Practice Flashcards
Flip to reveal answersWhich lipid is used to store energy?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 14 Flashcards — Lipids as energy stores
Sign up free to track progress and get spaced-repetition review schedules.
Question
Which lipid is used to store energy?
Answer
The **triglyceride** — one **glycerol** joined to **three fatty acids**.
Question
Where do animals store fat?
Answer
In **adipose tissue** — fat-storage cells under the skin and around organs.
Question
How much energy does a triglyceride store compared with carbohydrate?
Answer
About **twice** as much energy **per gram**.
Question
Why are triglycerides so energy-rich per gram?
Answer
Their long **fatty-acid tails** contain many energy-rich **C–H bonds** and little oxygen.
Question
Are triglycerides soluble or insoluble in water?
Answer
**Insoluble** — the fatty-acid tails are **hydrophobic** (water-repelling).
Question
Why is being insoluble an ADVANTAGE for a store?
Answer
Fat does not dissolve in the cell or draw water in by **osmosis**, so large amounts can be stored without upsetting the cell's water balance.
Question
Define hydrophobic.
Answer
**Water-repelling** — a non-polar part that does not mix with or dissolve in water.
Question
Define adipose tissue.
Answer
Animal tissue made of **fat-storage cells**; it stores triglycerides and forms an **insulating layer** under the skin.
Question
Besides energy, give two roles of the fat layer.
Answer
**Thermal insulation** (slows heat loss) and **protection / cushioning** of organs.
Question
Why does glucose dissolve in water but oil does not?
Answer
Glucose has many polar **–OH groups** that attract water; a triglyceride's tails are **non-polar / hydrophobic**, so they do not.
Question
Which is the long-term energy store: lipid or carbohydrate?
Answer
**Lipid** (triglyceride fat) is the long-term, high-capacity store; **carbohydrate (glycogen)** is the short-term, quick store.
Question
Why is fat a 'compact' store?
Answer
It holds lots of energy and carries no extra water, so it stores the **same energy for less mass**.
Question
Define triglyceride.
Answer
The energy-storage lipid: one **glycerol** molecule joined to **three fatty acids**.
Question
In an 'explain' answer, what must you do with each property?
Answer
**Pair it with its reason** — e.g. insoluble BECAUSE hydrophobic; high energy BECAUSE many C–H bonds.
Read the notes
Full study notes for Lipids as energy stores
Topic 2.1 hub
Carbohydrates and lipids
More from Topic 2.1
All flashcards in this topic
Biology exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free