal cells, two short cylinders of microtubules lying at right angles
Part of the centrosome, which is the major organizing centre of microtubules
Has a role in cell division, as well as giving rise to basal bodies that organize cilia and flagella.

Question 19

How does cell size relate to its efficiency?

Answer 19

Adequate surface area is required for the cell to do any type of cellular activities.
The smaller the cell, the ratio of its surface area compared to its volume is bigger than the bigger cells.
Volume = the needs of the cell; bigger the cell, the more nutrients it requires and the more waste it produces
Thus, smaller cells are more efficient and cells have modifications such as folding and flattening to increase its surface area

Question 20

What is the path of protein secretion? (7 steps)

Answer 20

1. Protein is manufactured at ribosomes on rough ER
2. Moves into the lumen of rough ER for modification
3. Moves through the lumen to the outer edges, and encloses in transport vesicles by blebbing
4. Transport vesicles move to the Golgi body and fuse
5. Golgi body modifies, sorts, stores, and packages again for transport
6. Golgi body packages the protein in secretory vesicles, as it blebbs off the Golgi body
7. Secretory vesicles move and fuse with the cell membrane -> SECRETION!

Question 21

Rough ER & Golgi body partnership

Answer 21

rough ER synthesizes and packages proteins for Golgi Body (transport vesicles) Golgi body further modifies, sorted and packaged for export (secretory vesicles)

Question 22

Nucleolus & ribosomes partnership

Answer 22

nucleolus produces rRNA which forms ribosomal subunits which travel to cytoplasm and forms ribosomes

Question 23

Vesicles & Golgi body partnership

Answer 23

Golgi body receives transport vesicles, modifies the contents and repackages into secretory vesicles

Question 24

Cell membrane & lysosomes partnership

Answer 24

materials enter the cell through cell membrane in vesicles, lysosomes fuse with vesicle to digest its content

Question 25

Chloroplasts & Mitochondria partnership

Answer 25

Chloroplasts produce carbohydrate through photosynthesis which in turn the mitochondria can use to make ATP

Question 26

Centrioles & Cilia/flagella partnership

Answer 26

Centrioles give rise to basal bodies which organize cilia/flagella

Question 27

What is homeostasis? (Sensor? Control center)

Answer 27

The tendency to maintain a stable, relatively constant internal state of body. (i.e., body temp, pH blood levels, etc)
This mechanism always consists of two parts: the sensor and the control center.
When a stimulus that affects the internal state occurs, the sensor detects and alerts the control center. Then, the control center causes an action to bring the conditions back to normal.

Question 28

What is negative feedback? (explain with example on exercise)

Answer 28

An action to achieve homeostasis
To bring your internal state back to normal, your body usually does something to OPPOSE the stimuli that caused the disruption. It is the opposing nature that these actions are called negative feedback.
i.e., when you exercise, your body temperature goes up. Your body will start producing sweat, blood flows to your skin to increase heat loss, etc, to bring the temperature back up.

Question 29

What is positive feedback? How is it different from negative feedback?

Answer 29

When your body does something that is in the same direction as the stimulus.
Can be dangerous (if you have a high fever, a positive feedback pushes the fever even higher)
Positive feedback helps the body cope with intermittent events (childbirth, blood clotting, etc) while negative feedback helps the body maintain homeostasis.